We analyze the entropy production and maximal extractable work from a squeezed thermal reservoir. The nonequilibrium quantum nature of reservoir induces an transfer with coherent contribution while modifying its part, allowing extraction single reservoir, as well great improvements in power efficiency for heat engines. Introducing modified Otto cycle, our approach fully characterizes operational regimes forbidden standard case, such refrigeration at same time, accompanied by efficiencies...

Quantum machine learning represents a promising avenue for data processing, also purposes of sequential temporal analysis, as recently proposed in quantum reservoir computing (QRC). The possibility to operate on several platforms and noise intermediate-scale devices makes QRC timely topic. A challenge that has not been addressed yet, however, is how efficiently include measurement realistic protocols, while retaining the memory needed time series processing preserving advantage offered by...

We discuss the thermodynamics of closed quantum systems driven out equilibrium by a change in control parameter and undergoing unitary process. compare work actually done on system with one that would be performed along ideal adiabatic isothermal transformations. The comparison latter leads to introduction irreversible work, while former inner friction. show these two quantities can treated equal footing, as both linked heat exchanged thermalization processes expressed relative entropies....

We consider the phenomenon of mutual synchronization in a fundamental quantum system two detuned harmonic oscillators dissipating into environment. identify conditions leading to this spontaneous showing that ability synchronize is related existence disparate decay rates and accompanied by robust discord information between oscillators, preventing leak from system.

Generalizing the quantifiers used to classify correlations in bipartite systems, we define genuine total, quantum, and classical multipartite systems. The measure give is based on use of relative entropy quantify "distance" between two density matrices. Moreover, show that, for pure states three qubits, both quantum obey a ladder ordering law fixed by two-body mutual informations, or, equivalently, one-qubit entropies.

We analyze the role of indirect quantum measurements in work extraction from systems nonequilibrium states. In particular, we focus on that can be obtained by exploiting correlations shared between system interest and an additional ancilla, where measurement backaction introduces a nontrivial thermodynamic tradeoff. present optimal state-dependent protocols for extracting both classical correlations, latter being measured discord. show that, while content fully extracted performing local...

We introduce the multipartite collision model, defined in terms of elementary interactions between subsystems and ancillas, show that it can simulate Markovian dynamics any open quantum system. develop a method to estimate an analytical error bound for repeated we use prove our scheme displays optimal scaling. Finally, provide simple decomposition model into gates, is efficiently simulable on computer according dissipative Church-Turing theorem, i.e., requires polynomial number resources.

Closed quantum systems exhibit different dynamical regimes, like many-body localization or thermalization, which determine the mechanisms of spread and processing information. Here we address impact these phases in reservoir computing, an unconventional computing paradigm recently extended into regime that exploits to solve nonlinear temporal tasks. We establish thermal phase is naturally adapted requirements report increased performance at thermalization transition for studied Uncovering...

The thermodynamics of quantum systems driven out equilibrium has attracted increasing attention in the last decade, connection with information and statistical physics, a focus on non-classical signatures. While first approach can deal average quantities over ensembles, order to establish impact environmental fluctuations during evolution, continuous measurement open system is required. Here, we provide an introduction general theoretical framework interpret for whose nonequilibrium...

Dissipative collective effects are ubiquitous in quantum physics, and their relevance ranges from the study of entanglement biological systems to noise mitigation computers. Here, we put forward first fully simulation dissipative phenomena on a real computer, based recently introduced multipartite collision model. First, theoretically accuracy this algorithm near-term computers with noisy gates, derive some rigorous error bounds that depend timestep model gate errors. These can be employed...

Quantum Reservoir Computing (QRC) exploits the information processing capabilities of quantum systems to solve non-trivial temporal tasks, improving over their classical counterparts. Recent progress has shown potential QRC exploiting enlarged Hilbert space, but real-time and achievement a advantage with efficient use resources are prominent challenges towards viable experimental realizations. In this work, we propose photonic platform suitable for based on physical ensemble reservoirs in...

