Remote Entanglement of Superconducting Qubits via Solid-State Spin Quantum Memories

Abstract

Quantum communication between remote superconducting systems is being studied intensively to increase the number of integrated superconducting qubits and to realize a distributed quantum computer. Since optical photons must be used for communication outside a dilution refrigerator, the direct conversion of microwave photons to optical photons has been widely investigated. However, the direct conversion approach suffers from added photon noise, heating due to a strong optical pump, and the requirement for large cooperativity. Instead, for quantum communication between superconducting qubits, we propose an entanglement distribution scheme using a solid-state spin quantum memory that works as an interface for both microwave and optical photons. The quantum memory enables quantum communication without significant heating inside the refrigerator, in contrast to schemes using high-power optical pumps. Moreover, introducing the quantum memory naturally makes it possible to herald entanglement and parallelization using multiple memories.

Diamond Integrated Quantum Nanophotonics: Spins, Photons and Phonons

“…Finally, piezo-electric materials have been proposed as a phononic interface between superconducting qubits and quantum memories based on color centers in diamond [407]. In this transduction scheme, a microwave photon is converted to a phonon via the piezoelectric effect, which further interacts with the quantum memory via spin-phonon coupling [506]. Quantum interference of the emitted photons thus enables entanglement of remote superconducting circuits.…”

“…Quantum interference of the emitted photons thus enables entanglement of remote superconducting circuits. An advantage of this quantum memory-based transduction scheme over direct microwave-to-optical-photon conversion is a potential reduction in heating of the cryostat on account of the lower laser power required, which might preserve the coherence of the superconducting resonators [506].…”

Diamond Integrated Quantum Photonics: A Review

“…Finally, piezo-electric materials have been proposed as a phononic interface between superconducting qubits and quantum memories based on color centers in diamond [436]. In this transduction scheme, a microwave photon is converted to a phonon via the piezoelectric effect, which further interacts with the quantum memory via spin-phonon coupling [461]. Quantum interference of the emitted photons thus enables entanglement of remote superconducting circuits.…”

“…Quantum interference of the emitted photons thus enables entanglement of remote superconducting circuits. An advantage of this quantum memory-based transduction scheme over direct microwave-to-optical-photon conversion is a potential reduction in heating of the cryostat on account of the lower laser power required, which might preserve the coherence of the superconducting resonators [461].…”