A photon-photon quantum gate based on Rydberg interactions in a cavity

该方案的目标是在中等精度的光学谐振腔内实现基于电磁诱导透明和里德堡阻挡的光子-光子可控非量子门。这一以前未实现的方案结合了里德堡封锁的优点和光学谐振器提供的优点。我们对现实参数进行了估计，预测在本提案的资金期内，闸门效率可以达到50%以上。这是相对于之前证明的线性光学量子计算高达11%的效率、谐振器中单个原子高达5%的效率以及自由空间里德堡门高达0.5%至8%的效率而言的重大改进。超过50%的预计效率接近于可以实现无后选择的纠缠双光子态的产生，并且超过了线性光学贝尔态分析器的基本极限。从长远来看，更高的效率将会实现。这将允许它产生越来越多光子的纠缠态。高性能的光子-光子门将用于量子中继器中的高性能光子Bell态检测，并有可能用于量子计算。

The objective of this proposal is to realize a photon-photon controlled NOT quantum gate based on electromagnetically induced transparency and Rydberg blockade inside an optical resonator of moderate finesse. This previously unimplemented scheme combines the advantages of Rydberg blockade with the advantages offered by optical resonators. We made estimates for realistic parameters, which predict that a gate efficiency above 50% can be reached within the funding period of this proposal. This is a major improvement relative to the previously demonstrated efficiencies of up to 11% in linear optical quantum computing, 5% for a single atom in a resonator, and 0.5% to 8% for a free-space Rydberg gate. The projected efficiency above 50% is near the point where production of an entangled two-photon state without postselection can be realized and where the fundamental limit for linear-optical Bell-state analyzers is outperformed. In the long run, even higher efficiencies will come into reach. This will allow it to produce entangled states of larger and larger numbers of photons. A high performance photon-photon gate would be useful for high-performance photonic Bell-state detection in quantum repeaters, and potentially for quantum computation.