State estimation with quantum extreme learning machines beyond the scrambling time

npj Quantum Information, Journal Year: 2025, Volume and Issue: 11(1)

Published: Feb. 3, 2025

Language: Английский

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Kirkwood-Dirac representations beyond quantum states and their relation to noncontextuality

Physical review. A/Physical review, A, Journal Year: 2024, Volume and Issue: 110(5)

Published: Nov. 6, 2024

Kirkwood-Dirac representations of quantum states are increasingly finding use in many areas within theory. Usually, this sort only applied to provide a representation (as complex functions over some set). We show how standard can be extended fully compositional all theory (including channels, measurements, and so on), prove that extension satisfies the essential features functoriality (namely, commutes with composition channels), linearity, quasistochasticity. Interestingly, positive operator-valued measure (POVM) element is uniquely picked out collection weak values for it relative bases defining representation. then if one find any everywhere real non-negative given experimental scenario or fragment theory, consistent principle generalized noncontextuality, key notion classicality foundations. also converse does not hold: even verifies defined herein) an experiment require negativity imaginarity, cannot generally conclude witnesses contextuality.

Language: Английский

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Energy exchange statistics and fluctuation theorem for nonthermal asymptotic states

Physical review. E, Journal Year: 2025, Volume and Issue: 111(1)

Published: Jan. 21, 2025

Energy exchange statistics between two bodies at different thermal equilibria obey the Jarzynski-Wójcik fluctuation theorem. The corresponding energy scale factor is difference of inverse temperatures associated to equilibrium. In this work, we consider a dissipative quantum dynamics leading system towards possibly nonthermal, asymptotic state. To generalize theorem nonthermal states, identify sufficient condition I for existence an η^{*} that unique, finite, and time independent, such characteristic function distribution becomes identically equal 1 any time. This plays role temperatures. We discuss physical interpretation I, showing it amounts almost complete memory loss initial robustness our results against quantifiable deviations from validity evaluated by experimental studies on single nitrogen-vacancy center subjected sequence laser pulses dissipation.

Language: Английский

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On Dynamical Measures of Quantum Information

Entropy, Journal Year: 2025, Volume and Issue: 27(4), P. 331 - 331

Published: March 21, 2025

In this work, we use the theory of quantum states over time to define joint entropy for timelike-separated systems. For systems that admit a dual description as being spacelike-separated, our notion recovers usual von Neumann bipartite and thus may be viewed spacetime generalization entropy. Such an is then used dynamical extensions entropy, conditional mutual information separated by action channel. We provide in-depth mathematical analysis such measures properties they satisfy. also formulation quantify loss/gain associated with evolution systems, which enables us formulate precise conservation processes. Finally, show how admits operational interpretation in terms quantifying amount state disturbance positive operator- valued measurement.

Language: Английский

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Compatibility of quantum measurements and the emergence of classical objectivity

Physical review. A/Physical review, A, Journal Year: 2025, Volume and Issue: 111(4)

Published: April 28, 2025

Language: Английский

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Quasi-probability distribution of work in a measurement-based quantum Otto engine

Physica A Statistical Mechanics and its Applications, Journal Year: 2025, Volume and Issue: unknown, P. 130650 - 130650

Published: May 1, 2025

Language: Английский

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Quantum simulations of macrorealism violation via the quantum nondemolition measurement protocol

Physical review. A/Physical review, A, Journal Year: 2025, Volume and Issue: 111(5)

Published: May 19, 2025

Language: Английский

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Interferometry of quantum correlation functions to access quasiprobability distribution of work

npj Quantum Information, Journal Year: 2024, Volume and Issue: 10(1)

Published: Nov. 11, 2024

Abstract The Kirkwood-Dirac quasiprobability distribution, intimately connected with the quantum correlation function of two observables measured at distinct times, is becoming increasingly relevant for fundamental physics and technologies. This distribution can take non-positive values, its experimental reconstruction becomes challenging when expectation values incompatible are involved. Here, we use an interferometric scheme aided by auxiliary system to reconstruct distribution. We experimentally demonstrate this in electron-nuclear spin associated a nitrogen-vacancy center diamond. By measuring characteristic function, work analyze behavior first second moments. Our results clarify physical meaning context thermodynamics. Finally, study uncertainty Hamiltonian via Robertson-Schrödinger relation, different initial states.

Language: Английский

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Separation of measurement uncertainty into quantum and classical parts based on Kirkwood-Dirac quasiprobability and generalized entropy

Journal of Physics A Mathematical and Theoretical, Journal Year: 2024, Volume and Issue: 57(46), P. 465303 - 465303

Published: Oct. 21, 2024

Measurement in quantum mechanics is notoriously unpredictable. The uncertainty measurement can arise from the noncommutativity between state and basis which intrinsically quantum, but it may also be of classical origin due to agent's ignorance. It fundamental as well practical importance cleanly separate two contributions directly accessed using laboratory operations. Here, we propose ways decomposition total additively into parts. In decompositions, a described by POVM (positive-operator-valued measure) over quantified respectively generalized nonadditive entropies outcomes; parts are identified, respectively, nonreality nonclassicality | captures simultaneously both negativity associated Kirkwood-Dirac quasiprobability relative interest PVM (projection-valued maximized all possible choices latter; and, remaining uncertainties identified Both decompositions shown satisfy few plausible requirements. minimum measurements given impurity certain entropies, entirely classical. We argue that nonvanishing genuine sufficient necessary prove contextuality via weak with postselection. Finally, suggest manifestation specific disturbance.

Language: Английский

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Polytopes of Absolutely Wigner Bounded Spin States

Quantum, Journal Year: 2024, Volume and Issue: 8, P. 1550 - 1550

Published: Dec. 4, 2024

Quasiprobability has become an increasingly popular notion for characterising non-classicality in quantum information, thermodynamics, and metrology. Two important distributions with non-positive quasiprobability are the Wigner function Glauber-Sudarshan function. Here we study properties of spin finite-dimensional systems draw comparisons its infinite-dimensional analog, focusing particular on relation to existence absolutely Wigner-bounded states. More precisely, investigate unitary orbits mixed states that characterized by functions lower-bounded a specified value. To this end, extend characterization set positive as linear eigenvalue constraints, which together define polytope centred maximally state simplex spin-j The lower bound determines relative size such bounded (AWB) polytopes their geometric characteristics. In each dimension Hilbert-Schmidt ball representing tight purity-based sufficient condition be AWB is exactly determined, while another necessary conjectured. Special attention given case where separates containing only from other because use negativity witness non-classicality. Comparisons made absolute symmetric separability positivity, additional details low numbers.

Language: Английский

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