Photon-Number Conserved Universal Quantum Logic Employing Continuous-Time Quantum Walk on Dual-Rail Qubit Arrays

TL;DR

This paper presents a superconducting circuit scheme using continuous-time quantum walks on dual-rail transmons to implement universal, photon-number conserving quantum logic with high fidelity and robustness against errors.

Contribution

It introduces a novel architecture combining dual-rail encoding and CTQW for universal quantum gates, enhancing fault tolerance and practicality in superconducting quantum computing.

Findings

Numerical simulations show robustness against dephasing and relaxation.

The scheme enables high-fidelity single-, two-, and three-qubit gates.

Leakage and relaxation are transformed into erasure errors, improving fault tolerance.

Abstract

We demonstrate a synergy between dual-rail qubit encoding and continuous-time quantum walks (CTQW) to realize universal quantum logic in superconducting circuits. Utilizing the photon-number-conserving dynamics of CTQW on dual-rail transmons, which systematically transform leakage and relaxation into erasure events, our architecture facilitates the suppression of population leakage and the implementation of high-fidelity quantum gates. We construct single-, two-, and three-qubit operations that preserve dual-rail encoding, facilitated by tunable coupler strengths compatible with current superconducting qubit platforms. Numerical simulations confirm robust behavior against dephasing, relaxation, and imperfections in coupling, underscoring the erasure-friendly nature of the system. This hardware-efficient scheme thus provides a practical pathway to early fault-tolerant quantum computation.