Role of Single Qubit Decoherence Time in Adiabatic Quantum Computation

TL;DR

This study numerically investigates how single-qubit decoherence impacts adiabatic quantum computation, revealing that computation time is not constrained by decoherence time even with small energy gaps.

Contribution

It demonstrates that adiabatic quantum computers can operate efficiently despite decoherence, challenging the assumption that decoherence time limits quantum computational speed.

Findings

Computation time is comparable to isolated systems, unaffected by single-qubit decoherence.

Small energy gaps do not significantly increase computation time.

Effective two-state model describes system behavior for small gaps.

Abstract

We have studied numerically the evolution of an adiabatic quantum computer in the presence of a Markovian ohmic environment by considering Ising spin glass systems with up to 20 qubits independently coupled to this environment via two conjugate degrees of freedom. The required computation time is demonstrated to be of the same order as that for an isolated system and is not limited by the single-qubit decoherence time $T_2^*$, even when the minimum gap is much smaller than the temperature and decoherence-induced level broadening. For small minimum gap, the system can be described by an effective two-state model coupled only longitudinally to environment.