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BEGIN:VEVENT
SUMMARY:Anyonic molecules in atomic fractional quantum Hall liquids: a qua
ntitative probe of fractional charge and anyonic statistics
DTSTART;VALUE=DATE-TIME:20201002T114500Z
DTEND;VALUE=DATE-TIME:20201002T120000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122614@agenda.infn.it
DESCRIPTION:Speakers: Alberto Muñoz de las Heras (University of Trento)\n
We study the quantum dynamics of massive impurities embedded in a strongly
interacting two-dimensional atomic gas driven into the fractional quantum
Hall (FQH) regime under the effect of a synthetic magnetic field. For sui
table values of the atom-impurity interaction strength\, each impurity can
capture one or more quasi-hole excitations of the FQH liquid\, forming a
bound molecular state with novel physical properties. An effective Hamilto
nian for such molecules is derived within the Born-Oppenheimer approximati
on\, which provides renormalized values for the effective mass\, charge an
d statistics of such anyonic molecules by combining the finite mass of the
impurity and the fractional charge and anyonic statistics of the quasi-ho
les. The anyonic statistics is shown to provide a long-range Aharonov-Bohm
-like interaction between molecules. The resulting relative phase of the d
irect and exchange scattering channels can be thus extracted from the angu
lar position of the interference fringes in the scattering cross section o
f a pair of colliding molecules. Different configurations providing direct
and quantitative insight on the fractional charge and the anyonic statist
ics of quasi-hole excitations in FQH liquids are highlighted for both cold
atoms and photonic systems.\n\nhttps://agenda.infn.it/event/23347/contrib
utions/122614/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122614/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Beers and Posters: Day 2
DTSTART;VALUE=DATE-TIME:20200930T173000Z
DTEND;VALUE=DATE-TIME:20200930T190000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122260@agenda.infn.it
DESCRIPTION:- P25 - Matteo Paris (University of Milan)\nNoisy propagation
of Gaussian states in optical media with finite bandwidth\n\n- P26 - Tomon
ori Matsushita (Hiroshima University)\nMeter sensitivity in quantum measur
ements\n\n- P27 - Alena Mastiukova (Moscow Institute of Physics and Techno
logy\, National Research University)\nSuppressing decoherence in quantum c
omputers with unitary operations\n\n- P28 - Kristina Majauskaite (Institut
e of Biochemistry\, Life Sciences Center\, Vilnius University)\nSpintronic
characteristics of self-assembled acetylcholine molecular complexes\n\n-
P29 - Martín Jiménez (Universidad Nacional de Córdoba)\nTwo-fermions mo
lecules in a harmonic trap with short-range interaction\n\n- P30 - Hasnaa
Hajji (Mohammed V University\, Faculty of Sciences)\nQutrit based semi-qua
ntum key distribution protocol\n\n- P31 - Amanuel Tamirat Getachew (Wolkit
e University)\nEntaglement-Based Quantum Mean Estimator Circuit\n\n- P32 -
Luca Fasolo (Politecnico di Torino and Istituto Nazionale di Ricerca Metr
ologica)\nA quantum model for rf-SQUIDs based metamaterials enabling 3WM a
nd 4WM Travelling Wave Parametric Amplification\n\n- P33 - Wandearley De S
ilva Dias (Universidade Federal de Alagoas)\nAperiodic space-inhomogeneous
quantum walks: Localization properties\, energy spectra\, and enhancement
of\nentanglement\n\n- P34 - Loris Maria Cangemi (University of Naples Fed
erico II)\nViolation of TUR in a periodically driven quantum work-to-work
converter\n\n- P35 - Anderson Buarque (Universidade Federal de Alagoas)\nS
elf-trapped quantum walks\n\n- P36 - Gustavo Martin Bosyk (Instituto de F
ísica La Plata\, CONICET-UNLP & Università degli Studi di Cagliari)\nGen
eralized coherent vector: definition and applications\n\n- P37 - Fadwa Ben
abdallah (LPHE-Modeling and Simulation\, Faculty of Sciences\, Mohammed V
University in Rabat)\nQuantum discord based on linear entropy and thermal
entanglement of qutrit-qubit spin chain under influence of\nthe external m
agnetic field\n\n- P38 - Revanth Badveli (Birla Institute of Technology an
d Science\, Pilani)\nCompressed Sensing Quantum State Tomography: An Alter
nate Approach\n\n- P39 - Utkarsh Azad (International Institute of Informat
ion Technology\, Hyderabad)\nQuantum Neural Networks - Towards an era of Q
uantum-Assisted Machine Learning\n\n- P40 - Giorgio Zarantonello (Leibniz
Universität Hannover)\nTowards fault-tolerant quantum computation based o
n near-field microwaves with trapped ions\n\n- P41 - Giacomo Guarnieri (Tr
inity College Dublin)\nQuantum fluctuations hinder finite-time information
erasure near the Landauer limit\n\n- P42 - Jan Tuziemski (Stockholm Unive
rsity).\nRelative decoherence in quantum reference frames\n\n- P43 - Gabri
el Matos (University of Leeds)\nQuantifying the efficiency of state prepar
ation via quantum variational eigensolvers\n\n- P44 - Kartikeya Rambhatla
(Shiv Nadar University)\nAdaptive phase estimation through a genetic algor
ithm\n\n- P45 - Manik Banik (Indian Institute of Science Education and Res
earch\, Thiruvananthapuram\, India)\nQuantum Advantage in Shared Randomnes
s Processing\n\n- P46 - Marcos Basso (Federal University of Santa Maria)\n
An uncertainty view on complementarity and a complementarity view on uncer
tainty\n\n- P47 - Colin Benjamin (National Institute of Science education
and research)\nTesting quantum speedups in exciton transport through a pho
tosynthetic complex using quantum stochastic walks\n\nhttps://agenda.infn.
it/event/23347/contributions/122260/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122260/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Beers and Posters: Day 1
DTSTART;VALUE=DATE-TIME:20200928T173000Z
DTEND;VALUE=DATE-TIME:20200928T190000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122245@agenda.infn.it
DESCRIPTION:- P1 - Gianluca Passarelli (University of Naples)\nVariational
counterdiabatic driving of the ferromagnetic p spin model\n\n- P2 - Enric
o Rebufello (Istituto Nazionale di Ricerca Metrologica and Politecnico di
Torino)\nIrreversibility in unitary quantum homogeneisation: Theory and Ex
periment\n\n- P3 - Rolando Ramirez Camasca (University of Sao Paulo)\nMemo
ry kernel and Divisibility of Gaussian Collisional Models\n\n- P4 - Jishnu
Rajendran (Università degli Studi di Catania)\nDetection of virtual phot
ons in superconducting architectures\n\n- P5 - Luca Pezzé\nA Quantum Phas
e Estimation Algorithm with Gaussian Spin States\n\n- P6 - Federico Roccat
i (UNIPA)\nQuantum correlations in a gravitational classical-channel model
\n\n- P7 - Shubhayan Sarkar (Centre for Theoretical Physics\, Polish Acade
my of Sciences)\nCertification of incomaptible measurements and entangled
subspaces using quantum steering\n\n- P8 - Giovanni Scala (BA)\nEntangleme
nt witnesses: overview of the technique and a new construction\n\n- P9 - V
ikash Mittal (Indian Institute of Science Education & Research (IISER) Moh
ali)\nPersistence of Topological Phases in Non-Hermitian Quantum Walks\n\n
- P10 - Mark Mitchinson (Trinity College Dublin)\nIn situ thermometry of a
cold Fermi gas via dephasing impurities\n\n- P11 - Kengo Matsuyama (Hiros
hima university)\nJoint measurement of non-classical correlations\n\n- P12
- Muzzamal Shaukat (Instituto de Telecomunicacoes\, Lisbon\, Portugal)\nD
ark Soliton Qudits: A novel Quantum Information Platform in Bose-Einstein
condensates\n\n- P13 - Owidiusz Makuta (Centre for Theoretical Physics\, P
olish Academy of Sciences)\nGenuinely entangled\, stabilised subspaces\n\n
- P14 - Mahshid Khazei Shadfar\nWitnessing non-Markovian effects of quantu
m processes through Hilbert-Schmidt speed\n\n- P15 - Filippo Vincentini (E
PFL)\nVariational neural network ansatz for steady-states in open quantum
systems\n\n- P16 - Shashank Gupta (S. N. Bose National Centre for Basic Sc
iences)\nDistillation of Genuine Tripartite Quantum Steering\n\n- P17 - An
dreas Geißler (School of Physics and Astronomy\, University of Nottingham
)\nLocalization effects in the disordered two-dimensional Bose-Hubbard-mod
el\n\n- P18 - Sergey Filippov (Moscow Institute of Physics and Technology\
, Steklov Mathematical Institute of Russian Academy of Sciences)\nMachine
learning non-Markovian quantum dynamics\n\n- P19 - Donato Farina (Scuola N
ormale Superiore di Pisa)\nGoing beyond Local and Global approaches for lo
calized thermal dissipation\n\n- P20 - Chandan Datta (Centre of New Techno
logies\, University of Warsaw)\nResolution of incoherent sources beyond th
e Rayleigh limit by array homodyning\n\n- P21 - Eloisa Cuestas (National C
ouncil of Scientific Research of Argentina and National University of Cord
oba)\nFermionic versus bosonic behavior of confined Wigner molecules\n\n-
P22 - Marco Cattaneo (IFISC (CSIC-UIB) and University of Turku)\nEfficient
ly simulable Multipartite Collision Model reproducing any Markovian master
equation\n\n- P23 - Claudio Bonizzoni (Istituto Nanoscienze CNR - Sezione
S3 di Modena)\nStorage and retrieval of microwave pulses with molecular s
pin ensembles\n\n- P24 - Bihalan Bhattacharya (S. N. Bose National Centre
for Basic Sciences)\nGenerating and detecting bound entanglement in two-qu
trits using a family of indecomposable positive maps\n\nhttps://agenda.inf
n.it/event/23347/contributions/122245/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122245/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Satellite Event: Tutorial Lecture "Structure of Quantum Channels"
DTSTART;VALUE=DATE-TIME:20200928T080000Z
DTEND;VALUE=DATE-TIME:20200928T100000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122220@agenda.infn.it
DESCRIPTION:Speakers: Laleh Memarzadeh (Sharif Universiy of Technology\, T
ehran)\nOne of the most promising tasks of quantum information is establis
hment of secure and reliable quantum communication channels over distant n
odes. Beside theoretical success in formalizing the role of quantum featur
es of systems for communication\, current technological progress supports
practical implementation of communication protocols. However\, the role of
quantum channels in quantum information science and technology is not res
tricted to communication protocols. The most general form of evolution of
quantum systems is described by a quantum channel or a completely positive
trace preserving (CPTP) map. Analyzing the mathematical structure of the
space of CPTP maps\, not only deepens our understanding on the nature of q
uantum evolution\, but also plays an important role in implementation of q
