arXiv subjects

Zehua Tian

Publications and source records attributed to Zehua Tian.

At least 19 recordsLinked to original sources

arXiv2026

Holographic superconductor with dark sector probed by entanglement entropy in higher dimensional AdS spacetime

We investigate the holographic entanglement entropy (HEE) with dark matter in a higher-dimensional AdS black hole spacetime including full back reaction, revealing its role as a diagnostic tool for critical phenomena in strongly coupled systems. By analyzing the HEE, we uncover distinct signatures of the metal/superconductor phase transition, demonstrating that the critical temperature is dynamically tuned by both the dark matter coupling strength and the chemical potential ratio between visible and dark matter sectors. Notably, near the criticality, the HEE exhibits a novel scaling behavior: it grows linearly with the dark matter coupling but displays a nonlinear, accelerated enhancement as the chemical potential ratio between the Maxwell and dark matter sectors increases.

hep-th↗

arXiv2026

Escape of quantum information across an analogue black hole horizon

The complete evaporation of black holes, as a natural endpoint of Hawking radiation, gives rise to the black hole information paradox, which fundamentally challenges the principles of unitarity and information conservation in quantum mechanics. Although the AdS/CFT correspondence indicates that information is preserved during black hole evaporation, the precise mechanism by which it is recovered from the Hawking radiation remains an open question. To explore a potential resolution, we investigate information transfer in a spin-chain model featuring an effective horizon realized via position-dependent couplings within an XY spin chain. We derive and demonstrate Page curve-like behavior, and analyze the transmission of quantum resources, such as entanglement and coherence, across the effective horizon. Our results show that quantum resources initially localized within an interior subsystem can be transferred to the exterior via particle radiation through the horizon. This study provides a novel perspective from quantum simulation on how information may escape from black holes, thereby contributing to the further understanding of the black hole information paradox.

gr-qc↗

arXiv2026

Probing Lorentz-invariance-violation with quantum coherence of Unruh-DeWitt detector

Testing Lorentz invariance violation (LIV) is notoriously difficult, as its characteristic energy scale, $M_\star$, in modified dispersion relations typically lies beyond current experimental reach. To enable a low-energy probe, we investigate the quantum coherence of an inertial Unruh-DeWitt (UDW) detector interacting with a massless scalar field with a Lorentz-violating dispersion relation $ω_{|\textbf{k}|}=|\textbf{k}|f(|\textbf{k}|/M_\star)$. Unlike the Lorentz-invariant case where quantum coherence is rapidity-independent, we find for the Lorentz-violating quantum field case the dynamics of detector's quantum coherence exhibits a strong dependence on its rapidity -- offering a potential low-energy signature of LIV. Applying this to the polymer-quantized scalar field theory inspired by loop quantum gravity, we show that the detector's quantum coherence exhibits a pronounced dependence on rapidity and undergoes a sharp transition near a critical rapidity $β_c \approx 1.3675$, a value within reach of existing facilities like the Relativistic Heavy Ion Collider. We also show how the detector's rapidity and its energy-level spacing enhance the response to the test of LIV. Our results establish quantum coherence as a sensitive and practical probe of LIV, providing a complementary avenue for testing quantum gravity-induced modifications to field theory.

hep-th↗

arXiv2026

Stronger Entanglement Dies Faster: Quantum Mpemba Effect in Dissipative Qubits

In classical thermodynamics, the Mpemba effect refers to the counterintuitive observation that hot water can freeze faster than cold water, manifesting as an anomalous crossing of dynamical trajectories. While analogues of this phenomenon have been explored in open quantum systems and spin-chain entanglement asymmetry, its connection to the finite-time decoupling of quantum correlations remains elusive. In this work, we report a distinct Mpemba effect for quantum entanglement in a dissipative quantum system associated with entanglement sudden death (ESD). By analyzing two qubits interacting with local amplitude damping reservoirs, we demonstrate that a more strongly entangled initial state can experience a faster collapse into a separable state than a more weakly entangled state. This anomalous decay stems from the competition between initial coherence and excited-state population, where the latter acts as a catalyst for ESD. We provide exact analytical derivations for the trajectory crossover and ESD time, and map the phase diagram to precisely identify the parameter regime where the effect occurs. Our results offer a new strategy for controlling the lifetime of quantum resources in dissipative environments.

