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arXiv 2102.00484cond-mat.supr-concond-mat.mes-hallquant-ph
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几秒钟内没有准粒子的超导体

A superconductor free of quasiparticles for seconds

E. T. Mannila, P. Samuelsson, S. Simbierowicz, J. T. Peltonen, V. Vesterinen, L. Grönberg, J. Hassel, V. F. Maisi, J. P. Pekola

摘要:

基于电子库珀配对的超导器件在现有和新兴技术中发挥着重要作用,从辐射探测器到量子计算机。它们的性能受到由破裂的库珀对形成的伪准粒子激发的限制。努力实现超低准粒子密度已达到时间平均数的激发的顺序在国家的最先进的设备。然而,准粒子群的动力学以及添加和删除个别激发的时间尺度仍然在很大程度上未被探索。在这里,我们实验证明了一个超导体完全免费的准粒子的持续时间长达几秒钟。我们通过测量电荷隧穿到正常金属接触面的方法来实时监测介观超导体上的准粒子数。安静的无激发期被时间上随机的库珀对断开事件中断,随后是毫秒内的电荷隧穿突发。我们的研究结果表明,没有准粒子的操作设备的可能性,具有潜在的改善性能。此外,我们的实验还探索了设备中非平衡准粒子的起源;在初始冷却后的几周内,库珀对断裂率的衰减排除了宇宙或长寿命放射源产生的过程。

英文摘要:

Superconducting devices, based on the Cooper pairing of electrons, play an important role in existing and emergent technologies, ranging from radiation detectors to quantum computers. Their performance is limited by spurious quasiparticle excitations formed from broken Cooper pairs. Efforts to achieve ultra-low quasiparticle densities have reached time-averaged numbers of excitations on the order of one in state-of-the-art devices. However, the dynamics of the quasiparticle population as well as the time scales for adding and removing individual excitations remain largely unexplored. Here, we experimentally demonstrate a superconductor completely free of quasiparticles for periods lasting up to seconds. We monitor the quasiparticle number on a mesoscopic superconductor in real time by measuring the charge tunneling to a normal metal contact. Quiet, excitation-free periods are interrupted by random-in-time Cooper pair breaking events, followed by a burst of charge tunneling within a millisecond. Our results demonstrate the possibility of operating devices without quasiparticles with potentially improved performance. In addition, our experiment probes the origins of nonequilibrium quasiparticles in our device; the decay of the Cooper pair breaking rate over several weeks following the initial cooldown rules out processes arising from cosmic or long-lived radioactive sources.

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