uantum information tasks. In this tutorial\, after a short review on the r
ole of quantum channels in communication\, we review the convex structure
of quantum channels as well as divisibility properties of quantum channels
. We will discuss how such an abstract knowledge leads to practical applic
ations such as quantum simulation.\n\nhttps://agenda.infn.it/event/23347/c
ontributions/122220/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122220/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Witnesses of coherence and dimension from multiphoton indistinguis
hability tests
DTSTART;VALUE=DATE-TIME:20200930T133000Z
DTEND;VALUE=DATE-TIME:20200930T133700Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122027@agenda.infn.it
DESCRIPTION:Speakers: Chiara Esposito ()\nThe quantum interference [1] is
a useful tool for the characterization of the single photon sources\, for
quantum computing and for quantum communication. In particular\, the indis
tinguishability and the superposition are the key elements of the quantum
interference and for this reason\, it is worth to develop better methods f
or their identification and quantification. We present an indistinguishabi
lity test for a multiphoton state based on two-photon Hong-Ou-Mandel tests
. Our approach [2] consists of an interferometer that allows measure simul
taneously the three photon overlaps on a four photon state produced by a s
pontaneous parametric down conversion(SPDC) source. As shown in Ref. [3]\,
we quantify the indistinguishability from the obtained value measured ove
rlaps. Starting from these measurements we infer precise bounds for the un
measured overlaps. For this purpose\, we assume two different models for t
he multiphoton state: generally mixed four-photon state [3]\, and the tens
or product of pure single-photon state [4]. Each model provides different
inequalities for the unmeasured overlaps. Furthermore\, changing the numbe
r and the arrangement of HOM tests performed between pair of photon\, i.e
having access to different pairwise overlaps\, other information can be re
trieved on the system. From the same inequalities\, we also can formulate
a coherence witness and dimension witness based on this overlaps estimatio
n\, as shown in Ref. [4]. This basis-independent coherence witness attests
that it is not possible to diagonalize the state on a given reference bas
is. We experimentally test this new coherence witness. In order to have a
three photon state in input and measure the three pairwise possible overla
ps\, we rearrange our interferometer. To obtain the coherence witness viol
ation\, we tune the different input state by photon polarization. We also
experimentally measure the Hilbert space dimension witness which attests i
f the space dimension of each photon state is up to two. For this purpose\
, we use the photon delay times as degree of freedom. In this way\, we hav
e three qudit states that violate the dimension witness. Our results confi
rm the validity of these novel coherence and dimension witnesses and they
provide a complete characterization of the single photon sources. Moreover
\, the identification of an undesired degree of freedom makes the dimensio
n witness very useful for quantum cryptography.\n\n [1] Flamini\, F.\, Spa
gnolo\, N.\, & Sciarrino\, F. “Photonic quantum information processing:
a review.” Reports on Progress in Physics\, 82(1)\, 016001 (2018).\n [2]
Giordani\, T.\, Brod\, D. J.\, Esposito\, C.\, Viggianiello\, N.\, Romano
\, M.\, Flamini\, F.\, ... & Sciarrino\, F. (2020). Experimental quantific
ation of four-photon indistinguishability. New Journal of Physics. \n[3] D
. J. Brod\, et al.\, “Witnessing genuine multiphoton indistinguishabilit
y\,” Phys. Rev. Lett. 122\, 063602 (2019).\n[4] D. J. Brod and E. F. Gal
vão\, “Quantum and classical bounds for unknown two-state overlaps”\n
\nhttps://agenda.infn.it/event/23347/contributions/122027/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122027/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Career panel: Industry
DTSTART;VALUE=DATE-TIME:20201002T153000Z
DTEND;VALUE=DATE-TIME:20201002T163000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122156@agenda.infn.it
DESCRIPTION:Panelists:\n\nMatteo Bina (Applied Materials Italia)\n\nFederi
co Mattei (IBM)\n\nRoberto Siagri (Eurotech)\n\nNiccolò Somaschi (Quandel
a)\n\nhttps://agenda.infn.it/event/23347/contributions/122156/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122156/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Career panel: Publishing
DTSTART;VALUE=DATE-TIME:20200930T153000Z
DTEND;VALUE=DATE-TIME:20200930T163000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122155@agenda.infn.it
DESCRIPTION:Panelists:\n\nKatiuscia Cassemiro (Physical Review X Quantum -
American Physical Society)\n\nJean-Sébastien Caux (University of Amsterd
am and SciPost)\n\nGaia Donati (Zurich Instruments)\n\nAlison Taylor (Opti
cal Society of America)\n\nhttps://agenda.infn.it/event/23347/contribution
s/122155/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122155/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Career panel: Academy
DTSTART;VALUE=DATE-TIME:20200928T153000Z
DTEND;VALUE=DATE-TIME:20200928T163000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122154@agenda.infn.it
DESCRIPTION:Panelists:\n\nMarcello Dalmonte (ICTP)\n\nGiovanna Morigi (Uni
versität des Saarlandes)\n\nSaverio Pascazio (Università di Bari)\n\nFab
io Sciarrino (La Sapienza Università di Roma)\n\nhttps://agenda.infn.it/e
vent/23347/contributions/122154/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122154/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Contextuality-by-default for behaviours in compatibility scenarios
DTSTART;VALUE=DATE-TIME:20201002T140700Z
DTEND;VALUE=DATE-TIME:20201002T141500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122044@agenda.infn.it
DESCRIPTION:Speakers: Alisson Tezzin (University of São Paulo)\nThe compa
tibility-hypergraph approach to contextuality (CA) and the contextuality-b
y-default approach (CbD) are usually seen as products of entirely differen
t views on how physical measurements and measurement contexts should be un
derstood: the latter is based on the idea that a physical measurement has
to be seen as a collection of random variables\, one for each context cont
aining that measurement\, while the imposition of the non-disturbance cond
ition as a physical requirement in the former precludes such interpretatio
n of measurements. The aim of our work is to show that the main idea behin
d CbD is already implicit in CA and to introduce in the latter important i
deas which arise from the former. We introduce in CA the non-degeneracy co
ndition\, which is the analogous of consistent connectedness\, and prove t
hat this condition is\, in general\, weaker than non-disturbance. The set
of non-degenerate behaviours defines a polytope\, therefore one can charac
terize non-degeneracy using linear inequalities. We introduce the idea of
extended contextuality for behaviours and prove that a behaviour is non-co
ntextual in the standard sense iff it is non-degenerate and non-contextual
in the extended sense. Finally\, we use extended scenarios and behaviours
to shed new light on our results.\n\nhttps://agenda.infn.it/event/23347/c
ontributions/122044/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122044/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Generic aspects of the resource theory of coherence
DTSTART;VALUE=DATE-TIME:20201002T140000Z
DTEND;VALUE=DATE-TIME:20201002T140700Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122034@agenda.infn.it
DESCRIPTION:Speakers: Giovanni Gramegna (B)\nThe class of incoherent opera
tions induces a pre-order on the set of quantum pure states. We study the
maximal success probability of incoherent conversion between pairs of n-di
mensional random pure states chosen independently\, and find an explicit f
ormula for its large-n asymptotic distribution. Our analysis shows that th
e statistics of the maximal conversion probability can be determined by th
e behaviour of the extreme values.\n\nhttps://agenda.infn.it/event/23347/c
ontributions/122034/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122034/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The quantum Wasserstein distance of order 1
DTSTART;VALUE=DATE-TIME:20201002T135200Z
DTEND;VALUE=DATE-TIME:20201002T140000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122025@agenda.infn.it
DESCRIPTION:Speakers: Giacomo De Palma (MIT)\nWe propose a generalization
of the Wasserstein distance of order 1 to the quantum states of n qudits.
Our proposal recovers the classical Wasserstein distance for quantum state
s diagonal in the canonical basis\, hence the distance between vectors of
the canonical basis coincides with the Hamming distance. Our distance is i
nvariant with respect to permutations of the qudits and unitary operations
acting on one qudit and is additive with respect to the tensor product. O
ur main result is a continuity bound for the von Neumann entropy with resp
ect to our distance\, which significantly strengthens the best continuity
bound with respect to the trace distance. We also propose a generalization
to quantum observables of the Lipschitz constant for functions\, which al
lows us to compute our distance with a semidefinite program. We prove a qu
antum version of Marton's transportation inequality and a quantum Gaussian
concentration inequality for the spectrum of quantum Lipschitz observable
s. Moreover\, we explore the contraction coefficient with respect to our d
istance of the n-th tensor power of a one-qudit quantum channel and of sha
llow quantum circuits. Our distance can have a large impact in quantum inf
ormation\, quantum computation and quantum machine learning\, and we discu
ss several possible applications.\n\nhttps://agenda.infn.it/event/23347/co
ntributions/122025/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122025/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manipulation and reconstruction of high-dimensional states
DTSTART;VALUE=DATE-TIME:20201002T134500Z
DTEND;VALUE=DATE-TIME:20201002T135200Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122045@agenda.infn.it
DESCRIPTION:Speakers: Alessia Suprano (Università di Roma "Sapienza")\nTh
e capability to control and manipulate high dimensional quantum states has
become relevant in several fields ranging from the probing of fundamental
s of quantum mechanics to the development of safer encryption algorithms.
