Department of Physics, Harvard University, Cambridge, MA 02138, USA.
Science. 2011 Sep 2;333(6047):1266-9. doi: 10.1126/science.1208066. Epub 2011 Aug 4.
Photons are excellent information carriers but normally pass through each other without consequence. Engineered interactions between photons would enable applications as varied as quantum information processing and simulation of condensed matter systems. Using an ensemble of cold atoms strongly coupled to an optical cavity, we found that the transmission of light through a medium may be controlled with few photons and even by the electromagnetic vacuum field. The vacuum induces a group delay of 25 nanoseconds on the input optical pulse, corresponding to a light velocity of 1600 meters per second, and a transparency of 40% that increases to 80% when the cavity is filled with 10 photons. This strongly nonlinear effect provides prospects for advanced quantum devices such as photon number-state filters.
光子是极好的信息载体，但通常会相互穿透而不会产生任何后果。光子之间的工程相互作用将能够实现各种应用，如量子信息处理和凝聚态系统的模拟。我们使用一组与光学腔强耦合的冷原子发现，通过介质传输的光可以用少量光子甚至用电磁场的真空来控制。真空会在输入光脉冲上产生 25 纳秒的群延迟，相当于光速为 1600 米每秒，当腔中填充 10 个光子时，透明度增加到 40%，增加到 80%。这种强非线性效应为先进的量子器件提供了前景，例如光子数态滤波器。
