arXiv subjects

Baocheng Zhang

Publications and source records attributed to Baocheng Zhang.

At least 37 records · Page 2Linked to original sources

arXiv2023

Enhanced anti-Unruh effect by simulated light-matter interactions

We investigate the transition of a two-level atom as the Unruh-Dewitt detector accelerated in the electromagnetic field in this paper. The enhancement of the transition probability is found for different field states under the conditions that the anti-Unruh effect appears. In particular, the enhancement is the most prominent when the field state takes the squeezed state. We also construct a new atomic trajectory to realize the effect of acceleration-induced transparency. Based on this, we show that the anti-Unruh effect still exists even at the specific atomic energy difference where acceleration-induced transparency happens.

hep-th↗

arXiv2023

Generation of entanglement between two laser pulses through gravitational interaction

We investigate entanglement generation between two pulses through the gravitational interaction in the framework of linearized quantum gravity. Different from the earlier suggestions that two massive particles can be entangled through the gravitational field produced by the particles themselves, we use the massless particles (a laser pulse) to generate the gravitational field. In our proposal, the propagating retarded effect of the gravitational perturbation generated by the laser pulses can be incorporated into the interaction, which is significant for supporting the assumption of local interaction. It is found that the locally linearized quantum gravitational interaction can indeed lead to the generation of entanglement between two pulses, and the result is dependent on the propagating time of the gravitational perturbation. We also provide a measurement suggestion using a Holometer-like interferometers structure to present this result of gravitation-induced entanglement, which could show that the gravitational mediator is quantum in future experiments.

gr-qc↗

arXiv2022

Entanglement and quantum teleportation under superposed gravitational fields

The influence of gravitational field on entanglement of bipartite states is investigated based on the recent idea of superposition states of gravitational field. Different from earlier considerations, we study the case where the gravitational field cannot be separated unitarily from the bipartite system in the final stage of the interaction. When the different gravitational field states are orthogonal, entanglement cannot be generated for an initial product state. If the different gravitational field states are non-orthogonal, entanglement can be generated and the amount of generated entanglement depends on an overlap parameter between different gravitational field states. The influence of gravitational field on the transfer of the state through quantum teleportation is also studied, which might lead to an observable effect since the quantum teleportation can be performed using macroscopic object.

quant-ph↗

arXiv2022

Constraints on the detection of topological charge of optical vortices using self-reference interferometry

Self-reference interferometry of optical vortices using a Michelson interferometer is investigated in this paper. It is found that the detection of topological charge (TC) for the optical vortices is constrained by some physical conditions. We present these conditions through the theoretical analyses, numerical simulation and experimental results. For different parameters, the maximal detectable TCs are different, which is helpful for the measurement of TC in the practical application. Within the range allowed by the constrained conditions, we also study the detection of TC using the interference pattern of two-way optical vortex by changing the inclined angle of one mirror of the Michelson interferometer.

physics.optics↗

arXiv2022

Effect of spacetime dimensions on quantum entanglement between two uniformly accelerated atoms

We investigate the entanglement dynamics for a quantum system composed of two uniformly accelerated Unruh-DeWitt detectors in different spacetime dimensions. It is found that the range of parameters in which entanglement can be generated is expanded but the amount of generated entanglement is decreased with the increasing spacetime dimension, by calculating the evolution of two-atom states using the method for open quantum systems. We study the entanglement evolution between two accelerated atoms for different initial two-atom states, and the influence of corresponding spacetime dimensions for every initial state is discussed. When the spacetime dimensions increase, the change of entanglement becomes slower with time. The influence of spacetime dimensions on the change of entanglement also expands to the case of the massive field. The time delay for entanglement generation is shown in different spacetime dimensions. In particular, entanglement decreases more quickly with the increasing spacetime dimensions compared with that in the case of the massless field. The recent found anti-Unruh effect is discussed, and a novel and interesting phenomenon is found that the Unruh effect in small spacetime dimensions can become the anti-Unruh effect in large spacetime dimensions with the same parameters.

gr-qc↗

arXiv2022

Observable effect of quantized cylindrical gravitational waves

We investigate the response of a model gravitational wave detector consisting of two particles to the quantized cylindrical gravitational waves and obtain a relation between the standard deviation of the distance between two particles and the distance from the source to the detector. It is found that the quantum effect carried by the cylindrical gravitational wave can be observed above Planck scale even though the source is as far as the cosmological horizon. The equation of motion for the change of the distance between two particles is obtained when the cylindrical gravitational waves pass. It is surprising that the dissipative term does not exist up to the first order approximation due to cylindrical symmetry of the gravitational wave.

