Proceedings, Volume 12, Issue 1

We study energy-transfer processes from a given quantum system, termed charger, to another one, i.e., the proper battery both in a closed and in an open quantum setting. We quantify the fraction ${\mathcal{E}}_{\mathrm{B}}\left(\tau \right)$ of energy stored in the battery that can be extra...

Defects, e.g., Vacancies (Vs) and Defect-impurity centers, e.g., Nitrogen-Vacancy complexes (NVs), in group IV materials (diamond, SiC, graphene) are unique systems for Quantum Technologies (QT). The control of their positioning is a key issue for an...

We review some recent results regarding the use of time-continuous measurements for quantum-enhanced metrology. First, we present the underlying quantum estimation framework and elucidate the correct figures of merit to employ. We then report results...

We propose a numerical technique suitable for simulating the dynamics of reduced density matrix of a qubit interacting with its environment. Our approach, based on a combination of short-iterative Lanczos method (SIL) and a flexible truncation scheme...

We have applied techniques of quantum phase estimation to the dynamical tracking of the optical activity of a solution of sucrose undergoing acid hydrolysis. We adopt a multiparameter approach that makes the estimation reliable and robust against set...

We address the use of squeezing in binary phase-shift-keyed (PSK) channels at fixed energy. In particular, we assess homodyne receivers against the Helstrom bound in the presence of phase noise. We also take into account possible imperfections in the...

This research analyzes the impact of the asymmetry of the quantum system and the range of control possibilities offered by dispersive media and the nanostructures. I investigated the asymmetric behavior of a two level system in the Jaynes-Cummings mo...

The study of nonclassical properties of quantum states is a relevant topic for fundamental Quantum Optics and Quantum Information applications. In the mesoscopic domain, promising results have been obtained using photon-number-resolving detectors. He...

Several spin qubit architectures have been proposed, theoretically investigated and realized at least on the scale of single devices in view of quantum computation and simulation applications. We focus our study on five qubit types: quantum dot spin...

We study the influence of dissipative frustration on the one dimensional Josephson junction chain. In particular we analyze the dissipative quantum phase transition between the chain being superconducting or insulating, the purity as a measure of qua...

The well-known Heisenberg–Robertson uncertainty relation for a pair of noncommuting observables, is expressed in terms of the product of variances and the commutator among the operators, computed for the quantum state of a system. Different mod...

We present new results concerning simulation of general quantum measurements (POVMs) by projective measurements (PMs) for the task of Unambiguous State Discrimination (USD). We formulate a problem of finding optimal strategy of simulation for given q...

We study theoretically and experimentally the behavior of an optomechanical system where two vibrating dielectric membranes are placed inside a driven Fabry-Pérot cavity. We prove that multi–element systems of mechanical resonators are s...

Understanding the transport mechanisms and properties of complex networks is fundamental for the comprehension of a vast class of phenomena, from state transfer on a spin network to light-harvesting in photosynthetic complexes. It has been theoretica...

Orbital angular momentum is a discrete degree of freedom that can access an infinite dimensional Hilbert space, thus enhancing the information capacity of a single optical beam. Continuous variables field quadratures allow achieving some quantum task...

We summarise here some relevant results related to non-equilibrium quantum systems. We characterise quantum phase transitions (QPT) in out-of-equilibrium quantum systems through a novel approach based on geometrical and topological properties of mixe...

The non-local manipulation of spin-entangled states by means of local gating in two parallel 2D topological insulators properly connected to two superconducting electrodes is studied. We calculate analytically the current-phase relationship of the Jo...

Phase estimation represents a significant example to test the application of quantum theory for enhanced measurements of unknown physical parameters. Several recipes have been developed, allowing to define strategies to reach the ultimate bounds in t...

We address the problem of efficiently and effectively compress density operators (DOs), by providing an efficient procedure for learning the most likely DO, given a chosen set of partial information. We explore, in the context of quantum information...

In this article we derive a closed form expression for the incompatibility condition in multi-parameter quantum metrology when the reference states are Fermionic Gaussian states. Together with the quantum Fisher information, the knowledge of the comp...

Dynamical decoupling sequences are a convenient tool to reduce decoherence due to intrinsic fluctuations with $1/f$ power spectrum hindering quantum circuits. We study the possibility to achieve an efficient universal two-qubit gate in the pr...

Quantum enhanced optical measurement protocols aim at reducing the uncertainty in the estimation of some physical quantities of a system below the shot-noise limit, classically unavoidable. In particular when small number of photons is used the shot...

Graphene Josephson Junctions (GJJ) in the regime of ballistic transport where current is carried by discrete energy states of Andreev-reflected coherent electron-hole pairs have been recently demonstrated in graphene heterostructures. Due to the non-...

The distribution of entangled quantum systems among the nodes of a network is a key task at the basis of the development of quantum technologies, e.g., quantum communication, quantum computation, etc. Many efforts have been devoted to identify strate...