Various engineering techniques of high dimensional quantum states have bee
n proposed\, but they strongly depend on the experimental platform and do
not provide a general scheme. Here\, we experimentally demonstrate an engi
neering protocol based on the Quantum Walk (QW) dynamic encoding the walke
r state in the orbital angular momentum (OAM) degree of freedom and the co
in state in the spin angular momentum (SAM). The QW dynamic allows the imp
lementation of a platform-independent scheme to engineer qudit states enco
ded in the walker system. Each step of the 5-steps QW is composed of a set
of wave-plates that manipulate the coin state and a peculiar device\, the
q-plate\, that can conditionally change the OAM according to the polariza
tion. Consequently\, the walker dynamics are controlled by a suitable choi
ce of step-dependent coin operators. Moreover\, decode the information sto
red in the OAM states is challenging experimentally and theoretically. Ind
eed\, the platforms proposed envisage additional instruments\, such as int
erferometry and spatial filtering\, that introduce damaging noise and loss
. In this regard\, we characterized structured beams where the helicoidal
wavefront is coupled with a not uniform distribution of the polarization o
n the transverse plane (Vector Vortex Beam)\, by using both supervised and
unsupervised machine learning techniques. In particular\, we obtained opt
imal results characterizing 15 experimental classes using both Convolution
al Neural Network or Support Vector Machine supported by Principal Compone
nt Analysis (PCA). The regression task is addressed too\, leveraging PCA t
o reconstruct a specific class of Vector Vortex Beams.\n\nhttps://agenda.i
nfn.it/event/23347/contributions/122045/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122045/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Noise-Resilient Variational Hybrid Quantum-Classical Optimization
DTSTART;VALUE=DATE-TIME:20201002T133700Z
DTEND;VALUE=DATE-TIME:20201002T134500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122033@agenda.infn.it
DESCRIPTION:Speakers: Laura Gentini (University of Florence)\nVariational
hybrid quantum-classical optimization represents one of the most promising
avenue to show the advantage of nowadays noisy intermediate-scale quantum
computers in solving hard problems\, such as finding the minimum-energy s
tate of a Hamiltonian or solving some machine-learning tasks. In these dev
ices noise is unavoidable and impossible to error-correct\, yet its role i
n the optimization process is not much understood\, especially from the th
eoretical viewpoint. Here we consider a minimization problem with respect
to a variational state\, iteratively obtained via a parametric quantum cir
cuit\, taking into account both the role of noise and the stochastic natur
e of quantum measurement outcomes. We show that the accuracy of the result
obtained for a fixed number of iterations is bounded by a quantity relate
d to the Quantum Fisher Information of the variational state. Using this b
ound\, we study the convergence property of the quantum approximate optimi
zation algorithm under realistic noise models\, showing the robustness of
the algorithm against different noise strengths.\n\nhttps://agenda.infn.it
/event/23347/contributions/122033/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122033/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entanglement of identical particles
DTSTART;VALUE=DATE-TIME:20201002T133000Z
DTEND;VALUE=DATE-TIME:20201002T133700Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122038@agenda.infn.it
DESCRIPTION:Speakers: Till Johann (Ruprecht-Karls-Universität Heidelberg)
\nEntanglement is a well defined and useful notion for distinguishable par
ticles. It provides a framework of locality and can be used as a resource
in quantum information and communication protocols. However\, for identica
l particles\, no universal accepted definition exists. The symmetrization
principle makes identical particle states look entangled when written in f
irst quantization notation. In particular\, the state of two hydrogen atom
s\, one on the moon and one on the earth\, which have never met each other
cannot be written as a tensor product. However\, because of the symmetriz
ation\, one also has to restrict the allowed operators on the Hilbert spac
e. This means that one cannot easily infer nontrivial correlations in the
systems by comparing the states of identical particles with their distingu
ishable counterparts. In my seminar\, I want to address the question of en
tanglement for identical particles\, with the particular example of the af
orementioned hydrogen atoms. We will use recently developed guiding princi
ples to motivate a useful notion of entanglement and show how to apply it
on this given problem.\n\nhttps://agenda.infn.it/event/23347/contributions
/122038/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122038/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Robust entanglement preparation against noise by controlling spati
al indistinguishability
DTSTART;VALUE=DATE-TIME:20201002T132200Z
DTEND;VALUE=DATE-TIME:20201002T133000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122060@agenda.infn.it
DESCRIPTION:Speakers: Farzam Nosrati (University of Palermo)\nInitializati
on of composite quantum systems into highly entangled states is usually a
must to enable their use for quantum technologies. However\, unavoidable n
oise in the preparation stage makes the system state mixed\, hindering thi
s goal. Here\, we address this problem in the context of identical particl
e systems within the operational framework of spatially localized operatio
ns and classical communication (sLOCC). We define the entanglement of form
ation for an arbitrary state of two identical qubits. We then introduce an
entropic measure of spatial indistinguishability as an information resour
ce. Thanks to these tools we find that spatial indistinguishability\, even
partial\, can be a property shielding non-local entanglement from prepara
tion noise\, independently of the exact shape of spatial wave functions. T
hese results prove quantum indistinguishability is an inherent control for
noise-free entanglement generation.\n\nhttps://agenda.infn.it/event/23347
/contributions/122060/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122060/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Characterising quantum correlations of fixed dimension
DTSTART;VALUE=DATE-TIME:20201002T131500Z
DTEND;VALUE=DATE-TIME:20201002T132200Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122048@agenda.infn.it
DESCRIPTION:Speakers: Carlo Sparaciari (UCL)\nWe give a converging semidef
inite programming hierarchy of outer approximations for the set of quantum
correlations of fixed dimension. Starting from the Navascués-Pironio-Ac
ín (NPA) hierarchy for general quantum correlations\, we identify additio
nal semidefinite constraints for any fixed dimension\, leading to analytic
al bounds on the convergence speed of the resulting hierarchy. Additionall
y\, we provide an algorithm\, built upon our hierarchy\, able to compute a
dditive approximations on the value of two-player free games with an assis
ting quantum system of fixed dimension\, and a given number of questions |
Q| and answers |A|. The computational time of our algorithm scales polynom
ially in |Q| and quasi-polynomially in |A|\, thereby improving on previous
ly known approximation algorithms for which worst-case run-time guarantees
were at best exponential in |Q||A|. To derive our analytical bounds on th
e convergence of the hierarchy\, we make a connection to the quantum separ
ability problem and employ\, as our main technical tool\, an improved mult
ipartite quantum de Finetti theorem with linear constraints.\n\nhttps://ag
enda.infn.it/event/23347/contributions/122048/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122048/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mitigating quantum errors with Mitiq
DTSTART;VALUE=DATE-TIME:20200930T140700Z
DTEND;VALUE=DATE-TIME:20200930T141500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122055@agenda.infn.it
DESCRIPTION:Speakers: Nathan Shammah (Unitary Fund)\nThis talk introduces
an open-source package for error-mitigation in quantum computation using z
ero-noise extrapolation. Error-mitigation techniques improve computational
performance (with respect to noise) using minimal overhead in quantum res
ources by relying on a mixture of quantum sampling and classical post-proc
essing techniques. Our error-mitigation package interfaces with multiple q
uantum computing software stacks\, and we demonstrate improved performance
on a variety of benchmarks performed on IBM and Rigetti quantum processor
s. We describe the library using code snippets to demonstrate usage and di
scuss features\, support\, and contribution guidelines.We also report on h
ow cloud-based interactive workshops have helped develop the library with
feedback from the research community.\n\nhttps://agenda.infn.it/event/2334
7/contributions/122055/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122055/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Modeling order-disorder phase transitions with a quantum annealer
DTSTART;VALUE=DATE-TIME:20200930T140000Z
DTEND;VALUE=DATE-TIME:20200930T140700Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122050@agenda.infn.it
DESCRIPTION:Speakers: Ilaria Siloi (University of Southern California)\nQu
antum annealers have grown in complexity to the point that devices with fe
w thousand qubits are approaching capacities to tackle material science pr
oblems. Starting from a representation of crystal structures in terms of n
etworks\, we develop models of order-disorder phase transitions for two pr
ototypical classes of materials (entropy stabilized alloys and perovskites
) that are directly implementable on the D-Wave devices. Cost functions ar
e built to encode the ordered phase\, while disordered phases appear as ex
cited states in the spectrum of the classical Ising Hamiltonian\, which ac
counts for the competing interactions in the material. Taking advantage of
the statistical nature of the quantum annealing\, we explore the energy l
andscape and generate all the structural models for each step of the order
-disorder phenomenon. Besides providing a correct description in terms of
critical temperatures\, our model allows us to access a wide range of stru
ctural models\, overcoming some limitations of classical methods.\n\nhttps
://agenda.infn.it/event/23347/contributions/122050/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122050/
END:VEVENT
BEGIN:VEVENT
SUMMARY:D-Wave as a generator of structural models in materials science
DTSTART;VALUE=DATE-TIME:20200930T135200Z
DTEND;VALUE=DATE-TIME:20200930T140000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122021@agenda.infn.it
DESCRIPTION:Speakers: Virginia Carnevali (Central Michigan University)\nA
tool capable to efficiently generate realistic structural models of disord
ered systems has been a goal of material science for many years. We show t
he feasibility of quantum annealing in exploring the energy landscape of m
aterials that deviate from the ideal crystalline phase\, specifically vaca
ncy defects in graphene and disordered silicon. By mapping the competing i
nteractions onto quadratic unconstrained binary optimization problems (QUB
O)\, our approach guarantees access to all the arrangements of the multipl
e defects on the graphene sheet respecting the relative formation energies
. In the case of silicon a large portion of the structural models with an
increasing disorder is encoded in the low energy spectrum of the QUBO form
ulation and detected in the annealing process. Our approach reproduces kno
wn results and provides a stepping-stone towards applications of quantum a
nnealing to more complex problems of physical-chemical interest.\n\nhttps:
//agenda.infn.it/event/23347/contributions/122021/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122021/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The complete spectrum of spin-1/2 XXZ chain at root of unity
DTSTART;VALUE=DATE-TIME:20200930T134500Z
DTEND;VALUE=DATE-TIME:20200930T135200Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122053@agenda.infn.it
DESCRIPTION:Speakers: Yuan Miao (Institute for Theoretical Physics\, Unive
rsity of Amsterdam)\nWe have studied the complete spectrum of spin-1/2 XXZ
chain at root of unity\, i.e. a paradigmatic model of quantum integrabili
ty. Making use of transfer matrix fusion relation\, we constructed a famil
y of 2-parameter transfer matrices\, which help us obtain all the eigensta
tes in terms of Bethe roots. This elucidates a long-standing problem dated
from the debate between McCoy and Baxter. We also exemplify the applicati
ons in the thermodynamic limit\, which explains the rôle of quasi-local Z
charge in the presence of quantum quenches and generalised hydrodynamics.
