Long-lived transitions occur naturally in atomic systems due to the abundance of selection rules inhibiting spontaneous emission. By contrast, transitions of superconducting artificial atoms typically have large dipoles and hence their lifetimes are determined by the dissipative environment of a macroscopic electrical circuit. We designed a multi-level fluxonium artificial atom such that the qubit's transition dipole can be exponentially suppressed by flux tuning, while it continues to dispersively interact with a cavity mode by virtual transitions to the non-computational states. Remarkably, energy decay time $T_1$ grew by two orders of magnitude, proportionally to the inverse square of the transition dipole, and exceeded the benchmark value of $T_1 greater than 2~{ms}$ (quality factor $Q_1 greater than 4\times 10^7$) without showing signs of saturation. Dephasing time was limited by the first-order coupling to flux noise to about $4~\mu s$. Our circuit validated the general principle of hardware-level protection against bit-flip errors and can be upgraded to the $0-\pi$ circuit [P. Brooks, A. Kitaev, J. Preskill, Phys. Rev. A{87}, 052306 (2013)], adding protection against dephasing and certain gate errors.

中文翻译：

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演示了超导量子比特免受能量衰减的保护

由于大量抑制自发发射的选择规则，长寿命跃迁在原子系统中自然发生。相比之下，超导人工原子的跃迁通常具有较大的偶极子，因此其寿命由宏观电路的耗散环境决定。我们设计了一个多级助焊剂人工原子，以便可以通过通量调整以指数方式抑制量子位的跃迁偶极子，而通过虚拟跃迁到非计算态继续与腔模进行色散相互作用。值得注意的是，能量衰减时间$ T_1 $与跃迁偶极子的平方成反比，增加了两个数量级，并超过了基准值$ T_1大于2〜{ms} $（质量因子$ Q_1大于4 \乘以10 ^ 7 $）而没有出现饱和的迹象。相移时间受到与磁通噪声的一阶耦合的限制，约为$ 4〜\ mu s $。我们的电路验证了针对位翻转错误的硬件级保护的一般原理，可以升级到$ 0- \ pi $电路[P. Brooks，A。Kitaev，J。Preskill，物理学。Rev. A {87}，052306（2013）]，增加了防止移相和某些门错误的保护。