Coherent spin manipulation in an exchange-only qubit

TL;DR

This paper demonstrates the initialization, manipulation, and measurement of a three-spin exchange-only qubit in a triple quantum dot, highlighting its coherence properties and theoretical control requirements.

Contribution

It provides experimental realization and theoretical analysis of a three-spin exchange-only qubit with simplified initialization and control protocols.

Findings

Successful qubit readout via multiplexed reflectometry

Decoherence aligns with gate voltage noise predictions

Theoretical framework for minimal initialization requirements

Abstract

Initialization, manipulation, and measurement of a three-spin qubit are demonstrated using a few-electron triple quantum dot, where all operations can be driven by tuning the nearest-neighbor exchange interaction. Multiplexed reflectometry, applied to two nearby charge sensors, allows for qubit readout. Decoherence is found to be consistent with predictions based on gate voltage noise with a uniform power spectrum. The theory of the exchange-only qubit is developed and it is shown that initialization of only two spins suffices for operation. Requirements for full multi-qubit control using only exchange and electrostatic interactions are outlined.