Department of Electrical Engineering, University of California, Riverside, California 92521, USA.
Phys Rev Lett. 2013 May 24;110(21):210501. doi: 10.1103/PhysRevLett.110.210501. Epub 2013 May 22.
We analyze a single-shot readout for superconducting qubits via the controlled catch, dispersion, and release of a microwave field. A tunable coupler is used to decouple the microwave resonator from the transmission line during the dispersive qubit-resonator interaction, thus circumventing damping from the Purcell effect. We show that, if the qubit frequency tuning is sufficiently adiabatic, a fast high-fidelity qubit readout is possible, even in the strongly nonlinear dispersive regime. Interestingly, the Jaynes-Cummings nonlinearity leads to the quadrature squeezing of the resonator field below the standard quantum limit, resulting in a significant decrease of the measurement error.
我们通过控制微波场的捕获、弥散和释放来分析超导量子比特的单次读出。通过使用可调谐耦合器，在弥散的量子比特-谐振器相互作用期间，将微波谐振器从传输线中解耦，从而避免了来自Purcell 效应的阻尼。我们表明，如果量子比特频率调谐足够绝热，则即使在强非线性弥散的情况下，也可以实现快速的高保真量子比特读出。有趣的是，Jaynes-Cummings 非线性导致了谐振器场的正交压缩，低于标准量子极限，从而显著降低了测量误差。
