Comment on "Sonoluminescence as Quantum Vacuum Radiation"

Sonoluminescence as a QED vacuum effect: Probing Schwinger's proposal

Several years ago Schwinger proposed a physical mechanism for sonoluminescence in terms of photon production due to changes in the properties of the quantum-electrodynamic (QED) vacuum arising from a collapsing dielectric bubble. This mechanism can be re-phrased in terms of the Casimir effect and has recently been the subject of considerable controversy. The present paper probes Schwinger's suggestion in detail: Using the sudden approximation we calculate Bogolubov coefficients relating the QED vacuum in the presence of the expanded bubble to that in the presence of the collapsed bubble. In th…

Sonoluminescence as a QED vacuum effect. II: Finite Volume Effects

In a companion paper [quant-ph/9904013] we have investigated several variations of Schwinger's proposed mechanism for sonoluminescence. We demonstrated that any realistic version of Schwinger's mechanism must depend on extremely rapid (femtosecond) changes in refractive index, and discussed ways in which this might be physically plausible. To keep that discussion tractable, the technical computations in that paper were limited to the case of a homogeneous dielectric medium. In this paper we investigate the additional complications introduced by finite-volume effects. The basic physical scenari…

Modelling Sonoluminescence

In single-bubble sonoluminescence, a bubble trapped by a sound wave in a flask of liquid is forced to expand and contract; exactly once per cycle, the bubble emits a very sharp ($< 50 ps$) pulse of visible light. This is a robust phenomenon observable to the naked eye, yet the mechanism whereby the light is produced is not well understood. One model that has been proposed is that the light is "vacuum radiation" generated by the coupling of the electromagnetic fields to the surface of the bubble. In this paper, we simulate vacuum radiation by solving Maxwell's equations with an additional term …

Observation of Nonclassical Photon Statistics in Single-Bubble Sonoluminescence

A cavitation bubble inside a liquid, under a specific set of conditions, can get trapped in an antinode of the ultrasonically driven standing wave and periodically emits visible photons (1,2). This conversion of sound to light phenomenon, known as sonoluminescence, can be seen with unaided eyes and occurs in multi- or single-bubble regimes. The sonoluminescence radiation spectrum analysis attributes a temperature of about 6,000 Kelvin to the bubble (3-5) -- close to the sun's surface temperature. The bubble dynamics, thermodynamics, and other physicochemical properties are well-explored and st…

Theory of quantum radiation observed as sonoluminescence

Sonoluminescence is explained in terms of quantum radiation by moving interfaces between media of different polarizability. In a stationary dielectric the zero-point fluctuations of the electromagnetic field excite virtual two-photon states which become real under perturbation due to motion of the dielectric. The sonoluminescent bubble is modelled as an optically empty cavity in a homogeneous dielectric. The problem of the photon emission by a cavity of time-dependent radius is handled in a Hamiltonian formalism which is dealt with perturbatively up to first order in the velocity of the bubble…

Comment on `Vacuum Rabi Splitting in a Semiconductor Circuit QED System' by Toida et al., Phys. Rev. Lett. 110, 066802 - Published 6 February 2013

Toida et al. claim in their recent article [Phys. Rev. Lett. 110, 066802 (2013)] that they `report a direct observation of vacuum Rabi splitting in a GaAs/AlGaAs double quantum dot (DQD) based charge qubit coupled with a superconducting coplanar waveguide (CPW) resonator'. In this comment, we challenge the main claims made in their paper and show that their results: a) do not provide any evidence of vacuum Rabi oscillations and b) do not provide any direct evidence of vacuum Rabi splitting.

Comment on 'Design and circuit simulation of nanoscale vacuum channel transistors' by J. Xu, Y. Qin, Y. Shi, Y. Yang and X. Zhang, Nanoscale Adv. 2020, 2, 3582

These comments aim to correct some apparent weaknesses in the theory of field electron emission given in a recent paper about nanoscale vacuum channel transistors, and to improve the presentation of this theory. In particular, it is argued that a "simplified" formula stated in the paper should not be used, because this formula is known to under-predict emission current densities by a large factor (typically around 300 for an emitting surface with local work function 4.5 eV). Thus, the "simplified" formula may significantly under-predict the practical performance of a nanoscale vacuum channel t…

Comment on "Quantum Friction - Fact or Fiction?"

If quantum friction existed [J.B. Pendry, New J. Phys. 12, 033028 (2010)] an unlimited amount of useful energy could be extracted from the quantum vacuum and Lifshitz theory would fail. Both are unlikely to be true.

