Transport-enabled entangling gate for trapped ions

TL;DR

This paper demonstrates a transport-enabled entangling gate for trapped ions, showing that ion transport can be integrated into quantum entangling operations with high fidelity.

Contribution

It introduces a method to perform a two-qubit entangling gate by transporting ions through a stationary laser beam, adapting calibration procedures for dynamic conditions.

Findings

Bell states with fidelities comparable to stationary gates

Transported ions achieve high-fidelity entanglement

Feasibility of integrating ion transport into quantum gates

Abstract

We implement a two-qubit entangling M{\o}lmer-S{\o}rensen interaction by transporting two co-trapped $^{40}\mathrm{Ca}^{+}$ ions through a stationary, bichromatic optical beam within a surface-electrode Paul trap. We describe a procedure for achieving a constant Doppler shift during the transport which uses fine temporal adjustment of the moving confinement potential. The fixed interaction duration of the ions transported through the laser beam as well as the dynamically changing ac Stark shift require alterations to the calibration procedures used for a stationary gate. We use the interaction to produce Bell states with fidelities commensurate to those of stationary gates performed in the same system. This result establishes the feasibility of actively incorporating ion transport into quantum information entangling operations.