Single electrons trapped by individual donors in semiconductors at low temperatures are promising qubit candidates due to their combination of the advantages of semiconductor and atomic systems. Donor-bound electrons have quasi-atomic electron wavefunctions, leading to much better homogeneity than electrons bound within self-assembled quantum dots. Furthermore, their semiconductor environment provides a natural localization and ease of fabrication that is absent in atomic and ion qubit systems.
The research performed in this project has shown that single electrons bound to fluorine donors in ZnSe quantum wells have spectroscopic properties very similar to the single electrons in quantum dots studied in other projects in the group, strongly suggesting that they will behave similarly as qubits. ZnSe is a very optically bright material and the lifetime of the donor-bound exciton state is shorter than that in quantum dots, which suggests that optical measurement and initialization could be performed more quickly in the donor system than in quantum dots. Furthermore, the homogeneity of the donor system produces similarly homogenous photons, simplifying optical coupling between two or more qubits.
Figure 1. Energy levels of the neutral donor ground state and the donor-bound exciton excited state in (a) Faraday and (c) Voigt geometry showing the optical transitions and polarization selection rules, along with the respective photoluminescent optical spectrum (b) and (d) as a function of magnetic field.
K. De Greve, S. M. Clark, D. Sleiter, K. Sanaka, T. D. Ladd, M. Panfilova, A. Pawlis, K. Lischka, and Y. Yamamoto, "Photon antibunching and magnetospectroscopy of a single fluorine donor in ZnSe," Appl. Phys. Lett. 97, 241913 (2010). [http://dx.doi.org/10.1063/1.3525579]
Kristiaan De Greve
Dr. Susan Clark
Dr. Kaoru Sanaka
Prof. Yoshihisa Yamamoto