A trapped ion quantum computer with robust entangling gates and quantum coherent feedback

TL;DR

This paper reports the construction of a small, high-fidelity five-qubit trapped ion quantum computer utilizing robust entangling gates and quantum coherent feedback, advancing the development of scalable quantum computing with ion traps.

Contribution

It introduces a five-qubit ion trap quantum computer with robust entangling gates and a quantum feedback system, enabling future quantum error correction.

Findings

High-fidelity single and two-qubit gates achieved

Implementation of a universal gate set for quantum computation

Development of a quantum coherent feedback system

Abstract

Quantum computers are expected to achieve a significant speed-up over classical computers in solving a range of computational problems. Chains of ions held in a linear Paul trap are a promising platform for constructing such quantum computers, due to their long coherence times and high quality of control. Here we report on the construction of a small, five-qubit, universal quantum computer using $^{88}\text{Sr}^{+}$ ions in an RF trap. All basic operations, including initialization, quantum logic operations, and readout, are performed with high fidelity. Selective two-qubit and single-qubit gates, implemented using a narrow linewidth laser, comprise a universal gate set, allowing realization of any unitary on the quantum register. We review the main experimental tools, and describe in detail unique aspects of the computer: the use of robust entangling gates and the development of a quantum coherent feedback system through EMCCD camera acquisition. The latter is necessary for carrying out quantum error correction protocols in future experiments.