arXiv subjects

Guolong Li

Publications and source records attributed to Guolong Li.

5 recordsLinked to original sources

arXiv2025

Enhancing ground-state cooling of center-of-mass motions via quantum squeezing from magnon nonlinearity

Cooling massive oscillators to quantum ground state is an essential prerequisite for their precise control, quantum memory, and quantum ultrasensitive measurement, etc. In a cavity-magnomechanical system, the magnon-mechanical coupling, enhanced by microwave cavity driving, can be utilized to cool the center-of-mass motion of a levitated magnetic sphere. In this work, we report that the cooling performance can be further improved by exploiting quantum squeezing stemming from magnonic self-Kerr nonlinearity inherent to the ferrimagnetic yttrium-iron-garnet (YIG) sphere. By means of suitable pump driving, the Kerr nonlinearity is converted into quantum squeezing, yielding considerable enhancement of the center-of-mass cooling with properly chosen optimal parameters. Moreover, we demonstrate that this improvement mechanism for cooling the massive magnetic sphere still works even in the unresolved-sideband regime where the mechanical frequency is smaller than the magnon decay rate. Eventually, we quantify the powers of the driving pumps for practical implementation of our scheme in a typical system. Our findings may provide a novel way to quantum fundamental researches and technologies.

quant-ph↗

arXiv2024

Ultimate tradeoff relation of quantum precision limits in multiparameter linear measurement

Linear measurements are widely applied in sensing classical signals, e.g., gravitational wave (GW), and are developing toward joint measurement of multiple parameters. In this work, focusing on multiparameter linear measurements of classical monochromatic signals, we establish an inherent tradeoff relation that tightly constrains the quantum limits on estimation precision. The tradeoff relation is fundamental since it is rooted in Heisenberg's uncertainty principle, and fully characterizes the dependence between the attainable precision limits on the estimated parameters. Eventually, we identify a necessary condition under which an optimal measurement protocol saturates the tradeoff relation, and show that the measurement phase can be regulated to implement flexible allocation of precision weights. Our finding can offer valuable guidance for detuned GW sensors in ultra-sensitive searches for post-merger remnants.

quant-ph↗

arXiv2024

Be More Real: Travel Diary Generation Using LLM Agents and Individual Profiles

Human mobility is inextricably linked to social issues such as traffic congestion, energy consumption, and public health; however, privacy concerns restrict access to mobility data. Recently, research have utilized Large Language Models (LLMs) for human mobility generation, in which the challenge is how LLMs can understand individuals' mobility behavioral differences to generate realistic trajectories conforming to real world contexts. This study handles this problem by presenting an LLM agent-based framework (MobAgent) composing two phases: understanding-based mobility pattern extraction and reasoning-based trajectory generation, which enables generate more real travel diaries at urban scale, considering different individual profiles. MobAgent extracts reasons behind specific mobility trendiness and attribute influences to provide reliable patterns; infers the relationships between contextual factors and underlying motivations of mobility; and based on the patterns and the recursive reasoning process, MobAgent finally generates more authentic and personalized mobilities that reflect both individual differences and real-world constraints. We validate our framework with 0.2 million travel survey data, demonstrating its effectiveness in producing personalized and accurate travel diaries. This study highlights the capacity of LLMs to provide detailed and sophisticated understanding of human mobility through the real-world mobility data.

cs.CY↗

arXiv2018

Phase-space geometric Sagnac interferometer for rotation sensing

Quantum information processing with geometric features of quantum states may provide promising noise-resilient schemes for quantum metrology. In this work, we theoretically explore phase-space geometric Sagnac interferometers with trapped atomic clocks for rotation sensing, which could be intrinsically robust to certain decoherence noises and reach high precision. With the wave guide provided by sweeping ring-traps, we give criteria under which the well-known Sagnac phase is a pure or unconventional geometric phase with respect to the phase space. Furthermore, corresponding schemes for geometric Sagnac interferometers with designed sweeping angular velocity and interrogation time are presented, and the experimental feasibility is also discussed. Such geometric Sagnac interferometers are capable of saturating the ultimate precision limit given by the quantum Cramér-Rao bound.

quant-ph↗

arXiv2016

Effects of microscopic dynamics on Brownian coagulation

We consider two different models for colloidal particles. In the first model, we consider their free motion to be diffusion while in the second model we take it to be integrated Ornstein-Uhlenbeck process. In both models, we derived collision estimates for pairs of particles. In particular, we found that these estimates would be different to the Brownian case even when the particles' free motion is Brownian at macroscopic scales. As a consequence, the coagulation kernel and diffusivity in the coagulation-diffusion equations would also be affected accordingly. We then proved that there exists a unique solution to the coagulation-diffusion equations in these cases under physically reasonable assumptions.

math.PR↗