\n\nhttps://agenda.infn.it/event/23347/contributions/122053/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122053/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vacancy-like dressed states in topological waveguide QED
DTSTART;VALUE=DATE-TIME:20200930T133700Z
DTEND;VALUE=DATE-TIME:20200930T134500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122043@agenda.infn.it
DESCRIPTION:Speakers: Luca Leonforte (University of Palermo)\nWe identify
a class of dressed atom-photon states forming at the same energy of the at
om at any coupling strength. As a hallmark\, their photonic component is a
n eigenstate of the bare photonic bath with a vacancy in place of the atom
. The picture allows to formalize and re-interpret all quantum optics phen
omena where atoms behave as perfect mirrors\, connecting in particular dre
ssed bound states (BS) in the continuum (or BIC) with geometrically-confin
ed photonic modes in a waveguide. Most notably\, when applied to photonic
lattices\, the framework allows to formulate for the first time a general
criterion to predict atom-photon dressed BS in lattices with topological p
roperties by putting them in one-to-one correspondence with photonic bound
modes whose occurrence is ruled by the known Atland-Zirnbauer classificat
ion. The criterion is applied to predict new classes of dressed BS in the
photonic Creutz-ladder and Haldane models. In the latter case\, states wit
h non-zero local photon flux occur where an atom is dressed by a photon or
biting around it\, a phenomenon so far unexplored in quantum optics.\n\nht
tps://agenda.infn.it/event/23347/contributions/122043/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122043/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bulk detection of time-dependent topological transitions in quench
ed chiral models
DTSTART;VALUE=DATE-TIME:20200930T132200Z
DTEND;VALUE=DATE-TIME:20200930T133000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122026@agenda.infn.it
DESCRIPTION:Speakers: Francesco Di Colandrea (Università degli Studi di N
apoli Federico II )\nThe topology of one-dimensional chiral systems is cap
tured by the winding number of the Hamiltonian eigenstates. We proved that
this invariant can be read-out by measuring the Mean Chiral Displacement
of a single-particle wavefunction that is connected to a fully localized o
ne via a unitary and translation-invariant map. Remarkably\, this implies
that the Mean Chiral Displacement can detect the winding number even when
the underlying Hamiltonian is quenched between different topological phase
s. We confirm experimentally these results in a photonic quantum walk\, re
alized in the transverse-momentum space of structured light.\n\nhttps://ag
enda.infn.it/event/23347/contributions/122026/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122026/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The Frustration of being Odd
DTSTART;VALUE=DATE-TIME:20200930T131500Z
DTEND;VALUE=DATE-TIME:20200930T132200Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122047@agenda.infn.it
DESCRIPTION:Speakers: Vanja Marić (SISSA Trieste\, RBI Zagreb)\nA central
tenant in the classification of phases is that boundary conditions cannot
affect the bulk properties of a system. In our works\, we show striking\,
yet puzzling\, evidence of a clear violation of this assumption. We study
some exactly solvable spin chains\, mappable to free fermions\, in a ring
geometry with an odd number of sites. In such a setting\, even at finite
sizes\, we are able to calculate directly the spontaneous magnetizations t
hat are traditionally used as order parameters to characterize the system'
s phases. We find that boundary conditions can destroy local order\, chang
e it\, and even induce a new quantum phase transition. \n\nMain references
: https://iopscience.iop.org/article/10.1088/1367-2630/aba064 https://arxi
v.org/abs/2002.07197\n\nhttps://agenda.infn.it/event/23347/contributions/1
22047/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122047/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Discrimination of Ohmic thermal baths by quantum dephasing probes
DTSTART;VALUE=DATE-TIME:20200928T140700Z
DTEND;VALUE=DATE-TIME:20200928T141500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122020@agenda.infn.it
DESCRIPTION:Speakers: Alessandro Candeloro ()\nThe discrimination of struc
tured baths at different temperatures by dephasing quantum probes is studi
ed. The exact reduced dynamic is derived\, and the minimum error probabili
ty is evaluated by three different kinds of quantum probes\, namely a qubi
t\, a qutrit\, and a quantum register made of two qubits. The results indi
cate that dephasing quantum probes are useful in discriminating low values
of temperature and that lower probabilities of error are achieved for int
ermediate values of the interaction time. A qutrit probe outperforms a qub
it one in the discrimination task\, whereas a register made of two qubits
does not offer any advantage compared to two single qubits used sequential
ly.\n\nhttps://agenda.infn.it/event/23347/contributions/122020/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122020/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Critical Quantum Metrology with a Finite-Component Quantum Phase T
ransition
DTSTART;VALUE=DATE-TIME:20200928T140000Z
DTEND;VALUE=DATE-TIME:20200928T140700Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122029@agenda.infn.it
DESCRIPTION:Speakers: Simone Felicetti (Istituto di Fotonica e Nanotecnolo
gie\, Consiglio Nazionale delle Ricerche IFN-CNR)\nPhysical systems close
to a quantum phase transition exhibit a divergent susceptibility\, suggest
ing that an arbitrarily high precision may be achieved by exploiting quant
um critical systems as probes to estimate a physical parameter. However\,
such an improvement in sensitivity is counterbalanced by the closing of th
e energy gap\, which implies a critical slowing down and an inevitable gro
wth of the protocol duration. In this contribution\, we present different
metrological protocols that exploit the superradiant phase transition of t
he quantum Rabi model\, a finite-component system composed of a single two
-level atom interacting with a single bosonic mode. We show that\, in spit
e of the critical slowing down\, critical quantum optical probes can achie
ve a quantum-enhanced time scaling of the sensitivity in frequency-estimat
ion protocols.\n\nhttps://agenda.infn.it/event/23347/contributions/122029/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122029/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bayesian multiphase estimation at the Heisenberg limit
DTSTART;VALUE=DATE-TIME:20200928T135200Z
DTEND;VALUE=DATE-TIME:20200928T140000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122031@agenda.infn.it
DESCRIPTION:Speakers: Valentin Gebhart (QSTAR\, CNR-INO and University of
Napoli)\nQuantum (multi-)parameter estimation provides the central ingredi
ent for many quantum technological tasks like\, e.g.\, quantum computation
or precision measurements. Previous work focussed mainly on single phase
estimation at the fundamental limit\, the Heisenberg limit\, or on multiph
ase estimation at an optimal point. Here\, we propose a quantum algorithm
to measure d completely unknown phases and provide numerical evidence for
Heisenberg limited precision of the algorithm. We show that the algorithm
can outperform single phase estimation and discuss a possible quantum opti
cal implementation.\n\nhttps://agenda.infn.it/event/23347/contributions/12
2031/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122031/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A machine learning approach to Bayesian parameter estimation
DTSTART;VALUE=DATE-TIME:20200928T134500Z
DTEND;VALUE=DATE-TIME:20200928T135200Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122058@agenda.infn.it
DESCRIPTION:Speakers: Samuel Nolan (QSTAR\, INO-CNR and LENS)\nBayesian es
timation is a powerful theoretical paradigm for the operation of quantum s
ensors. However\, the Bayesian method for statistical inference generally
suffers from demanding calibration requirements\, that have so far restric
ted its use to systems that can be explicitly modelled. In this theoretica
l study\, we formulate parameter estimation as a classification task and u
se artificial neural networks to efficiently perform Bayesian estimation.
We show that the network's posterior distribution is centred at the true (
unknown) value of the parameter within an uncertainty given by the inverse
Fisher information\, representing the ultimate sensitivity limit for the
given apparatus. When only a limited number of calibration measurements ar
e available\, our machine-learning based procedure outperforms naive calib
ration methods. Our machine-learning based procedure is model independent\
, and is thus well suited to a black box sensor where an explicit model is
unavailable. Thus\, our work paves the way for Bayesian quantum sensors t
hat can take advantage of complex\, potentially non-classical quantum stat
es\, which can significantly enhance the sensitivity of future devices.\n\
nhttps://agenda.infn.it/event/23347/contributions/122058/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122058/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Noisy quantum metrology enhanced by continuous nondemolition measu
rement
DTSTART;VALUE=DATE-TIME:20200928T131500Z
DTEND;VALUE=DATE-TIME:20200928T132300Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122061@agenda.infn.it
DESCRIPTION:Speakers: Matteo Rossi (University of Turku)\nIn this work\, w
e show that\, by exploiting continuous quantum nondemolition measurement\,
it is possible to preserve quantum advantage in a frequency estimation (o
r magnetometry) measurement scheme even in the presence of independent dep
hasing noise\, usually the most detrimental type of noise. We thus verify
that such enhancement is preserved thanks to non-classical correlations\,
namely spin squeezing\, which are dynamically generated by the measurement
itself. Remarkably\, our scheme does not require the preparation of any e
ntangled\, or non-classically correlated state of the probe: the probe is
initialized in a classical coherent spin state and the resources required
for the quantum enhancement are dynamically created during the conditional
evolution. We moreover provide evidence that our results are robust and h
old true in a wide range of noise intensities and even in the presence of
inefficient measuring devices.\n\nhttps://agenda.infn.it/event/23347/contr
ibutions/122061/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122061/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum multiphase estimation in an integrated photonic circuit
DTSTART;VALUE=DATE-TIME:20200928T133800Z
DTEND;VALUE=DATE-TIME:20200928T134500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122066@agenda.infn.it
DESCRIPTION:Speakers: Emanuele Polino (La Sapienza)\nQuantum Metrology is
one of the most important quantum technologies where quantum resources are
exploited to enhance the estimation of unknown parameters [1]. In this co
ntext\, since realistic scenarios generally involve more than one paramete
r\, quantum multiparameter estimation is a central and very active researc
h area. Nevertheless\, in such relatively new field\, several open questio
ns are still present and experimental platforms able to perform multiparam
eter estimation protocols have to be developed. We realized a reconfigurab
le photonic integrated circuit\, built through the femtosecond lase writin
g technique\, able to perform simultaneous multiphase estimation with phot
onic quantum states. The circuit realizes a three arm interferometer and i
s highly tunable\, so that the two independent phase shifts between the in
terfetometer's arms can be tuned. Firstly\, we demonstrate quantum enhance
d two-phases estimation by using two-photon probes [2]. Then we provide a
demonstration of a Bayesian adaptive protocol able to saturate\, in the li
mited data regime\, the sensitivity bound (Cramer-Rao bound) on the estima
tion of the two phases when single photon probes are employed [3].\n\n\n [
1] E. Polino\, M. Valeri\, N. Spagnolo\, and F. Sciarrino\, AVS Quantum Sc
ience 2\, 024703 (2020). \n[2] E. Polino\, M. Riva\, M. Valeri\, R. Silves
tri\, G. Corrielli\, A. Crespi\, N. Spagnolo\, R. Osellame\, and F. Sciarr
ino\, Optica 6\, 288 (2019). \n[3] M. Valeri\, E. Polino\, D. Poderini\, I
. Gianani\, G. Corrielli\, A. Crespi\, R. Osellame\, N. Spagnolo\, and F.