quant-ph↗

arXiv2026

Scrambling-Enhanced Quantum Battery Charging in Black Hole Analogues

Black holes constitute nature's fastest quantum information scramblers, a phenomenon captured by gravitational analogue systems such as position-dependent XY spin chains. In these models, scrambling dynamics are governed exclusively by the hopping interactions profile, independent of system size. Utilizing such curved spacetime analogues as quantum batteries, we explore how the black hole scrambling affects charging via controlled quenches of preset scrambling parameters. Our analysis reveals that the intentionally engineered difference between post-quench and pre-quench scrambling parameters could significantly enhance both maximum stored energy $E_{\max}$ and peak charging power $P_{\max}$ in the quench charging protocol. Furthermore, the peaks of extractable work and stored energy coincide. This is because the system's evolution under a weak perturbation remains close to the ground state, resulting in a passive state energy nearly identical to the ground state energy. The optimal charging time $τ_*$ exhibits negligible dependence on the preset initial horizon parameter $x_{h0}$, while decreasing monotonically with increasing quench horizon parameter $x_{ht}$. This temporal compression confines high-power operation to regimes with strong post-quench scrambling $x_{ht} > x_{h0}$, demonstrating accelerated charging mediated by spacetime-mimicking scrambling dynamics.

quant-ph↗

arXiv2025

Harvesting entanglement from the Lorentz-violating quantum field vacuum in a dipolar Bose-Einstein condensate

We theoretically propose an experimentally viable scheme to explore the transfer of nonclassical correlations from a dipolar Bose-Einstein condensate (BEC) to a pair of impurities immersed in it. Operating at ultra-low temperature, density fluctuations of the dipolar BEC emulate a vacuum field with Lorentz-violating dispersion, while the two impurities function as Unruh-DeWitt detectors for the BEC quasiparticles. We study the harvesting of entanglement from the quantum vacuum of this analogue Lorentz-violating quantum field by spatially separated Unruh-DeWitt detectors. Our analysis reveals key parameter dependencies that optimize the harvesting of entanglement. In particular, unlike the Lorentz-invariant case, smoother detector switchings does not enhance the entanglement harvesting efficiency from the Lorentz-violating quantum field vacuum. Moreover, the strength of the Lorentz-invariant violation can shift the optimal energy structure of the detectors for harvesting entanglement from the Lorentz-violating quantum field vacuum-a clear deviation from the Lorentz-invariant scenario. As a fundamental quantum mechanical setup, our quantum fluid platform provides an experimentally realizable testbed for examining the entanglement harvesting protocol from an effective Lorentz-violating quantum field vacuum using a pair of impurity probers, which may also has potential implications for exploring the Lorentz-invariant violation in quantum field theory.

quant-ph↗

arXiv2025

Experimental Demonstration of the Timelike Unruh Effect with a Trapped-Ion System

The Unruh effect predicts that an accelerated observer perceives the Minkowski vacuum as a thermal bath, but its direct observation requires extreme accelerations beyond current experimental reach. Foundational theory [Olson & Ralph, Phys. Rev. Lett. 106, 110404 (2011)] shows that an equivalent thermal response, known as the timelike Unruh effect, can occur for detectors following specific timelike trajectories without acceleration, enabling laboratory tests with stationary yet time-dependent detectors. Here, we report a proof-of-principle demonstration of the timelike Unruh effect in a quantum system of trapped ion, where a two-level spin serves as the detector and is temporally coupled to the ambient field encoded in the ion's vibrational motion. Specifically, we study both excitation and emission dynamics of the detector moving along a spacetime trajectory in the future/past light cone, and demonstrate the thermal response of the detector to the Minkowski vacuum that resembles the Unruh effect. This work establishes a controllable tabletop platform for exploring relativistic quantum physics under accessible laboratory conditions.

quant-ph↗

arXiv2025

Open quantum battery in three-dimensional rotating black hole spacetime

We investigate the charging performance of a quantum battery coupled to a scalar field in the background of a three-dimensional rotating black hole. We show that for Dirichlet boundary conditions, the black hole rotation enhances the charging performance at finite times when the quantum battery's energy level spacing is smaller than the charging amplitude, whereas it degrades the charging performance in other parameter regimes. Notably, as the black hole approaches extremal rotation, charging performance undergoes significant amplification or suppression, depending on the parameter regime. This indicates that the performance of quantum battery can probe critical properties of black holes. Additionally, regarding the energy flow in quantum battery, it is further demonstrated that the energy extraction from vacuum fluctuations via dissipation, and rotation suppresses the quantum battery's capacity to extract this energy. Our findings not only advance the relativistic dissipation dynamics of quantum battery but also propose a novel method to detect black hole rotation and extremal-state transitions.

