arXiv subjects

Baocheng Zhang

Publications and source records attributed to Baocheng Zhang.

At least 19 recordsLinked to original sources

arXiv2026

The influence of lunar tidal potential on clock frequencies at different positions on Earth

With the advancements in clock timing technology, increasingly smaller time differences can be distinguished. Therefore, it is critical to investigate the fractional frequency shift of clocks at different locations on Earth. In this paper, we study it systematically under the influence of a subtle lunar tidal potential based on a new method. Our calculations in the geocentric Fermi frame show that when two clocks are located at the same latitude, the longitude difference changes the fractional frequency shift between them. A similar phenomenon occurs when there is a difference in latitude between two clocks on the ground at the same longitude. Interestingly, when the Moon's longitude changes, the phase and amplitude of the lunar tidal fractional frequency shift between two clocks with the same longitude difference will change, while the change in the Moon's latitude only affects the amplitude of the fractional frequency shift of these two clocks. Our results provide useful information for the calibration and synchronization of clocks on Earth.

astro-ph.EP↗

arXiv2026

Radiation Entropy in asymptotically AdS Black Holes within f(Q) Gravity

We employ the island rule to investigate the radiation entropy of asymptotically AdS black holes in the framework of f(Q) gravity. Through an analysis based on the Euclidean action, we find that the area term of the generalized entropy must be modified, which in turn leads to a modification of the island rule itself. Using the corrected rule to compute the radiation entropy for the eternal asymptotically AdS black hole reveals that, the result diverges as the cutoff surface is moved outward, indicating the breakdown of the s-wave approximation. For a collapsing asymptotically AdS black hole, the radiation entropy is dominated by the area term, with a logarithmic correction proportional to the area, which is consistent with the predictions of quantum gravity theories. Furthermore, both the radiation entropy and the Page time are ultimately influenced by the choice of the f(Q) model, implying that information regarding the underlying gravitational model is encoded in the final radiation entropy.

hep-th↗

arXiv2025

Entanglement is protected by acceleration-induced transparency in thermal field

The acceleration-induced transparency (AIT) effect has been suggested recently to amply the transition probability of the two-level detctor and offers a potential avenue for the experimental detection of the Unruh effect. In this paper, we explore the influence of the AIT effect on quantum entanglement between two detectors accelerated in a thermal field background, since the thermal backgound field cannot be avoided completely in any experiments. Interestingly, we find that although the backgound thermal field generally degrade the entanglement between the detectors, the AIT effect can effectively protect it.

quant-ph↗

arXiv2025

Generation of frequency entanglement by rotating Doppler effect

We propose a method to generate the frequency entanglement, allowing a continuous generation of entangled two-photon states in a hybrid degree of freedom by post-manipulation. Our method is based on type-II spontaneous parametric down-conversion in a nonlinear crystal and the rotation Doppler effect by rotating the q-plates, without preset discrete frequency entanglement. This allows the arbitrary modification of frequency entangled photons in a wide frequency range at room temperature, offering enhanced flexibility for quantum information tasks and quantum metrology. We also analyze the entanglement state by a combined calculation for the joint spectrum and Hong-Ou-Mandel interference of the two photons, which can be used to reconstruct a restricted density matrix in the frequency space.

quant-ph↗

arXiv2025

Island rules for the noncommutative black hole

In the context of noncommutative black holes, we reconsider the island rule and reproduce the Page curve. Since the radiation entropy of the noncommutative black hole will eventually diverge in the absence of islands, it is crucial to include the contribution of islands in the radiation process to recover the Page curve. When cutoff surface is far from event horizon, we find that the existence of islands helps to improve the radiation entropy and avoid its divergence at the late stage, while the radiation entropy for the commutative black hole with islands is still divergent in this case. When cutoff surface is close to event horizon, the existence of islands can lead to the radiation process consistent with the Page curves for both the commutative and noncommutative black holes, but it is interesting to obtain a significantly delay Page time for the noncommutative case, allowing us to avoid considering the contribution of islands for a sufficiently long period of time.

hep-th↗

arXiv2025

Measurement of the inner horizon in the analog of rotating BTZ black holes by an improved photon fluid