Dissipation induced by interactions with an external environment typically hinders the performance of quantum computation, but in some cases can be turned out as a useful resource. We show potential enhancement dissipation field reservoir computing introducing tunable local losses spin network models. Our approach based on continuous is able not only to reproduce dynamics previous proposals computing, discontinuous erasing maps also enhance their performance. Control damping rates shown...

The quantum theory of rotation angles (S. M. Barnett and D. T. Pegg, Phys. Rev. A, 41, 3427-3425 (1990)) is generalised to non-integer values the orbital angular momentum. This requires introduction an additional parameter, orientation a phase discontinuity associated with fractional We apply our formalism propagation light modes momentum in paraxial non-paraxial regime.

We discuss the emergence of spontaneous synchronization for an open spin-pair system interacting only via a common environment. Under suitable conditions, and even in presence detuning between natural precession frequencies two spins, they are shown to reach long-lasting transient behavior where oscillate phase. explore connection such establishment robust quantum correlations analyzing differences dissipative dephasing effects.

Synchronization is one of the paradigmatic phenomena in study complex systems. It has been explored theoretically and experimentally mostly to understand natural phenomena, but also view technological applications. Although several mechanisms conditions for synchronous behavior spatially extended systems networks have identified, emergence this phenomenon largely unexplored quantum until very recently. Here we discuss synchronization different harmonic oscillators relaxing towards a...

We study the relative strength of classical and quantum correlations, as measured by discord, for two-qubit states. Quantum correlations appear only in presence while reverse is not always true. identify family states that maximize discord a given value show largest attainable mixed greater than pure The difference between entanglement emphasized remarkable fact these do are, some cases, even separable. Finally, random generation density matrices uniformly distributed over whole Hilbert...

The distance between a quantum state and its closest not having certain property has been used to quantify the amount of correlations corresponding that property. This approach allows unified view various kinds present in system. In particular, using relative entropy as measure, total can be meaningfully separated classical part thanks an additive relation involving only distances states. Here, we investigate measure square norm, already define so-called geometric discord. We thus consider...

We study the relationship between collective phenomena of super- and subradiance spontaneous synchronization quantum systems. To this aim we revisit case two detuned qubits interacting through a pure dissipative bosonic environment, which contains minimal ingredients for our analysis. By using Liouville formalism, are able to find analytically ultimate connection these phenomena. that dynamical is due presence longstanding coherence ground state system subradiant state. finally show that,...

We show a dissipative phase transition in driven nonlinear quantum oscillator which discrete time-translation symmetry is spontaneously broken two different ways. The corresponding regimes display either or incommensurate time-crystal order, we analyze numerically and analytically beyond the classical limit, addressing observable dynamics, phenomenology (laboratory rotating) frames, Liouvillian spectral features, fluctuations. Via an effective semiclassical description, that diffusion...

The interaction of a quantum system, which is not accessible by direct measurement, with an external probe can be exploited to infer specific features the system itself. We introduce probing scheme based on emergence spontaneous synchronization between out-of-equilibrium qubit, in contact environment, and qubit. Tuning frequency leads transition phase antiphase. sharp these two regimes locally monitoring dynamics alone allows one reconstruct shape spectral density environment.

We consider structured environments modeled by bosonic quantum networks and investigate the probing of their spectral density, structure, topology. demonstrate how to engineer a desired density changing network structure. Our results show that can be very accurately detected via locally immersed probe for virtually any configuration. Moreover, we entire structure reconstructed using single probe. illustrate our findings presenting examples densities topology genuine complexity.

Abstract Fast and robust quantum state transfer (QST) is a major requirement in control scalable information processing. Topological protection has emerged as promising route for the realization of QST against sizable imperfections network. Here, scheme presented topologically protected edge states dimeric Su–Schrieffer–Heeger spin chain assisted by Landau–Zener tunneling. As compared to topological protocols based on Rabi flopping proposed recent works, method more advantageous terms...