Sciarrino\, arXiv preprint arXiv:2002.01232 (2020).\n\nhttps://agenda.infn
.it/event/23347/contributions/122066/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122066/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Super-resolution Optical Fluctuation Imaging—fundamental estimat
ion theory perspective
DTSTART;VALUE=DATE-TIME:20200928T133000Z
DTEND;VALUE=DATE-TIME:20200928T133800Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122041@agenda.infn.it
DESCRIPTION:Speakers: Stanisław Kurdziałek (Faculty of Physics\, Univers
ity of Warsaw)\nWe provide a rigorous quantitative analysis of super-resol
ution imaging techniques which exploit temporal fluctuations of luminosity
of the sources in order to beat the Rayleigh limit. We define an operatio
nally justified resolution gain figure of merit\, that allows us to connec
t the estimation theory concepts with the ones typically used in the imagi
ng community\, and derive fundamental resolution bounds that scale at most
as the fourth-root of the mean luminosity of the sources. We fine-tune an
d benchmark the performance of state-of-the-art methods\, focusing on the
cumulant based image processing techniques\, taking into account the impac
t of limited photon number and sampling time.\n\nhttps://agenda.infn.it/ev
ent/23347/contributions/122041/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122041/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Continuous-time quantum walks in the presence of a quadratic pertu
rbation
DTSTART;VALUE=DATE-TIME:20200928T132300Z
DTEND;VALUE=DATE-TIME:20200928T133000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-122065@agenda.infn.it
DESCRIPTION:Speakers: Luca Razzoli (Università di Modena e Reggio Emilia)
\nWe address the properties of continuous-time quantum walks with Hamilton
ians of the form $H= L + \\lambda L^2$\, being $L$ the Laplacian matrix of
the underlying graph and being the perturbation $\\lambda L^2$ motivated
by its potential use to introduce next-nearest-neighbor hopping. We consid
er cycle\, complete\, and star graphs because paradigmatic models with low
/high connectivity and/or symmetry. First\, we investigate the dynamics of
an initially localized walker. Then\, we devote attention to estimating t
he perturbation parameter $\\lambda$ using only a snapshot of the walker d
ynamics. Our analysis shows that a walker on a cycle graph is spreading ba
llistically independently of the perturbation\, whereas on complete and st
ar graphs one observes perturbation-dependent revivals and strong localiza
tion phenomena. Concerning the estimation of the perturbation\, we determi
ne the walker preparations and the simple graphs that maximize the Quantum
Fisher Information. We also assess the performance of position measuremen
t\, which turns out to be optimal\, or nearly optimal\, in several situati
ons of interest. Besides fundamental interest\, our study may find applica
tions in designing enhanced algorithms on graphs.\n\nhttps://agenda.infn.i
t/event/23347/contributions/122065/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/122065/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum computing model of an artificial neuron with continuously
valued input data
DTSTART;VALUE=DATE-TIME:20200930T123000Z
DTEND;VALUE=DATE-TIME:20200930T124500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121264@agenda.infn.it
DESCRIPTION:Speakers: Stefano Mangini (University of Pavia)\nArtificial n
eural networks have been proposed as potential algorithms that could benef
it from being implemented and run on quantum computers. In particular\, th
ey hold promise to greatly enhance Artificial Intelligence tasks\, such as
image elaboration or pattern recognition. The elementary building block o
f a neural network is an artificial neuron\, i.e. a computational unit per
forming simple mathematical operations on a set of data in the form of an
input vector. Starting from the design of a previously introduced quantum
artificial neuron [1]\, which fully exploits the use of superposition stat
es to encode binary valued input data\, during the talk it will be shown h
ow the implementation of the quantum neuron can be further generalized to
accept continuous- instead of discrete-valued input vectors\, without incr
easing the number of qubits [2]. This further step is crucial to allow for
a direct application of gradient descent based learning procedures\, whic
h would not be compatible with binary-valued data encoding. \n\n[1] Tacchi
no\, F.\, Macchiavello\, C.\, Gerace\, D. et al. (2019). An artificial neu
ron implemented on an actual quantum processor. npj Quantum Inf 5\, 26. ht
tps://doi.org/10.1038/s41534-019-0140-4 \n[2] Mangini\, S.\, Tacchino\, F.
\, Gerace\, D.\, Macchiavello\, C. and Bajoni\, D. (2020). Quantum computi
ng model of an artificial neuron with continuously valued input data. Mach
ine Learning: Science and Technology. https://doi.org/10.1088/2632-2153/ab
af98\n\nhttps://agenda.infn.it/event/23347/contributions/121264/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121264/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum Zeno and anti-Zeno effect in non-Markovian decay process o
f single-photon polarization states
DTSTART;VALUE=DATE-TIME:20201002T150000Z
DTEND;VALUE=DATE-TIME:20201002T151500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121269@agenda.infn.it
DESCRIPTION:Speakers: Salvatore Virzì (INRiM\, Università di Torino)\nT
he quantum Zeno effect is a feature of quantum-mechanical systems allowing
a system's time evolution to be freezed\, or at least slowed down\, by me
asuring the system frequently enough [1-5]. On the contrary\, it is also p
ossible to exploit frequent measurements to accelerate the system's evolut
ion\, obtaining the quantum anti-Zeno effect. In my presentation\, I will
describe an experiment investigating quantum Zeno and anti-Zeno effects in
the non-Markovian decay process of single-photon polarization states. In
our implementation\, we simulate a noisy quantum channel exploiting a set
of half wave-plates introducing correlated random phase shifts between the
vertical and horizontal polarization components. Each phase shift represe
nts a stochastic process defined by a random variable\, sampled each time
by a specific probability distribution depending on the previous phase shi
fts (non-Markovian behavior). This stochastic polarization dephasing leads
to a decay of the probability to find the system in its initial state. To
induce the Zeno effect\, we perform repeated measurements by inserting a
polarizer between subsequent wave-plates. By controlling the interplay bet
ween the application of a sequence of repeated measurements and the probab
ility distribution characterizing the noise of the channel\, it is possibl
e to induce on the quantum state both Zeno or anti-Zeno effect. This exper
iment represents a proof of principle of a technique allowing to control t
he dynamics of a quantum system in any realistic physical scenario affecte
d by time-correlated noise. In real scenarios\, the randomness on the phas
e can be due to imperfections of the measurement apparatus or to the inter
action with an external reservoir\, usually entailing non-Markovianity [7]
in the observed quantum system. \n \n[1] B. Misra and E.C.G. Sudarshan. T
he Zeno's paradox in quantum theory\, J. Math. Phys. 18\, 756 (1977). \n[2
] W.M. Itano\, D.J. Heinzen\, J.J. Bollinger\, and D.J. Wineland. Quantum
Zeno effect\, Phys. Rev. A 41\, 2295 (1990). \n[3] P. Kwiat\, H. Weinfurte
r\, T. Herzog\, A. Zeilinger\, and M.A. Kasevich. Interaction-Free Measure
ment\, Phys. Rev. Lett. 74\, 4763 (1995). \n[4] A.G. Kofman and G. Kurizki
. Quantum Zeno effect on atomic excitation decay in resonators\, Phys. Rev
. A 54\, R3750(R) (1996). \n[5] A.G. Kofman and G. Kurizki. Acceleration o
f quantum decay processes by frequent observations\, Nature 405\, 546-550
(2000). \n[6] F. Piacentini\, A. Avella\, E. Rebufello\, R. Lussana\, F. V
illa\, A. Tosi\, M. Gramegna\, G. Brida\, E. Cohen\, L. Vaidman\, I.P. Deg
iovanni\, and M. Genovese. Determining the quantum expectation value by me
asuring a single photon\, Nat. Phys. 13\, 1191 (2017). \n[7] A. Rivas\, S.
F. Huelga\, and M.B. Plenio. Quantum non-Markovianity: characterization\,
quantification and detection\, Rep. Prog. Phys. 77\, 094001 (2014).\n\nhtt
ps://agenda.infn.it/event/23347/contributions/121269/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121269/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Decoherence-Free Rotational Degrees of Freedom for Quantum Applica
tions
DTSTART;VALUE=DATE-TIME:20201002T144500Z
DTEND;VALUE=DATE-TIME:20201002T150000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121260@agenda.infn.it
DESCRIPTION:Speakers: Francesco Cosco (Ulm University)\nQuantum metrology
and sensing represent promising near term applications of quantum technol
ogies as they require the control of a few or even single quantum systems.
However\, a central challenge common to all quantum sensor designs is the
necessity to achieve both robustness to environmental noise and\, at the
same time\, high sensitivity to a signal of interest. This task becomes ev
en more challenging when considering massive particles whose translational
degrees of freedom are highly susceptible to first order (gradient) fluct
uations of external fields\, thus inhibiting the generation of long-lived
macroscopic quantum superpositions.
