Remote entanglement of superconducting systems using solid-state spin quantum memory*

Quantum communication between remote superconducting systems is intensively studied to increase the number of integrated superconducting qubits and realize a distributed quantum computer. Since optical photon must be used for communication outside a dilution refrigerator, direct conversion of microwave photon to optical photon have been widely investigated. However, the direct conversion approach suffers from added photon noise, heating due to the strong optical pump, requirement of large cooperativity. Instead, teleportation-based transduction schemes are receiving increased attention [1,2,3]. For the quantum communication between superconducting qubits, we consider a theoretical (experimental) limit of an entanglement distribution scheme using solid-state spin quantum memory (e.g. color center in diamond), which can be used as an interface for both microwave and optical photon. The quantum memory enables heralded entanglement generation without significant optical pump power and added photon noise.

[1] C. Zhong et al., PRL 124, 010511 (2020).

[2] S. Krastanov et al., PRL 127, 040503 (2021).

[3] T. Neuman et al., NPJ Quantum Inf. 7, 121 (2021).