论文标题
使用大光子数量
Quantum non-demolition dispersive readout of a superconducting artificial atom using large photon numbers
论文作者
论文摘要
读取超导性人工原子的状态通常依赖于分散耦合到读出谐振器。对于给定的系统噪声温度，增加谐振器中循环光子数$ \ bar {n} $可以实现较短的测量时间，因此有望减少由自发原子过渡引起的读数错误。但是，通常观察到增加$ \ bar {n} $也提高了这些过渡率。在这里，我们提出了一个人工原子，其中我们测量了前两个状态之间过渡速率的总体平坦依赖性，该函数是$ \ bar {n} $的函数，最高$ \ bar {n} \ oft200 $。尽管我们观察到随着读数功率的增加，我们观察到分散转移的预期减少，但信噪比会随着$ \ bar {n} $的增加而不断提高。即使没有使用参数放大器，$ \ bar {n} = 74 $，我们分别测量了99％和93％的保真度，分别用于反馈辅助的地面和激发态准备。
Reading out the state of superconducting artificial atoms typically relies on dispersive coupling to a readout resonator. For a given system noise temperature, increasing the circulating photon number $\bar{n}$ in the resonator enables a shorter measurement time and is therefore expected to reduce readout errors caused by spontaneous atom transitions. However, increasing $\bar{n}$ is generally observed to also increase these transition rates. Here we present a fluxonium artificial atom in which we measure an overall flat dependence of the transition rates between its first two states as a function of $\bar{n}$, up to $\bar{n}\approx200$. Despite the fact that we observe the expected decrease of the dispersive shift with increasing readout power, the signal-to-noise ratio continuously improves with increasing $\bar{n}$. Even without the use of a parametric amplifier, at $\bar{n}=74$, we measure fidelities of 99% and 93% for feedback-assisted ground and excited state preparation, respectively.