gr-qc↗

arXiv2021

Change of quantum correlation for two simultaneously accelerated observers

The influence of Unruh effect on the quantum and classical correlation of a quantum entangled state is investigated, when one or two of the observers are accelerated. It is found that the quantum and classical correlation would approach to a finite value with the increase of the acceleration when only one observer is accelerated, but they would decrease to zero quickly when two observers are accelerated. The latter result implies that the gravitational field would break the correlation obviously when the acceleration is caused by the gravitational field. Thus, when the two observers stay in the gravitational field, the quantum or classical correlation would not easy to be preserved for a long time.

gr-qc↗

arXiv2021

Anti-Unruh effect in the thermal background

We study the influence of the thermal background on the existence of the anti-Unruh effect. For the massless scalar field, we present that the anti-Unruh effect can appear when the detector is accelerated in the thermal field, which is shown to be absent when accelerating in the Minkowski vacuum. For the massive scalar field, it is found that the anti-Unruh effect which exists in the case for accelerated detectors in the vacuum can disappear when the background temperature increases. We use the many-body entangled quantum state to study the situation of the massive scalar field. When the many-body state is accelerated, its entanglement is decreasing with the increase of the background temperature and the phenomenon of the sudden death for entanglement occurs. This provides a valuable indication that the anti-Unruh effect can exist below some specific background temperature, dependent on the actual experimental environment.

hep-th↗

arXiv2020

The Local Lorentz Symmetry Violation and Einstein Equivalence Principle

Lorentz symmetry violation (LV) was recently proposed to be testable with a new method, in which the effect of the violation is described as a certain local interaction [R. Shaniv, et al, PRL 120, 103202 (2018)]. We revisit this LV effect in the paper and show that it is not only local, but it also represents a classical violation according to the recent quantum formulation of the Einstein equivalence principle (EEP). Based on a harmonically trapped spin-1/2 atomic system, we apply the results of table-top experiments testing LV effect to estimate the corresponding violation parameter in the quantum formulation of EEP. We find that the violation parameter is indeed very small, as expected by the earlier theoretical estimation.

quant-ph↗

arXiv2020

Influence of acceleration on multi-body entangled quantum states

We study the influence of acceleration on the twin-Fock state which is a class of specific multibody entangled quantum state and was already realized experimentally with high precision and sensitivity. We show that the multi-body quantum entanglement can be increased with the acceleration, consistent with the "anti-Unruh effect" in reference to the counterintuitive cooling previously pointed out for an accelerated detector coupled to the vacuum. In particular, this kind of entanglement increase can lead to the improvement of the phase sensitivity, which provides a way to test the anti-Unruh effect in the future experiments.

quant-ph↗

arXiv2020

A protocol of potential advantage in the low frequency range to gravitational wave detection with space based optical atomic clocks

A recent proposal describes space based gravitational wave (GW) detection with optical lattice atomic clocks [Kolkowitz et. al., Phys. Rev. D 94, 124043 (2016)] [1]. Based on their setup, we propose a new measurement method for gravitational wave detection in low frequency with optical lattice atomic clocks. In our method, n successive Doppler signals are collected and the summation for all these signals is made to improve the sensitivity of the low-frequency GW detection. In particular, the improvement is adjustable by the number of Doppler signals, which is equivalent to that the length between two atomic clocks is increased. Thus, the same sensitivity can be reached but with shorter distance, even though the acceleration noises lead to failing to achieve the anticipated improvement below the inflection point of frequency which is determined by the quantum projection noise. Our result is timely for the ongoing development of space-born observatories aimed at studying physical and astrophysical effects associated with low-frequency GW.

gr-qc↗

arXiv2020

A divergent volume for black holes calls for no "firewall"

The presumption that Hawking radiations are thermally distributed can be considered to result from their entanglement with the internal degrees of freedom for a black hole. This leads to the "firewall" paradox if unitary evolution continues into Page's time when a black hole evaporates away half of its initial entropy. However, if the interior of a black hole houses sufficient degrees of freedom to maintain entanglement with the outside at all times, unitarity can be preserved during the complete radiation process and no firewall will be required. This paper proposes a scenario that rescinds firewall by introducing the concept of volume for a black hole. Based on the operational definition by Christodoulou and Rovelli [1], we show that the volume and its associated entropy for a collapsed black hole diverges if the final evaporation stage is treated using noncommutative space. This implicates the interior of a black hole possesses adequate space to store information for a black hole of any mass, like the inside of a "magician's bag".

