arXiv subjects

Xing Heng

Publications and source records attributed to Xing Heng.

5 recordsLinked to original sources

arXiv2026

Entanglement Drives Common Noise into the Strong-Coupling Regime

Under Gaussian collective dephasing parallel to the signal, the superdecoherence of an $N$-atom Greenberger--Horne--Zeilinger (GHZ) state cancels its gain in Fisher information, so GHZ frequency sensitivity is limited to an atom-number-independent floor. We demonstrate that this floor is a property of Gaussian diffusion: a single common phase kick can at most randomize the phase of an $N$-atom coherence, so discrete events at rate $Γ$ cannot dephase any coherence order faster than $2Γ$. At the same single-atom coherence time, finite-rate Poisson kicks with an absolutely continuous amplitude law therefore saturate the order-$N$ decay rate and restore Heisenberg scaling. We prove that Gaussian diffusion is the worst case for GHZ and Dicke-cat probes under this calibration, that only the Brownian component of Lévy phase noise sets the asymptotic floor, and that the $1/N$ exponent is optimal for parallel Ramsey protocols. These results identify the counting statistics of the common noise, rather than its spectrum, as the property that bounds superdecoherence.

quant-ph↗

arXiv2025

Search for a parity-violating long-range spin-dependent interaction

High-sensitivity quantum sensors are a promising tool for experimental searches for beyond-Standard-Model interactions. Here, we demonstrate an atomic comagnetometer operating under a resonantly-coupled hybrid spin-resonance (HSR) regime to probe P-odd, T-even interactions. The HSR regime enables robust nuclear-electron spin coupling, enhancing measurement bandwidth and stability without compromising the high sensitivity of spin-exchange relaxation-free magnetometers. To minimize vibration noise from velocity-modulated sources, we implement a multistage vibration isolation system, achieving a vibration noise reduction exceeding 700-fold. We establish new constraints on vector-boson-mediated parity-violating interactions, improving experimental sensitivity by three orders of magnitude compared to previous limits. The new constraints complement existing astrophysical and laboratory studies of potential extensions to the Standard Model.

quant-ph↗

arXiv2025

Dark Matter Search with a Resonantly-Coupled Hybrid Spin System

Recent advances in tabletop quantum sensor technology have enabled searches for nongravitational interactions of dark matter (DM). Traditional axion DM experiments rely on sharp resonance, resulting in extensive scanning time to cover a wide mass range. In this work, we present a broadband approach in an alkali-${}^{21}$Ne spin system. We identify two distinct hybrid spin-coupled regimes: a self-compensation (SC) regime at low frequencies and a hybrid spin resonance (HSR) regime at higher frequencies. By utilizing these two distinct regimes, we significantly enhance the bandwidth of ${}^{21}$Ne nuclear spin compared to conventional nuclear magnetic resonance, while maintaining competitive sensitivity. We present a comprehensive broadband search for axion-like dark matter, covering 5 orders of magnitude of Compton frequencies range within $[10^{-2}, \, 10^3]$ Hz. We set new constraints on the axion dark matter interactions with neutrons and protons, accounting for the effects of DM stochasticity. For the axion-neutron coupling, our results reach a low value of $|g_{ann}|\le 3\times 10^{-10}$ in the frequency range $[2\times 10^{-2}, \, 4]$ Hz surpassing astrophysical limits and providing the strongest laboratory constraints in the $[10, \, 100]$ Hz range. For the axion-proton coupling, we offer the best terrestrial constraints for the frequency ranges $[2\times 10^{-2}, \, 5]$Hz and $[16, \, 7\times 10^{2}]$ Hz.

hep-ph↗

arXiv2025

New Constraints on Axion Mediated Dipole-Dipole Interactions

The search for axions sits at the intersection of solving critical problems in fundamental physics, including the strong CP problem in QCD, uncovering the nature of dark matter, and understanding the origin of the universe's matter-antimatter asymmetry. The measurement of axion-mediated spin-dependent interactions offers a powerful approach for axion detection. However, it has long been restricted to regions outside the 'axion window' due to a significant trade-off: the need to effectively suppress the magnetic leakage from highly polarized spin sources while simultaneously detecting sub-femtotesla level exotic physics signals at sub-decimeter-scale distances. In this work, we report new experimental results on axion-mediated exotic spin-spin interactions using an iron-shielded SmCo$_5$ spin source in combination with a specially designed self-compensation comagnetometer. Employing a composite shielding structure, we achieved a suppression of the magnetic field by up to $10^{11}$. This enabled us to establish new constraints on the coupling between electrons and neutrons, surpassing previous experimental limits by more than 10000 times within the axion window. Furthermore, we also set strongest constraints on the coupling between electrons and protons. The proposed method holds substantial potential not only for advancing the search for new physics beyond the Standard Model but also for enabling transformative applications in biological and chemical research.

hep-ph↗

arXiv2024

Constraining Ultralight Dark Matter through an Accelerated Resonant Search

Experiments aimed at detecting ultralight dark matter typically rely on resonant effects, which are sensitive to the dark matter mass that matches the resonance frequency. In this study, we investigate the nucleon couplings of ultralight axion dark matter using a magnetometer operating in a nuclear magnetic resonance (NMR) mode. Our approach involves the use of a $^{21}$Ne spin-based sensor, which features the lowest nuclear magnetic moment among noble-gas spins. This configuration allows us to achieve an ultrahigh sensitivity of 0.73 fT/Hz$^{1/2}$ at around 5 Hz, corresponding to energy resolution of approximately 1.5$\times 10^{-23}\,\rm{eV/Hz^{1/2}}$. Our analysis reveals that under certain conditions it is beneficial to scan the frequency with steps significantly larger than the resonance width. The analytical results are in agreement with experimental data and the scan strategy is potentially applicable to other resonant searches. Further, our study establishes stringent constraints on axion-like particles (ALP) in the 4.5--15.5 Hz Compton-frequency range coupling to neutrons and protons, improving on prior work by several-fold. Within a band around 4.6--6.6 Hz and around 7.5 Hz, our laboratory findings surpass astrophysical limits derived from neutron-star cooling. Hence, we demonstrate an accelerated resonance search for ultralight dark matter, achieving an approximately 30-fold increase in scanning step while maintaining competitive sensitivity.

hep-ph↗