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

• Applicant: Privatdozent Dr. Stephan Dürr
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428461323

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.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1929: Giant Interactions in Rydberg Systems (GiRyd)
• International Connection: Denmark
• Cooperation Partner: Professor Dr. Thomas Pohl