自由费米子系统中的纠缠、子系统粒子数和拓扑

Boiling Quantum Vacuum: Thermal Subsystems from Ground-State Entanglement

In certain special circumstances, such as in the vicinity of a black hole or in a uniformly accelerating frame, vacuum fluctuations appear to give rise to a finite-temperature environment. This effect, currently without experimental confirmation, can be interpreted as a manifestation of quantum entanglement after tracing out vacuum modes in an unobserved region. In this work, we identify a class of experimentally accessible quantum systems where thermal density matrices emerge from vacuum entanglement. We show that reduced density matrices of lower-dimensional subsystems embedded in $D$-dimens…

Entanglement echo and dynamical entanglement transitions

We formulate dynamical phase transitions in subsystems embedded in larger quantum systems. Introducing the entanglement echo as an overlap of the initial and instantaneous entanglement ground states, we show its analytic structure after a quench provides natural definition of dynamical phase transitions in the subsystem. These transitions come in two varieties, the entanglement-type transitions and the bulk-type Loschmidt transitions. The entanglement-type transitions arise from periodic reorganization of quantum correlations between the subsystem and its environment, manifesting in instantane…

Quantum entanglement in a four-partite hybrid system containing three macroscopic subsystems

The combination of different quantum systems may allow the exploration of the distinctive features of each system for the investigation of fundamental phenomena as well as for quantum technologies. In this work we consider a setup consisting of an atomic ensemble enclosed within a laser-driven optomechanical cavity, having the moving mirror further (capacitively) coupled to a low frequency LC circuit. This constitutes a four-partite optoelectromechanical quantum system containing three macroscopic quantum subsystems of a different nature, viz, the atomic ensemble, the massive mirror and the LC…

Entanglement polarization for the topological quadrupole phase

We propose the entanglement dipole polarization to describe the topological quadrupole phase. The quadrupole moment can be regarded as a pair of the dipole moment, in which the total dipole moment is canceled. The entanglement polarization, we propose, is useful to detect such a constituent dipole polarization. We first introduce partitions of sites in the unit cell and divide the system into two subsystems. Then, introducing an entanglement Hamiltonian by tracing out one of the subsystems partly, we compute the dipole polarization of the occupied states associated with the entanglement Hamilt…

参量驱动的量子比特-光子混合系统：耗散诱导的量子纠缠和真空中的光子产生

Parametrically driven hybrid qubits-photon systems: dissipation-induced quantum entanglement and photon production from vacuum

考虑了参变驱动量子比特-腔系统在两个子系统之间耦合能量的周期性调制下的耗散演化，这将导致反旋过程的放大.我们揭示了这个混合系统的一个非常丰富的动力学行为。特别地，我们发现其中一个子系统中的能量耗散可以增强另一个子系统中的量子效应。例如，即使在稳态下，最佳腔衰减也有助于稳定量子位之间的纠缠和量子相关性，并补偿有限的量子位弛豫。相反，量子比特子系统中的能量耗散导致了强调制下真空光子产生的增强，但同时破坏了量子比特之间的量子并发和量子互信息。我们的结果为量子信息处理中的非定常腔量子电动力学提供了更深层次的理解，对耗散量子态工程具有重要意义。