耦合安德列夫自旋量子比特中的热量子关联：超导相位与自旋轨道相互作用的相互影响
Thermal Quantum Correlations in Coupled Andreev Spin Qubits: Interplay of Superconducting Phase and Spin-Orbit Interaction
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中文总结 AI 辅助
研究耦合超导自旋量子比特系统的热量子关联，用局部量子费舍尔信息等量化，分析多因素影响。发现量子关联随温度降、受隧穿和自旋轨道作用影响，超导相位有周期性，揭示其微观机制及相关因素对保护量子资源的作用。
中文摘要 AI 辅助
我们研究了在自旋轨道相互作用下，由有效安德列夫自旋量子比特哈密顿量描述的两个耦合超导自旋量子比特系统中的热量子关联。使用局部量子费舍尔信息（LQFI）和局部量子不确定性（LQU）作为量子关联量化器，分析了超导相位差、隧穿幅度、自旋轨道耦合和温度对系统非经典特性的影响。获得了热密度矩阵的解析表达式并用于评估这两个量。结果表明，量子关联随温度升高单调下降，而更强的隧穿和自旋轨道相互作用显著增强其鲁棒性。超导相位通过调制有效交换耦合引入明显的周期性行为，导致建设性和破坏性干涉机制，强烈影响关联。通过分析有效哈密顿量的能谱，证明量子关联的增强与基态和第一激发态之间能隙的增加密切相关，这抑制了热激发并稳定了相关基态。此外，在整个研究参数空间中，LQFI始终大于LQU，反映出其对量子涨落和局部参数估计的更高灵敏度。这些发现揭示了安德列夫自旋量子比特中热量子关联的微观机制，并突出了相位工程、自旋轨道相互作用和隧穿在混合超导量子器件中保护量子资源的重要作用。
英文摘要
We investigate thermal quantum correlations in a system of two coupled superconducting spin qubits described by an effective Andreev spin-qubit Hamiltonian in the presence of spin-orbit interaction. Using Local Quantum Fisher Information (LQFI) and Local Quantum Uncertainty (LQU) as quantum-correlation quantifiers, we analyze the effects of the superconducting phase difference, tunneling amplitude, spin-orbit coupling, and temperature on the nonclassical properties of the system. Analytical expressions for the thermal density matrix are obtained and employed to evaluate both quantities. Our results show that quantum correlations decrease monotonically with increasing temperature, while stronger tunneling and spin-orbit interaction significantly enhance their robustness. Moreover, the superconducting phase introduces a pronounced periodic behavior through the modulation of the effective exchange couplings, leading to constructive and destructive interference regimes that strongly influence the correlations. By analyzing the energy spectrum of the effective Hamiltonian, we demonstrate that the enhancement of quantum correlations is closely associated with an increased energy gap between the ground and first excited states, which suppresses thermal excitations and stabilizes the correlated ground state. Furthermore, LQFI is consistently larger than LQU throughout the investigated parameter space, reflecting its higher sensitivity to quantum fluctuations and local parameter estimation. These findings reveal the microscopic mechanism governing thermal quantum correlations in Andreev spin qubits and highlight the important roles of phase engineering, spin-orbit interaction, and tunneling in protecting quantum resources in hybrid superconducting quantum devices.