Casimir energy for spherically symmetric dispersive dielectric media

We consider the vacuum energy of the electromagnetic field in the background of spherically symmetric dielectrics, subject to a cut-off frequency in the dispersion relations. The effect of this frequency dependent boundary condition between media is described in terms of the {\it incomplete} $ζ$-functions of the problem. The use of the Debye asymptotic expansion for Bessel functions allows to determine the dominant (volume, area, ...) terms in the Casimir energy. The application of these expressions to the case of a gas bubble immersed in water is discussed, and results consistent with Schwing…

Reply to: Reply to "On the heat transfer across a vacuum gap mediated by Casimir force"

Here we reply to the comment of Li et al. (arXiv:2009.09377) on the preprint (arXiv:2003.00760) of our publication (Z. Naturforsch. A 75, 803-807; DOI:10.1515/zna-2020-0204).

Penning trap and vacuum noise

A number of comments are provided on Rogers's model experiment to measure the circular Unruh vacuum noise by means of a hyperbolic Penning trap inside a microwave cavity. It is suggested that cylindrical Penning traps, being geometrically simpler, and controlled almost at the same level of accuracy as the hyperbolic trap, might be a better choice for such an experiment. Besides, the microwave modes of the trap itself, of known analytical structure, can be directly used in trying to obtain measurable results for such a tiny noise effect.

Comment on `Wedges, cones, cosmic strings and their vacuum energy'

A recent paper (2012 \emph{J. Phys.\ A} \textbf{45} 374018) is extended by investigating the behavior of the regularized quantum scalar stress tensor near the axes of cones and their covering manifold, the Dowker space. A cone is parametrized by its angle $θ_1$, where $θ_1=2π$ for flat space. We find that the tensor components have singularities of the type $r^γ$, but the generic leading $γ$ equals ${4π\over θ_1} - 2$, which is negative if and only if $θ_1>2π$, and is a positive integer if $θ_1={2π\over N}$. Thus the functions are analytic in those cases that can be solved by the method of ima…

Comment on the sign of the Casimir force

I show that reflection positivity implies that the force between any mirror pair of charge-conjugate probes of the quantum vacuum is attractive. This generalizes a recent theorem of Kenneth and Klich to interacting quantum fields, to arbitrary semiclassical bodies, and to quantized probes with non-overlapping wavefunctions. I also prove that the torques on charge-conjugate probes tend always to rotate them into a mirror-symmetric position.

Comment on "Universal Thermal Radiation Drag on Neutral Objects"

In a recent letter [Phys. Rev. Lett. 91, 220801 (2003)], V. Mkrtchian and co-workers calculated the radiation pressure force on a moving body, assuming the electromagnetic field to be at temperature $T,$ and the velocity to be much smaller than $c.$ They considered both dielectrics and conductors, and related the effect to Casimir dissipative forces. Here we claim that their approach may only apply in the Rayleigh-Ganz scattering regime, which corresponds to very small particles and/or electromagnetically rarefied media. Moreover, we argue that their interpretation in terms of the Casimir effe…

Vacuum Entanglement Harvesting in the Ising Model

The low-energy states of quantum many body systems, such as spin chains, are entangled. Using tensor network computations, we demonstrate a protocol that distills Bell pairs out of the ground state of the prototypical transverse-field Ising model. We explore the behavior of rate of entanglement distillation in various phases, and possible optimizations of the protocol. Finally, we comment on the protocol as we approach quantum criticality defining a continuum field theory.

Comments on Entanglement Negativity in Holographic Field Theories

We explore entanglement negativity, a measure of the distillable entanglement contained in a quantum state, in relativistic field theories in various dimensions. We first give a general overview of negativity and its properties and then explain a well known result relating (logarithmic) negativity of pure quantum states to the Renyi entropy (at index $1/2$), by exploiting the simple features of entanglement in thermal states. In particular, we show that the negativity of the thermofield double state is given by the free energy difference of the system at temperature $T$ and $2\,T$ respectively…

对J.Qin等人《超越N00N态的无条件且鲁棒的量子计量优势》，PRL 130, 070801 (2023)及J.A. H. Nielsen等人《超越N00N态的确定性量子相位估计》，PRL 130, 123603 (2023)的评论

Comment on J.Qin et al., Unconditional and Robust Quantum Metrological Advantage beyond N00N States, PRL 130, 070801 (2023) and J.A. H. Nielsen et.al., Deterministic Quantum Phase Estimation beyond N00N States. PRL 130, 123603 (2023)

本文评论指出，Qin等人和Nielsen等人基于压缩真空相位传感声称的无条件量子计量优势，其证据（每次试验或每个探测光子的QFI）未计入构建估计器的总资源，统计上不合理，故在一致资源核算下该优势不成立。

黑体总内能定义最新突破性进展

Breaking news on last achievements on the definition of the black-body total internal energy

本文回顾黑体总内能定义的历史，评述2018-2024年最新进展：纳入卡西米尔能量以避免真空灾变，并通过一维半经典模拟质疑经典物理在量子黑体中的作用。