Ultracold atoms and trapped ions are among the most promising platforms for implementing quantum technologies. On the one hand, neutral atoms form large ensembles of particles that behave coherently at ultra-low temperatures and can be individually confined using optical tweezers. On the other hand, trapped ions form much smaller clouds that can be controlled at the single-particle level....
Dual-unitary circuits are a class of quantum systems for which exact calculations of various quantities are possible, even for circuits that are nonintegrable. The array of known exact results paints a compelling picture of dual-unitary circuits as rapidly thermalizing systems. However, in this Letter, we present a method to construct dual-unitary circuits for which some simple initial states...
Light-matter platforms are fundamental for a variety of applications in quantum information
processing, among others [1].
At the level of pure electronic systems coupled solely to light, such as in the case of
structured subwavelength arrays of quantum emitters trapped in optical lattices, I will
describe the emergence of cooperative behavior: the optical response can be...
The study of the dynamics of open quantum systems is of great importance both for the theoretical implications and for the practical applications to quantum technologies. While the Markovian regime is a good approximation in most cases, many systems and environments display a non-Markovian behavior. In this talk, I will present some work done on the dynamics of non-Markovian systems, including...
Single Quantum is the leading manufacturer of Superconducting Nanowire Single Photon Detectors (SNSPDs), devices increasingly essential for research laboratories and companies all over the world. This talk will begin with an introduction of the company and our main products, to then focus on our R&D activities, aiming at developing SNSPDs as an enabling technology for quantum applications,...
Collective effects, such as Dicke superradiant emission, can enhance the performance of a quantum device. Here, we study the heat current flowing between a cold and a hot bath through an ensemble of N qubits, which are collectively coupled to the thermal baths. We find a regime where the collective coupling leads to a quadratic scaling of the heat current with N in a finite-size scenario....
Exciton-polaritons are hybrid light-matter excitations arising from the strong coupling between an electromagnetic mode and an excitonic transition of a semiconductor material. As mixed particles, they get the best of two worlds: low effective mass and long coherence from their photonic component and strong interactions from their matter component.
This unique mixture of features makes them...
Describing strongly interacting electrons is one of the crucial challenges of modern quantum
physics. A comprehensive solution to this electron correlation problem would simultaneously
exploit both the pairwise interaction and its spatial decay. By taking a quantum information
perspective, we explain how this structure of realistic Hamiltonians gives rise to two
conceptually different...
Nitrogen-vacancy (NV) centers in diamond have emerged as exceptionally promising candidates for the implementation of quantum technologies. These centers exhibit atom-like properties, characterized by long-lived spin quantum states and well-defined optical transitions, all within a robust solid-state device. Notably, the electron spins of NV centers can be easily initialized, controlled, and...
Any circuit is in one-to-one correspondence with a logical table that specifies, upon any given input state, what the output state of the ideal circuit should be. Since classical states are perfectly distinguishable in principle, at least at a fundamental level the calibration of classical circuits does not therefore present any difficulty. This is in stark contrast with the quantum case...
Quantum sensors are an established technology that has opened up new possibilities for precision sensing in various scientific fields. The use of entanglement for quantum-enhancement is paving the way for the development of next-generation sensors that can reach the ultimate precision limits set by quantum physics. However, determining how state-of-the-art sensing platforms may be used to...
Optomechanics studies the interaction of light with moving objects, an essential resource for sensing, metrology, and the investigation of fundamental aspects of quantum mechanics with mesoscopic systems. By eliminating clamping losses and the background gas, optically levitated objects can reach an extreme degree of isolation from the environment, enabling free-space quantum control of...
The behavior of many dissipative systems is generally described by a non-Markovian dynamics. Memory effects associated to non-Markovianity may lead to revival of coherence and entanglement and may be exploited as resources for quantum computation [1,2]. In this work, we study a toy model system of a qubit coupled to an incoherent impurity [3-5] which has been shown to exhibit a transition from...
Core-level spectroscopy provides valuable information about the local chemical environment of atoms in molecules by probing core-electronic structure whereas valence-level spectroscopy offers valuable insight into hybridization and bonding via valence-electronic structure. Despite their similarity, modeling core-electronic structure is challenging owing to large orbital-relaxation effects...
Quantum statistical models (i.e., families of normalized density matrices) and quantum measurements (i.e., positive operator-valued measures) can be regarded as linear maps: the former, mapping the space of effects to the space of probability distributions; the latter, mapping the space of states to the space of probability distributions. The images of such linear maps are called the testing...
