arXiv subjects

Liantuan Xiao

Publications and source records attributed to Liantuan Xiao.

At least 19 recordsLinked to original sources

arXiv2026

Quantum Lock-In Detection via Successive Adiabatic Evolution

In recent years, quantum lock-in detection has emerged as a promising technique to accurately detect weak signals submerged in background noise. However, the signal-to-noise ratio of existing protocols is severely limited by spectral leakage resulting from control operations implemented in pulse form. Here, we propose a general protocol for realizing quantum lock-in detection by employing successive quantum adiabatic evolution. In our protocol, the signal modulation is achieved by adiabatically controlling the time evolution of the quantum probe, which enables the implementation of sinusoidal modulation functions. The realization of sinusoidal-wave modulation substantially mitigates the problem of spectral leakage and facilitates the extraction of the complete characteristics of the target signals. We present a practical implementation scheme of adiabatic quantum lock-in detection based on nitrogen-vacancy centers in diamond, and demonstrate that the proposed protocol possesses strong resilience against experimental imperfections. Our results establish adiabatic quantum lock-in detection as a robust and experimentally accessible approach to detection of weak alternating signals in noisy environments, thus promoting the advance of real-world quantum sensing technologies.

quant-ph↗

arXiv2026

Local pair correlations and network geometry govern collective oscillations in nonreciprocal Ising networks

Nonreciprocal many-body dynamics can develop a swap phase characterized by spontaneous global oscillations far from equilibrium. To determine how local nonreciprocal interactions predict global oscillations and how broadly this prediction applies, we compare mean-field theory, independent-node theory, and nearest-neighbor spin-coupling theory for a two-spin nonreciprocal Ising model on networks of fixed coordination number ($z=4$). Nearest-neighbor spin-coupling theory retains nine independent joint edge probabilities. Monte Carlo benchmarks show that it predicts the oscillation amplitude, angular momentum, and period on edge-swapped networks with a 2.1\% aggregate mean absolute relative error. We then extend the square lattice to degree-preserving edge-swapped networks and find sharply different behavior. With increasing system size, the oscillation amplitude and angular momentum decay strongly on the periodic square lattice but remain nearly size independent on edge-swapped networks. These results show that identical local parameters do not determine the macroscopic phase. The contrasting finite-size trends identify network geometry as a key determinant of collective oscillations at fixed local interaction parameters.

cond-mat.stat-mech↗

arXiv2026

Stochastic Liouville-transport theory of light-atom interaction noise in thermal atomic vapors

Atom-light interaction noise can limit thermal-vapor sensing. Existing theories often treat internal-state dynamics, finite-mode atomic motion, and stochastic renewal separately, obscuring their coupled contributions to measured noise. We develop a general stochastic Liouville-transport theory, tested against polarization-resolved resonant Cs D$_2$ spectra. Joint experiment-theory analysis identifies atom-light noise below approximately 100 kHz as transit-dominated. Ballistic motion through the finite Gaussian mode modulates both the coupling-weighted effective atom number and trajectory-dependent Rabi coupling, producing predominantly common-mode noise. Boundary renewal introduces atoms with independently sampled ground-state sublevels, generating differential population fluctuations with opposite effects on the circular channels. Under an applied longitudinal magnetic field, experiment and theory show the same qualitative nonmonotonic change in common-mode suppression, supporting Zeeman redistribution of the channel responses. The framework can analyze noise in other thermal-atom sensors, including Rydberg-atom electric-field measurements.

quant-ph↗

arXiv2026

High-frequency dual-channel lock-in detection via rapidly oscillating driving

Here we propose a general protocol for dual-channel lock-in detection of high-frequency ac signals. We find that the effect of a high-frequency target signal can be modulated through the application of rapidly oscillating driving fields. Based on this mechanism, we develop a quantum dual-channel lock-in detection protocol for high-frequency signals, which not only extends the accessible frequency range of quantum sensing but also enables the simultaneous estimation of the signal amplitude and initial phase. Furthermore, we present a feasible implementation scheme of the protocol based on nitrogen-vacancy centers in diamond. Numerical simulations demonstrate that the proposed protocol can effectively filter out background noise and significantly improve the signal-to-noise ratio. Our results provide a promising approach for realizing noise-resistant detection of weak signals in the high-frequency regime.

