Energy Decay in Superconducting Josephson-Junction Qubits from Nonequilibrium Quasiparticle Excitations
Energy Decay in Superconducting Josephson-Junction Qubits from Nonequilibrium Quasiparticle Excitations
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DOI：
10.1103/physrevlett.103.097002
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发表时间：
2009-08-28
影响因子：
8.6
通讯作者：
Aumentado, J.
中科院分区：
文献类型：
--
作者：
Martinis, John M.;Ansmann, M.;Aumentado, J.
我们计算了非平衡准粒子的约瑟夫森量子比特和超导共振器的能量衰减率。从实验中得到的衰变率与基于准粒子密度n（qp）=10/μ m（3）的先前测量的预测一致，这表明非平衡准粒子是Josephson量子比特的重要退相干源。准粒子的能量衰减和扩散的计算也表明，先前设计的间隙和陷阱结构，减少准粒子的密度，应重新设计，以提高其效率。这个模型还解释了约瑟夫森量子比特和谐振器的一个显著特征--随着温度的升高，衰变率略有降低。
We calculate the energy decay rate of Josephson qubits and superconducting resonators from nonequilibrium quasiparticles. The decay rates from experiments are shown to be consistent with predictions based on a prior measurement of the quasiparticle density n(qp)=10/mu m(3), which suggests that nonequilibrium quasiparticles are an important decoherence source for Josephson qubits. Calculations of the energy-decay and diffusion of quasiparticles also indicate that prior engineered gap and trap structures, which reduce the density of quasiparticles, should be redesigned to improve their efficacy. This model also explains a striking feature in Josephson qubits and resonators-a small reduction in decay rate with increasing temperature.