Digital Coherent Control of a Superconducting Qubit
Digital Coherent Control of a Superconducting Qubit
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DOI：
10.1103/physrevapplied.11.014009
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发表时间：
2019-01-07
影响因子：
4.6
通讯作者：
McDermott, R.
中科院分区：
文献类型：
--
作者：
Leonard, E., Jr.;Beck, M. A.;McDermott, R.
高保真的门操作对于实现容错量子计算机至关重要。此外，实现门操作所需的物理资源必须能随系统规模高效扩展。超导量子比特领域的一个长期目标是将超导量子电路与近端经典低温控制系统紧密集成。在此，我们使用在量子比特芯片上共同制造的单磁通量子（SFQ）脉冲驱动器对超导transmon量子比特进行相干控制。脉冲驱动器通过弱电容耦合向量子比特发送一系列量化磁通脉冲；当脉冲间的定时与量子比特振荡周期的倍数相匹配时，就能实现量子比特状态的相干旋转。我们使用交错随机基准测试测量出基于SFQ的门的保真度约为95%。门保真度受到耗散性SFQ驱动器中准粒子产生的限制。我们对准粒子导纳的耗散和色散贡献进行了表征，并讨论了抑制准粒子中毒的缓解策略。这些结果为将大规模超导量子比特阵列与SFQ控制元件集成以实现低延迟反馈和稳定开辟了道路。
High-fidelity gate operations are essential to the realization of a fault-tolerant quantum computer. In addition, the physical resources required to implement gates must scale efficiently with system size. A longstanding goal of the superconducting qubit community is the tight integration of a superconducting quantum circuit with a proximal classical cryogenic control system. Here we implement coherent control of a superconducting transmon qubit using a single-flux quantum (SFQ) pulse driver cofabricated on the qubit chip. The pulse driver delivers trains of quantized flux pulses to the qubit through a weak capacitive coupling; coherent rotations of the qubit state are realized when the pulse-to-pulse timing is matched to a multiple of the qubit oscillation period. We measure the fidelity of SFQ-based gates to be approximately 95% using interleaved randomized benchmarking. Gate fidelities are limited by quasiparticle generation in the dissipative SFQ driver. We characterize the dissipative and dispersive contributions of the quasiparticle admittance and discuss mitigation strategies to suppress quasiparticle poisoning. These results open the door to integration of large-scale superconducting qubit arrays with SFQ control elements for low-latency feedback and stabilization.