gr-qc↗

arXiv2025

Quantum Simulation of Oscillatory Unruh Effect with Superposed Trajectories

The Unruh effect predicts an astonishing phenomenon that an accelerated detector would detect counts despite being in a quantum field vacuum in the rest frame. Since the required detector acceleration for its direct observation is prohibitively large, recent analog studies on quantum simulation platforms help to reveal various properties of the Unruh effect and explore the not-yet-understood physics of quantum gravity. To further reveal the quantum aspect of the Unruh effect, analogous experimental exploration of the correlation between the detector and the field, and the consequences for coherent quantum trajectories of the detector without classical counterparts, are essential steps but are currently missing. Here, we utilize a laser-controlled trapped ion to experimentally simulate an oscillating detector coupled with a cavity field. We observe joint excitation of both the detector and the field in the detector's frame, coincide with the coordinated dynamics predicted by the Unruh effect. Particularly, we simulate the detector moving in single and superposed quantum trajectories, where the latter case shows coherent interference of excitation. Our demonstration reveals properties of quantum coherent superposition of accelerating trajectories associated with quantum gravity theories that have no classical counterparts, and may offer a new avenue to investigate phenomena in quantum field theory and quantum gravity. We also show how a generalization of the method and results in this work may be beneficial for direct observation of the Unruh effect.

quant-ph↗

arXiv2025

Dissipation suppression for an Unruh-DeWitt battery with a reflecting boundary

In the framework of open quantum systems, we study the dynamics of an accelerated quantum battery (QB), modeled as an Unruh-DeWitt detector interacting with a real massless scalar quantum field. The QB is driven by an external classical force acting as a charger. A major challenge in this setup is the environment-induced decoherence, which leads to energy dissipation of the QB. Accelerated motion exacerbates this dissipation, manifesting effects analogous to those experienced by a static QB in a thermal bath in free space, consistent with the Unruh effect. To overcome these challenges, we introduce a reflecting boundary in a space, which modifies the vacuum fluctuations of the field and leads to a position-dependent suppression of dissipation for the Unruh-DeWitt QB. Our analysis reveals that as the QB approaches the boundary, the relevant dissipation is significantly reduced. In particular, when the QB is placed extremely close to the boundary, the dissipation is nearly eliminated, as if the QB were a closed system. Furthermore, we identify a characteristic length scale associated with the acceleration of QB. When the distance between the QB and the boundary is much smaller than this scale, the boundary effectively suppresses dissipation, and this suppression effect becomes identical for both an accelerated QB and a static QB in a thermal bath. Conversely, when the distance is beyond this scale, the suppression effect weakens and manifests a significant difference between these two cases. Our findings demonstrate the potential of boundary-induced modifications in vacuum fluctuations to effectively suppress dissipation, offering valuable insights for optimizing QB performance. This work paves the way for the development of high-efficiency quantum energy storage systems in the relativistic framework.

hep-th↗

arXiv2025

Using nanokelvin quantum thermometry to detect timelike Unruh effect in a Bose-Einstein condensate

It is found that the Unruh effect can not only arise out of the entanglement between two sets of modes spanning the left and right Rindler wedges, but also between modes spanning the future and past light cones. Furthermore, an inertial Unruh-DeWitt detector along a spacetime trajectory in one of these cones may exhibit the same thermal response to the vacuum as that of an accelerated detector confined in the Rindler wedge. This feature thus could be an alternative candidate to verify the ``Unruh effect", termed as the timelike Unruh effect correspondingly. In this paper we propose to detect the timelike Unruh effect by using an impurity immersed in a Bose-Einstein condensate (BEC). The impurity acts as the detector which interacts with the density fluctuations in the condensate, working as an effective quantum field. Following the paradigm of the emerging field of quantum thermometry, we combine quantum parameter estimation theory with the theory of open quantum systems to realize a nondemolition Unruh temperature measurement in the nanokelvin (nK) regime. Our results demonstrate that the timelike Unruh effect can be probed using a stationary two-level impurity with time-dependent energy gap immersed in a BEC within current technologies.