quant-ph↗

arXiv2026

Single-sideband-interference twin-field quantum key distribution without global phase locking

Twin-field quantum key distribution (TF QKD) can overcome the fundamental rate loss limit of repeaterless quantum links, but its practical deployment has long been hindered by the requirement of global phase locking between two independent lasers. By revisiting the fundamental principles of optical interference, this work reveals that interference in TF QKD inherently relies only on the instantaneous phase alignment of two independent optical pulses at the moment they temporally overlap, rather than on continuous global phase synchronization. Guided by this insight, we propose and demonstrate a single-sideband-interference TF-QKD protocol that eliminates global phase locking. Each user employs an IQ modulator to generate a weak single sideband as the quantum signal, while the intrinsically phase-correlated optical carrier propagates as a real-time phase reference. Carrier interference at the receiver enables real-time phase extraction and feedback compensation for the sidebands. Unlike prior no phase locking approaches requiring second- or microsecond-level coherence, in principle, our scheme reduces this requirement to nanoseconds. We achieve 98% interference visibility over 100.8 km fibre and secure key rates surpassing the PLOB bound in the high-loss regime, providing a simpler route towards practical long-distance quantum communication networks.

quant-ph↗

arXiv2026

High-sensitivity and high-resolution collaborative determination of birefringence coefficient using weak measurement

Precise nanofilm birefringence characterization is essential for high-sensitivity polarization response and strong anti-interference detection in photodetectors. We present a high-sensitivity and high-resolution birefringence coefficient determination system for nm-level membranes based on weak measurement, addressing the sensitivity-resolution trade-off. A tunable bandwidth light source is exploited to achieve simultaneous and complementary measurements of momentum (P-pointer) and intensity (I-pointer), enabling calibration-free operation across various bandwidths, and to realize high-precision phase difference monitoring of the measured membranes. This method maps the birefringence effect to a weak-value amplified signal of spectral shift and light intensity. The optimal resolution, achieved at a spectral width of 6 nm, is $1.12 \times 10^{-8}$ RIU, while the optimal sensitivity is achieved when the light source is a narrow-linewidth coherent laser, reaching 4710 mV/RIU. The linear range of the system covers a broad birefringence coefficient range for crystals, from $10^{-6}$ to 0.1. Furthermore, the auxiliary optical path eliminates substrate interference, achieving a detection limit of birefringence coefficient as low as $10^{-8}$ RIU. This approach, characterized by high precision, high sensitivity, and strong robustness, provides an effective solution for the detection of optical nano-thin membrane parameters.

physics.optics↗

arXiv2026

Time series learning in a many-body Rydberg system with emergent collective amplification

Interacting Rydberg atoms constitute a versatile platform for the realization of non-equilibrium states of matter. Close to phase transitions, they respond collectively to external perturbations, which can be harnessed for technological applications in the domain of quantum metrology and sensing. Owing to the controllable complexity and straightforward interpretability of Rydberg atoms, we can observe and tune the emergent collective amplification. Here, we investigate the application of an interacting Rydberg vapour for the purpose of time series prediction. The vapour is driven by a laser field whose Rabi frequency is modulated in order to input the time series. We find that close to a non-equilibrium phase transition, where collective effects are amplified, the capability of the system to learn the input becomes enhanced. This is reflected in an increase of the accuracy with which future values of the time series can be predicted. Using the Lorenz time series and temperature data as examples, our work demonstrates how emergent phenomena enhance the capability of noisy many-body systems for data processing and forecasting.

