The Conference on Quantum gases, fundamental interactions and cosmology- Third Edition (QFC 2022) will be held in Pisa from 26 to 28 October 2022.
After QFC2017 and QFC2019 (see the menu on the left for infos), the Conference will be in its third edition of a series of appointments to be held each second year.
Aim of the conference is to bring together scientists in both experimental and theoretical physics from the fields of ultracold quantum gases, fundamental interactions, and cosmology, with the desire of sharing and brainstorming on challenging open common problems, which can be zoomed in and out via a cross-disciplinary approach.
The mutual frontiers among these three apparently separated disciplines have been recently blossoming with new innovative, cutting edge research. To the well-established connections between cosmology and high-energy physics, current bright examples are the research activities in analogue gravity and superfluid analogies of cosmological phenomena, and of quantum simulations of lattice gauge theories using ultracold atoms in optical lattices. We intend to use this momentum and opportunities to establish strong collaborations among participants and leading groups to open new pathways leading to breakthrough results, in this spirit, keynote speakers of the first and second editions have been invited to join the Scientific Advisory Board.
The QFC2022 edition will deal with three broad interdisciplinary areas:
T1. Equations of state of compact objects
T2. Tests of General relativity
T3. Quantum analog simulators for fundamental interactions and cosmology
Each of these area of research will be discussed from the three perspectives of Quantum gases (Q), Fundamental interactions (F) and Cosmology (C).
QFC2022 will be in presence. Given the spirit of the Conference, we indeed preferred to move to 2022 the edition due in 2021, to have better chances to remain in presence. We also know that we are living in the pandemic, which has taught most important lessons about priorities to those open to learn. One of them is about the capacity of planning with clear mind on priorities and, at the same time, of living the moment in full. Please periodically check on the left menu about the updates on the current rules to enter Italy and attending an event of QFC type.
In QFC meetings science and arts are intertwinned, given that they share experimentation, creativity, and the use of very dense forms of symbolic languages, to produce beauty, inspire, and engage. Pisa is a town of science and arts. We are working at the cultural and social program of the QFC2022 edition, which you can discover at the due time on the left menu.
We look forward to meeting you at QFC2022!
In the recent years, the quantum simulation community has developed great interest in the interplay between coherent and dissipative dynamics. A prominent example is the case of measurement-induced phase transitions (MIPTs) which have been found in a wide range of systems, from discrete circuit models to cold atoms. MIPTs are typically characterized by the distinct behavior of non-linear quantities in the density operator — such as the entanglement entropy that varies from an area-law to a volume-law— but remain hard to detect experimentally for moderate system sizes. While a big focus on these systems has been on detecting the transition point, the role of the dissipative and coherent interplay in the system dynamics has remained unclear. In this work, we study the role that dissipation has on early and longer time dynamical observables and how it competes with the coherent evolution, in both interacting and non-interacting cold atomic systems. We find that these quantities exhibit distinct behavior that allow to probe the different phases in the transition and exhibit interesting signatures beyond the focus on MIPTs.
Ultra-cold quantum gases promise to boost the sensitivity of inertial matter-wave interferometers and open the avenue to achieve higher accuracies. In fundamental physics, these sensors are pursued e.g. for testing quantum mechanics, general relativity, detection of gravitational waves or scrutinizing concepts for dark matter and energy. Exploiting quantum gases for high-precision interferometry places high demands on their control and manipulation. We take benefit of various platforms such as the very-long-baseline atom interferometer, the Bremen drop tower, the Einstein elevator in Hannover, sounding rockets and the international space station to advance the necessary methods and achieve the targeted resolution. The DLR-mission MAIUS-1 demonstrated Bose-Einstein condensation and performed first interferometry experiments during the space travel of a sounding rocket. NASA’s Cold Atom Laboratory continues this research in orbit on the ISS.
Starting from a rubidium Bose-Einstein condensate, recently lowest expansion energies have been achieved by us in the Bremen drop tower as required for extending atom interferometry over several seconds. Exploring these methods to quantum mixtures not only opens up new physics in the absence of buoyancy, but also adds challenges for exploiting these mixtures for interferometry. Interferometers based on two different chemical elements have been proposed for quantum tests of the equivalence principle on the ISS as well as on satellites. Currently we prepare a sounding rocket mission to investigate the simultaneous generation and manipulation of potassium and rubidium condensates. Together with CAL, these experiments will prepare the DLR-NASA multi-user facility BECCAL for research on quantum gas mixtures and interferometry as well as enhance the readiness level of methods required for STE-QUEST, a proposal for a satellite mission currently studied within ESA’s VOYAGE 2050 program.
