Quantum jumps of light recording the birth and death of a photon in a cavity
Quantum jumps of light recording the birth and death of a photon in a cavity
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DOI：
10.1038/nature05589
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发表时间：
2007-03-15
期刊：
影响因子：
64.8
通讯作者：
Haroche, Serge
中科院分区：
文献类型：
--
作者：
Gleyzes, Sebastien;Kuhr, Stefan;Haroche, Serge
在连续观测下的微观量子系统在其状态之间表现出随机的突然跳跃。这种量子特征的检测需要在系统演化期间重复多次的量子非破坏（QND）测量（1-3）。虽然已经观察到被捕获的大质量粒子（电子，离子或分子（4-8））的量子跳跃，但这对于光量子来说更具挑战性。标准的光电探测器会吸收光，因此无法两次探测到相同的光子。因此，有必要使用一个透明的计数器，可以“看到”光子而不破坏它们（3）。此外，光需要存储比QND检测时间长得多的持续时间。在这里，我们报告的实验中，我们满足这些具有挑战性的条件，并观察光子数的量子跳跃。微波光子在超导腔中存储长达半秒的时间，并被非吸收原子流反复探测。原子干涉仪测量由非共振腔场引起的原子偶极相移，因此最终的原子状态直接揭示了腔中单个光子的存在。由数百个原子组成的序列，在同一状态下高度相关，被突然的状态切换打断。这些电报信号记录了单个光子的诞生、生命和死亡。将类似的QND过程应用于具有数十个光子的介观场，应该为量子到经典边界的探索开辟新的视角（9，10）。
A microscopic quantum system under continuous observation exhibits at random times sudden jumps between its states. The detection of this quantum feature requires a quantum non-demolition (QND) measurement(1-3) repeated many times during the system's evolution. Whereas quantum jumps of trapped massive particles ( electrons, ions or molecules(4-8)) have been observed, this has proved more challenging for light quanta. Standard photodetectors absorb light and are thus unable to detect the same photon twice. It is therefore necessary to use a transparent counter that can 'see' photons without destroying them(3). Moreover, the light needs to be stored for durations much longer than the QND detection time. Here we report an experiment in which we fulfil these challenging conditions and observe quantum jumps in the photon number. Microwave photons are stored in a superconducting cavity for times up to half a second, and are repeatedly probed by a stream of non-absorbing atoms. An atom interferometer measures the atomic dipole phase shift induced by the non-resonant cavity field, so that the final atom state reveals directly the presence of a single photon in the cavity. Sequences of hundreds of atoms, highly correlated in the same state, are interrupted by sudden state switchings. These telegraphic signals record the birth, life and death of individual photons. Applying a similar QND procedure to mesoscopic fields with tens of photons should open new perspectives for the exploration of the quantum-to-classical boundary(9,10).