We present a superconducting device showing a clear parity effect in the number of electrons, even when there is, on average, a single nonequilibrium quasiparticle present and the parity of the island switches due to quasiparticles tunneling in and out of the device at rates on the order of 100 Hz. We detect the switching by monitoring in real time the charge state of a superconducting island connected to normal leads by tunnel junctions. The quasiparticles are created by Cooper pairs breaking on the island at a rate of a few kHz. We demonstrate that the pair breaking is caused by the backaction of the single-electron transistor used as a charge detector. With sufficiently low probing currents, our superconducting island is free of quasiparticles 97% of the time.
Field-controlled breaking and restoration of parity-time symmetry in Josephson interference
Institute of Physics, Academia Sinica（中央研究院物理研究所）；Department of Engineering and System Science, National Tsing Hua University（国立清华大学工程与系统科学系）；Nanoscience and Technology Program, Taiwan International Graduate Program, Academia Sinica（中央研究院台湾国际研究生学院纳米科技计划）；Department of Physics, National Sun Yat-Sen University（国立中山大学物理系）；Program on Key Materials, Academy of Innovative Semiconductor and Sustainable Manufacturing (AISSM), National Cheng Kung University（国立成功大学创新半导体与永续制造学院关键材料计划）；Department of Physics, National Cheng Kung University（国立成功大学物理系）；Taiwan Consortium of Emergent Crystalline Materials (TCECM), National Science and Technology Council（国家科学及技术委员会台湾新兴晶体材料联盟）
