arXiv subjects

Lin Xin

Publications and source records attributed to Lin Xin.

7 recordsLinked to original sources

arXiv2025

Optically accessible high-finesse millimeter-wave resonator for cavity quantum electrodynamics with atom arrays

Cavity quantum electrodynamics (QED) is a powerful tool in quantum science, enabling preparation of non-classical states of light and scalable entanglement of many atoms coupled to a single field mode. While the most coherent atom-photon interactions have been achieved using superconducting millimeter-wave cavities coupled to Rydberg atoms, these platforms so far lack the optical access required for trapping and addressing individual atomic qubits. We present a millimeter-wave Fabry-P\'erot cavity with finesse $5.8(1) \times 10^7$ at a temperature of 1 K providing generous transverse optical access (numerical aperture 0.56). Conflicting goals of strong atom-photon coupling and optical access motivate a near-confocal geometry. Close to confocality, however, post-paraxial corrections to the cavity spectrum introduce unexpected degeneracies between transverse modes, leading to excess cavity loss. Modeling these corrections allows for tuning the cavity geometry to evade this loss, producing a high finesse that will enable cavity QED experiments with trapped atoms deep in the strong coupling regime.

quant-ph↗

arXiv2022

Squeezed Ground States in a Spin-1 Bose-Einstein Condensate

We generate spin squeezed ground states in an atomic spin-1 Bose-Einstein condensate tuned nearthe quantum critical point between the polar and ferromagnetic quantum phases of the interactingspin ensemble. In contrast to typical non-equilibrium methods for preparing atomic squeezed statesby quenching through a quantum phase transition, squeezed ground states are time-stationary andremain squeezed for the lifetime of the condensate. A squeezed ground state with a metrologicalimprovement up to 6-8 dB and a constant squeezing angle maintained over 2 s is demonstrated.

cond-mat.quant-gas↗

arXiv2021

Fast generation of time-stationary spin-1 squeezed states by non-adiabatic control

A protocol for the creation of time-stationary squeezed states in a spin-1 Bose condensate is proposed. The method consists of a pair of controlled quenches of an external magnetic field, which allows tuning of the system Hamiltonian in the vicinity of a phase transition. The quantum fluctuations of the system are well described by quantum harmonic oscillator dynamics in the limit of large system size, and the method can be applied to a spin-1 gas prepared in the low or high energy polar states.

cond-mat.quant-gas↗

arXiv2020

Generator Versus Segmentor: Pseudo-healthy Synthesis

This paper investigates the problem of pseudo-healthy synthesis that is defined as synthesizing a subject-specific pathology-free image from a pathological one. Recent approaches based on Generative Adversarial Network (GAN) have been developed for this task. However, these methods will inevitably fall into the trade-off between preserving the subject-specific identity and generating healthy-like appearances. To overcome this challenge, we propose a novel adversarial training regime, Generator versus Segmentor (GVS), to alleviate this trade-off by a divide-and-conquer strategy. We further consider the deteriorating generalization performance of the segmentor throughout the training and develop a pixel-wise weighted loss by muting the well-transformed pixels to promote it. Moreover, we propose a new metric to measure how healthy the synthetic images look. The qualitative and quantitative experiments on the public dataset BraTS demonstrate that the proposed method outperforms the existing methods. Besides, we also certify the effectiveness of our method on datasets LiTS. Our implementation and pre-trained networks are publicly available at https://github.com/Au3C2/Generator-Versus-Segmentor.

cs.CV↗

arXiv2018

Correlation and Entanglement dynamics for two atoms distributed in two isolated thermal cavities

In this paper, correlation dynamics for two two-level atoms distributed in two isolated thermal cavities are studied, where the atomic state is initially prepared in a maximum entangled zero-and-two-excitation superposition state. We use two nonclasscal measures including geometric quantum discord via Schatten one norm and concurrence to analyze correlation dynamics for the two atoms when the two cavities have the same or different mean photon numbers. We find though correlation dynamics for these two measures have different features, they have the same characteristics in some particular time when the nonclassical correlation is robust against thermal photon numbers. This result may be important in quantum information processing and quantum computation.

quant-ph↗

arXiv2018

Spin-1 Bosons in the Presence of Spin-orbit Coupling

In this paper, I'm going to talk about the theoretical and experimental progress in studying spin-orbit coupled spin-1 bosons. Realization of spin-orbit coupled quantum gases opens a new avenue in cold atom physics. In particular, the interplay between spin-orbit coupling and inter-atomic interaction leads to many intriguing phenomena. Moreover, the non-zero momentum of ground states can be controlled by external fields, which allows for good quantum control.

cond-mat.quant-gas↗

arXiv2018

Exploring Non-Abelian Geometric Phases in Spin-1 Ultracold Atoms

Non-Abelian and non-adiabatic variants of Berry's geometric phase have been pivotal in the recent advances in fault tolerant quantum computation gates, while Berry's phase itself is at the heart of the study of topological phases of matter. The geometrical and topological properties of the phase space of spin$-1$ quantum states is richer than that of spin$-1/2$ quantum states and is relatively unexplored. For instance, the spin vector of a spin-1 system, unlike that of a spin$-1/2$ system, can lie anywhere on or inside the Bloch sphere representing the phase space. Recently, a generalization of Berry's phase that encapsulates the topology of spin-1 quantum states has been formulated in J. Math. Phys., 59(6), 062105. This geometric phase includes loops that go inside the Bloch sphere and is carried by the tensor of spin fluctuations, unlike Berry's phase which is carried by the global phase of the quantum state. Furthermore, due to a mathematical singularity at the center of the Bloch sphere, the class of loops that pass through the center are called singular loops and are significant because their geometric phase is non-Abelian. In contrast with Berry's phase for spin$-1/2$ systems, whose properties come from the topology of a sphere, the properties of singular loop geometric phases come from the topology of the real projective plane $\mathbb{RP}^2$, which is more non-trivial. Here we use coherent control of ultracold $^{87}$Rb atoms in an optical trap to experimentally explore this geometric phase for singular loops in a spin-1 quantum system.

cond-mat.quant-gas↗