We have studied interactions between two capacitively coupled GaAs/AlGaAs few-electron double quantum dots. Each double quantum dot defines a tunable two-level system, or qubit, in which a single excess electron occupies either the ground state of one dot or the other. Applying microwave radiation we resonantly drive transitions between states and non-invasively measure occupancy changes using proximal quantum point contact charge detectors. The level structure of the interacting two-qubit system is probed by driving it at a fixed microwave frequency whilst varying the energy detuning of both double dots. We observe additional resonant transitions consistent with a simple coupled two-qubit Hamiltonian model.
@article{arxiv.0907.2409,
title = {Microwave-Driven Transitions in Two Coupled Semiconductor Charge Qubits},
author = {K. D. Petersson and C. G. Smith and D. Anderson and P. Atkinson and G. A. C. Jones and D. A. Ritchie},
journal= {arXiv preprint arXiv:0907.2409},
year = {2009}
}