arXiv subjects

Ziqian Tang

Publications and source records attributed to Ziqian Tang.

7 recordsLinked to original sources

arXiv2026

Aziz and Howl's Gravity-Induced Entanglement Channel is Essentially Classical Mechanics

Aziz and Howl argued that a classical gravitational field can generate quantum entanglement through a quantum-field-theoretic channel mediated by virtual matter propagation. However, their claimed channel is more naturally and accurately understood as semiclassical wavepacket motion in an external gravitational field, rather than as a distinctively quantum-field-theoretic entangling effect. Moreover, the result of their perturbative computation is incorrectly magnified: they selected a discontinuous wavefunction with infinite kinetic energy as the initial state and simultaneously treated it as stationary. Once a correct treatment using Gaussian wavepacket is adapted, the resulting effect will be negligibly small.

quant-ph↗

arXiv2025

Matter-Mediated Entanglement by Classical Gravity under Realistic Matter Dynamics

Gravity-induced entanglement (GIE) is widely regarded as key evidence of nonclassical gravity. Recent work, however, argues that a classical gravitational background can generate entanglement through virtual matter propagation between separated masses. Here we show that this mechanism is negligible once realistic matter dynamics is taken into account. For bound or condensed matter, the binding potential converts the claimed long-range matter-mediated interaction into an exponentially short-ranged one, with an attenuation length of only a few picometers for representative binding energies-well below atomic dimensions and therefore negligible under experimentally relevant distances. For unbound matter, the channel remains negligible before significant wave-packet overlap, while after overlap the packets no longer represent two spatially separated subsystems. Thus the proposed classical matter-mediated mechanism does not challenge the usual interpretation of GIE as evidence for nonclassical gravity once physical localization and finite-time matter dynamics are treated consistently.

quant-ph↗

arXiv2025

Quantum-classical gravity distinction in reservoir-engineered massive quantum system

Massive quantum systems have emerged as compelling tabletop interface-systems for testing the quantum nature of gravity. However, conventional schemes that focus on directly using gravity to induce entanglement suffer from overwhelming environmental decoherence: maintaining entanglement between two oscillators requires an impractically high mechanical quality factor. In this work, we put forward an alternative reservoir-engineered scheme, whose core function is to quantify how gravity modifies (rather than prepares) the steady-state entanglement. Compared to quantum gravity, classical gravity introduces additional dissipative channels, which in turn give rise to distinct entanglement characteristics and thus enable the discrimination between the two types of gravity. Notably, this entanglement difference can still be maintained even when the mechanical quality factor is far below the threshold required by conventional schemes. Moreover, it demonstrates significant robustness against non-gravitational couplings, specifically, those like Casimir and Coulomb forces that are inherent in experimental setups. Our scheme relaxes the experimental requirements for verifying quantum gravity, thereby paving a new path toward its near-term realization.

quant-ph↗

arXiv2025

Cavity Optomechanical Probe of Gravity Between Massive Mechanical Oscillators

Exploring gravitational interactions between objects with small masses has become increasingly timely. Concurrently, oscillators with masses ranging between milligrams and grams in cavity optomechanical systems sparked interest for probing gravity, and even investigating gravity within macroscopic quantum systems. Here we present a measurement scheme for probing gravity in a microwave optomechanical setup that incorporates periodic gravitational modulation between the test mass and the driven source mass at the milligram scale. Optomechanically induced transparency (OMIT) can be utilized to sense the gravitational interactions between test masses and source masses. Specifically, the relative variation in the height of the OMIT peak, expressed as $|1 + re^{iϕ}|^2 - 1$, where $r$ represents the ratio of the amplitude of the gravitational driving force to the radiation pressure force of the probe tone, and $ϕ$ denotes their phase difference, can reach up to 2.3\% under plausible experimental conditions. This work may facilitate cavity-optomechanical probing of gravitational coupling between milligram-scale mechanical oscillators, a mass regime where quantum and gravitational effects converge.

quant-ph↗

arXiv2025

Optimal Form Factors for Experimental Proposals on Gravity-Induced Entanglement

The interface between quantum mechanics and gravity remains an unresolved issue. Recent advances in precision measurement suggest that detecting gravity-induced entanglement in oscillator systems could provide key evidence for the quantum nature of gravity. However, thermal decoherence imposes strict constraints on system parameters. For entanglement to occur, mechanical frequency $ω_m$, dissipation rate $γ_m$, environmental temperature $T$, oscillator density $ρ$, and the form factor $Λ$-determined by the geometry and arrangement of oscillators-must satisfy a specific constraint. This constraint, intrinsic to the noise model, is considered universal and cannot be improved by quantum control. Given the difficulty in further optimizing $ω_m$, $γ_m$, $ρ$, and $T$, optimizing $Λ$ can relax the constraints on these parameters. In this work, we prove that the form factor has a supremum of $2π$, revealing a fundamental limit of the oscillator system. We propose designs that approach this supremum, nearly an order of magnitude higher than typical spherical oscillators. This optimization could ease experimental constraints and bring quantum gravity validation based on gravity-induced entanglement closer to realization.

quant-ph↗

arXiv2023

Test gravitational waves in sandwich wave background

The scattering of test fields by sandwich waves has been studied extensively. It has been found that for a variety of test fields, the energy of the scattered waves is amplified. In this paper, Scattering of test gravitational waves by sandwich waves are calculated by solving gravitational perturbations in the sandwich wave background. Dependence of their energy amplification with respect to the sandwich wave parameters and the incident wave parameters are examined. The results show that in some cases, the energy of the outgoing test gravitational wave is amplified as well.

gr-qc↗

arXiv2022

Causal Network Condensation

In this paper, we introduce a generalized topological quantum field theory based on the symmetric monoidal category which we call causal network condensation since it can be regarded as a generalization of spin network construction of Baez, Turaev-Viro model and causal set theory. In this paper we introduce some new concepts, including causal network category, causal network diagrams, and their gauge transformations. Based on these concepts, we introduce the nerve functor for the symmetric monoidal category. It can be regarded as a generalization of the nerve functor for simplicial category.

math.CT↗