Chemical and Quantum Physics, School of Applied Sciences, RMIT University, Melbourne, Victoria 3001, Australia.
Chemical and Quantum Physics, School of Applied Sciences, RMIT University, Melbourne, Victoria 3001, Australia and Virtual Nanoscience Laboratory, CSIRO Materials Science and Engineering, Parkville, Victoria 3052, Australia.
Phys Rev Lett. 2013 Feb 15;110(7):077002. doi: 10.1103/PhysRevLett.110.077002. Epub 2013 Feb 12.
One of the key problems facing superconducting qubits and other Josephson junction devices is the decohering effects of bistable material defects. Although a variety of phenomenological models exist, the true microscopic origin of these defects remains elusive. For the first time we show that these defects may arise from delocalization of the atomic position of the oxygen in the oxide forming the Josephson junction barrier. Using a microscopic model, we compute experimentally observable parameters for phase qubits. Such defects are charge neutral but have nonzero response to both applied electric field and strain. This may explain the observed long coherence time of two-level defects in the presence of charge noise, while still coupling to the junction electric field and substrate phonons.
超导量子比特和其他约瑟夫森结器件面临的关键问题之一是双稳材料缺陷的退相干效应。尽管存在各种唯象模型，但这些缺陷的真正微观起源仍然难以捉摸。我们首次表明，这些缺陷可能源于形成约瑟夫森结势垒的氧化物中氧原子位置的离域。我们使用微观模型计算了相量子比特的实验可观测参数。这些缺陷是电中性的，但对施加的电场和应变有非零响应。这可以解释在存在电荷噪声的情况下，观察到的两能级缺陷具有较长的相干时间，同时仍然与结电场和衬底声子耦合。
