Measurement of energy decay in superconducting qubits from nonequilibrium quasiparticles
Measurement of energy decay in superconducting qubits from nonequilibrium quasiparticles
复制标题
DOI：
10.1103/physrevb.84.024501
复制
发表时间：
2011-07-01
影响因子：
3.7
通讯作者：
Martinis, John M.
中科院分区：
文献类型：
--
作者：
Lenander, M.;Wang, H.;Martinis, John M.
准粒子是超导量子比特中一种重要的退相干机制，它可以用一个推广的Mattis-Bardeen理论的复导纳来描述。通过隧道结注入非平衡准粒子，定性地验证了位相量子比特中衰减率和跃迁频率的预期变化。由于它们的相对变化在预测值的4%以内，该理论可以可靠地用于推断准粒子密度。我们描述了衰减速率的稳定如何允许确定量子比特的能量驰豫是否受非平衡准粒子的限制。
Quasiparticles are an important decoherence mechanism in superconducting qubits, and can be described with a complex admittance that is a generalization of the Mattis-Bardeen theory. By injecting nonequilibrium quasiparticles with a tunnel junction, we verify qualitatively the expected change of the decay rate and transition frequency in a phase qubit. With their relative change in agreement to within 4 % of prediction, the theory can be reliably used to infer quasiparticle density. We describe how settling of the decay rate may allow determination of whether qubit energy relaxation is limited by nonequilibrium quasiparticles.