Bosonic dark matter particles with hypothetical ultralight mass down to the order of a trillionth of an electronvolt have a de Borgolie wavelength in galactic length scales. The manifested quantum wave nature in astrophysical length scale suppresses and stabilizes the formation of small-scale structures with the uncertainty principle, and it is called fuzzy dark matter, which can be described by the Schrödinger-Poisson equation. Motivated by the concepts in atomic Bose-Einstein condensate, we examine the degree of spatial coherence of the field configuration in fuzzy dark matter halos. The compact soliton stabilized by the quantum pressure with a flat central density profile and full coherence sits at the centre of a halo and is surrounded by an incoherent field whose density follows the Navarro-Frenk-White profile and exhibits turbulent features. This spatial transition from coherence to incoherence can be well characterized by two parameters according to a generalized empirical core-halo profile, whose oscillations are found to be anti-correlated to the oscillation of the peak value of the power spectrum of the halo; their oscillation frequencies scale with the soliton core density. The outer halo reaches a quasi-steady state with a fixed distribution profile in the vortex energy spectrum, unveiling the vortical core structure, and the mean intervortex spacing is found to be correlated to the characteristic granule size.
We acknowledge funding from European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 897324 (upgradeFDM).
Atom Interferometry for gravity measurements is now approaching its precision limits set by the
Standard Quantum Limit (SQL) of phase estimation [1]. Within the bounds of the SQL, the minimum
statistical uncertainty in gravity measurements scales as 1/√N , where N is the number of atoms entering
the interferometer. Quantum entanglement is an important resource that can potentially improve this
scaling with atom number and therefore the sensitivity of atom interferometers beyond classical limits.
In this context I will present a recently developed apparatus for the production of entangled squeezed
states of strontium atoms that can be injected in a matter-wave interferometer with separated arms. The
core of the apparatus is a high-finesse optical ring cavity conceived in order to induce strong collective
coupling between the atomic ensemble and the cavity mode. I will show that this setup allows for
optical and atomic access for interferometer operation and for homogeneous atom-light interaction -
essential requirements for the operation of atom interferometers. This setup will enable the production
of squeezed states either by quantum nondemolition measurement or by deterministic protocols such as
one-axis twisting [2]. Motivated by the recent achievement of squeezing in an optical atomic clock [3], I
will present our work towards the realization of a squeezed atom interferometer based on the strontium
1S0-3P0 optical clock transition.
We draw a picture of physical systems that allows us to recognize what
“time” is by requiring consistency with the way that time enters the
fundamental laws of Physics. Elements of the picture are two
non-interacting and yet entangled quantum systems, one of which acting
as a clock. The setting is based on the Page and Wootters mechanism,
with tools from large-N quantum approaches. Starting from an overall
quantum description, we first take the classical limit of the clock
only, and then of the clock and the evolving system altogether; we thus
derive the Schrödinger equation in the first case, and the Hamilton
equations of motion in the second.
Once the classical formalism is connected with a full quantum
description, ideal tools emerge for breaking through some of the
obstacles that make quantum gravity so difficult to process. In
particular, we suggest that our approach may provide a link between the
geodesic principle and the Schrödinger equation; furthermore, taking
into account a possible interaction between evolving system and clock.
Work in this direction is in progress and will be also reported,
particularly referring to the case of Schwartzschild black holes and
Hawking radiation.
The Born rule describes the probability of obtaining a specific outcome when measuring an observable of a given quantum system. As it has an intrinsic frequentist meaning, the Born rule only holds when it is possible to consider, at least in principle, many replicas of the system under examination. Hence, its use becomes delicate when dealing with systems for which having any copy is impossible, including cosmological models and many scenarios involving quantum mechanics and gravity.
In this talk, we introduce an effective Born rule, which, under reasonable conditions, allows one to use the outputs of (many) previous measurements to make previsions on the outcomes of future observations for non-replicable quantum systems. Then, we study the dynamics of a repeatedly measured Unruh-De Witt detector interacting with a scalar quantum field, for which using such an approximate Born rule is necessary. Specifically, we analyse the detector's dynamics under the assumption that the state of the field collapses after each measurement and investigate the statistics learned by observers measuring the detector, i.e. how they can use acquired outcomes to make educated guesses about the results of later measurements. We perform this analysis within the framework of the theory of Unruh-De Witt detectors in flat and curved spacetime, modified to include the measurement-induced collapse of the quantum field's state. Finally, we give explicit results for detectors moving along inertial and accelerated trajectories.
The Sachdev-Ye-Kitaev (SYK) model [1,2,3] describes a strongly-correlated quantum many-body system of $q/2$-body interactions with many intriguing properties. From the condensed-matter perspective, it provides a phenomenological description of quantum critical regions, and is a prototpye of strange metals which exhibit non-Fermi liquid behavior of linear-in-temperature resistivity [4]. Furthermore, the model exhibits maximal quantum chaos by saturating the Maldacena--Shenker--Stanford bound for the quantum Lyapunov exponent of out-of-time-order-correlators [5]. The SYK model is also of great interest from a cosmological point-of-view, as it exhibits a conformal symmetry at low energies, and has been found to be holographically dual to black holes with two-dimensional anti-de Sitter horizons [1].
