Quantum non-demolition detection of an itinerant microwave photon
Quantum non-demolition detection of an itinerant microwave photon
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DOI：
10.1038/s41567-018-0066-3
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发表时间：
2018-06-01
期刊：
影响因子：
19.6
通讯作者：
Nakamura, Y.
中科院分区：
文献类型：
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作者：
Kono, S.;Koshino, K.;Nakamura, Y.
光子探测器是在量子极限下测量电磁波的基本工具（1，2），并且在新兴的量子技术（如通信（3），传感（4）和计算（5））中需求量很大。特别令人感兴趣的是量子非破坏（QND）型探测器，它将电磁波投射到光子数基础上（6-10）。这与吸收光子以触发“点击”的传统光子检测器（2）形成鲜明对比。最近在光域中使用腔中的单个原子证明了长期寻求的飞行光子的QND检测（11，12）。然而，微波的对应物一直难以捉摸，尽管最近在微波量子光学中使用超导电路取得了进展（13-19）。在这里，我们实现了一个确定性的纠缠门之间的超导量子比特和一个巡回微波光子反射的腔包含量子比特。利用量子纠缠和高保真量子比特读出，我们实现了对单个光子的QND探测，量子效率为0.84，光子存活概率为0.87。我们的方案可以作为一个构建模块的量子网络连接遥远的量子比特模块，以及微波光子计数装置的多光子信号。
Photon detectors are an elementary tool to measure electromagnetic waves at the quantum limit(1,2) and are heavily demanded in the emerging quantum technologies such as communication(3), sensing(4) and computing(5). Of particular interest is a quantum non-demolition (QND)-type detector, which projects an electromagnetic wave onto the photonnumber basis(6-10). This is in stark contrast to conventional photon detectors(2) that absorb a photon to trigger a 'click'. The long-sought QND detection of a flying photon was recently demonstrated in the optical domain using a single atom in a cavity(11,12). However, the counterpart for microwaves has been elusive despite the recent progress in microwave quantum optics using superconducting circuits(13-19). Here, we implement a deterministic entangling gate between a superconducting qubit and an itinerant microwave photon reflected by a cavity containing the qubit. Using the entanglement and the highfidelity qubit readout, we demonstrate a QND detection of a single photon with the quantum efficiency of 0.84 and the photon survival probability of 0.87. Our scheme can serve as a building block for quantum networks connecting distant qubit modules as well as a microwave-photon-counting device for multiple-photon signals.