Quantum non-demolition measurement of photon
Light cannot be usually observed without losses. The laser beam propagating in free space can be seen by dust in air. In the case of weak light consisted from a few number of photons, the quantum state is destructed by the losses. A transparent detector which does not interrupt the propagation of light will be useful for quantum information processing based on post-selections.
It is not a ridiculous dream. Such technique is called as the quantum non-demolition measurement (QND), which many scientists try to realize it. In the microwave frequency domain, QND has been already realized by S. Haroche’s group, who won the Nobel physics prize in 2012. However, in the optical frequency domain, QND is difficult due to the short lifetime of the optical transition.
By combining cavity QED technique with single atoms in optical frequency domain, we are trying to demonstrate a new method of QND. A new experimental system is under construction (Figure 3-1).
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