Replacement-Type Quantum Gates

TL;DR

This paper introduces replacement-type quantum gates that utilize candidate qubits to produce targeted output states, potentially enhancing noise bias preservation and error correction in quantum computing architectures.

Contribution

The paper presents a novel paradigm of replacement-type quantum gates, including specific implementations with spin and neutral atom qubits, and analyzes their error rates and noise bias preservation.

Findings

Error rates predicted near the threshold of the XZZX surface code

Gates approximately preserve innate noise bias

Potential for improved quantum error correction architectures

Abstract

We introduce the paradigm of replacement-type quantum gates. This type of gate introduces input qubits, candidate qubits, and output qubits. The candidate qubits are prepared such, that a displacement conditional on the input qubit results in the targeted output state. Finally, the circuit continues with the output qubits constructed from the candidate qubits instead of the input qubits, thus the name "replacement-type gate". We present examples of replacement-type $X$ and $\mathrm{CNOT}$ gates realized with spin qubits and with neutral atom qubits with error rates predicted near the threshold of the XZZX surface code. By making use of the extended Hilbert space, including the position of the particles, these gates approximately preserve the innate noise bias of the qubits. The gate preserves the noise bias which motivates advanced quantum computer architectures with quantum error correction.