hep-th↗

arXiv2025

Dissipative dynamics of an open quantum battery in the BTZ spacetime

We consider how charging performances of a quantum battery, modeled as a two-level system, are influenced by the presence of vacuum fluctuations of a quantum field satisfying the Dirichlet, transparent, and Neumann boundary conditions in the BTZ spacetime. The quantum battery is subjected to an external static driving which works as a charger. Meanwhile, the quantum field is assumed to be coupled to both longitudinal and transverse spin components of the quantum battery including decoherence and pure dephasing mechanisms. Charging and discharging dynamics of the quantum battery are derived by extending the previous open quantum system approach in the relativistic framework to this more general scenario including both the driving and multiple coupling. Analytic expressions for the time evolution of the energy stored are presented. We find that when the driving amplitude is stronger/weaker than the energy-level spacing of the quantum battery the pure dephasing dissipative coupling results in better/worse charging performances than the decoherence dissipative coupling case. We also find that higher Hawking temperature helps to improve the charging performance under certain conditions compared with the closed quantum buttery case, implying the feasibility of energy extraction from vacuum fluctuations in curved spacetime via dissipation in charging protocol. Different boundary conditions for quantum field may lead to different charging performance. Furthermore, we also address the charging stability by monitoring the energy behaviour after the charging protocol has been switched off. Our study presents a general framework to investigate relaxation effects in curved spacetime, and reveals how spacetime properties and field boundary condition affect the charging process, which in turn may shed light on the exploration of the spacetime properties and thermodynamics via the charging protocol.

hep-th↗

arXiv2024

Geometric phase assisted detection of Lorentz-invariance violation from modified dispersion at high energies

Many theories of quantum gravity propose Lorentz-violating dispersion relations of the form $ω_{|\mathbf{k}|}=|\mathbf{k}|f(|\mathbf{k}|/M_\star)$, which approximately recover to the Lorentz invariance, $ω_{|\mathbf{k}|}\approx|\mathbf{k}|$, at the energy scales much below $M_\star$. However, usually such a scale is assumed to be near the Planck scale, thus the feature of the Lorentz-violating theory is weak and its experimental test becomes extremely challenging. Since the geometric phase (GP) is of accumulative and sensitive nature to weak effects, here we explore the GP acquired by an inertial atomic detector that is coupled to a quantum field with this kind of Lorentz-violating dispersion. We show that for the Lorentz-violating field theory case the GP depends on the velocity of the detector, which is quite different from the Lorentz symmetry case where the GP is independent of the detector's velocity. In particular, we show that the GP may present a drastic low-energy Lorentz violation for any $f$ that dips below unity somewhere. We apply our analysis to detecting the polymer quantization motivated by loop quantum gravity, and show the detector acquires an experimentally detectable GP with the assist of detector's velocity that below current ion collider rapidities. Furthermore, the accumulative nature of GP might facilitate the relevant detection significantly.

hep-th↗

arXiv2024

Entanglement dynamics in $κ$-deformed spacetime

We treat two identical and mutually independent two-level atoms that are coupled to a quantum field as an open quantum system. The master equation that governs their evolution is derived by tracing over the degree of freedom of the field. With this, we compare the entanglement dynamics of the two atoms moving with different trajectories in $κ$-deformed and Minkowski spacetimes. Notably, when the environment-induced interatomic interaction does not exist, the entanglement dynamics of two static atoms in $κ$-deformed spacetime are reduced to that in Minkowski spacetime in the case that the spacetime deformation parameter $κ$ is sufficiently large as theoretically predicted. However, if the atoms undergo relativistic motion, regardless of whether inertial or non-inertial, their entanglement dynamics in $κ$-deformed spacetime behave differently from that in Minkowski spacetime even when $κ$ is large. We investigate various types of entanglement behavior, such as decay and generation, and discuss how different relativistic motions, such as uniform motion in a straight line and circular motion, amplify the differences in the entanglement dynamics between the $κ$-deformed and Minkowski spacetime cases. In addition, when the environment-induced interatomic interaction is considered, we find that it may also enhance the differences in the entanglement dynamics between these two spacetimes. Thus, in principle, one can tell whether she/he is in $κ$-deformed or Minkowski spacetime by checking the entanglement behavior between two atoms in certain circumstances.

