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The superconducting quasicharge qubit

机译:超导quasichargequbit

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The non-dissipative nonlinearity of Josephson junctions(1)converts macroscopic superconducting circuits into artificial atoms(2), enabling some of the best-controlled qubits today(3,4). Three fundamental types of superconducting qubit are known(5), each reflecting a distinct behaviour of quantum fluctuations in a Cooper pair condensate: single-charge tunnelling (charge qubit(6,7)), single-flux tunnelling (flux qubit(8)) and phase oscillations (phase qubit(9)or transmon(10)). Yet, the dual nature of charge and flux suggests that circuit atoms must come in pairs. Here we introduce the missing superconducting qubit, 'blochnium', which exploits a coherent insulating response of a single Josephson junction that emerges from the extension of phase fluctuations beyond 2 pi (refs.(11-14)). Evidence for such an effect has been found in out-of-equilibrium direct-current transport through junctions connected to high-impedance leads(15-19), although a full consensus on the existence of extended phase fluctuations is so far absent(20-22). We shunt a weak junction with an extremely high inductance-the key technological innovation in our experiment-and measure the radiofrequency excitation spectrum as a function of external magnetic flux through the resulting loop. The insulating character of the junction is manifested by the vanishing flux sensitivity of the qubit transition between the ground state and the first excited state, which recovers rapidly for transitions to higher-energy states. The spectrum agrees with a duality mapping of blochnium onto a transmon, which replaces the external flux by the offset charge and introduces a new collective quasicharge variable instead of the superconducting phase(23,24). Our findings may motivate the exploration of macroscopic quantum dynamics in ultrahigh-impedance circuits, with potential applications in quantum computing and metrology.A fundamental superconducting qubit is introduced: 'blochnium' is dual to the transmon, relies on a circuit element called hyperinductance, and its fundamental physical variable is the quasicharge of the Josephson junction.
机译:Josephson结的非耗散非线性(1)将宏观超导电路转换为人工原子(2),使得今天的一些最佳控制的Qubits(3,4)。已知三种基本类型的超导量子比特(5),每个基本类型反映了Cooper对冷凝物中的量子波动的不同行为:单电荷隧道(电荷量子比特(6,7)),单通通量隧道(通量qubit(8) )和相位振荡(相位量子位(9)或透射仪(10))。然而,充电和助焊剂的双重性表明电路原子必须成对出现。在这里,我们介绍了缺少的超导Qubit,'blochnium',其利用单个约瑟夫森结的连贯绝缘响应从2 pi超出2 pi的相位波动的延伸产生的一个连贯的绝缘响应(refs。(11-14))。通过连接到高阻抗引线(15-19)的交界处的交叉点存在于平衡直流运输中发现了这种效果的证据,但到目前为止,虽然对存在延长相波动的存在充分共识(20- 22)。我们使用极高的电感来分流弱交界处 - 我们实验中的关键技术创新 - 并通过所产生的环路测量作为外部磁通量的函数的射频激励光谱。结束结的绝缘特性通过地面状态和第一激发状态之间的Qubit转变的消失磁通敏感性而表现为迅速恢复到更高能量状态的转变。频谱与Blochnium的二元映射到透射仪上,偏移电荷替换外部通量,并引入新的集体Quasacge变量而不是超导阶段(23,24)。我们的发现可能激发宏观阻抗电路中的宏观量子动态的探索,具有量子计算和计量中的潜在应用。引入了基本超导量子网:'Blochnium'是双向透射仪的,依赖于称为高风管的电路元件,和它的基本物理变量是约瑟夫森交界处的Quasicharge。

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  • 来源
    《Nature》 |2020年第7825期|368-371|共4页
  • 作者单位

    Univ Maryland Dept Phys College Pk MD 20742 USA;

    Univ Maryland Dept Phys College Pk MD 20742 USA;

    Univ Maryland Dept Phys College Pk MD 20742 USA;

    Univ Maryland Dept Phys College Pk MD 20742 USA|Natl Tsinghua Univ Hsinchu Taiwan;

    Univ Maryland Dept Phys College Pk MD 20742 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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  • 正文语种 eng
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