Centre for Cold Matter, Imperial College, Prince Consort Road, London SW7 2BW, UK.
Nat Commun. 2011 Aug 9;2:418. doi: 10.1038/ncomms1428.
Cavity quantum electrodynamics describes the fundamental interactions between light and matter, and how they can be controlled by shaping the local environment. For example, optical microcavities allow high-efficiency detection and manipulation of single atoms. In this regime, fluctuations of atom number are on the order of the mean number, which can lead to signal fluctuations in excess of the noise on the incident probe field. Here we demonstrate, however, that nonlinearities and multi-atom statistics can together serve to suppress the effects of atomic fluctuations when making local density measurements on clouds of cold atoms. We measure atom densities below 1 per cavity mode volume near the photon shot-noise limit. This is in direct contrast to previous experiments where fluctuations in atom number contribute significantly to the noise. Atom detection is shown to be fast and efficient, reaching fidelities in excess of 97% after 10 μs and 99.9% after 30 μs.
腔量子电动力学描述了光与物质之间的基本相互作用，以及如何通过改变局部环境来控制这些相互作用。例如，光学微腔可以实现高效的单原子检测和操控。在这种情况下，原子数的涨落量级与平均值相当，这可能导致入射探测场的噪声超过信号涨落。然而，我们在这里证明，在对冷原子云进行局部密度测量时，非线性和多原子统计可以共同抑制原子涨落的影响。我们在光子散粒噪声极限附近的每个腔模体积中测量到低于 1 个原子的密度。这与之前的实验形成了鲜明对比，在之前的实验中，原子数的涨落对噪声有显著贡献。我们还证明了原子的探测速度快、效率高，在 10 μs 后达到超过 97%的保真度，在 30 μs 后达到 99.9%。
