Quantum gate using qubit states separated by terahertz

TL;DR

This paper demonstrates a two-qubit quantum gate using electronic states separated by a terahertz frequency in a single ion, employing stimulated Raman transitions and Ramsey interferometry to observe quantum dynamics.

Contribution

It introduces a novel approach to quantum gates by utilizing qubit states separated by terahertz frequencies in a single ion, expanding the possibilities for quantum computing architectures.

Findings

Successful implementation of a two-qubit gate with terahertz-separated states.

Observation of quantum dynamics via Ramsey interferometry.

Controlled NOT operation demonstrated in a single trapped ion.

Abstract

A two-qubit quantum gate is realized using electronic excited states in a single ion with an energy separation on the order of a terahertz times the Planck constant as a qubit. Two phase locked lasers are used to excite a stimulated Raman transition between two metastable states $D_{3/2}$ and $D_{5/2}$ separated by 1.82 THz in a single trapped $^{40}$Ca$^+$ ion to construct a qubit, which is used as the target bit for the Cirac-Zoller two-qubit controlled NOT gate. Quantum dynamics conditioned on a motional qubit is clearly observed as a fringe reversal in Ramsey interferometry.