近日，爱尔兰科克大学学院的Manuel Odelli及其研究小组与德国达姆施塔特工业大学的Vladimir M. Stojanovic合作并取得一项新进展。经过不懈努力，他们利用增强的绝热捷径方法解释玻色子约瑟夫森结中自旋压缩的扭转动力学。相关研究成果已于2024年8月12日在国际知名学术期刊《物理评论A》上发表。

利用绝热捷径（Shortcuts to Adiabaticity，STA）及其最新开发的增强版（eSTA），该研究团队在此证明，这种类型的动力学可用于在内部玻色子约瑟夫森结中快速且稳健地制备自旋压缩态，即两种不同内部（超精细）状态（单玻色子模式）的冷玻色子原子凝聚体，它们通过拉比旋转耦合在一起。

假设该系统的初始状态是在给定线性耦合强度（与时间相关）初始值下的基态，且非线性耦合强度保持不变，研究人员着手确定线性（拉比）耦合强度的时间依赖性，以便使用基于STA和eSTA的方法生成自旋压缩态。然后，研究人员通过评估相干自旋压缩和数目压缩参数以及目标自旋压缩态的保真度，来表征该系统修正后的扭转动力学。

通过这种方式，研究人员证明了eSTA方法允许在该系统中特别稳健地实现强自旋压缩态，其性能始终优于绝热和基于STA的对应方法，即使对于包含数百个粒子的系统也是如此。这一方法也可用于生成计量上有用的非高斯态。

据悉，自旋压缩的扭转动力学源于Lipkin-Meshkov-Glick型哈密顿量中的单轴扭转（在集体自旋算符中表现为非线性），和横向场转动（线性）项的相互作用，且这两项均具有恒定（与时间无关）的前置因子。

附：英文原文

Title: Twist-and-turn dynamics of spin squeezing in bosonic Josephson junctions: Enhanced shortcuts-to-adiabaticity approach

Author: Manuel Odelli, Andreas Ruschhaupt, Vladimir M. Stojanovic

Issue&Volume: 2024/08/12

Abstract: The twist-and-turn dynamics of spin squeezing results from the interplay of the one-axis-twisting (nonlinear in the collective-spin operators) and the transverse-field turning (linear) term in the underlying Lipkin-Meshkov-Glick-type Hamiltonian, both with constant (time-independent) prefactors. Using shortcuts to adiabaticity (STA) and the recently developed enhanced version thereof (eSTA), we demonstrate here that dynamics of this type can be utilized for a fast and robust preparation of spin-squeezed states in internal bosonic Josephson junctions, i.e., condensates of cold bosonic atoms in two different internal (hyperfine) states (single-boson modes) coupled through Rabi rotations. Assuming that the initial state of this system is its ground state for a given initial value of the (time-dependent) linear coupling strength and that the nonlinear coupling strength remains constant, we set out to determine the time dependence of the linear (Rabi) coupling strength that allows for the generation of spin-squeezed states using the STA- and eSTA-based approaches. We then characterize the modified twist-and-turn dynamics of this system by evaluating the coherent spin-squeezing and number-squeezing parameters, as well as the fidelity of the target spin-squeezed states. In this way, we show that the eSTA approach allows for a particularly robust realization of strongly spin-squeezed states in this system, consistently outperforming its adiabatic and STA-based counterparts, even for systems with several hundred particles. Our method could also be employed for the generation of metrologically-useful non-Gaussian states.

DOI: 10.1103/PhysRevA.110.022610

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.022610