Photon shot noise dephasing in the strong-dispersive limit of circuit QED
Photon shot noise dephasing in the strong-dispersive limit of circuit QED
复制标题
DOI：
10.1103/physrevb.86.180504
复制
发表时间：
2012-11-12
影响因子：
3.7
通讯作者：
Schoelkopf, R. J.
中科院分区：
文献类型：
--
作者：
Sears, A. P.;Petrenko, A.;Schoelkopf, R. J.
在强色散极限下，由于量子比特与其读出腔的耦合，我们研究了超导transmon量子比特的光子散粒噪声消相。由于光子的每次随机到达或离开都将使量子比特完全失相，因此我们可以通过原位改变腔模式填充和衰减率来控制量子比特经历失相事件的速率。这使我们能够验证与理论预测相匹配的纯脱相机制，并且实际上解释了在最近的transmon实验中作为低温恒温器温度的函数所看到的增加的脱相。我们观察到，当腔体与环境解耦时，相干时间大幅增加，并且在实施滤波后发现，当用单个哈恩回波校正时，小约瑟夫森结的固有相干性大于几百微秒。类似的滤波和热化可能对其他量子比特设计很重要，以防止光子散粒噪声成为脱相的主要来源。
We study the photon shot noise dephasing of a superconducting transmon qubit in the strong-dispersive limit, due to the coupling of the qubit to its readout cavity. As each random arrival or departure of a photon is expected to completely dephase the qubit, we can control the rate at which the qubit experiences dephasing events by varying in situ the cavity mode population and decay rate. This allows us to verify a pure dephasing mechanism that matches theoretical predictions, and in fact explains the increased dephasing seen in recent transmon experiments as a function of cryostat temperature. We observe large increases in coherence times as the cavity is decoupled from the environment, and after implementing filtering find that the intrinsic coherence of small Josephson junctions when corrected with a single Hahn echo is greater than several hundred microseconds. Similar filtering and thermalization may be important for other qubit designs in order to prevent photon shot noise from becoming the dominant source of dephasing.