gr-qc↗

arXiv2019

Enhancing test precision for local Lorentz symmetry violation with entanglement

A recent proposal for testing Lorentz symmetry violation (LSV) presents a formulation where the effect of violation is described as a local interaction [R. Shaniv, et al, Phys. Rev. Lett. 120, 103202 (2018)]. An entangled ion pair in a decoherence free subspace (DFS) is shown to double the signal to noise ratio (SNR) of one ion, while (even)-N/2 such DFS pairs in a collective entangled state improve SNR by N times, provided the state parity or the even/odd numbers of ions can be measured. It remains to find out, however, how such fiducial entangled states can be prepared at nonexponentially small success rates. This work suggests two types of many particle entangled states for testing LSV: the maximally entangled NOON state, which can achieve Heisenberg limited precision; and the balanced spin-1 Dicke state, which is readily available in deterministic fashion. We show that the latter also lives in a DFS and is immune to stray magnetic fields. It can achieve classical precision limit or the standard quantum limit (SQL) based on collective population measurement without individual atom resolution. Given the high interests in LSV and in entanglement assisted quantum metrology, our observation offers additional incentives for pursuing practical applications of many atom entangled states.

quant-ph↗

arXiv2018

Would quantum entanglement be increased by anti-Unruh effect?

We study the "anti-Unruh effect" for an entangled quantum state in reference to the counterintuitive cooling previously pointed out for an accelerated detector coupled to the vacuum. We show that quantum entanglement for an initially entangled (spacelike separated) bipartite state can be increased when either a detector attached to one particle is accelerated or both detectors attached to the two particles are in simultaneous accelerations. However, if the two particles (e.g., detectors for the bipartite system) are not initially entangled, entanglement cannot be created by the anti-Unruh effect. Thus, within certain parameter regime, this work shows that the anti-Unruh effect can be viewed as an amplification mechanism for quantum entanglement.

gr-qc↗

arXiv2017

On the entropy associated with the interior of a black hole

The investigation about the volume of a black hole is closely related to the quantum nature of the black hole. The entropy is a significant concept for this. A recent work by Majhi and Samanta [Phys. Lett. B 770 (2017) 314] after us presented a similar conclusion that the entropy associated with the volume is proportional to the surface area of the black hole, but the proportionality coefficient is different from our earlier result. In this paper, we clarify the difference and show that their calculation is unrelated to the interior of the black hole.

gr-qc↗

arXiv2017

Smarr formula for BTZ black holes in general three-dimensional gravity models

Recent studies have presented the interpretation of thermodynamic enthalpy for the mass of BTZ black holes and the corresponding Smarr formula. All these are made in the background of three-dimensional (3D) general relativity. In this paper, we extend such interpretation into general 3D gravity models. It is found that the direct extension is unfeasible and some extra conditions are required to preserve both the Smarr formula and the first law of black hole thermodynamics. Thus, BTZ black hole thermodynamics enforces some constraints for general 3D gravity models, and these constraints are consistent with all previous discussions.

gr-qc↗

arXiv2016

Infinite Volume of Noncommutative Black Hole Wrapped by Finite Surface

The volume of a black hole under noncommutative spacetime background is found to be infinite, in contradiction with the surface area of a black hole, or its Bekenstein-Hawking (BH) entropy, which is well-known to be finite. Our result rules out the possibility of interpreting the entropy of a black hole by counting the number of modes wrapped inside its surface if the final evaporation stage can be properly treated. It implies the statistical interpretation for the BH entropy can be independent of the volume, provided spacetime is noncommutative. The effect of radiation back reaction is found to be small and doesn't influence the above conclusion.

gr-qc↗

arXiv2016

Thermodynamics of acoustic black holes in two dimensions

It is well-known that the thermal Hawking-like radiation can be emitted from the acoustic horizon, but the thermodynamic-like understanding for acoustic black holes was rarely made. In this paper, we will show that the kinematic connection can lead to the dynamic connection at the horizon between the fluid and gravitational models in two dimension, which implies that there exists the thermodynamic-like description for acoustic black holes. Then, we discuss the first law of thermodynamics for the acoustic black hole via an intriguing connection between the gravitational-like dynamics of the acoustic horizon and thermodynamics. We obtain a universal form for the entropy of acoustic black holes, which has an interpretation similar to the entropic gravity. We also discuss the specific heat, and find that the derivative of the velocity of background fluid can be regarded as a novel acoustic analogue of the two-dimensional dilaton potential, which interprets why the two-dimensional fluid dynamics can be connected to the gravitational dynamics but difficult for four-dimensional case. In particular, when a constraint is added for the fluid, the analogue of a Schwarzschild black hole can be realized.

hep-th↗