We study how to include the inner horizon in the analog of rotating black holes using photon fluids. We find that a vortex beam carrying an improved phase can simulate the rotating BTZ black holes experimentally. In the experiment, we develop a new photon fluid model in a graphene/methanol thermal optical solution, and measure the variation of photon fluid velocity with the radial position using a Fourier plane light spot localization method, while also determining the variation of phonon velocity with the same radial position from the optical vortex intensity distribution. The result provides an extension for the application of optical vortex and a potential possibility for the future experimental exploration about the properties of BTZ black holes and even the anti-de Sitter space.

gr-qc↗

arXiv2025

Harvesting entanglement from the cylindrical gravitational wave spacetime

We investigate the entanglement harvesting protocol within the context of cylindrical gravitational waves given first by Einstein and Rosen, focusing on the interactions between non-relativistic quantum systems and linearized quantum gravity. We study how two spatially separated detectors can extract entanglement from the specific spacetime in the presence of gravitational waves, which provides a precise quantification of the entanglement that can be harvested using these detectors. In particular, we obtain the relation between harvested entanglement and the distance to wave sources that emits gravitational waves and analyze the detectability using quantum Fisher information. The enhanced detectability demonstrates the advantages of cylindrical symmetric gravitational waves.

gr-qc↗

arXiv2025

Quantum correlation and origin of Hawking radiation for mass-superposed BTZ black holes

We investigate the mass superposition of BTZ black holes using the velocity correlation function. Interestingly, the quantum signatures of BTZ black hole mass superposition can be revealed by the velocity correlation peaks. Additionally, different mass superpositions for the same mass ratio can be distinguished, a phenomenon not previously documented. We also find that the correlation function method can pinpoint the location where Hawking radiations are generated, even for masssuperposed BTZ black holes. This supports the concept of a quantum atmosphere as the origin locus of Hawking radiation, even in quantum-superposed spacetime.

hep-th↗

arXiv2025

The information loss problem and Hawking radiation as tunneling

In this paper, we review some methods that tried to solve the information loss problem. In particular, we revisit the solution based on Hawking radiation as tunneling, and provide a detailed statistical interpretation on the black hole entropy in terms of the quantum tunneling probability of Hawking radiation from the black hole. In addition, we show that black hole evaporation is governed by a time-dependent Schrodinger equation that sends pure states into pure states rather than into mixed states (Hawking had originally established that the final result would be mixed states). This is further confirmation of the fact that black hole evaporation is unitary.

gr-qc↗

arXiv2024

Influence of field mass and acceleration on entanglement generation

We explore the entanglement dynamics of two detectors undergoing uniform acceleration and circular motion within a massive scalar field, while also investigating the influence of the anti-Unruh effect on entanglement harvesting. Contrary to the conventional understanding of the weak anti-Unruh effect, where entanglement typically increases, we observe that the maximum entanglement between detectors does not exhibit a strict monotonic dependence on detector acceleration. Particularly at low accelerations, fluctuations in the entanglement maxima show a strong correlation with fluctuations in detector transition rates.We also find that the maximum entanglement of detectors tends to increase with smaller field mass. Novelly, our findings indicate the absence of a strong anti-Unruh effect in (3+1)-dimensional massive scalar fields. Instead, thermal effects arising from acceleration contribute to a decrease in the detector entanglement maximum.

hep-th↗

arXiv2024

Gravity-induced transparency

We investigate the transition amplitudes of the Unruh-DeWitt detector within the Schwarzschild spacetime background and discover gravity-induced transparency phenomena akin to the earlier acceleration-induced transparency. This is confirmed through calculations performed in both the Hartle-Hawking and Unruh states. The similarity between free-falling detectors in these states and accelerated detectors in electromagnetic fields is noteworthy, as it parallels the scenario in which acceleration-induced transparency phenomena occur.

hep-th↗

arXiv2024

Is equivalence principle valid for quantum gravitational field?

