用约瑟夫森电路探测非阿贝尔几何相位

研究了一种基于超导约瑟夫森电路探测非阿贝尔几何相位不对易特征的理论方案，实现了在宏观量子电路中对几何相位不对易性的探测。研究结果表明：通过调控外加磁通，体系能够产生两重简并的暗态并自然地诱导了几何相位。设置两个复合演化过程，考察体系在同一量子态占据几率的差值，可以直接地表征几何相位的不对易特征。进一步的可行性和优势分析表明，该方案具有便易的操控性和较好的量子相干性，从而为实验上研究非阿贝尔几何相位的不对易特征提供一种有效的途径。     

Robust Quantum Computation with Superconducting Charge Qubits via Coherent Pulses

To achieve robust gate operations on superconducting charge qubits, we theoretically propose a feasible scheme to realize geometric quantum computation via coherent pulses. Only by adiabatically tuning the microwave pulses applied to the gate capacitance can the Berry phases associated with the system be acquired, from which we construct a universal set of geometric gates. Combining the geometric approach with the coherent pulse technique, robust quantum operations aimed at combating noise errors may be implemented experimentally.     

Shortcut-based quantum gates on superconducting qubits in circuit QED

Construction of optimal gate operations is significant for quantum computation. Here an efficient scheme is proposed for performing shortcut-based quantum gates on superconducting qubits in circuit quantum electrodynamics (QED). Two four-level artificial atoms of Cooper-pair box circuits, having sufficient level anharmonicity, are placed in a common quantized field of circuit QED and are driven by individual classical microwaves. Without the effect of cross resonance, one-qubit NOT gate and phase gate in a decoupled atom can be implemented using the invariant-based shortcuts to adiabaticity. With the assistance of cavity bus, a one-step SWAP gate can be obtained within a composite qubit-photon-qubit system by inversely engineering the classical drivings. We further consider the gate realizations by adjusting the microwave fields. With the accessible decoherence rates, the shortcut-based gates have high fidelities. The present strategy could offer a promising route towards fast and robust quantum computation with superconducting circuits experimentally.