In this talk I will discuss how it is possible to perform quantum information tasks in superconducting quantum devices using microwave guides and propagating photons. In the first half of the talk I will discuss how superconducting qubits couple to microwave guides, implementing canonical models of quantum optics and condensed matter physics. This includes both strong and ultrastrong coupling...
Controlling the topological properties of quantum matter is a major goal of condensed matter physics. A major effort in this direction has been devoted to using classical light in the form of Floquet drives to manipulate and induce states with non-trivial topology. A different route can be achieved with cavity photons. In this talk, I will discuss a prototypical model for topological phase...
Amperean superconductivity is an exotic phenomenon stemming from attractive effective electron-electron interactions (EEEIs) mediated by a transverse gauge field. Originally introduced in the context of quantum spin liquids and high-Tc superconductors, Amperean superconductivity has been recently proposed to occur at temperatures on the order of 1-20 K in two-dimensional, parabolic-band,...
A key figure of merit in optomechanics is the single-photon quantum cooperativity (Cq). Recent works achieved a large cooperativity by engineering resonators with ultra-low mechanical and optical losses [1]. A complementary approach is to enhance optomechanical interactions while working with modest optical and mechanical quality factors. Less stringent bandwidth limitations in optomechanical...
Tensor network states are widely and very successfully used for the simulation of models of strongly correlated systems. These models are often an oversimplification of real materials. In this talk I will show how tensor network methods can be used in the context of combinations of density functional theory for realistic band structures and embedding methods such as the dynamical mean-field...
In this talk, I present our recent study about transport in Weyl semimetals with spatially varying nodal tilt profiles. We discuss two complementary approaches that characterise the electron flow: solutions of the semi-classical equations of motion, in analogy to those encountered in black hole spacetimes, and large-scale microscopic simulations of a scattering region surrounded by...
Neural network quantum states have delivered state of the art results for the calculation of ground states for systems beyond the reach of more conventional techiniques.
Such variational ansatzes have also been applied to the simulation of the dynamics of systems at equilibrium or far from it.
In this talk I will discuss recent advancements in the treatment of the dynamics with a particular...
We study the counting statistics of the asymmetric simple inclusion process (ASIP), which describes the dissipative transport of bosons along a one dimensional lattice. By combining exact numerical simulations with a field-theoretical analysis, we evaluate the current fluctuations for this process and determine their asymptotic scaling. Surprisingly, our findings show that the ASIP falls into...
There is a range of interesting physical scenarios that include both many-body quantum systems and strongly coupled structured environments that lead to a non-Markovian evolution. However, almost all methods for the study of many-body systems only consider closed or Markovian dynamics, while methods for the study of non-Markovian open quantum systems are generally restricted to small system...
Non-abelian gauge fields emerge naturally in the description of adiabatically evolving quantum systems. In this talk we show that they also play a role in Thouless pumping in the presence of degenerate bands. Specifically, we consider a photonic Lieb lattice and show that when the lattice parameters are slowly modulated, the propagation of the photons bears the fingerprints of the underlying...
We investigate the autonomous generation of multi-partite entangled states in a dual-rail waveguide QED configuration. Here, qubits arranged along two separated photonic waveguides are illuminated by the output of a nondegenerate parametric amplifier, which drives them into a strongly correlated steady state. We show that in this setup, there exists a large family of pure steady states, for...
Boson sampling is a computational problem that has been proposed as a candidate to obtain an unequivocal quantum computational advantage. The problem consists in sampling from the output distribution of indistinguishable bosons in a linear interferometer. There is strong evidence that such an experiment is hard to classically simulate, but it is naturally solved by dedicated photonic quantum...
The control of large photonic integrated devices, processing tailored entangled resources of error-protected qubits, is an important step towards realising an all-photonic quantum computer. Measurement-based encodings, computing tasks and applications, showing improvements in such devices´ computational performance, will be shown. Furthermore, future perspectives on the advantages of the...
Most of the modern Quantum Key Distribution (QKD) and Quantum Random Number Generation (QRNG) systems require the usage of the Field Programmable Gate Array (FPGA) technology as it can guarantee the deterministic behavior necessary for dealing with qubit generation and readout. Nevertheless, the System-on-a-Chip (SoC) technology, which integrates both an FPGA and a CPU and allows for a very...
Multi-photon entangled state is the key ingredient in realizing measurement-based quantum computing. The current proposals for universal quantum computation require simultaneously high generation rates, high fidelity, and low loss, which are beyond the capability of the current experimental systems. In this work, we address this critical problem by demonstrating the on-chip deterministic...
Trapped ions are one of the most promising platforms in the field of quantum computing and simulation. Technology nowadays offers incredible tools to trap and manipulate individual particles down to the quantum level, but the current state of the art allows to maintain control of these systems only up to a certain size. One of the most pressing roadblocks to overcome is to make laser beam...
Decoherence and crosstalk are two adversaries when aiming to parallelize a quantum algorithm: on the one hand, the execution of gates in parallel reduces decoherence due to a shorter runtime, but on the other hand, parallel gates in close proximity are vulnerable to crosstalk. This challenge is visible in Rydberg atom quantum computers where atoms experience strong van der Waals interactions...
A major driving force of the field of levitodynamics — the levitation
and control of microobjects in vacuum — is the possibility of generating
macroscopic quantum states of the center-of-mass motion of a levitated
nanoparticle. Not only can these states help address questions about
the interplay between gravity of quantum physics or the nature of
wavefunction collapse, but their mere...
