用腔分叉放大器测量量子比特的退相干
Measuring the Decoherence of a Quantronium Qubit with the Cavity Bifurcation Amplifier
摘要：
超导量子比特的分散读出具有速度快和侵入性小的优点。我们已经开发了这样的放大器，腔分叉放大器（CBA）[10]，并将其应用于量子素量子比特的读出[2]。它由一个嵌入在微波片上谐振器中的约瑟夫森结组成。与约瑟夫森分叉放大器[17]相比，其具有分流结的片上电容器，谐振器基于施加预定频率的简单共面波导，并且其其他RF特性（如品质因数）易于控制和优化。在适当的微波辐射条件下，CBA具有两个亚稳态。CBA采用哪种状态取决于耦合到CBA结的量子比特的状态。由于MHz重复率和大的信噪比，我们可以直接表明，当在最佳点（sweet spot）（对一阶栅极电荷波动不敏感的点）偏置时，相干性受到1/f栅极电荷噪声的限制。这种架构适合使用具有多路复用读出的多谐振器芯片进行可扩展的量子计算。
英文摘要：
Dispersive readouts for superconducting qubits have the advantage of speed and minimal invasiveness. We have developed such an amplifier, the Cavity Bifurcation Amplifier (CBA) [10], and applied it to the readout of the quantronium qubit [2]. It consists of a Josephson junction embedded in a microwave on-chip resonator. In contrast with the Josephson bifurcation amplifier [17], which has an on-chip capacitor shunting a junction, the resonator is based on a simple coplanar waveguide imposing a pre-determined frequency and whose other RF characteristics like the quality factor are easily controlled and optimized. Under proper microwave irradiation conditions, the CBA has two metastable states. Which state is adopted by the CBA depends on the state of a quantronium qubit coupled to the CBA's junction. Due to the MHz repetition rate and large signal to noise ratio we can show directly that the coherence is limited by 1/f gate charge noise when biased at the sweet spot - a point insensitive to first order gate charge fluctuations. This architecture lends itself to scalable quantum computing using a multi-resonator chip with multiplexed readouts.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
