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arXiv 2402.05046quant-ph
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通过观察重复激发量子比特的发射来监测腔的能量

Monitoring the energy of a cavity by observing the emission of a repeatedly excited qubit

Hector Hutin, Antoine Essig, Réouven Assouly, Pierre Rouchon, Audrey Bienfait, Benjamin Huard

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发表信息：
Phys. Rev. Lett. 133, 15360 (2024)
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AI总结：

本研究利用色散耦合量子比特的荧光测量，实现了单次光子计数与腔内光子数跟踪，观察到光子逐一离开腔时的量子跃迁，为玻色子码量子纠错提供了新方法。

摘要：

大型量子系统（谐振子或qudit）中的激发数可以通过色散耦合的量子比特以量子非破坏性方式进行测量。这通常需要一系列量子比特脉冲，这些脉冲编码了关于光子数的各种二元问题。最近，一种基于由相同脉冲序列驱动的量子比特荧光测量的方法被引入用于跟踪腔中的光子数，从而简化了其监测过程，并引发了关于该方案测量反作用的有趣问题。使用超导电路的首次实现展示了如何以这种方式测量平均光子数。在这里，我们提出了一项实验，由于腔衰减率比色散耦合率和量子比特发射率小4个数量级，该实验实现了单次光子计数和数量跟踪。创新的陷波滤波器和基于pogo-pin的接触使得这些看似不兼容的特性成为可能。我们表征了脉冲序列下的量子比特动力学。我们通过监测量子比特荧光来监测光子数，观察到了随着光子逐一离开腔而发生的量子跃迁。此外，我们提取了测量率和诱导退相干率，并将它们与理论模型进行了比较。我们的方法可以应用于玻色子码或qudits上的量子纠错协议。

英文摘要：

The number of excitations in a large quantum system (harmonic oscillator or qudit) can be measured in a quantum nondemolition manner using a dispersively coupled qubit. It typically requires a series of qubit pulses that encode various binary questions about the photon number. Recently, a method based on the fluorescence measurement of a qubit driven by a train of identical pulses was introduced to track the photon number in a cavity, hence simplifying its monitoring and raising interesting questions about the measurement backaction of this scheme. A first realization with superconducting circuits demonstrated how the average number of photons could be measured in this way. Here we present an experiment that reaches single-shot photocounting and number tracking owing to a cavity decay rate 4 orders of magnitude smaller than both the dispersive coupling rate and the qubit emission rate. An innovative notch filter and pogo-pin-based galvanic contact makes possible these seemingly incompatible features. The qubit dynamics under the pulse train is characterized. We observe quantum jumps by monitoring the photon number via the qubit fluorescence as photons leave the cavity one at a time. Additionally, we extract the measurement rate and induced dephasing rate and compare them to theoretical models. Our method could be applied to quantum error correction protocols on bosonic codes or qudits.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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