电路量子电动力学系统中自旋量子比特相干调控的理论研究

Circuit quantum electrodynamics (CQED) system provides a substantial platform for large-scale integration, coherent manipulation and non-demolition measurement of solid-state qubits. Electron spins are promising candidates for encoding qubit states due to their long decoherence time. It has attracted much attention to study how to integrate spin qubits into CQED systems, and optimally combine their merits to produce maximal effects. Our previous results have shown that by suitably choosing the coupling scheme, extra charge noise induced by transmission line resonator can be effectively suppressed, leaving the nuclear spin noise to be the leading decoherence source. This project focuses on the coherent manipulation of spin qubits in CQED systems. Based on the interaction among spin qubits, microwave photons and nuclear spin field, we will explore the dynamics of the combined system, especially the spin decoherence process, and propose efficient methods towards extending decoherence time. We will study the entanglement between two remote spin qubits, and its stability under nuclear spin environment. Considering the peculiar features of CQED we will conceive possible mechanism for a joint readout of qubit-qubit correlations.

电路量子电动力学系统为实现量子比特的大规模集成化、量子态的相干操纵以及非破坏性测量等提供了重要途径。具有较长退相干时间的电子自旋被视为量子比特的良好载体。如何将自旋量子比特集成于电路量子电动力学系统，并有效发挥两者各自的优势，已成为固态量子计算领域的热点。我们的前期工作表明，通过恰当选择耦合方式，由电路腔带来的电荷噪声可以得到有效抑制。此时，核自旋噪声成为影响系统相干性的主要因素。本项目拟针对电路量子电动力学系统的特点，研究核自旋环境下自旋量子比特的相干调控。通过考察自旋量子比特与微波光子及核自旋环境三者之间的相互作用，来研究系统动力学演化，以期探寻延长退相干时间的新策略；分析微波光子辅助下自旋纠缠态的制备，探讨核自旋噪声对自旋纠缠态稳定性的影响机制；拟制定利用辐射场探测自旋纠缠态的新方案。

具有长退相干时间的电子自旋一直被视为量子比特的良好载体，如何将自旋量子比特集成于电路量子电动力学系统，并发挥两者各自的优势，已成为固态量子计算领域的热点。本项目着重研究了基于量子点的量子电动力学系统，首次提出了利用传输线探测量子点系统中核自旋场涨落的有效机制，分析了耦合的量子点-传输线系统的动力学过程。此外，我们还研究了具有Cv3对称性的三量子点系统中的量子光学现象，指出该系统可以有效调节输出信号的极化属性。