Motivated by these rich features, we present a proposal for the analog quantum simulation of the SYK model in a table-top cavity QED experiment consisting of a cloud of fermionic atoms interacting with the eigenmodes of an optical cavity. We theoretically show how effective dynamics arise in this many-body system which are of SYK $q=4$ form, i.e., all-to-all two-body interactions with randomly distributed amplitudes. We compare and contrast the spectral properties of the effective Hamiltonian to those of the SYK model, and discuss potential experimental imperfections and challenges.
Further, we present a numeric study of universal dynamics (initial state independence) of equal-time correlators after global quenches into the SYK model. Through large parts of the evolution, these universal dynamics are well approximated by a Gaussian decay, which we show to be described well be an effective master equation for the disorder-averaged SYK dynamics [6].
Our work provides a stepping-stone for the realisation of the SYK model, thereby making the complex dynamics of this strongly correlated system accessible in the laboratory. Not only does this provide the enticing prospect of studying the many unique properties of this model, but also of other strongly correlated variations along the way.
[1] S. Sachdev, “Bekenstein–Hawking Entropy and Strange Metals,” Phys. Rev. X 5, 041025 (2015).
[2] A. Kitaev, “A simple model of quantum holography,” Talks given at “Entanglement in Strongly-Correlated Quantum Matter,” (Part 1, Part 2), KITP (2015).
[3] J. Maldacena and D. Stanford, “Remarks on the Sachdev-Ye-Kitaev model,” Phys. Rev. D 94, 106002 (2016).
[4] D. Chowdhury, A. Georges, O. Parcollet and S. Sachdev, “Sachdev-Ye-Kitaev Models and Beyond: A Window into Non-Fermi Liquids,” (2021), arXiv:2109.05037.
[5] J. Maldacena, S. H. Shenker, and D. Stanford, “A bound on chaos,” J. High Energ. Phys. 2016, 106 (2016).
[6] S. Bandyopadhyay, P. Uhrich, A. Paviglianiti, and P. Hauke, “Universal equilibration dynamics of the Sachdev-Ye-Kitaev model,” (2021), arXiv:2108.01718
In most cosmological models, rapid expansion of space is a vital ingredient to explain the structure and contents of the universe. Therefore it is of great importance to have an experimental system in which a quantum field is subject to such an expansion. Here, we present an experimental implementation of a two-dimensional effective expanding space-time for phonons in a potassium Bose-Einstein condensate, which is described by a scalar quantum field in an FLRW space-time. Spatial curvature is realized by shaping the density profile of the condensate. We confirm the implementation of both hyperbolic and spherical geometries by studying wave packet propagation. The expansion of space is implemented by a temporal control of the atomic interaction. With different ramp shapes we realise uniform, accelerated and decelerated expansions. In all cases, the expansion gives rise to excitations on the condensate’s density. Statistical analysis of the excitation structure and its time evolution reveals the production of phononic quasi-particles and allows the distinction between different expansion histories.
When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero- momentum state forming a superfluid. Chiral perturbation theory provides a very powerful tool for studying this phase. However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic. We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework. As a first step, we perform a low-density expansion of the chiral Lagrangian valid close to the onset of the Bose-Einstein condensation. We obtain an effective theory that can be mapped to a Gross-Pitaevskii Lagrangian in which, remarkably, all the coefficients depend on the isospin chemical potential. The low- density expansion becomes unreliable deep in the pion condensed phase. For this reason, we develop an alternative field expansion deriving a low-energy Lagrangian analog to that of quantum magnets. By integrating out the “radial” fluctuations we obtain a soft Lagrangian in terms of the Nambu-Goldstone bosons arising from the breaking of the pion number symmetry. Finally, we test the robustness of the second-order transition between the normal and the pion condensed phase when next-to-leading-order chiral corrections are included. We determine the range of parameters for turning the second-order phase transition into a first-order one, finding that the currently accepted values of these corrections are unlikely to change the order of the phase transition.
The equation of state (EoS) of dense nuclear matter is a basic ingredient for modeling a variety of astrophysical phenomena related to neutron stars (NSs), as core-collapse supernovae and binary neutron star (BNS) mergers. Determining the correct EoS which describes NSs is thus a fundamental problem of nuclear physics, particle physics and astrophysics, and major efforts have been made during the last few decades to solve it by measuring different NS properties using the data collected by various generations of X-ray and γ-ray satellites and by ground-based radio-telescopes. The recent detection of gravitational waves from the BNS mergers, GW170817 and GW190425 is giving a big boost to the research on dense matter physics. Gravitational wave signals, from BNS inspiral and particularly from the BNS post-merger phase (which could be detected by the 3rd generation of gravitational wave detectors) offer in fact a unique opportunity to test different EoS models. Computing the EoS of nuclear matter from the underlying nuclear interactions is a demanding and challenging theoretical task. Recently, chiral effective field theory (ChEFT) opened a new and systematic way to derive nuclear interactions with a direct connection to QCD via its symmetries.
In this contribution we present fully microscopic calculations of the EoS of dense and hot nuclear matter performed using the Brueckner-Bethe-Goldstone (BBG) many-body theory extended to finite temperature. We next apply our new EoS models to describe non-rotating NSs and the dynamics of BNS mergers.