Ion-atom two-qubit quantum gate based on phonon blockade

TL;DR

This paper proposes a theoretical scheme for a universal two-qubit CNOT gate between an ion and an atom using Rydberg excitation and phonon blockade, with potential for quantum computing and networking.

Contribution

It introduces a novel ion-atom hybrid gate protocol leveraging phonon blockade, expanding quantum gate options in hybrid systems.

Findings

Gate fidelity of about 90% with realistic parameters.

Demonstrates phonon blockade as a mechanism for ion-atom entanglement.

Discusses pathways to improve gate fidelity.

Abstract

We theoretically demonstrate the universal two-qubit CNOT gate between an ionic and an atomic qubit relying on Rydberg excitation of the atom and the resulting phonon blockade in the motional states of the harmonically trapped ion. The phonon blockade arises due to strong ion-atom interaction when the atom is excited to a Rydberg state. For realistic parameters, the gate fidelity is found to be about $90\%$. In a previous paper [S. Mudli {\it et al.} Phys. Rev. A 110, 062618 (2024)], it was shown that a trapped ion can mediate interaction between two largely separated Rydberg atoms, and this mediated interaction can be leveraged to perform a universal two-qubit gate operation between neutral atom qubits in optical tweezers. These demonstrations suggest that an ion-atom hybrid system can serve as a resourceful platform or module for quantum computing and quantum networking as it can utilize the best features of charged as well as neutral atom qubits. Finally, we discuss how to achieve higher gate fidelity by extending our proposed protocol and operating in a different parameter regime.