Interfacing a quantum dot spin with a photonic circuit
Physical Review Letters
American Physical Society
A scalable optical quantum information processor is likely to be a waveguide circuit with integrated sources, detectors, and either deterministic quantum-logic or quantum memory elements. With microsecond coherence times, ultrafast coherent control, and lifetime-limited transitions, semiconductor quantum-dot spins are a natural choice for the static qubits. However their integration with flying photonic qubits requires an on-chip spin-photon interface, which presents a fundamental problem: the spin-state is measured and controlled via circularly-polarised photons, but waveguides support only linear polarisation. We demonstrate here a solution based on two orthogonal photonic nanowires, in which the spin-state is mapped to a path-encoded photon, thus providing a blue-print for a scalable spin-photon network. Furthermore, for some devices we observe that the circular polarisation state is directly mapped to orthogonal nanowires. This result, which is physically surprising for a non-chiral structure, is shown to be related to the nano-positioning of the quantum-dot with respect to the photonic circuit.
This work was funded by EPSRC Grants No. EP/G001642, No. EP/J007544, and No. EP/G004366/1, and as part of project SPANGL4Q, under FET-Open Grant No. FP7-284743. The FDTD calculations used the computational facilities of the Advanced Computing Research Centre (Bristol). We thank D. N. Krizhanovskii, L. R. Wilson, P. Kok, and D. M. Whittaker for helpful discussions and comments on the manuscript.
This is the final version of the article. Available from American Physical Society via the DOI in this record.
Vol. 110, article 037402