Toward development of a quantum transducer to hybridize superconducting and ion trap quantum computers.

Quantum information processing is poised to revolutionize the global information system with dramatically enhanced computational power capable of unlocking solutions to previously unsolvable problems. To date, the two leading platforms are trapped ion- and superconducting circuit-based architectures. Trapped ion qubits exhibit long coherence times and efficient remote entanglement, while superconducting circuits offer scalability and fast quantum gate speeds. In the pursuit of optimal quantum processing, storage, and teleportation, a dedicated hybrid quantum system will perform fast information processing encoded in superconducting circuit qubits and store and teleport the processed information in the form of trapped ion qubits. Due to the significant difference in mass and dimension, direct coupling between the macroscopic superconducting circuits and a microscopic atomic ion is either slow or far off-resonance. To tackle this critical issue, we propose applying circular Rydberg states of strontium (Sr) atoms hypersensitive to a microwave field to interact with the superconducting qubits. Immediately after that, the short-lived Rydberg qubits will be transferred to long-lived spin qubits in Sr⁺ ions by a selective ion-core excitation. Several recently demonstrated state-of-the-art technologies will be implemented on a millimeter-scale chip, including trapping and shuttling neutral atoms along an optical nanofiber and on-chip THz ionization of Rydberg atoms.