Reverse Isolation and Backaction of the SLUG Microwave Amplifier
Reverse Isolation and Backaction of the SLUG Microwave Amplifier
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SLUG 微波放大器的反向隔离和反作用
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
R. McDermott
中科院分区：
文献类型：
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作者：
T. Thorbeck;S. Zhu;E. Leonard;R. Barends;J. Kelly;J. Martinis;R. McDermott
一个理想的量子位测量放大器必须不仅提供高增益和接近量子极限的噪声性能，而且还将精密的量子电路与噪声的下游测量级隔离，同时产生可忽略的反作用。在这里，我们使用超导低电感波动电流计（SLUG）微波放大器读出超导transmon量子比特，我们表征了SLUG的反向隔离和测量反作用。对于适当的直流偏置，SLUG实现的反向隔离优于商用低温隔离器。此外，SLUG反作用主要由器件中耗散元件的热发射决定。当SLUG以脉冲模式操作时，可以使用没有低温隔离器或循环器的测量链来表征transmon量子位，而量子位性能没有可测量的退化。
An ideal preamplifier for qubit measurement must not only provide high gain and near quantum-limited noise performance, but also isolate the delicate quantum circuit from noisy downstream measurement stages while producing negligible backaction. Here we use a Superconducting Low-inductance Undulatory Galvanometer (SLUG) microwave amplifier to read out a superconducting transmon qubit, and we characterize both reverse isolation and measurement backaction of the SLUG. For appropriate dc bias, the SLUG achieves reverse isolation that is better than that of a commercial cryogenic isolator. Moreover, SLUG backaction is dominated by thermal emission from dissipative elements in the device. When the SLUG is operated in pulsed mode, it is possible to characterize the transmon qubit using a measurement chain that is free from cryogenic isolators or circulators with no measurable degradation of qubit performance.