Optical Barium Ion Qubit

TL;DR

This paper demonstrates an optical qubit using a single Ba+ ion with a transition near telecom wavelengths, showing fast oscillations and a method to quantify gate errors, advancing quantum communication prospects.

Contribution

It introduces a Ba+ ion qubit operating at telecom-compatible wavelengths using diode lasers, with demonstrated fast oscillations and a new technique for error quantification.

Findings

Bit-flip oscillation rate of 250 kHz

Coherence time exceeds 3 ms

Technique for quantifying qubit gate errors

Abstract

We demonstrate an optical single qubit based on 6S1/2 to 5D5/2 quadrupole transition of a single Ba+ ion operated by diode based lasers only. The resonance wavelength of the 6S1/2 to 5D5/2 quadrupole transition is about 1762 nm which suitably falls close to the U-band of the telecommunication wavelength. Thus this qubit is a naturally attractive choice towards implementation of quantum repeater or quantum networks using existing telecommunication networks. We observe continuous bit-flip oscillations at a rate of about 250 kHz which is fast enough for the qubit operation as compared to the measured coherence time of over 3 ms. We also present a technique to quantify the bit-flip error in each qubit NOT gate operation.