Implementation of three-qubit Toffoli gate in a single step

TL;DR

This paper proposes a scheme for implementing a high-fidelity, single-step three-qubit Toffoli gate using coupled qubits and photon fields, optimizing parameters to minimize errors and decoherence effects.

Contribution

The paper introduces a realizable single-step Toffoli gate scheme based on modified Jaynes-Cummings models and parameter tuning, simplifying multi-qubit gate implementation.

Findings

Single-step Toffoli gate can be achieved with parameter tuning.

High fidelity is possible by adjusting photon-qubit and qubit-qubit couplings.

Decoherence effects are manageable with proper system parameter choices.

Abstract

Single-step implementations of multi-qubit gates are generally believed to provide a simpler design, a faster operation, and a lower decoherence. For coupled three qubits interacting with a photon field, a realizable scheme for a single-step Toffoli gate is investigated. We find that the three qubit system can be described by four effective modified Jaynes-Cummings models in the states of two control qubits. Within the rotating wave approximation, the modified Jaynes-Cummings models are shown to be reduced to the conventional Jaynes-Cummings models with renormalized couplings between qubits and photon fields. A single-step Toffoli gate is shown to be realizable with tuning the four characteristic oscillation periods that satisfy a commensurate condition. Possible values of system parameters are estimated for single-step Toffli gate. From numerical calculation, further, our single-step Toffoli gate operation errors are discussed due to imperfections in system parameters, which shows that a Toffoli gate with high fidelity can be obtained by adjusting pairs of the photon-qubit and the qubit-qubit coupling strengthes. In addition, a decoherence effect on the Toffoli gate operation is discussed due to a thermal reservoir.