(Invited) Coherent Manipulation of a Si/SiGe-based Singlet-Triplet Qubit

Abstract

Electrically defined silicon-based qubits are expected to show improved quantum memory characteristics in comparison with GaAs-based devices due to reduced hyperfine interactions with nuclear spins. Silicon-based qubit devices have proved more challenging to build than their GaAs-based counterparts, but recently several groups have reported substantial progress in single-qubit initialization, measurement, and coherent operation. We report coherent control of electron spins in two coupled quantum dots in an undoped Si/SiGe heterostructure, forming two levels of a singlet-triplet qubit. We measure a nuclei-induced T2* of 365 {plus minus} 11 ns, an increase over similar measurements in GaAs-based quantum dots by nearly two orders of magnitude. This value for T2* is consistent with theoretical expectations for our estimated dot sizes and a natural abundance of 29Si.