quant-ph↗

arXiv2026

Observation of interaction-induced fast Thouless pumping of solitons

Thouless pumping provides a paradigmatic platform for studying the effects of interactions on topological transport in periodically driven systems. However, most studies have been constrained by adiabatic conditions, which preclude exploration of interaction-driven novel topological states at high driving frequencies. Here, we experimentally investigate the interplay between interaction and modulation frequency in Thouless pumping realized in a periodically modulated lattice in momentum space of atomic Bose-Einstein condensate. We observe fast Thouless pumping of matterwave solitons at intermediate interactions, with no counterpart in the non- or weakly interacting regimes. Beyond the boundary of topological phase transition induced by interaction, nonadiabatic quantized pumping of solitons emerges at high modulation frequencies over a broad interaction range, in good agreement with theoretical calculations, while the solitons remain trapped in the low-frequency adiabatic pumping regime. Our work opens new avenues for accelerating topological transport in driven quantum systems and engineering fast topological devices.

cond-mat.quant-gas↗

arXiv2026

Quantum compressed sensing

How many measurements are fundamentally required to capture a signal. Shannon's information theory established the bedrock of this question in 1948, the Nyquist Shannon theorem set the first answer, and compressed sensing (CS) rewrote it in 2006 by reducing the required measurement number to M = O(Klog(N/K)) for a K sparse signal. Here, we propose quantum compressed sensing (QCS), a paradigm that reframes signal acquisition as a unitary quantum evolution. By encoding high dimensional signal information into a single quantum probe state, then introducing domain-alignment evolution,a physically realizable unitary transformation that maps the sparse basis directly onto the measurement basis. QCS executes the support-set search at the quantum level without consuming measurement trials. The logarithmic penalty vanishes, compressing the required measurement number from the classical bound to M =O(K) and reducing reconstruction from ill posed optimization to linear estimation. We experimentally validate QCS using frequency and time domain sparse signals, confirming that the measurement number scales linearly with sparsity and decouples entirely from the signal dimension. Our work provides a physical pathway toward ultimate information acquisition efficiency, with broad implications for sensing, imaging, and communication.

quant-ph↗

arXiv2026

Quantum Compressed Sensing Enables Image Classification with a Single Photon

Image classification is a core task of intelligent sensing, conventionally follows a sequential imaging then processing pipeline. However, redundant high-dimensional image reconstruction is inherently inefficient, especially in photon limited scenarios. Here we report a photon level image classification method using quantum compressed sensing, which reformulates the classification task as a sparse signal measurement problem directly oriented toward class labels. By exploiting the parallelism of photonic quantum superposition states, a single photon can be encoded the complete spatial information of a high-dimensional image. Through a diffractive deep neural network, we physically construct a dedicated measurement basis aligned with the class space, enabling signal-dependent adaptive compressive measurement. Ideally, our method can extract class information via a single quantum projective measurement, reducing the required number of measurements from the logarithmic scaling O(Klog(N/K)) of classical compressed sensing to the constant-order information-theoretic limit M = K = 1. Experimental results show that a classification accuracy of 69.0% can be achieved by using a single-photon detection event as the decision criterion, while it increases to 95.0% with four-photon detection events. This work demonstrates image classification at the energy efficiency limit and introduces a measurement as decision framework. It provides a foundation for intelligent sensing systems that operate under extreme photon budgets and harsh environments.

quant-ph↗

arXiv2026

Detecting Complex-Energy Braiding Topology in a Dissipative Atomic Simulator with Transformer-Based Geometric Tomography

Machine learning (ML) is shaping our exploration of topological matter, whose existence is inherently tied to the geometry of quantum states or energy spectra. In non-Hermitian systems, distinctive spectral geometry can lead to topological braiding of complex-energy bands, yet directly probing this topology-geometry interplay remains challenging. Here, we introduce a Transformer-based ML framework to capture this interplay and experimentally demonstrate it in a dissipative cold-atom simulator. Using a Bose-Einstein condensate, we engineer tunable dissipative two-level systems whose complex eigenenergies form braids. Owing to the density-dependent dissipation, the instantaneous energy braids exhibit topologically distinct structures at short and long times. The Transformer not only accurately predicts topological invariants for diverse energy braids but also, through its self-attention mechanism, autonomously highlights band crossings as the governing underlying geometric feature. Our work paves the way for ML-guided exploration of non-Hermitian topological phases in cold atoms and beyond.

