Quantum-dot spin–photon entanglement via frequency downconversion to telecom wavelength

De Greve, K. et al. (2012) Quantum-dot spin–photon entanglement via frequency downconversion to telecom wavelength. Nature, 491(7424), pp. 421-425. (doi:10.1038/nature11577)

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Long-distance quantum teleportation and quantum repeater technologies require entanglement between a single matter quantum bit (qubit) and a telecommunications (telecom)-wavelength photonic qubit1, 2, 3, 4, 5. Electron spins in III–V semiconductor quantum dots are among the matter qubits that allow for the fastest spin manipulation6, 7 and photon emission8, 9, but entanglement between a single quantum-dot spin qubit and a flying (propagating) photonic qubit has yet to be demonstrated. Moreover, many quantum dots emit single photons at visible to near-infrared wavelengths, where silica fibre losses are so high that long-distance quantum communication protocols become difficult to implement10. Here we demonstrate entanglement between an InAs quantum-dot electron spin qubit and a photonic qubit, by frequency downconversion of a spontaneously emitted photon from a singly charged quantum dot to a wavelength of 1,560 nanometres. The use of sub-10-picosecond pulses at a wavelength of 2.2 micrometres in the frequency downconversion process provides the necessary quantum erasure to eliminate which-path information in the photon energy. Together with previously demonstrated indistinguishable single-photon emission at high repetition rates11, 12, the present technique advances the III–V semiconductor quantum-dot spin system as a promising platform for long-distance quantum communication.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Hadfield, Professor Robert
Authors: De Greve, K., Yu, L., McMahon, P.L., Pelc, J.S., Natarajan, C.M., Kim, N.Y., Abe, E., Maier, S., Schneider, C., Kamp, M., Höfling, S., Hadfield, R., Forchel, A., Fejer, M.M., and Yamamoto, Y.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:Nature
Publisher:Nature Publishing Group
ISSN (Online):1476-4687
Published Online:14 November 2012

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