Presentation materials
Femtosecond laser micromachining (FLM) is a versatile technique that allows cost-effective and rapid fabrication of 3D photonic integrated circuits providing devices for various applications, ranging from lab-on-a-chip to quantum interferometry. Up to date, the possibility to reconfigure the operations performed by these circuits mainly relies on thermal phase shifters. However, the actuation...
Entanglement-based protocols for quantum key distribution (QKD) provide additional layers of security compared to single-photon prepare-and-measure approaches, despite presenting the challenge of a less immediate hardware implementation. As remarkable technical achievements have been used to demonstrate entanglement-based QKD over longer and longer distances [1], the main opportunity for...
Photon-number resolving detectors have experienced a wide spread throughout the last decades and proved to be versatile for a large number of applications. 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 especially detrimental for the...
The optomechanical behaviour of a driven high finesse Fabry-Pรฉrot cavity containing two vibrating dielectric Si3N4 membranes will be presented. The presence of the second membrane inside the optical cavity enhances the optomechanical coupling making this system interesting to reach the strong-coupling regime [1-2]. Moreover, the presence of two optical resonators provides the opportunity to...
The realization of a robust and scalable nanophotonic platform which efficiently integrates quantum emitters as on-demand sources of non-classical light is crucial to the successful development of photonic quantum technologies. However, conventional strategies to on-chip integration, based on lithographic processes in semiconductors, typically introduce dephasing effects which broaden the...
Ultrastrong coupling (USC) 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...
In this talk we explore the possibility of performing Heisenberg limited quantum metrology of a phase, without any prior, by employing only maximally entangled states. Starting from the estimator introduced by Higgins et al. in New J. Phys. 11, 073023 (2009), the main result discussed in the talk is an analytical upper bound on the associated Mean Squared Error which is monotonically...
Quantum emitters coupled to EM fields in waveguides provide a controllable and experimentally feasible testbed to observe interesting physical phenomena; in particular, the emergence of bound states in the continuum opens new possibilities to generate states with specific entanglement properties. We characterize analytically the bound states for any number of emitters, showing that the finite...
Artificial neural networks have been proposed as potential algorithms that could benefit from being implemented and run on quantum computers. In particular, they hold promise to greatly enhance Artificial Intelligence tasks, such as image elaboration or pattern recognition. The elementary building block of a neural network is an artificial neuron, i.e. a computational unit performing simple...
The loss of qubits poses one of the fundamental obstacles towards large-scale and fault-tolerant quantum information processors. In this work, we design and characterize a complete toolbox for a full cycle of qubit loss detection and correction on a minimal instance of a topological surface code. This includes a quantum non-demolition measurement of a qubit loss event that conditionally...
Among the possible frameworks to encode the quantum bit, semiconductor-based implementations possibly present the highest potential in terms of scalability and compatibility with current nanoelectronics industry. In this talk, I will outline two different platforms for the realization of the qubit in semiconductor devices, and present the numerical approach we adopted for their...
The dynamics of complex materials can be conveniently investigated through pump-probe techniques. Here we present a simple quantum theoretical model that is used to interpret the results of a recently performed pump-probe experiment on Copper Germanate [1]. In this context, in order to study the electron-phonon coupling in the material, lattice vibrations are excited by an infrared pump pulse...
In the last decade, Superconducting Quantum Circuits (SQCs) based on Josepshon Junctions (JJs) showed that a working quantum processor can be successfully built and operated to perform Quantum Information Processing (QIP) 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...
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 suitable 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...
In 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 --- which leads to a very convenient description of density matrices. Our results will focus on thermal states of the quantum Ising chain in transverse field, for which...
We draw a picture of physical systems that allows us to recognize what is this thing called "time" by requiring consistency not only with our notion of time but also with the way time enters the fundamental laws of Physics, independently of one using a classical or a quantum description. Elements of the picture are two non-interacting and yet entangled quantum systems, one of which acting as a...
We fully characterize the mechanism by which nonclassicality according to the Glauber P-function can be conditionally generated on one mode of a two-mode Gaussian quantum state by generic Gaussian measurements on the other mode. For two-mode squeezed thermal states (TMSTs), we visualize the whole set of conditional states constructing Gaussian steering triangoloids and we show that...
I discuss general argument to show that if a physical system can mediate locally the generation of entanglement between two quantum systems, then it itself must be non-classical. Remarkably, the argument does not assume any classical or quantum formalism to describe the mediating physical system: the result follows from general information-theoretic principles, drawn from the recently proposed...
Giant 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...
Quantum metrology and sensing represent promising near term applications of quantum technologies 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 even more...
The 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 measuring the system frequently enough [1-5]. On the contrary, it is also possible to exploit frequent measurements to accelerate the system's evolution, obtaining the quantum anti-Zeno effect. In my presentation, I will describe an experiment...
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 suitable 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...
