Experimentally Realizable C-NOT Gate in a Flux Qubit/Resonator System

TL;DR

This paper demonstrates a microwave pulse sequence for implementing a high-fidelity C-NOT gate in a flux qubit/resonator system, highlighting the impact of qubit leakage and decoherence on fidelity.

Contribution

It introduces an experimentally feasible pulse sequence for a C-NOT gate with high fidelity in flux qubit/resonator systems, addressing leakage and decoherence issues.

Findings

Achieved a process fidelity of 0.988 for a two-qubit system under ideal conditions.

Fidelity drops to 0.903 under current experimental conditions.

Qubit leakage to higher resonator levels significantly reduces gate fidelity.

Abstract

In this paper we present an experimentally realizable microwave pulse sequence that effects a Controlled NOT (C-NOT) gate operation on a Josephson junction-based flux-qubit/resonator system with high fidelity in the end state. We obtained a C-NOT gate process fidelity of 0.988 (0.980) for a two (three) qubit/resonator system under ideal conditions, and a fidelity of 0.903 for a two qubit/resonator system under the best, currently achieved, experimental conditions. In both cases, we found that "qubit leakage" to higher levels of the resonator causes a majority of the loss of fidelity, and that such leakage becomes more pronounced as decoherence effects increase.