Application of quantum inequalities to quantum optics

Marecki, Piotr

doi:10.1103/physreva.66.053801

Cited by 17 publications

(20 citation statements)

References 16 publications

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“…For intermediate scales, the QWEI allows for a limited violation of the classical WEC; bounds of this type therefore appear to be the natural remnant of the WEC in quantum field theory. We mention briefly that related bounds appear elsewhere in quantum field theory [36] and quantum mechanics [7]; QEIs have also been used to place constraints on exotic spacetimes [25,39,42].…”

Section: Quantum Energy Inequalitiesmentioning

confidence: 99%

Quantum Energy Inequalities and Stability Conditions in Quantum Field Theory

Fewster

2007

Rigorous Quantum Field Theory

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Summary. We give a brief review of quantum energy inequalities (QEIs) and then discuss two lines of work which suggest that QEIs are closely related to various natural properties of quantum field theory which may all be regarded as stability conditions. The first is based on joint work with Verch, and draws connections between microscopic stability (microlocal spectrum condition), mesoscopic stability (QEIs) and macroscopic stability (passivity). The second direction considers QEIs for a countable number of massive scalar fields, and links the existence and scaling properties of QEIs to the spectrum of masses. The upshot is that the existence of a suitable QEI with polynomial scaling is a sufficient condition for the model to satisfy the Buchholz-Wichmann nuclearity criterion. We briefly discuss on-going work with Ojima and Porrmann which seeks to gain a deeper understanding of this relationship.

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Section: Quantum Energy Inequalitiesmentioning

confidence: 99%

Quantum Energy Inequalities and Stability Conditions in Quantum Field Theory

Fewster

2007

Rigorous Quantum Field Theory

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“…An important aspect of our treatment is the numerical analysis of these bounds. To some extent this is motivated by the recent observation of Marecki [29] that QIs may have observational consequences in quantum optics; it is therefore important to know how sharp analytically tractable bounds are. The techniques used here may also be of independent interest, and we give a detailed account in Sect.…”

Section: Introductionmentioning

confidence: 99%

Quantum Inequalities in Quantum Mechanics

Eveson

Fewster

Verch

2005

Ann. Henri Poincaré

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Abstract. We study a phenomenon occuring in various areas of quantum physics, in which an observable density (such as an energy density) which is classically pointwise nonnegative may assume arbitrarily negative expectation values after quantisation, even though the spatially integrated density remains nonnegative. Two prominent examples which have previously been studied are the energy density (in quantum field theory) and the probability flux of rightwardsmoving particles (in quantum mechanics). However, in the quantum field context, it has been shown that the magnitude and space-time extension of negative energy densities are not arbitrary, but restricted by relations which have come to be known as 'quantum inequalities'. In the present work, we explore the extent to which such quantum inequalities hold for typical quantum mechanical systems. We derive quantum inequalities of two types. The first are 'kinematical' quantum inequalities where spatially averaged densities are shown to be bounded below. Specifically, we obtain such kinematical quantum inequalities for the current density in one spatial dimension (imposing constraints on the backflow phenomenon) and for the densities arising in Weyl-Wigner quantization. The latter quantum inequalities are direct consequences of sharp Gårding inequalities. The second type are 'dynamical' quantum inequalities where one obtains bounds from below on temporally averaged densities. We derive such quantum inequalities in the case of the energy density in general quantum mechanical systems having suitable decay properties on the negative spectral axis of the total energy.Furthermore, we obtain explicit numerical values for the quantum inequalities on the onedimensional current density, using various spatial averaging weight functions. We also improve the numerical value of the related 'backflow constant' previously investigated by Bracken and Melloy. In many cases our numerical results are controlled by rigorous error estimates.

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“…On the other hand, Marecki [8] just identified ω o t o = τ as the fraction of the period F T in which squeezing occurred, omitted the factor of π, and also had an additional factor of 2, thus obtaining R(…”

Section: Interpretation Of Squeezing and Observation Timementioning

confidence: 99%

“…A quantum inequality has been derived for squeezed light by Marecki [8]. Squeezed light has a nonclassical distribution of the quadrature components, which may be considered as the canonical momentum and position components of an equivalent harmonic oscillator corresponding to the frequency of the electromagnetic radiation being considered.…”

Section: Introductionmentioning

confidence: 99%

Testing a Quantum Inequality with a Meta-analysis of Data for Squeezed Light

Maclay

Davis

2019

Found Phys

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In quantum field theory, coherent states can be created that have negative energy density, meaning it is below that of empty space, the free quantum vacuum. If no restrictions existed regarding the concentration and permanence of negative energy regions, it might, for example, be possible to produce exotic phenomena such as Lorentzian transversable wormholes, warp drives, time machines, violations of the second law of thermodynamics, and naked singularities. Quantum Inequalities (QIs) have been proposed that restrict the size and duration of the regions of negative quantum vacuum energy that can be accessed by observers. However, QIs generally are derived for situations in cosmology and are very difficult to test. Direct measurement of vacuum energy is difficult and to date no QI has been tested experimentally. We test a proposed QI for squeezed light by a meta-analysis of published data obtained from experiments with optical parametric amplifiers (OPA) and balanced homodyne detection. Over that last three decades, researchers in quantum optics have been trying to maximize the squeezing of light and the quantum vacuum and have succeeded in reducing the variance in the quantum vacuum fluctuations to -15 dB. To apply the QI, a time sampling function is required. In our meta-analysis different time sampling functions for the QI were examined, but in all physically reasonable cases the QI is violated by much or all of the measured data. This brings into question the basis for QI. Possible explanations are given for this surprising result.

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Application of quantum inequalities to quantum optics

Cited by 17 publications

References 16 publications

Quantum Energy Inequalities and Stability Conditions in Quantum Field Theory

Quantum Energy Inequalities and Stability Conditions in Quantum Field Theory

Quantum Inequalities in Quantum Mechanics

Testing a Quantum Inequality with a Meta-analysis of Data for Squeezed Light

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