In this talk\, we address this chall
enge by designing the shape of rigid bodies such that their rotational deg
rees of freedom can be made robust against decoherence from distant source
s\, while at the same time allowing for interaction with signals from near
by sources. To this end we introduce a systematic method\, based on the ma
thematical theory of spherical t-designs\, to construct rigid bodies whose
rotational states are degenerate up to a desired order of the multipole e
xpansion of their energy in a perturbing potential. This allows for the ge
neration of long-lived macroscopic quantum superpositions of rotational de
grees of freedom and the robust generation of entanglement between two or
more such solids with applications in robust quantum sensing and precision
metrology as well as quantum registers.\n\nhttps://agenda.infn.it/event/2
3347/contributions/121260/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121260/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mechanism of decoherene-free coupling between giant atoms
DTSTART;VALUE=DATE-TIME:20201002T143000Z
DTEND;VALUE=DATE-TIME:20201002T144500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121231@agenda.infn.it
DESCRIPTION:Speakers: Dario Cilluffo (Università degli Studi di Palermo\,
Dipartimento di Fisica e Chimica - Emilio Segrè)\nGiant atoms are a new
paradigm of quantum optics going beyond the usual local coupling. Building
on this\, a new type of decoherence-free (DF) many-body Hamiltonians was
shown in a broadband waveguide. Here\, these are incorporated in a general
framework (not relying on master equations) and contrasted to dispersive
DF Hamiltonians with normal atoms: the two schemes are shown to correspond
to qualitatively different ways to match the same general condition for s
uppressing decoherence. Next\, we map the giant atoms dynamics into a casc
aded collision model (CM)\, providing an intuitive interpretation of the c
onnection between non-trivial DF Hamiltonians and coupling points topology
. The braided configuration is shown to implement a scheme where a shuttli
ng system subject to periodic phase kicks mediates a DF coupling between t
he atoms. From the viewpoint of CMs theory\, this shows a collision model
where ancillas effectively implement a dissipationless\, maximally-entangl
ing two-qubit gate on the system.\n\nhttps://agenda.infn.it/event/23347/co
ntributions/121231/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121231/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Witnesses of non-classicality beyond quantum theory
DTSTART;VALUE=DATE-TIME:20201002T124500Z
DTEND;VALUE=DATE-TIME:20201002T130000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121266@agenda.infn.it
DESCRIPTION:Speakers: Chiara Marletto (University of Oxford)\nI discuss g
eneral argument to show that if a physical system can mediate locally the
generation of entanglement between two quantum systems\, then it itself mu
st be non-classical. Remarkably\, the argument does not assume any classic
al or quantum formalism to describe the mediating physical system: the res
ult follows from general information-theoretic principles\, drawn from the
recently proposed constructor theory of information. This argument provid
es the indispensable theoretical basis for recently proposed tests of non-
classicality in gravity\, based on witnessing gravitationally-induced enta
nglement in quantum probes.\n\nhttps://agenda.infn.it/event/23347/contribu
tions/121266/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121266/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nonclassical steering and the Gaussian steering triangoloids
DTSTART;VALUE=DATE-TIME:20201002T123000Z
DTEND;VALUE=DATE-TIME:20201002T124500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121261@agenda.infn.it
DESCRIPTION:Speakers: Massimo Frigerio (Università degli Studi di Milano)
\nWe fully characterize the mechanism by which nonclassicality according t
o the Glauber P-function can be conditionally generated on one mode of a t
wo-mode Gaussian quantum state by generic Gaussian measurements on the oth
er mode. For two-mode squeezed thermal states (TMSTs)\, we visualize the w
hole set of conditional states constructing Gaussian steering triangoloids
and we show that nonclassicality can be induced in this way if and only i
f the initial state is EPR-steerable. In the more general case\, we recogn
ize two types of quantum correlations: weak and strong nonclassical steeri
ng\, the former being independent of entanglement\, and the latter implyin
g EPR steerability. We show that EPR-steering and weak/strong nonclassical
steering merge precisely for TMSTs\, and we discuss applications of this
result to one-sided device-independent quantum key distribution and noisy
propagation of twin-beam states.\n\nhttps://agenda.infn.it/event/23347/con
tributions/121261/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121261/
END:VEVENT
BEGIN:VEVENT
SUMMARY:There is only one time
DTSTART;VALUE=DATE-TIME:20201002T121500Z
DTEND;VALUE=DATE-TIME:20201002T123000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121259@agenda.infn.it
DESCRIPTION:Speakers: Alessandro Coppo (Università degli studi di Firenze
)\nWe draw a picture of physical systems that allows us to recognize what
is this thing called "time" by requiring consistency not only with our not
ion of time but also with the way time enters the fundamental laws of Phys
ics\, independently of one using a classical or a quantum description. Ele
ments of the picture are two non-interacting and yet entangled quantum sys
tems\, one of which acting as a clock\, and the other one doomed to evolve
. The setting is based on the so called "Page and Wootters (PaW) mechanism
"\, and updates\, with tools from Lie-Group and large-N quantum approaches
. The overall scheme is quantum\, but the theoretical framework allows us
to take the classical limit\, either of the clock only\, or of the clock a
nd the evolving system altogether\; we thus derive the Schrödinger equati
on in the first case\, and the Hamilton equations of motion in the second
one. Suggestions about possible links with general relativity and gravity
are also put forward.\n\nhttps://agenda.infn.it/event/23347/contributions/
121259/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121259/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entanglement of formation of mixed many-body quantum states using
tensor networks
DTSTART;VALUE=DATE-TIME:20201002T120000Z
DTEND;VALUE=DATE-TIME:20201002T121500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121225@agenda.infn.it
DESCRIPTION:Speakers: Luca Arceci (Università di Padova)\nIn this talk\,
we will present an algorithm to compute the entanglement of formation for
mixed many-body quantum states by using tensor networks. Indeed\, we will
introduce a new tensor network ansatz --- the Tree Tensor Operator --- whi
ch leads to a very convenient description of density matrices. Our results
will focus on thermal states of the quantum Ising chain in transverse fie
ld\, for which we could consider up to 22 spins.\n\nhttps://agenda.infn.it
/event/23347/contributions/121225/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121225/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Full control of nonlinear processes in Josephson parametric amplif
iers for readout of superconducting qubits
DTSTART;VALUE=DATE-TIME:20200930T150000Z
DTEND;VALUE=DATE-TIME:20200930T151500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121267@agenda.infn.it
DESCRIPTION:Speakers: Alessandro Miano (University of Naples Federico II)
\nIn the last decade\, Superconducting Quantum Circuits (SQCs) based on Jo
sepshon Junctions (JJs) showed that a working quantum processor can be suc
cessfully built and operated to perform Quantum Information Processing (QI
P) on a system made of many superconducting qubits. The key ingredient to
reach such an achievement are the endless possibilities allowed by SQCs in
order to efficiently control and readout superconducting qubits\, and the
research on these interface devices is at the edge of technological advan
ces in QIP. Efficient readout of superconducting qubits requires coherent
amplification of single microwave photon signals while preserving a high S
ignal to Noise Ratio (SNR) in order to reach high single-shot readout fide
lity. This task can be achieved by driving parametric processes in superco
nducting nonlinear oscillators\, allowing coherent energy transfer between
a strong pump and a single microwave photon signal that carries the resul
t of a Quantum Non-Demolition measurement on a qubit. Thanks to these tech
niques\, it is possible to build Quantum Limited Amplifiers (QLA) that can
generate well detectable signals with SNR being degraded only by the leas
t amount imposed by quantum mechanical principles. A QLA can be built arou
nd Josephson microwave circuits that synthesize nonlinear Hamiltonians wit
h the required characteristics\, and established devices are nowadays used
in every superconducting quantum computing experiment. However\, the trig
onometric nature of the Josephson nonlinearities makes their independent c
ontrol a challenging task. We show how is possible to improve the synthesi
s capabilities of Josephson Hamiltonians with a “Gradiometric SNAIL Para
metric Amplifier” (G-SPA)\, a novel Josephson parametric amplifier that
allows complete tuning of its nonlinearities via in-situ magnetic fluxes.
Our approach expands the tunability range of the parametric processes\, al
lowing independent choice of their participation in the treatment of singl
e photon signals and opening to many new applications for these devices.\n
\nhttps://agenda.infn.it/event/23347/contributions/121267/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121267/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vibrational modulation of electronic transitions in Copper Germana
te: a theoretical model
DTSTART;VALUE=DATE-TIME:20200930T144500Z
DTEND;VALUE=DATE-TIME:20200930T150000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121265@agenda.infn.it
DESCRIPTION:Speakers: Stefano Marcantoni (University of Nottingham)\nThe
dynamics of complex materials can be conveniently investigated through pum
p-probe techniques. Here we present a simple quantum theoretical model tha
t is used to interpret the results of a recently performed pump-probe expe
riment on Copper Germanate [1]. In this context\, in order to study the el
ectron-phonon coupling in the material\, lattice vibrations are excited by
an infrared pump pulse and d-d electronic transitions are probed with a v
isible pulse.\n\n[1] A. Marciniak\, et al. arXiv:2003.13447\n\nhttps://age
nda.infn.it/event/23347/contributions/121265/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121265/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Semiconductor qubits based on hole spins in CMOS devices and edge-
states in Hall interferometers
DTSTART;VALUE=DATE-TIME:20200930T143000Z
DTEND;VALUE=DATE-TIME:20200930T144500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121228@agenda.infn.it
DESCRIPTION:Speakers: Laura Bellentani (S3 CNR-Nano)\nAmong the possible
frameworks to encode the quantum bit\, semiconductor-based implementations
possibly present the highest potential in terms of scalability and compat
ibility with current nanoelectronics industry. In this talk\, I will outli
ne two different platforms for the realization of the qubit in semiconduct
or devices\, and present the numerical approach we adopted for their chara
cterization in full-scale simulations. The first approach\, pursued within
the recently started IQubits EU project [1]\, focuses on the use and engi
neering of fabricated CMOS devices to implement hole/electron spin qubits.
