IBM TJ Watson Research Center, Yorktown Heights, New York 10598, USA.
Phys Rev Lett. 2012 Dec 14;109(24):240505. doi: 10.1103/PhysRevLett.109.240505. Epub 2012 Dec 11.
We report a system where fixed interactions between noncomputational levels make bright the otherwise forbidden two-photon |00}→|11} transition. The system is formed by hand selection and assembly of two discrete component transmon-style superconducting qubits inside a rectangular microwave cavity. The application of a monochromatic drive tuned to this transition induces two-photon Rabi-like oscillations between the ground and doubly excited states via the Bell basis. The system therefore allows all-microwave two-qubit universal control with the same techniques and hardware required for single qubit control. We report Ramsey-like and spin echo sequences with the generated Bell states, and measure a two-qubit gate fidelity of F(g)=90% (unconstrained) and 86% (maximum likelihood estimator).
我们报告了一个系统，其中非计算水平之间的固定相互作用使 otherwise forbidden two-photon |00}→|11} transition 变得明亮。该系统由在矩形微波腔内部手动选择和组装两个离散组件 transmon 风格超导量子位形成。应用调谐到该跃迁的单色驱动通过贝尔基诱导在基态和双激发态之间的双光子 Rabi 类似振荡。因此，该系统允许使用与单量子位控制相同的技术和硬件进行全微波两量子比特通用控制。我们报告了使用生成的贝尔态的 Ramsey 样和自旋回波序列，并测量了两量子比特门保真度 F(g)=90%（无约束）和 86%（最大似然估计器）。