cond-mat.quant-gas↗

arXiv2026

High-resolution wide-field magnetic imaging with sparse sampling using nitrogen-vacancy centers

Nitrogen-vacancy (NV) centers in diamond enable quantitative magnetic imaging, yet practical implementations must balance spatial resolution against acquisition time (and thus per-pixel sensitivity). Single-NV scanning magnetometry achieves genuine nanoscale resolution, nonetheless requires typically a slow pixel-by-pixel acquisition. Meanwhile, wide-field NV-ensemble microscopy provides parallel readout over a large field of view, however is jointly limited by the optical diffraction limit and the sensor-sample standoff. Here, we present a sparse-sampling strategy for reconstructing high-resolution wide-field images from only a small number of measurements. Using simulated NV-ensemble detection of ac magnetic fields, we show that a mean-adjusted Bayesian estimation (MABE) framework can reconstruct 10000-pixel images from only 25 sampling points, achieving SSIM values exceeding 0.999 for representative smooth field distributions, while optimized dynamical-decoupling pulse sequences yield an approximately twofold improvement in magnetic-field sensitivity. The method further clarifies how sampling patterns and sampling density affect reconstruction accuracy and suggests a route toward faster and more scalable magnetic-imaging architectures that may extend to point-scanning NV sensors and other magnetometry platforms, such as SQUIDs, Hall probes, and magnetic tunnel junctions.

quant-ph↗

arXiv2026

Self-Supervised Learning with Noisy Dataset for Rydberg Microwave Sensors Denoising

We report a self-supervised deep learning framework for Rydberg sensors that enables single-shot noise suppression matching the accuracy of multi-measurement averaging. The framework eliminates the need for clean reference signals (hardly required in quantum sensing) by training on two sets of noisy signals with identical statistical distributions. When evaluated on Rydberg sensing datasets, the framework outperforms wavelet transform and Kalman filtering, achieving a denoising effect equivalent to 10,000-set averaging while reducing computation time by three orders of magnitude. We further validate performance across diverse noise profiles and quantify the complexity-performance trade-off of U-Net and Transformer architectures, providing actionable guidance for optimizing deep learning-based denoising in Rydberg sensor systems.

quant-ph↗

arXiv2025

Reactive near-field subwavelength microwave imaging with a non-invasive Rydberg probe

Non-invasive microwave field imaging--accurately mapping field distributions without perturbing them--is essential in areas such as aerospace engineering, biomedical imaging and integrated-circuit diagnostics. Conventional metal probes, however, inevitably perturb reactive near fields: they act as strong scatterers that drive induced currents and secondary radiation, remap evanescent components and thereby degrade both accuracy and spatial resolution, particularly in the reactive near-field regime that is most relevant to these applications. Here we demonstrate, to our knowledge for the first time, reactive near-field subwavelength imaging of microwave fields using the quantum non-demolition properties of Rydberg atoms, realized with a compact, non-invasive single-ended fibre-integrated Rydberg probe engineered to minimize field disturbance. The probe achieves an imaging resolution of {\unboldmath$λ/56$}, and the measured field distributions agree with full-wave simulations with structural similarity approaching unity, confirming both its subwavelength spatial resolution and its genuinely non-invasive character compared with conventional metal-based probes. Because the atomic sensor is intrinsically isotropic, the same device can faithfully image multi-dimensional field structures without orientation-dependent calibration. Our results therefore establish a general, non-invasive route to high-accuracy, subwavelength reactive near-field microwave imaging, with particular promise for applications such as chip-defect detection and integrated-circuit diagnostics, where even small perturbations by the probe can mask the underlying physics of interest.

