Operational Resource Theory of Continuous-Variable Nonclassicality

Yadin, Benjamin; Binder, Felix C.; Thompson, Jayne; Narasimhachar, Varun; Gu, Mile; Kim, M. S.

doi:10.1103/physrevx.8.041038

Cited by 107 publications

(129 citation statements)

References 111 publications

(146 reference statements)

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“…In addition, our study paves the way to the application of other criticalities appearing in quantum-optical models [20,[31][32][33] in quantum metrology. Finally, by focusing on the time-scaling and on a finite-component system, our analysis challenges the standard framework in which the fundamental resources needed to achieve metrological quantum advantage are assessed [34][35][36][37].…”

Section: Analysis Of Resourcesmentioning

confidence: 99%

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Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

et al. 2020

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Physical systems close to a quantum phase transition exhibit a divergent susceptibility, suggesting that an arbitrarily-high precision may be achieved by exploiting quantum critical systems as probes to estimate a physical parameter. However, such an improvement in sensitivity is counterbalanced by the closing of the energy gap, which implies a critical slowing down and an inevitable growth of the protocol duration. Here, we design different metrological protocols that make use of the superradiant phase transition of the quantum Rabi model, a finite-component system composed of a single two-level atom interacting with a single bosonic mode. We show that, in spite of the critical slowing down, critical quantum optical systems can lead to a quantum-enhanced time-scaling of the quantum Fisher information, and so of the measurement sensitivity.In a system close to a critical point, small variations of physical parameters may lead to dramatic changes in the equilibrium state properties. The possibility of exploiting this sensitivity for metrological purposes is well known, and it has already been applied in classical devices, e.g. in superconducting transition-edge sensor [1]. Besides, the development of quantum metrology has extensively shown that quantum states can outperform their classical counterparts for sensing tasks [2]. Therefore, a question naturally arises: what sensitivity can be achieved using interacting systems close to a quantum-critical point? In the last few years, this question has attracted growing interest and it has been addressed by different methods [3][4][5][6][7][8][9]. These studies may be roughly divided in two classes.The first approach, which we will call the "dynamical" paradigm [5,7], focus on the time evolution induced by a Hamiltonian close to a critical point. In this approach, one prepares a probe system in a suitably chosen state, lets it evolve according to the critical Hamiltonian, and finally measures it. This bear close similarity to the standard interferometric paradigm of quantum metrology [2]. On the other hand, the "static" approach [3, 6] is based on the equilibrium properties of the system. It consists in preparing and measuring the system ground state in the unitary case, or the system steady-state when open quantum systems are considered. In proximity of the phase transition the susceptibility of the equilibrium state diverges, and so it does the achievable measurement precision. Unfortunately, the time required to prepare the equilibrium state diverges as well, both in the unitary [10] and in the driven-dissipative case [11,12], a behavior called critical slowing down. Only very re-cently, it has been demonstrated that for a large class of spin models these two approaches are formally equivalent [9], and that they both make it possible to achieve the optimal scaling limit of precision with respect to system size and to measurement time. These results were obtained considering spin systems that undergo quantum phase transitions in the thermodynamic limit, where the numb...

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Section: Analysis Of Resourcesmentioning

confidence: 99%

“…The first term in (35) originates from the Hamiltonian dynamics. We will define the eigenmatrices of this evolution: BM i + M i B T = λ i M i .…”

Section: Metrology In the Superradiant Phasementioning

confidence: 99%

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

et al. 2020

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“…all mixtures of coherent states [30]. A number of witnesses, measures and monotones of optical nonclassicality have been designed [23,26, with the goal to identify non optical classical states and to quantify the degree of non optical classicality of any state. Those quantities are often hard to compute, to measure, or to give a clear physical meaning.…”

Section: Quadrature Coherence Scale and Optical (Non)classicalitymentioning

confidence: 99%

Quadrature Coherence Scale Driven Fast Decoherence of Bosonic Quantum Field States

Hertz

Bièvre

2020

Phys. Rev. Lett.

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We introduce, for each state of a bosonic quantum field, its quadrature coherence scale (QCS), a measure of the range of its quadrature coherences. Under coupling to a thermal bath, the purity and QCS are shown to decrease on a time scale inversely proportional to the QCS squared. The states most fragile to decoherence are therefore those with quadrature coherences far from the diagonal. We further show a large QCS is difficult to measure since it induces small scale variations in the state's Wigner function. These two observations imply a large QCS constitutes a mark of "macroscopic coherence". Finally, we link the QCS to optical classicality: optical classical states have a small QCS and a large QCS implies strong optical nonclassicality.

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“…Interest in non-classicality aspects has recently renewed being stimulated by the ongoing resource theories of various quantum properties [14]. Attempts to produce a resource theory of non-classicality [15,16,17] are in fact based on the identification of the set of classical states and classical operations. We point out that in Refs.…”

Section: Introductionmentioning

confidence: 99%

A geometric measure of non-classicality

Marian¹,

Marian²

2020

Phys. Scr.

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This paper aims to stress the role of the Cahill-Glauber quasi-probability densities in defining, detecting, and quantifying the non-classicality of field states in quantum optics. As such, we investigate non-classicality of a pure single-mode state of the radiation field by using the one-mode coherent states as a reference set of classical states. The distance between a given pure state and the set of all pure classical states is here called a geometric degree of non-classicality. It turns out that any such distance is expressed in terms of the maximal value of the Husimi Q function. As an insightful application we consider the de-Gaussification process produced when preparing a state by adding p photons to a pure Gaussian one. For a coherent-state input, we get an analytic degree of non-classicality which compares interestingly with the previously evaluated entanglement potential. Then we show that the non-classicality degrees of the one-and two-photon-added squeezed vacuum states are larger than that of the original input state.

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Operational Resource Theory of Continuous-Variable Nonclassicality

Cited by 107 publications

References 111 publications

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

Quadrature Coherence Scale Driven Fast Decoherence of Bosonic Quantum Field States

A geometric measure of non-classicality

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