Entanglement Detection and Characterization of Topological States

我们从量子信息的角度研究了量子多体系统中的几种涌现现象。利用量子Fisher信息（QFI）从理论上研究了受扰复曲面码的拓扑相位。我们证明了量子猝灭后拓扑有序的热化和无序辅助稳定。我们研究了有限温度下的二维复曲面代码，并表明拓扑顺序不能生存。利用一个19量子比特的超导电路，制备了多量子比特纠缠态，并对其进行了表征。用10个量子比特，我们测量了以前从未测量过的非线性压缩参数。对于所有19个量子比特，我们观察到超过标准量子极限的9.89 dB的量子增益，这表明量子增强估计灵敏度的高水平纠缠。我们采用了一个一维12量子位SC电路来识别不同状态的强和弱热化机制。使用梯形SC电路，我们模拟了XX-阶梯和XX-链模型。我们在XX阶梯中发出热化和信息扰乱的信号，这在XX链中是不存在的。我们在IBM的量子计算平台上实现了确定性的单向C-not门和单向X旋转。我们使用多体纠缠来检测使用16 SC量子比特的动力学相变。我们通过控制NV中心的相邻核自旋展示了多个耗散通道的工程，并观察了QFI进出环境的流动。

We studied several emergent phenomena in quantum many-body systems from the perspective of quantum information. We theoretically studied topological phases in perturbed toric codes using quantum Fisher information (QFI). We showed thermalization and disorder-assisted stabilization of topological order after a quantum quench. We studied the 2D toric code at finite temperatures and showed that topological order cannot survive. Using a 19-qubit superconducting (SC) circuit, we generated and characterized multi-qubit entangled states. With 10 qubits, we measured the nonlinear squeezing parameter that had never been measured before. With all 19 qubits, we observed a metrological gain of 9.89 dB over the standard quantum limit, indicating a high level of entanglement for quantum-enhanced estimation sensitivity. We employed a 1D 12-qubit SC circuit to identify regimes of strong and weak thermalization with different states. Using a ladder-type SC circuit, we simulated both the XX-ladder and XX-chain models. We signaled thermalization and information scrambling in the XX ladder, which are absent in the XX chain. We realized a deterministic one-way C-not gate and one-way X rotations on IBM’s quantum-computing platform. We used multipartite entanglement to detect dynamical phase transitions using 16 SC qubits. We demonstrated the engineering of multiple dissipative channels by controlling adjacent nuclear spins of a NV center and observed the QFI’s flows to and from the environment.