This paper investigates a semi-device-independent protocol for quantum randomness generation constructed on the prepare-and-measure scenario based on the on-off-keying encoding scheme and with various detection methods, i.e., homodyne, heterodyne, and single photon detection schemes. The security estimation is based on lower bounding the guessing probability for a general case and is...
We study the incoherent transport of bosonic particles through a one dimensional lattice with different left and right hopping rates, as modelled by the asymmetric simple inclusion process (ASIP). Specifically, we show that as the current passing through this system increases, a transition occurs, which is signified by the appearance of a characteristic zigzag pattern in the stationary...
The relationship between many-body interactions and dimensionality is key to emergent quantum phenomena. A striking example is the Bose gas, which upon confinement to one dimension (1D) obeys an infinite set of conservation laws, prohibiting thermalization and steering dynamics. We experimentally demonstrate that the integrable dynamics of a Bose gas can persist deep within the dimensional...
We study theoretically the non-equilibrium dynamics of a two-dimensional (2D) uniform Bose superfluid following a quantum quench, from its short-time (prethermal) coherent dynamics to its long-time thermalization. Using a quantum hydrodynamic description combined with a Keldysh field formalism, we derive quantum kinetic equations for the low-energy phononic excitations of the system and...
We present a novel method for simulating the noisy behaviour of quantum computers, which allows to efficiently incorporate environmental effects in the driven evolution implementing the gates on the qubits. We show how to modify the noiseless gate executed by the computer to include any Markovian noise, hence resulting in what we will call a noisy gate. We compare our method with the IBM...
We present a novel method for simulating the noisy behaviour of quantum computers, which allows to efficiently incorporate environmental effects in the driven evolution implementing the gates on the qubits. We show how to modify the noiseless gate executed by the computer to include any Markovian noise, hence resulting in what we will call a noisy gate. We compare our method with the IBM...
Adiabatic quantum computers, such as the quantum annealers developed by D-Wave Systems Inc., have gained significant attention in recent years due to their potential for quantum computation. They are also increasingly being used in hybrid classical-quantum approaches to solve complex problems.
For instance, autoregressive neural networks have been employed to accelerate Monte Carlo...
We present a scheme for the amplification of electromagnetically induced acoustic transparency
(EIAT) in a superconducting transmon circuit. Recently, EIAT has been demonstrated experimentally
in a three-level ladder-type superconducting artificial atom [G Andersson et al, Phys. Rev. Lett. 124,
240 402 (2020)]. In this experiment, the authors have noticed only 20% transmission of...
LGTs are at the core of fundamental physics and, recently, substantial theoretical and experimental efforts have gone into simulating LGTs using quantum technologies.
In the quantum realm, entanglement plays a crucial role and its detection can be efficiently performed using entanglement witnesses.
Yet, entanglement witnessing in LGTs is extremely challenging due to the gauge constraints,...
Recently, the existence of Dicke-like equilibrium superradiant phase transitions in cavity QED many-body system has been put into question — resulting in no-go theorems on spontaneous photon condensation. Specifically, the no-go theorems tells us that the superradiant phase transition is prohibited as long as a single-mode purely electrical vector potential is considered, with the transition...
Adiabaticity can be used to improve accuracy and precision of many quantum control procedures such as quantum annealing, adiabatic quantum computing and ground state preparation. However, processes need to be implemented very slowly to achieve the adiabatic limit, lengthening control sequences and increasing the susceptibility of the system to decoherence. One approach to overcoming this...
We demonstrate and compare the on-chip Hong-Ou-Mandel interference between two micro-ring resonators and two straight waveguides used as indistinguishable twin photons sources for quantum photonic applications.
Understanding and controlling light-matter interactions is a cornerstone of physics and an essential resource for quantum technologies, communication and metrology. Levitated nano-objects offer a new paradigm to study the interaction between electromagnetic fields and matter at the very interface between quantum optics and macroscopic electrodynamics [1]. What is intriguing about levitated...
Variational quantum algorithms (VQA) are mainly designed to obtain an approximation for the ground state of a target Hamiltonian. Methods based on VQA for calculating excited states currently involve high-depth unitary implementation or state-specific optimizations on top of previously-found ground states. To directly extend the VQA framework to excited states, we propose an algorithm based on...
Studies about the possible exploitation of the Hubbard-Stratonovich transformation to the implementation of multi-qubit quantum gates in circuit-based quantum processors.
Variational Quantum Simulation (VQS) is one of the most promising techniques for near-term quantum computing. However, its performance is strongly affected by the ability of classical optimizers to deal with noise. In this context, I will first introduce Gaussian Process Models (GPM), a well-established machine learning technique to fit functionals with error bars, and then show how they can...
Variational quantum algorithms offer fascinating prospects for the solution of combinatorial optimization problems using digital quantum computers. However, the achievable performance in such algorithms and the role of quantum correlations therein remain unclear. Here, we shed light on this open issue by establishing a tight connection to the seemingly unrelated field of quantum metrology:...
Classical simulations of quantum algorithms play a pivotal role in the development of quantum computing devices. They are essential both for providing benchmark data for validation and for representing a crucial term of comparison to justify claims of quantum speed-up in the solution of computational problems.
In this study, we investigate the supervised learning of output expectation...
We develop and implement an efficient Tree Tensor Network based algorithm for computing the finite temperature many-body density matrix. This approach is particularly important because, since physical systems can never be cooled down to absolute zero temperature, a complete description of the physics behind the quantum computing devices has to account for finite temperature effects. However,...