hep-th↗

arXiv2023

Direct Characteristic-Function Tomography of the Quantum States of Quantum Fields

Herein, we propose a novel strategy for implementing a direct readout of the symmetric characteristic function of the quantum states of quantum fields without the involvement of idealized measurements, an aspect that has always been deemed ill-defined in quantum field theory. This proposed scheme relies on the quantum control and measurements of an auxiliary qubit locally coupled to the quantum fields. By mapping the expectation values of both the real and imaginary parts of the field displacement operator to the qubit states, the qubit's readout provides complete information regarding the symmetric characteristic function. We characterize our technique by applying it to the Kubo-Martin-Schwinger (thermal) and squeezed states of a quantum scalar field. In addition, we have discussed general applications of this approach to analogue-gravity systems, such as Bose-Einstein condensates, within the scope of state-of-the-art experimental capabilities. This proposed strategy may serve as an essential in understanding and optimizing the control of quantum fields for relativistic quantum information applications, particularly in exploring the interplay between gravity and quantum, for example, the relation to locality, causality, and information.

quant-ph↗

arXiv2022

Probing Lorentz-Invariance-Violation Induced Nonthermal Unruh Effect in Quasi-Two-Dimensional Dipolar Condensates

The Unruh effect states an accelerated particle detector registers a thermal response when moving through the Minkowski vacuum, and its thermal feature is believed to be inseparable from Lorentz symmetry: Without the latter, the former disappears. Here we propose to observe analogue circular Unruh effect using an impurity atom in a quasi-two-dimensional Bose-Einstein condensate (BEC) with dominant dipole-dipole interactions between atoms or molecules in the ultracold gas. Quantum fluctuations in the condensate possess a Bogoliubov spectrum $ω_{\mathbf k}=c_0|{\mathbf k}|f(\hbar\,c_0|{\mathbf k}|/M_\ast)$, working as an analogue Lorentz-violating quantum field with the Lorentz-breaking scale $M_\ast$, and the impurity acts as an effective Unruh-DeWitt detector thereof. When the detector travels close to the sound speed, observation of the Unruh effect in our quantum fluid platform becomes experimentally feasible. In particular, the deviation of the Bogoliubov spectrum from the Lorentz-invariant case is highly engineerable through the relative strength of the dipolar and contact interactions, and thus a viable laboratory tool is furnished to experimentally investigate whether the thermal characteristic of Unruh effect is robust to the breaking of Lorentz symmetry.

quant-ph↗

arXiv2022

Probing cosmic string spacetime through parameter estimation

Quantum metrology studies the ultimate precision limit of physical quantities by using quantum strategy. In this paper we apply the quantum metrology technologies to the relativistic framework for estimating the deficit angle parameter of cosmic string spacetime. We use a two-level atom coupled to electromagnetic fields as the probe and derive its dynamical evolution by treating it as an open quantum system. We estimate the deficit angle parameter by calculating its quantum Fisher information(QFI). It is found that the quantum Fisher information depends on the deficit angle, evolution time, detector initial state, polarization direction, and its position. We then identify the optimal estimation strategies, i.e., maximize the quantum Fisher information via all the associated parameters, and therefore optimize the precision of estimation. Our results show that for different polarization cases the QFIs have different behaviors and different orders of magnitude, which may shed light on the exploration of cosmic string spacetime.

quant-ph↗

arXiv2022

Gravity enhanced quantum spatial target detection

Quantum illumination can utilize entangled light to detect the low-reflectivity target that is hidden in a bright thermal background. This technique is applied to the detection of an object in the curved spacetime of the Earth, in order to explore how the curvature of spacetime affects quantum illumination. It is found that the spatial quantum illumination with entangled state transmitter outperforms that with coherent-state transmitter in the near-Earth curved spacetime. Moreover, either the quantum illumination system or the coherent-state system is employed, and gravity can enhance the spacetime target detection by reducing the thermal signal at the receiver. Besides, our model in principle can be applied to microwave quantum illumination and thus provides, to some degree, a theoretical foundation for the upcoming spatial quantum radar technologies.

gr-qc↗