Coherent spin manipulation in an exchange-only qubit

Laird, E A and Taylor, J M and DiVincenzo, DP and Marcus, C M and Hanson, M P and Gossard, A C (2010) Coherent spin manipulation in an exchange-only qubit. Physical review B, 82 (7): 075403. ISSN 1098-0121

Abstract

Initialization, two-spin coherent manipulation, and readout of a three-spin qubit are demonstrated using a few-electron triple quantum dot. The three-spin qubit is designed to allow all operations for full qubit control to be tuned via nearest-neighbor exchange interaction. Fast readout of charge states takes advantage of multiplexed reflectometry. Decoherence measured in a two-spin subspace 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 multiqubit control using only exchange and electrostatic interactions are outlined.