A giant atom is a quantum emitter that can be coupled to the field non-locally at a set of coupling points [1]. Such a new generation of emitters can nowadays be implemented in circuit QED setups, where some spectacular effects - unachievable with normal atoms - have already been observed. One of these is the possibility to enable chiral (i.e. fully uni-directional) emission upon proper...
In the previous work Rhy. Rev. Lett 126, 063601, we have established a general framework for studying vacancy-like dressed state (VDS) in a generic photonic bath coupled to a normal atom. Here we extend this theory to giant-atom case. We point out that only if a giant atom is coupled to a bath whose energy spectrum possess chiral-symmetry (not necessarily transitionally invariant) and the...
Classical shadows are a powerful method for learning many properties of quantum states in a sample-efficient manner, by making use of randomized measurements. Random local Pauli measurements [1] and shallow shadows [2–4] provide optimal protocols for estimating expectation values of local observables.
On the contrary, the Clifford global-twirling protocol [1] is optimal for estimating global...
Josephson junctions are one of the fundamental building blocks of superconducting quantum devices. With applications ranging from circuit quantum electrodynamics experiments to quantum information processing and quantum sensing, reliable and reproducible devices, and related microfabrication processes, represent a corner stone for every experimental group in the field. There are different...
This study is concerned with the investigation of the continuity of Quantum Fisher Information (QFI) between two states, one experimentally generated , σ=(σ,∂_x σ), and one theoretically derived, ρ=(ρ,∂_x ρ), in different systems such as qubits, exponential density matrices and noise-free quantum dynamics [1, 2, 3, 4].
In quantum parameter estimation, the QFI exhibits universal continuity,...
We investigate the performance of a one dimensional dimerized XY chain as a quantum battery. Such integrable model shows a rich quantum phase diagram which emerges through a mapping of the spins into auxiliary fermionic degrees of freedom. We consider a charging protocol relying on the double quench of an internal parameter, notably the strength of the dimerization. Within this picture we...
Generating bipartite entanglement in quantum computing technologies is widely regarded as a pivotal benchmark. However, multipartite entanglement can appear when solving a complicated optimization problem where the correlation between multiple qubits is beneficial. Understanding whether such entanglement contributes to achieving a feasible solution is crucial from both algorithmic and hardware...
The ground-state of an artificial atom coupled to quantized modes in the Ultra-Strong Coupling regime is entangled and contains an arbitrary number of virtual photons.
The problem of their detection, raised since the very birth of the field, still awaits experimental demonstration despite the theoretical efforts in the last decade.
In a recent work [1] it has been shown that experimental...
We theoretically study how the peculiar properties of the vacuum state of an ultra-strongly coupled system can affect basic light-matter interaction processes. In this unconventional electromagnetic environment, an additional emitter no longer couples to the bare cavity photons, but rather to the polariton modes emerging from the ultra-strong coupling, and the effective light-matter...
In recent cold atom experiments, the utilization of internal degrees of freedom as synthetic dimensions has enabled the simulation of higher-dimensional systems. Specifically, magnetic quantum numbers have been employed to transform a 1D chain of atoms into a synthetic 2D lattice, resulting in the realization of an integer quantum Hall state. However, this configuration introduces highly...
Characterizing the effects of the interaction between quantum systems and their environment is a key challenge in the development of Quantum Technologies. Among the several possibilities, classifying whether the noise is correlated and Markovian has important implications on the dynamics of the system. In this work we consider the simplest quantum network in which correlations can be...
Abstract
The control of superconducting qubits demands advanced instruments and software capable of handling rapid pulses with arbitrary waveforms across microwave frequencies. Traditionally, achieving such precision involved up and down-conversion techniques, merging lower-frequency pulses with higher-frequency tones. This approach often requires multiple instruments per qubit,...
In recent years, the investigation of quantum systems out of equilibrium contributed to the advancement of quantum thermodynamics. In particular, the study of quantum batteries, small quantum mechanical systems able to temporarily store energy and further release it on-demand, recently emerged as a fast-growing subject in this field.
In this framework we have characterized the performances...
Negatively charged Nitrogen-Vacancy (NV-) colour centre in diamond is a well-known and characterized point defect with notable properties such as photostable bright fluorescence and spin states that can be initialised and read out, making it of great appeal for quantum technology applications.
