High-Fidelity Single-Shot Toffoli Gate via Quantum Control

TL;DR

This paper presents a high-fidelity, single-shot Toffoli gate for superconducting transmon qubits, achieving 99.9% fidelity and comparable speed to two-qubit gates using an advanced quantum control algorithm.

Contribution

It introduces a novel quantum control method to implement a single-shot Toffoli gate with high fidelity and speed, improving over traditional decomposition methods.

Findings

Achieved 99.9% fidelity for the Toffoli gate.

Implemented the gate in a time comparable to two-qubit gates.

Utilized an enhanced Differential Evolution algorithm for control optimization.

Abstract

A single-shot Toffoli, or controlled-controlled-NOT, gate is desirable for classical and quantum information processing. The Toffoli gate alone is universal for reversible computing and, accompanied by the Hadamard gate, forms a universal gate set for quantum computing. The Toffoli gate is also a key ingredient for (non-topological) quantum error correction. Currently Toffoli gates are achieved by decomposing into sequentially implemented single- and two-qubit gates, which requires much longer times and yields lower overall fidelities compared to a single-shot implementation. We develop a quantum-control procedure to construct a single-shot Toffoli gate for three nearest-neighbor-coupled superconducting transmon systems such that the fidelity is 99.9% and is as fast as an entangling two-qubit gate under the same realistic conditions. The gate is achieved by a non-greedy quantum control procedure using our enhanced version of the Differential Evolution algorithm.