Entanglement can be generated through the gravitational interaction between two massive bodies that are initially in a product state. This shows that the gravitational field is quantum. When the third massive body is introduced and the gravitational interaction only between the third body with either one of the former two bodies is considered, we find that no entanglement is generated between the former two bodies up to the monopole approximation, even though the considered gravitational interaction is quantum. This resembles the behavior of two accelerating two-level atoms that is usually regarded as the Unruh-DeWitt detectors. By linking the acceleration to that generated by the gravitational field, we show that the equivalence principle is still valid even though the gravitational field is quantum.

gr-qc↗

arXiv2023

Noncommutative information is revealed from the static detector outside the black hole

We investigate the transition behavior of the two-level atom as the Unruh-DeWitt detector outside a noncommutative black hole. When the mass of the black hole is small enough, the difference between the commutative and noncommutative black hole can be distinguished. In particular, an evident fluctuation appearing at a far distance from the horizon by calculating the quantum Fisher information of the transition rate with regard to the local Hawking temperature provides a novel and interesting result about the information extraction of the noncommutativity for a small-mass black hole.

hep-th↗

arXiv2023

Reveal the lost entanglement for accelerated atoms in the high-dimensional spacetime

When atoms are accelerated in the vacuum, entanglement among atoms will degrade compared with the initial situation before the acceleration. In this paper, we propose a novel and interesting view that the lost entanglement can be recovered completely when the high-dimensional spacetime is exploited, in the case that the acceleration is not too large, since the entanglement loss rate caused by the large acceleration is faster than the recovery process. We also calculate the entanglement change caused by the anti-Unruh effect and found that the lost entanglement could just be recovered part by the anti-Unruh effect, and the anti-Unruh effect could only appear for a finite range of acceleration when interaction time scale is approximately shorter than the reciprocal of the energy gap in two dimensional spacetime. The limit case of zero acceleration is also investigated, which gives an analytical interpretation for the increase or recovery of entanglement.

hep-th↗

arXiv2023

Influence of gravitational waves on quantum multibody states

Based on the freely-falling Unruh-Dewitt model, we study the influence of gravitational waves on the quantum multibody states, i.e. the twin-Fock (TF) state and the mixture of Dicke states. The amount of entanglement of quantum many-body states decreases first and then increases with increasing frequency of gravitational waves. In particular, for some fixed frequencies of gravitational waves, entanglement will increase with the increasing amplitude of gravitational waves, which is different from the usual thought of gravity-induced decoherence and could provide a novel understanding for the quantum property of gravitational waves.

hep-th↗

arXiv2023

Vectorial Doppler complex spectrum and its application to the rotational detection

Vectorial polarized fields of light has been applied to detect the rotational velocity by the rotational Doppler effect, but the measurement was made for the rotation of a single-particle system. When the rotational surface is rough, the scattered vectorial Doppler signal spectrum is complex. In this paper, we make the complex spectrum analyses using orbital angular momentum modal expansion method. It is found that the highest peak in the Fourier form of the complex spectrum is obtained at the frequency shift 2lΩ related to the topological charge (l) of the incident vortex light and the rotational velocity (Ω) of the rough surface. Based on the complex spectrum analysis, we construct a method to measure the magnitude and direction of the rotational velocity simultaneously for a general object, which has the practical application in remote sensing and astronomy.

physics.optics↗

arXiv2023

An optical analogue for rotating BTZ black holes

We demonstrate an optical realization for the rotating BTZ black hole using the recent popular photon fluid model in an optical vortex but with a new proposed expression for the optical phase. We also give the numerical realization for the optical vortex to ensure that it can be generated experimentally. Different from the earlier suggestions for the analogue rotating black holes, our proposal includes an inner horizon in the analogue black hole structure. Such structure can keep for a long distance for the convenience of observing analogue Hawking or Penrose radiations.

gr-qc↗

arXiv2023

Shielding of Penrose superradiance in optical black holes

We investigate the effect of superradiance shielding for the analogue rotating black holes simulated by optical vortices by calculating the radial motion of massless particles in such spacetime background. We add the conditions $E 0$ to judge the classically forbidden region of superradiance. It is found that the superradiance forbidden region exists near the static limit inside the ergosphere,which will limit the classical Penrose process for the particles with some specific energies and angular momenta. Once these particles satisfying the superradiance conditions aremeasured at the outside of the ergosphere, this shows that the Penrose process can be quantum.

gr-qc↗