Specifically, the latter can benefit from forming NV- defects in the proximity of the diamond...
In this work, a direct quantum implementation of the Doktorov formulae for calculating the vibronic
spectrum of molecules under the harmonic approximation is presented. The classically hard
problem of estimating the Franck-Condon (FC) factors is solved by using the Duschinsky matrices
as the only input via the Doktorov quantum circuit. This approach offers the advantage of avoiding
basis...
Abstract
Superconducting quantum circuits stand out as a prominent platform for quantum computers. The most diffused qubit design is the transmon qubit, a type of charge qubit that operates at a significantly different ratio of Josephson energy ($E_J$) to charging energy ($E_C$). This unique feature exponentially reduces the sensitivity to $1/f$ charge noise without increasing the...
The purpose of this work is to use a Quantum Annealer (QA) to solve the homogeneous Bethe-Salpeter equation (hBSE)[1] for two massive scalars interacting via the exchange of a massive scalar, a problem previously addressed with classical computation [2]. To achieve this, we transform the hBSE,by a suitable discretization, into a non-symmetric generalized eigenvalue problem (GEVP) (see Ref. [2]...
We simulate topological dissipative phases in a one-dimensional chain of trapped ions with their vibrational degrees of freedom. First, we study non-reciprocity in a two-ion parametric dimer and then we analyze topological amplification in large chains where Coulomb long-range couplings become apparent.
The existence of topologically non-trivial phases leads to the presence of edge states...
Fuel cells offer an elegant means of harnessing the chemical energy stored within the bonds of hydrogen and oxygen, converting it into electrical energy. However, existing fuel cell technologies suffer by a significant overpotential during the oxygen reduction reaction (ORR) at the cathode.
Given hydrogen's pivotal role as a promising low-carbon and sustainable fuel for the future, there is a...
The interplay of quantum fluctuations and interactions can yield novel quantum phases of matter with fascinating properties. Understanding the physics of such systems is a very challenging problem as it requires to solve quantum many body problems—which are generically exponentially hard to solve on classical computers. In this context, universal quantum computers are potentially an ideal...
Experiments with Rydberg atom arrays open up new possibilities to investigate two-dimensional interacting quantum systems away from equilibrium and they call for us to push also numerical simulations in this regime. I will discuss how combining the time-dependent variational principle with two families of ansatz for the variational wave function — artificial neural networks and tree tensor...
Quantitative characterization of two-qubit entanglement purification protocols is introduced. Our approach is based on the concurrence and the hit-and-run algorithm applied to the convex set of all two-qubit states. We demonstrate that pioneering protocols are unable to improve the estimated initial average concurrence of almost uniformly sampled density matrices, however, as it is known, they...
When a Rydberg atom and a ground state “perturber” atom encounter one another in an ultracold gas, they interact via an oscillatory potential mediated by the scattering of the Rydberg electron off of the perturber. Sufficiently deep wells form in the oscillations of this potential that the perturber becomes trapped, binding the two atoms together into a molecule. This unusual mechanism is also...
Ultracold dilute Bose-Fermi mixtures are systems that offer a large degree of tunability and are highly controllable, allowing for the investigation of substantially different conditions and quantum effects in matter. In such a mixture with a pairing interaction, one can study the competition between the formation of fermionic composite molecules and the tendency of bosons towards...
Current public-key cryptography standard is based on the RSA algorithm [1], whose security relies on the practical difficulty of factoring semiprimes as the product of two large prime numbers. While traditionally applied for encryption, lattice-based cryptography, as exemplified by Schnorr's algorithm [2], offers a different avenue to decompose RSA keys. This algorithm encodes prime factors...
Published by the American Physical Society (APS), Physical Review X (PRX) is an open-access publication that aims to publish outstanding research in all areas of physics.
In this talk, I will introduce the APS, the Physical Review family of journals, and PRX in particular. I will then explain in detail all phases of the peer review process, and how editors reach their decisions. Finally,...
I will introduce digitized counterdiabatic quantum computing (DCQC) as a novel paradigm for compressing digital quantum algorithms. It consists of a suitable digitization of the accelerated counterdiabatic dynamics of an adiabatic quantum computation, which encodes the chosen industry use case. I will exemplify DCQC to the class of optimization problems: digitized counterdiabatic quantum...