Ultrastrongly coupled quantum hardware may increase the speed of quantum state processing in distributed architectures, allowing to approach fault-tolerant threshold. We show that circuit QED architectures in the ultrastrong coupling regime, which ha...

The ultrastrong coupling regime of light-matter interaction is achieved when the coupling strength is a significant fraction of the natural frequencies of the noninteracting parts. Physics in this regime has recently attracted great interest, both th...

Quantum correlations of identical particles are important for quantum-enhanced technologies. The recently introduced non-standard approach to treat identical particles is here exploited to show the effect of particle indistinguishability on the chara...

Until very recently, two-photon interaction processes have been considered only as arising from second- or higher-order effects in driven systems, and so limited to extremely small coupling strengths. However, a variety of novel physical phenomena em...

We report the presence of an asymmetry that arises when considering the performances of quantum communication channels whose outputs are connected via a rigid, distance-preserving, yet not completely-positive, transformation. From a classical perspec...

Combining machine learning and quantum information. [...]

When two operators A and B do not commute, the calculation of the exponential operator ${\mathrm{e}}^{A+B}$ is a difficult and crucial problem. The applications are vast and diversified: to name but a few examples, quantum evolutions, product formulas,...

The observation of genuine quantum features of nano-mechanical motion is a key goal for both fundamental and applied quantum science. To this end, a promising approach is the stabilization of nonclassical features in the presence of dissipation, by m...

An investigated process can be studied in terms of the causal relations among the involved variables, representing it as a causal model. Some causal models are particularly relevant, since they can be tested through mathematical constraints between t...

We develop a perturbation theory to estimate the finite time corrections around a quasi static trajectory, in which a quantum system is able to equilibrate at each instant with its environment. The results are then applied to non equilibrium thermody...

Digital quantum simulators are among the most appealing applications. [...]

We discuss the quantum annealing of the fully-connected ferromagnetic p-spin model in a dissipative environment at low temperature. This model, in the large p limit, encodes in its ground state the solution to the Grover’s problem of searching in uns...

This extended abstract contains an outline of the work reported at the conference IQIS2018. We show that it is possible to exploit a thermalization process to extract work from a resource system R to a bipartite system S. To do this, we propose a sim...

We consider a semi-infinite waveguide with linear dispersion coupled to a qubit, in which a dressed bound state in the continuum (BIC) is known to exist. We predict that this BIC can be excited with significant probability via multi-photon scattering...

Josephson junctions drive the operation of superconducting qubits and they are the key for the coupling and the interfacing of superconducting qubit components with other quantum platforms. They are the only means to introduce non linearity in a supe...

Nowadays, the transmission of quantum information, especially for the distribution of cryptographic keys, is required on a global scale. The main obstacle to overcome in free-space communication is the presence of turbulence, which causes both spatia...

The out-of-equilibrium dynamics of many body systems has recently received a burst of interest, also due to experimental implementations. The dynamics of observables, such as magnetization and susceptibilities, and quantum information related quantit...

We introduce the notion of privacy in quantum estimation by considering an one-parameter family of isometries taking one input into two output systems. It stems on the separate and adversarial control of the two output systems as well as on the local...

We discuss two quantum simulation schemes in which the coupling to an external bath may give rise to novel and interesting many-body physics. Namely, we first address the effect of local Markovian baths on the quantum annealing dynamics of an Ising-l...

It is unrealistic to control all of the degrees of freedom of a high-dimensional quantum system. Here, we consider a scenario where our direct access is restricted to a small subsystem S that is constantly interacting with the rest of the system E. W...

Novel concepts, perspectives and challenges in measuring and controlling an open quantum system via sequential schemes are shown. We discuss how similar protocols, relying both on repeated quantum measurements and dynamical decoupling control pulses,...

Lee’s field-theoretical model describes the interaction between a qubit and a structured bosonic field. We study the mathematical properties of the Hamiltonian of the single-excitation sector of the theory, including a possibly “singular” qubit-field...

We consider two alternative procedures which can be used to control the evolution of a generic finite-dimensional quantum system, one hinging upon a strong continuous coupling with a control potential and the other based on the application of frequen...

The 11th Italian Quantum Information Science conference (IQIS 2018) took place in Catania, Italy, at the Monastero dei Benedettini, from September 17 to 20, 2018. IQIS 2018 was organized by the Department of Physics and Astronomy “E. Majorana” of the...

The dynamical Casimir effect (DCE) manifests itself in the ultrastrong matter-field coupling (USC) regime, as a consequence of the nonadiabatic change of some parameters of a system. We show that the DCE is a fundamental limitation for standard quant...

We analytically express the loss of entanglement between the components of a quantum device due to the generation of quantum correlations with its environment, and show that such loss diminishes when the latter is macroscopic and displays a semi-clas...