Doubling Qubits in a Trapped-Ion System via Vibrational Dual-Rail Encoding

TL;DR

This paper introduces a dual-rail vibrational encoding scheme in trapped-ion systems, enabling scalable, all-to-all connected quantum computation with nearly doubled logical qubits by integrating internal and vibrational qubits.

Contribution

It proposes a novel dual-rail vibrational encoding for qubits, extending to a hybrid system that nearly doubles logical qubits while maintaining connectivity.

Findings

Demonstrated preparation and measurement of dual-rail vibrational qubits

Implemented universal single- and two-qubit gates

Proposed multi-qubit controlled gate methods

Abstract

Vibrational modes of trapped ions have traditionally served as quantum buses to mediate internal qubits. However, with recent advances in quantum control, it has become possible to use these vibrational modes directly as quantum computational resources, such as bosonic qubits. Here, we propose a dual-rail encoding scheme in which a dual-rail qubit is encoded by two vibrational modes that share a single phonon. We present the preparation, measurement, and implementation of single- and two-qubit gates, enabling universal quantum computation. The dual-rail qubit system offers scalability and all-to-all connectivity. Moreover, we extend the dual-rail qubit system to a logical internal qubit--dual-rail qubit hybrid system by incorporating internal qubits into the dual-rail qubit system as another type of logical qubit. The hybrid system nearly doubles the number of available logical qubits compared to conventional trapped-ion quantum computers while maintaining all-to-all connectivity. Additionally, we propose a method for implementing multi-qubit controlled gates and discuss potential applications that can leverage the advantages of the hybrid system. Our scheme provides a practical framework for an internal qubit-boson qubit hybrid system.