The experimental characterization of a 22-nm FDSOI MOSFETs [2] has proved
the formation of a double hole/electron quantum dot in the Si/SiGe channe
l\, which potentially enables the monolithic integration of the control an
d readout circuitry on the same die [3]. The hole states are controlled by
the top and back gates\, while the spin is manipulated by electric-dipole
spin resonance. Within a multiscale approach\, we compute the single-hole
states by diagonalizing the k·p Luttinger-Kohn Hamiltonian\, starting fr
om a realistic confining potential\, simulated by means of the “Ginestra
” software [4]. Prospects for scalability are included\, starting from t
he simulation of double quantum dot systems in Si/SiGe MOSFETS\, with a pa
rticular emphasis on the effects of Coulomb interactions and correlations.
The second approach exploits topologically-protected edge states in the I
nteger Quantum Hall regime for a flying implementation of the quantum bit\
, with a coherence length up to 10 micrometers [5]. The qubit propagates a
t the edges of a confined 2DEG\, while the inter-channel scattering rotate
s their state. Hall interferometers implement this manipulation protocol t
o realize single and two-qubit operation on the fly. We present our propos
al for a Hall conditional phase shifter and show its feasibility for phase
rotation up to π [6]. The exact two-electron wavefunction is evolved in
the full-scale 2D potential of the device\, where single-charges are injec
ted as Gaussian wavepackets of edge states. Our numerical approach involve
s HPC techniques to include exactly the interplay between Coulomb repulsio
n and the device geometry\, whose tuning is crucial for logic operations.
\n\n[1] www.iqubits.eu. \n[2] S. Bonen et al.\, IEEE Electron Device Lette
rs\, 40 127-130 (2019). \n[3] M. J. Gong et al.\, 2019 IEEE Radio Frequenc
y Integrated Circuits Symposium (RFIC)\, Boston\, MA\, USA\, pp. 111-114 (
2019). \n[4] www.mdlsoft.com. \n[5] P. Roulleau et al.\, Phys. Rev. Lett.
100\, 126802 (2008)\; E Bocquillon et al.\, Science 339 6123 (2013). \n[6]
L. Bellentani\, G. Forghieri\, P. Bordone and A. Bertoni\, Phys. Rev. B 1
02\, 035417 (2020).\n\nhttps://agenda.infn.it/event/23347/contributions/12
1228/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121228/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Fighting qubit loss in topological QEC codes: theory and experimen
t
DTSTART;VALUE=DATE-TIME:20200930T124500Z
DTEND;VALUE=DATE-TIME:20200930T130000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121270@agenda.infn.it
DESCRIPTION:Speakers: Davide Vodola (Bologna University)\nThe loss of qub
its poses one of the fundamental obstacles towards large-scale and fault-t
olerant quantum information processors. In this work\, we design and chara
cterize a complete toolbox for a full cycle of qubit loss detection and co
rrection on a minimal instance of a topological surface code. This include
s a quantum non-demolition measurement of a qubit loss event that conditio
nally triggers a restoration procedure\, mapping the logical qubit onto a
new encoding on the remaining qubits. The demonstrated methods\, implement
ed here in a trapped-ion quantum processor\, are applicable to other quant
um computing architectures and codes\, including leading 2D and 3D topolog
ical quantum error correcting codes. These tools complement previously dem
onstrated techniques to correct computational errors\, and in combination
constitute essential building blocks for complete and scalable quantum err
or correction.\n\nhttps://agenda.infn.it/event/23347/contributions/121270/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121270/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bound states in the continuum in arrays of quantum emitters
DTSTART;VALUE=DATE-TIME:20200930T121500Z
DTEND;VALUE=DATE-TIME:20200930T123000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121263@agenda.infn.it
DESCRIPTION:Speakers: Davide Lonigro (University of Bari & INFN)\nQuantum
emitters coupled to EM fields in waveguides provide a controllable and exp
erimentally feasible testbed to observe interesting physical phenomena\; i
n particular\, the emergence of bound states in the continuum opens new po
ssibilities to generate states with specific entanglement properties. We c
haracterize analytically the bound states for any number of emitters\, sho
wing that the finite spacing between the emitters and the structure of the
field dispersion relation become relevant and yield nonperturbative effec
ts.\n\nhttps://agenda.infn.it/event/23347/contributions/121263/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121263/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Achieving Heisenberg scaling with maximally entangled states: an a
nalytic upper bound for the attainable root mean square error
DTSTART;VALUE=DATE-TIME:20200930T120000Z
DTEND;VALUE=DATE-TIME:20200930T121500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121229@agenda.infn.it
DESCRIPTION:Speakers: Federico Belliardo (Scuola Normale Superiore\, Pisa)
\nIn this talk we explore the possibility of performing Heisenberg limited
quantum metrology of a phase\, without any prior\, by employing only maxi
mally entangled states. Starting from the estimator introduced by Higgins
et al. in New J. Phys. 11\, 073023 (2009)\, the main result discussed in t
he talk is an analytical upper bound on the associated Mean Squared Error
which is monotonically decreasing as a function of the square of the numbe
r of quantum probes used in the process. The analyzed protocol is non-adap
tive and requires in principle (for distinguishable probes) only separable
measurements. From the practical point of view\, at difference with the p
revious works\, where it was required the states sizes to grow as the powe
rs of two\, we are often able to extract Heisenberg Scaling from an arbitr
ary sequence of entangled states sizes\, possibly realizable in a laborato
ry. We also explore how the strategy changes in presence of probe loss or
fluctuations of the phase.\n\nhttps://agenda.infn.it/event/23347/contribut
ions/121229/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121229/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adiabatic Quantum Operations with UltraStrongly Coupled Artificial
Atoms
DTSTART;VALUE=DATE-TIME:20200928T144500Z
DTEND;VALUE=DATE-TIME:20200928T150000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121262@agenda.infn.it
DESCRIPTION:Speakers: Luigi Giannelli (Dipartimento di Fisica e Astronomia
“Ettore Majorana”\, Universitá di Catania)\nUltrastrong coupling (US
C) between light and matter has been recently achieved in architectures of
solid state artificial atoms coupled to cavities. Such architectures may
provide new building blocks for quantum state processing\, where ultrafast
operations could be performed. However faster dynamics has a cost. Indeed
USC breaks the symmetry associated with the conservation of the number of
excitations\, leading to a series of new physical effects of great fundam
ental interest but detrimental for quantum state processing. In particular
the highly entangled nature of the eigenstates\, dressed by a potentially
very large number of virtual photons\, leads to leakage of excitation via
the dynamical Casimir effect (DCE) and via decay. In this work we analyze
quantum operations between two artificial atoms ultrastrongly coupled to
a cavity\, operating as a virtual bus. We show that an adiabatic protocol
similar to STIRAP may overcome the problem of leakage. Ideally the cavity
is never populated and thus it is expected to greatly reduce the impact of
DCE and decay. We show that high fidelity operations can be performed for
moderate couplings in the USC regime and fidelities higher than the ones
obtained in the strong coupling regime (SC\, where the rotating wave appro
ximation holds) can be obtained. Moreover\, optimal control theory allows
for properly crafted controls that extend the high fidelity region to even
larger couplings. The protocol is extremely robust agaist DCE\, in the ab
sence of decoherence yields almost 100% fidelity for remote state transfer
and multiqubit entanglement generation. It is also resilient to decay due
to leakage from the cavity\, which is the main decoherence mechanism for
present USC architectures. In this more realistic scenario it is seen that
for larger coupling (entering the deep strong coupling regime) the fideli
ty decreases due to the interplay between decoherence and DCE. Our results
suggest that adiabatic manipulations\, may be a promising tool for quantu
m state processing in the USC regime.\n\nhttps://agenda.infn.it/event/2334
7/contributions/121262/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121262/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Integrated Organic Molecules for Quantum Technologies
DTSTART;VALUE=DATE-TIME:20200928T143000Z
DTEND;VALUE=DATE-TIME:20200928T144500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121232@agenda.infn.it
DESCRIPTION:Speakers: Maja Colautti (CNR-Ino - European Laboratory for Non
-Linear Spectroscopy (LENS))\nThe realization of a robust and scalable nan
ophotonic platform which efficiently integrates quantum emitters as on-dem
and sources of non-classical light is crucial to the successful developmen
t of photonic quantum technologies. However\, conventional strategies to o
n-chip integration\, based on lithographic processes in semiconductors\, t
ypically introduce dephasing effects which broaden the transition linewidt
h of the emitter and are detrimental for its coherence properties. Moreove
r\, such fabrication techniques are intrinsically limited to planar geomet
ries and in this sense are difficult to scale up to a big number of integr
ated emitters. In the present contribution we demonstrate an alternative p
latform based on molecules that preserve near-Fourier-limited fluorescence
even when embedded in polymeric photonic structures [1]. Deterministic in
tegration is achieved in three-dimensions via direct laser writing (DLW) a
round selected molecular emitters\, with a fast\, inexpensive and scalable
fabrication process. In particular\, organic molecules of dibenzoterrylen
e (DBT) are embedded in anthracene (Ac) nanocrystals (NCs)\, which have sh
own photostable single-photon emission\, near to lifetime-limited linewidt
hs at 3K [2]\, and are especially suitable for the integration in polymeri
c devices. We integrate DBT:Ac NCs via DLW on different substrates and at
variable heights in different polymeric designs. Enhanced light extraction
is achieved in a micro-dome solid-immersion-lens\, reporting unprecedente
d detected count rates for a single cold molecule and efficient coupling t
o a single-mode fiber. The proposed technology may represent an important
step in the integration of single emitters into robust quantum protocols b
ased on molecules\, including arrays of indistinguishable single-photon so
urces. In this latter merit\, we will also discuss the possibility of usin
g an all-optical approach to independently shift the transition frequency
of individual emitters and bring them into resonance\, with spacial resolu
tion at the micron level and maintaining the coherent spectral properties
[3].\n\n[1] M. Colautti et al.\, Adv. Quantum Technol.\, (2020) doi:10.100
2/qute.202000004 \n[2] S. Pazzagli et al.\, ACSNano 12\, 4295–4303 (2018
). \n[3] M. Colautti et al.\, Under Review\n\nhttps://agenda.infn.it/event
/23347/contributions/121232/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121232/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Two-membrane cavity optomechanics
DTSTART;VALUE=DATE-TIME:20200928T124500Z
DTEND;VALUE=DATE-TIME:20200928T130000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121268@agenda.infn.it
DESCRIPTION:Speakers: Paolo Piergentili (University of Camerino)\nThe opto
mechanical behaviour of a driven high finesse Fabry-Pérot cavity containi
ng two vibrating dielectric Si3N4 membranes will be presented. The presenc
e of the second membrane inside the optical cavity enhances the optomechan
ical coupling making this system interesting to reach the strong-coupling
regime [1-2]. Moreover\, the presence of two optical resonators provides t
he opportunity to couple mechanical resonators with very similar frequenci
es. This pave the way to the realization of an efficient state transfer an
d even entanglement between the mechanical oscillators. Multi-element syst
ems of micro/nano-mechanical resonators offer promising prospects for expl
oring multi-oscillators synchronization [3-5]. The first experimental char
acterization of the optical\, mechanical\, and especially optomechanical p
roperties of a sandwich constituted of two parallel membranes within an op
tical cavity will be reported. We find that the optomechanical coupling st
rength is enhanced by constructive interference when the two membranes are
positioned to form an inner cavity which is resonant with the driving fie
ld. Specifically\, we determine a gain of ∼2.47 in the coupling strength
of the relative mechanical motion with respect to the single membrane con
figuration [3]. Finally\, the behaviour of the non-linear dynamics of such
a system in a pre-synchronization regime where both large and small ampli
tude resonator motions are transduced in a nontrivial way by the non-linea
r response of the optical probe beam\, will be discussed [5].\n\n[1] J. Li
\, A. Xuereb\, N. Malossi\, and D. Vitali\, J. Opt.\, 18\, 084001\, 2016 \
n[2] J. Li\, G. Li\, S. Zippilli\, D. Vitali\, and T. Zhang\, Phys. Rev. A
.\, 95\, 043819\, 2017 \n[3] P. Piergentili\, L. Catalini\, M. Bawaj\, S.
