High-fidelity state detection and tomography of a single ion Zeeman qubit

TL;DR

This paper demonstrates near-perfect state detection and tomography of a single ion qubit, achieving high fidelity measurements crucial for quantum computing and process characterization.

Contribution

The authors achieve high-fidelity Zeeman qubit detection and state tomography in a single trapped Sr+ ion, advancing quantum measurement precision.

Findings

Readout fidelity of 0.9989(1) for qubit state detection

State tomography fidelity of 0.9979(2)

Full characterization of detection process via quantum process tomography

Abstract

We demonstrate high-fidelity Zeeman qubit state detection in a single trapped 88 Sr+ ion. Qubit readout is performed by shelving one of the qubit states to a metastable level using a narrow linewidth diode laser at 674 nm followed by state-selective fluorescence detection. The average fidelity reached for the readout of the qubit state is 0.9989(1). We then measure the fidelity of state tomography, averaged over all possible single-qubit states, which is 0.9979(2). We also fully characterize the detection process using quantum process tomography. This readout fidelity is compatible with recent estimates of the detection error-threshold required for fault-tolerant computation, whereas high-fidelity state tomography opens the way for high-precision quantum process tomography.