quant-ph↗

arXiv2025

Observation of gauge field induced non-Hermitian helical skin effects

Synthetic gauge fields and non-Hermitian skin effects are pivotal to topological phases and non-Hermitian physics, each recently attracting great interest across diverse research fields. Realizing skin effects typically require nonreciprocal couplings or on-site gain and loss. Here, we theoretically and experimentally report that, under gauge fields, reciprocal dissipative couplings can nontrivially give rise to an unprecedented nonreciprocal skin effect, hosting pseudospin degree of freedom and featuring helical transport, dubbed as the ``helical pseudospin skin effect". Before introducing the gauge fields, this model exhibits localized pseudospin edge modes and extended bulk modes, without skin effects. As the gauge field strength is applied from $0$ to $π$, we observe the emergence of two distinct pseudospin skin effects and their topological transitions: the hybrid-order and second-order helical pseudospin skin effects. Our findings not only highlight gauge field enriched non-Hermitian topology, but also brings pseudospin-momentum locking into skin effects.

cond-mat.mes-hall↗

arXiv2025

Engineering photonic dispersion relation and atomic dynamics in waveguide QED setup via long-range hoppings

Non-trivial dispersion relations engineered in photonic waveguide for the precise control of atomic dynamics has recently attracted considerable attention. Here, we study a system in which atoms are coupled to one-dimensional coupled-resonator waveguides with long-range hoppings. By carefully engineering the jth-order nearest neighbor (JNN) hoppings between resonators, we construct linear dispersion relations with the chiral characteristic. To quantify the degree of linearity, we analyze the propagation fidelities of Gaussian wave packets in these waveguides. Furthermore, we demonstrate that such coupled-resonator waveguides can serve as versatile platforms for enabling directional atomic radiation and absorption. Beyond linear dispersion relations, more general forms, including quadratic and cubic relations, can also be achieved through tailored JNN-hoppings. Our study thus provides a unified framework for simulating atom-environment couplings with arbitrary dispersion relations.

quant-ph↗

arXiv2025

Electric-field control of pure spin photocurrent in germanene

The electrical control of pure spin current remains a central challenge in spintronics, particularly in time-reversal symmetric systems composed of nonmagnetic elements, where spin and electric fields interact only indirectly. In this work, we develop a theoretical framework for electrically tuning pure spin photocurrent in two-dimensional materials with time-reversal symmetry via a gate electric field. Through theoretical analysis, we demonstrate that in systems with spin-orbit coupling and in-plane mirror symmetry, an out-of-plane electric field induces spin splitting and reversal in the band structure near the Fermi energy, enabling magnitude control and direction reversal of the pure spin photocurrent. To validate this mechanism, we perform first-principles calculations on germanene, an experimentally realized two-dimensional material. Beyond amplitude modulation, we reveal that reversing the direction of the applied electric field leads to a corresponding reversal of the pure spin photocurrent. Furthermore, we show that the pure spin photocurrent can be tuned by varying the photon energy and the incident angle of light, providing additional degrees of control over spin transport. These findings establish a robust strategy for electric-field-controlled pure spin transport in two-dimensional materials, offering new possibilities for the development of optospintronic devices.

cond-mat.mes-hall↗

arXiv2025

Noise-tolerant correlated coincidence imaging based on super-correlated light at 1550 nm

Single-photon-level imaging at 1550 nm is a key driver for significant advancements in the next-generation laser detection technology. This cutting-edge approach plays a vital role in space ranging, target recognition, and three-dimensional remote sensing. However, it has faced severe challenges such as insufficient noise-tolerant performance. Here, we introduced noise-tolerant correlated coincidence imaging (CCI) based on super-correlated light. The light source, generated through nonlinear interaction between a pulsed laser and a photonic crystal fiber, exhibits a broader power-law photon number probability distribution and extremely strong photon correlation (with second-order correlation function $g^{(2)}(0)$ up to 18,166). Our noise-tolerant CCI can resist random environmental noise up to 100,000 times stronger than the echo signal photons. Super-correlated light offers an exceptionally strong noise tolerance for single-photon-level imaging in extreme environments with intense noise, paving the way for the future development of extremely sensitive light detection.

physics.optics↗