One of the key aspects in the realization of large-scale fault-tolerant quantum computers is quantum error correction (QEC). The first essential step of QEC is to encode the logical state into physical qubits in a fault-tolerant manner. Recently, flag-based protocols have been introduced that use ancillary qubits to flag harmful errors. However, there is no clear recipe for finding a compact...
I will describe digital, analog, and digital-analog quantum computing paradigms. Furthermore, I will discuss the possibility of reaching quantum advantage for industry use cases with current quantum computers in trapped ions, superconducting circuits, neutral atoms, and photonic systems.
Quantum statistical mechanics allows us to extract thermodynamic information from a microscopic description of a many-body system. A key step is the calculation of the density of states, from which the partition function and all finite-temperature equilibrium thermodynamic quantities can be calculated. In this work, we devise and implement a quantum algorithm to perform an estimation of the...
Efficient transport and harvesting of excitation energy under low light conditions is an important process in nature and quantum technologies alike. Here we formulate a quantum optics perspective to excitation energy transport in configurations of two-level quantum emitters with a particular emphasis on eciency and robustness against disorder. We study a periodic geometry of emitter rings with...
Flat Bands (FBs) are dispersionless energy bands, feature that makes such systems extremely sensitive to small perturbations and non-linearities. Here, we examine the case in which the non-linearity is introduced through the coupling of two-level emitters (almost) resonant to the FB energy.
Surprisingly, we find that a FB seeds a new type of detuning independent exponentially localized...
We experimentally demonstrate an optical bistability between two hyperfine ground states of trapped, cold atoms, using a single mode of an optical resonator in the collective strong coupling regime. Whereas in the familiar case, the bistable region is created through atomic saturation, we report an effect between states of high quantum purity, which is essential for future information storage....
Quantum chemistry problem is one of the attractive targets for demonstrating quantum advantage of quantum computing technology. Having strongly correlated systems as the main target, I would like to discuss what new classical computing techniques need to be developed to help quantum computing algorithms to solve the electronic structure problem. Encoding the electronic Hamiltonian in the...
Quantum computers hold promise to improve the efficiency of quantum simulations of materials and to enable the investigation of systems and properties that are more complex than tractable at present on classical architectures. Here, we discuss a computational framework to carry out electronic structure calculations of solids on noisy intermediate-scale quantum computers using embedded Green’s...
Within the last two decades, Quantum Technologies have made tremendous progress, from proof of principle demonstrations to real life applications, such as Quantum Key Distribution (QKD) and Quantum Random Number Generators (QRNGs). We will discuss the results that we have recently obtained in our group at the University of Padova towards the realization of secure QRNGs and mature and efficient...
Single-photon sources based on semiconductor quantum dots find several applications in quantum
information processing due to their high single-photon indistinguishability, on-demand generation, and low
multiphoton emission. In this context, the generation of entangled photons represents a challenging task with
a possible solution relying on the interference in probabilistic gates of...
Quantum technologies based on guided and integrated photonics represent a field in fully expansion due to the possibility of covering a wide panel of quantum light-based applications while exploiting system miniaturization to develop and test ambitious and scalable architectures. In this talk, I will present our results on the development of telecom-compatible photonics solutions, for...
Over the past two decades, quantum photonic devices have exploded in scale and complexity, with application to every corner of quantum information science. However, the writing is on the wall: to make scalable photonic quantum technology, we must do away with postselection and its exponentially poor scaling. This means building dynamic quantum circuits, featuring measurement and feedforward,...
The generation and manipulation of quantum states of light is required for key applications, such as photonic quantum simulation, linear optical quantum computing, quantum communication protocols, and quantum metrology. In this context, I will present our recent achievements in using single organic molecules as bright and stable sources of coherent single photons in the solid state. Among our...
In the last years, key European projects have lead the acceleration of technology readiness for the quantum Communication ecosystem. ThinkQuantum, spin-off of Unipd, provider of technologies and solutions for fiber networks, free-space terrestrial links and the Space domain (form satellites payloads to Optical Ground Station) and key player in the European QComm ecosystem will report about its...
The Multi-Reference Electronic Structure Theory involves choosing an active space with knowledge of the subspace's spatial and energetic information within the Hilbert space of a molecular electronic Hamiltonian that exhibits strong correlation. This process can be automated with the help of an AI assistant. This paper presents such an assistant that utilizes tools like the Approximate Pair...