Zippilli\, N. Malossi\, R. Natali\, D. Vitali\, and G. Di Giuseppe\, New J
. Phys.\, 20\, 101001\, 2018 \n[4] W. Li\, P. Piergentili\, J. Li\, S. Zip
pilli\, R. Natali\, N. Malossi\, G. Di Giuseppe\, and D. Vitali\, Phys. Re
v. A\, 101\, 013802\, 2020 \n[5] P. Piergentili\, W. Li\, R. Natali\, N. M
alossi\, D. Vitali\, and G. Di Giuseppe\, in preparation\n\nhttps://agenda
.infn.it/event/23347/contributions/121268/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121268/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cross-Talk effects on conditional measurements
DTSTART;VALUE=DATE-TIME:20200928T123000Z
DTEND;VALUE=DATE-TIME:20200928T124500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121230@agenda.infn.it
DESCRIPTION:Speakers: Giovanni Chesi (Università degli Studi di Pavia)\nP
hoton-number resolving detectors have experienced a wide spread throughout
the last decades and proved to be versatile for a large number of applica
tions. In particular\, Multi-Pixel Photon Counters (MPPC) have been shown
to be promising for Quantum Optics applications [1\,2\,3]. Unfortunately\,
these detectors are typically affected by correlated noise\, which is esp
ecially detrimental for the detection of quantum correlations. The most im
portant source of correlated noise is the Optical Cross-Talk (OCT)\, i.e.
a photon emitted by a decelerating photoelectron fires a neighboring pixel
\, thus providing a spurious count. We have recently shown [4\;5\;6\;7] th
at a commercial class of MPPC\, i.e. the silicon photomultipliers\, allows
to detect the nonclassicality of a conditional state even in the presence
of the OCT. In particular\, we generated a multimode twin-beam state and
used the silicon photomultipliers to perform conditional measurements. We
successfully revealed the sub-Poissonianity of the conditional state. Howe
ver\, as far as we know\, a theoretical description of a conditional measu
rement in the presence of the OCT is still lacking. Here\, we extend the m
odel for the conditional measurements with photon counting introduced in [
8] by including the effect of the OCT. We provide the statistics of the nu
mber of detected photons for the conditional state and retrieve the analyt
ic expression of the related Fano factor. \n\n[1] I. Afek et al.\, “Quan
tum state measurements using multipixel photon detectors\,” Phys. Rev. A
79\, 043830(1-6) (2009). \n[2] D. A. Kalashnikov et al.\, “Measurement
of two-mode squeezing with photon number resolving multipixel detectors\,
” Opt. Lett. 27\, 14(2829-2831) (2012).\n[3] G. Chesi et al.\, “Optimi
zing Silicon photomultipliers for Quantum Optics\,” Sci. Rep. 9\, 7433(1
-12) (2019). \n[4] G. Chesi et al.\, “Measuring nonclassicality with sil
icon photomultipliers\,” Opt. Lett. 44\, 6(1371-1374) (2019). \n[5] G. C
hesi et al.\, “Effects of nonideal features of silicon photomultipliers
on the measurements of quantum correlations\,” Int. J. Quantum Inf. 17\,
1941012 (2019).\n [6] G. Chesi et al.\, “Autocorrelation functions: a u
seful tool for both state and detector characterisation\,” Quantum Meas.
Quantum Metrol. 6\, 1(1-6) (2019). \n[7] M. Bondani et al.\, “Measuring
nonclassicality of mesoscopic twin-beam states with Silicon Photomultipli
ers\,” Proceedings 12\, 48-52 (2019). \n[8] A .Allevi et al.\, “Condit
ional measurements on multimode pairwise entangled states from spontaneous
parametric downconversion”\, EPL 92\,1-6 (2010).\n\nhttps://agenda.infn
.it/event/23347/contributions/121230/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121230/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entanglement-based quantum key distribution using a deterministic
quantum dot photon source
DTSTART;VALUE=DATE-TIME:20200928T121500Z
DTEND;VALUE=DATE-TIME:20200928T123000Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121227@agenda.infn.it
DESCRIPTION:Speakers: Francesco Basso Basset (Sapienza University of Rome
)\nEntanglement-based protocols for quantum key distribution (QKD) provide
additional layers of security compared to single-photon prepare-and-measu
re approaches\, despite presenting the challenge of a less immediate hardw
are implementation. As remarkable technical achievements have been used to
demonstrate entanglement-based QKD over longer and longer distances [1]\,
the main opportunity for further development is related to multiphoton em
ission. This is a fundamental limitation for state-of-the-art photon sourc
es based on spontaneous parametric down-conversion\, which can be solved u
sing deterministic quantum emitters. Here we focus on semiconductor quantu
m dots\, which can generate nearly on-demand photon pairs with record-low
multiphoton emission [2] and Bell state fidelity currently up to 98% [3].
We experimentally demonstrate the viability of this technology in a realis
tic urban communication scenario [4]. We employ a modified asymmetric Eker
t protocol and perform QKD comparing two choices of quantum channel: over
a 250 m single-mode fiber and in free-space between two buildings across t
he campus of the Sapienza University of Rome. The key exchange is successf
ully performed with error rates of 3–4%\, well below the protocol thresh
old\, and with substantial violations of the Bell inequality. The results
are discussed in relation to the technical solutions employed for transfer
ring the signal and to the current state of development of the source. In
this regard\, an outlook is presented based on the latest and foreseen adv
ances in source design that can lead to unprecedented pair emission rates
and boost secure key exchange over long distances.\n\n[1] Yin J.\, et al.\
, Nature 582\, 501–505 (2020). \n[2] Schweickert L.\, et al.\, Applied P
hysics Letters 112\, 093106 (2018). \n[3] Huber D.\, et al.\, Physical Rev
iew Letters 121\, 033902 (2018). \n[4] Basso Basset F.\, Valeri M.\, et al
.\, arXiv:2007.12727 (2020).\n\nhttps://agenda.infn.it/event/23347/contrib
utions/121227/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121227/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Structured glass for low power actuation of thermal phase shifters
DTSTART;VALUE=DATE-TIME:20200928T120000Z
DTEND;VALUE=DATE-TIME:20200928T121500Z
DTSTAMP;VALUE=DATE-TIME:20210225T222218Z
UID:indico-contribution-23347-121226@agenda.infn.it
DESCRIPTION:Speakers: Simone Atzeni (Politecnico di Milano)\nFemtosecond l
aser micromachining (FLM) is a versatile technique that allows cost-effect
ive and rapid fabrication of 3D photonic integrated circuits providing dev
ices for various applications\, ranging from lab-on-a-chip to quantum inte
rferometry. Up to date\, the possibility to reconfigure the operations per
formed by these circuits mainly relies on thermal phase shifters. However\
, the actuation of an integrated microheater requires several hundreds of
milliwatts (around 600 mW) to induce a 2π phase shift in FLM devices oper
ating at telecom wavelength\, thus preventing the integration of more than
a few microheaters on the same chip. Therefore\, we devised a new FLM fab
rication process\, based on water-assisted-laser-ablation\, able to reduce
the power dissipation for a given phase shift of more than one order of m
agnitude\, with no compromise either on the compactness or on the passive
optical performance of the circuit. We realized Mach-Zehnder interferomete
rs encompassing high-quality optical waveguides in aluminum borosilicate g
lass (0.29 dB/cm propagation losses and 0.27 dB/facet coupling losses at 1
550 nm) and two different types of thermally insulating microstructures. I
n particular\, isolation trenches on the sides of the heated photon path a
nd bridge waveguides\, structures in which the glass is ablated also under
the optical path. As a result\, interferometers featuring trenches show a
reconfiguration period of 57 mW\, whilst bridge waveguide ensures a reduc
tion of the power dissipation required to induce a 2π phase shift down to
37 mW. In the end\, we performed the same experimental measurements in a
vacuum environment\, demonstrating a further reduction in the required pow
er dissipation when air is removed from the ablated regions. The advantage
s of structured devices are also underlined by performing thermal crosstal
k measurements. These results will lead to an increase of the devices comp
lexity attainable with FLM technology\, opening new scenarios both in clas
sical and quantum information applications.\n\nhttps://agenda.infn.it/even
t/23347/contributions/121226/
LOCATION:Online event
URL:https://agenda.infn.it/event/23347/contributions/121226/
END:VEVENT
END:VCALENDAR