Fundamental quantum limits to waveform detection

Tsang, Mankei; Nair, Ranjith

doi:10.1103/physreva.86.042115

Cited by 194 publications

(309 citation statements)

References 56 publications

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“…We do not report a corresponding value at NLO, since, at that order, only the Λ=600 MeV case show some (late) saturating behavior. Constraints on L are not yet stringent, and can be quoted as L = 70 ± 25 MeV [18].…”

Section: Nuclear and Neutron Matter Calculations: Results And DImentioning

confidence: 99%

“…We then assess the accuracy with which infinite nuclear matter properties and the isospin asymmetry energy can be predicted from order-by-order calculations in chiral effective field theory. Identifying the dominant sources of uncertainty in nuclear many-body calculations is an important open problem, especially as more stringent constraints on the EoS of neutron-rich matter and its density dependence are becoming available [18]. In computing the EoS, we employ the nonperturbative particle-particle ladder approximation, which re-sums an important class of diagrams accounting for Pauli-blocking in the medium.…”

Section: Introductionmentioning

confidence: 99%

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Toward order-by-order calculations of the nuclear and neutron matter equations of state in chiral effective field theory

et al. 2015

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We calculate the nuclear and neutron matter equations of state from microscopic nuclear forces at different orders in chiral effective field theory and with varying momentum-space cutoff scales. We focus attention on how the order-by-order convergence depends on the choice of resolution scale and the implications for theoretical uncertainty estimates on the isospin asymmetry energy. Specifically we study the equations of state using consistent NLO and N 2 LO (next-to-next-to-leading order) chiral potentials where the low-energy constants cD and cE associated with contact vertices in the N 2 LO chiral three-nucleon force are fitted to reproduce the binding energies of 3 H and 3 He as well as the beta-decay lifetime of 3 H. At these low orders in the chiral expansion there is little sign of convergence, while an exploratory study employing the N 3 LO two-nucleon force together with the N 2 LO three-nucleon force give first indications for (slow) convergence with low-cutoff potentials and poor convergence with higher-cutoff potentials. The consistent NLO and N 2 LO potentials described in the present work provide the basis for estimating theoretical uncertainties associated with the order-by-order convergence of nuclear many-body calculations in chiral effective field theory.

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Section: Nuclear and Neutron Matter Calculations: Results And DImentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Toward order-by-order calculations of the nuclear and neutron matter equations of state in chiral effective field theory

et al. 2015

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“…The existence of QMFSs does not contradict proven quantum limits to classical information processing, such as the quantum Cramér-Rao bound on waveform estimation [29,42,43] and the Helstrom bound on waveform detection [42][43][44], as all such limits are derived from quantum mechanics. This implies that proven quantum limits should either involve incompatible observables outside a QMFS or have effectively classical origins.…”

Section: Figmentioning

confidence: 99%

Evading Quantum Mechanics: Engineering a Classical Subsystem within a Quantum Environment

2012

Self Cite

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Quantum mechanics is potentially advantageous for certain information-processing tasks, but its probabilistic nature and requirement of measurement backaction often limit the precision of conventional classical information-processing devices, such as sensors and atomic clocks. Here we show that, by engineering the dynamics of coupled quantum systems, it is possible to construct a subsystem that evades the measurement backaction of quantum mechanics, at all times of interest, and obeys any classical dynamics, linear or nonlinear, that we choose. We call such a system a quantum-mechanics-free subsystem (QMFS). All of the observables of a QMFS are quantum-nondemolition (QND) observables; moreover, they are dynamical QND observables, thus demolishing the widely held belief that QND observables are constants of motion. QMFSs point to a new strategy for designing classical information-processing devices in regimes where quantum noise is detrimental, unifying previous approaches that employ QND observables, backaction evasion, and quantum noise cancellation. Potential applications include gravitational-wave detection, optomechanical-force sensing, atomic magnetometry, and classical computing. Demonstrations of dynamical QMFSs include the generation of broadband squeezed light for use in interferometric gravitational-wave detection, experiments using entangled atomic-spin ensembles, and implementations of the quantum Toffoli gate. According to quantum mechanics, a measurement of the position of an object must introduce uncertainty to its momentum, called the measurement backaction noise. Since position is coupled to momentum, as the object evolves in time, the backaction noise can perturb the position and contaminate subsequent position measurements. Scientists studying gravitational-wave detection, concerned that this dynamical effect of measurement backaction would place a fundamental limit to the detectors, proposed a general solution: If a quantum observable, represented by a self-adjoint operator OðtÞ in the Heisenberg picture, can be made to commute with itself at times t and t 0 when the observable is measured, viz.,then O can be measured repeatedly with no quantum limits on the predictability of these measurements. In particular, this means that quantum mechanics does not limit the detection of a classical signal that affects O.An observable that obeys Eq. (1) (1) is satisfied, the conjugate observables do not feed back onto the QND observable at the times of interest.The most well-known QND observables are ones that remain static in the absence of classical signals, viz.,

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“…This is also referred to as balanced homodyne detection. Rigorously speaking, a field quadrature is not always the optimal out-going observable to measure, especially when we are aiming at detecting a very weak displacement signal [11,39]. However, these more optimal observables to detect will be nonlinear (i.e., in terms of field quadratures), and will likely depend on features of a specific waveform we aim at -these would be undesirable because in practice we have many families of possible waveforms that need to be detected.…”

Section: Weak Force Measurement and The Standard Quantum Limitmentioning

confidence: 99%

Macroscopic quantum mechanics: theory and experimental concepts of optomechanics

Chen¹

2013

J. Phys. B: At. Mol. Opt. Phys.

276

302

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Abstract. Rapid experimental progress has recently allowed the use of light to prepare macroscopic mechanical objects into nearly pure quantum states. This research field of quantum optomechanics opens new doors toward testing quantum mechanics, and possibly other laws of physics, in new regimes. In the first part of this paper, I will review a set of techniques of quantum measurement theory that are often used to analyze quantum optomechanical systems. Some of these techniques were originally designed to analyze how a classical driving force passes through a quantum system, and can eventually be detected with optimal signal-to-noise ratio -while others focus more on the quantum state evolution of a mechanical object under continuous monitoring. In the second part of this paper, I will review a set of experimental concepts that will demonstrate quantum mechanical behavior of macroscopic objects -quantum entanglement, quantum teleportation, and the quantum Zeno effect. Taking the interplay between gravity and quantum mechanics as an example, I will review a set of speculations on how quantum mechanics can be modified for macroscopic objects, and how these speculations -and their generalizations -might be tested by optomechanics.

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Fundamental quantum limits to waveform detection

Cited by 194 publications

References 56 publications

Toward order-by-order calculations of the nuclear and neutron matter equations of state in chiral effective field theory

Toward order-by-order calculations of the nuclear and neutron matter equations of state in chiral effective field theory

Evading Quantum Mechanics: Engineering a Classical Subsystem within a Quantum Environment

Macroscopic quantum mechanics: theory and experimental concepts of optomechanics

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