Fault-tolerant multiqubit geometric entangling gates using photonic cat-state qubits

TL;DR

This paper presents a theoretical protocol for implementing robust, fault-tolerant multiqubit geometric gates using photonic cat-state qubits, enhancing quantum computing efficiency and error correction.

Contribution

It introduces a novel geometric gate protocol that suppresses phase-flip errors, maintains error bias, and is robust against parameter imperfections in photonic cat-state qubits.

Findings

Achieves high-fidelity multiqubit entangling gates in short times.

Suppresses phase-flip errors, leaving only correctable bit-flip errors.

Maintains robustness against noise and parameter variations.

Abstract

We propose a theoretical protocol to implement multiqubit geometric gates (i.e., the M{\o}lmer-S{\o}rensen gate) using photonic cat-state qubits. These cat-state qubits stored in high-$Q$ resonators are promising for hardware-efficient universal quantum computing. Specifically, in the limit of strong two-photon drivings, phase-flip errors of the cat-state qubits are effectively suppressed, leaving only a bit-flip error to be corrected. Because this dominant error commutes with the evolution operator, our protocol preserves the error bias, and, thus, can lower the code-capacity threshold for error correction. A geometric evolution guarantees the robustness of the protocol against stochastic noise along the evolution path. Moreover, by changing detunings of the cavity-cavity couplings at a proper time, the protocol can be robust against parameter imperfections (e.g., the total evolution time) without introducing extra noises into the system. As a result, the gate can produce multi-mode entangled cat states in a short time with high fidelities.