Entangled photon pairs are an important resource in quantum optics1, and are essential for quantum information2 applications such as quantum key distribution3,4 and controlled quantum logic operations5. The radiative decay of biexcitons—that is, states consisting of two bound electron–hole pairs—in a quantum dot has been proposed as a source of triggered polarization-entangled photon pairs6. To date, however, experiments have indicated that a splitting of the intermediate exciton energy yields only classically correlated emission7,8,9. Here we demonstrate triggered photon pair emission from single quantum dots suggestive of polarization entanglement. We achieve this by tuning the splitting to zero, through either application of an in-plane magnetic field or careful control of growth conditions. Entangled photon pairs generated ‘on demand’ have significant fundamental advantages over other schemes10,11,12,13, which can suffer from multiple pair emission, or require post-selection techniques or the use of photon-number discriminating detectors. Furthermore, control over the pair generation time is essential for scaling many quantum information schemes beyond a few gates. Our results suggest that a triggered entangled photon pair source could be implemented by a simple semiconductor light-emitting diode14.
Subscribe to Journal
Get full journal access for 1 year
only $3.83 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Walls, D. F. & Milburn, G. J. Quantum Optics (Springer, Berlin, 1994)
Bouwmeester, D., Ekert, A. K. & Zeilinger, A. The Physics of Quantum Information (Springer, Berlin, 2000)
Ekert, A. K. Quantum cryptography based on Bell's theorem. Phys. Rev. Lett. 67, 661–663 (1991)
Gisin, N., Ribordy, G., Tittel, W. & Zbinden, H. Quantum cryptography. Rev. Mod. Phys. 74, 145–195 (2002)
Knill, E., Laflamme, R. & Milburn, G. J. A scheme for efficient quantum computation with linear optics. Nature 409, 46–52 (2001)
Benson, O., Santori, C., Pelton, M. & Yamamoto, Y. Regulated and entangled photons from a single quantum dot. Phys. Rev. Lett. 84, 2513–2516 (2000)
Stevenson, R. M. et al. Quantum dots as a photon source for passive quantum key encoding. Phys. Rev. B 66, 081302 (2002)
Santori, C., Fattal, D., Pelton, M., Solomon, G. S. & Yamamoto, Y. Polarization-correlated photon pairs from a single quantum dot. Phys. Rev. B 66, 045308 (2002)
Ulrich, S. M., Strauf, S., Michler, P., Bacher, G. & Forchel, A. Triggered polarization-correlated photon pairs from a single CdSe quantum dot. Appl. Phys. Lett. 83, 1848–1850 (2003)
Shih, Y. H. & Alley, C. O. New type of Einstein-Podolsky-Rosen-Bohm experiment using pairs of light quanta produced by optical parametric down conversion. Phys. Rev. Lett. 61, 2921–2924 (1988)
Ou, Z. Y. & Mandel, L. Violation of Bell's inequality and classical probability in a two-photon correlation experiment. Phys. Rev. Lett. 61, 50–53 (1988)
Kiess, T. E., Shih, Y. H., Sergienko, A. V. & Alley, C. O. Einstein-Podolsky-Rosen-Bohm experiment using pairs of light quanta produced by type-II parametric down-conversion. Phys. Rev. Lett. 71, 3893–3897 (1993)
Fattal, D. et al. Entanglement formation and violation of Bell's inequality with a semiconductor single photon source. Phys. Rev. Lett. 92, 037903 (2004)
Yuan, Z. et al. Electrically driven single-photon source. Science 295, 102–105 (2002)
Edamatsu, K., Oohata, G., Shimizu, R. & Itoh, T. Generation of ultraviolet entangled photons in a semiconductor. Nature 431, 167–170 (2004)
Santori, C., Fattal, D., Vučković, J., Solomon, G. S. & Yamamoto, Y. Indistinguishable photons from a single-photon device. Nature 419, 594–597 (2002)
Aspect, A., Grangier, P. & Roger, G. Experimental realization of Einstein-Podolsky-Rosen-Bohm Gedankenexperiment: A new violation of Bell's inequalities. Phys. Rev. Lett. 49, 91–94 (1982)
Gammon, D., Snow, E. S., Shanabrook, B. V.,, Katzer, D. S. & Park, D. Fine structure splitting in the optical spectra of single GaAs quantum dots. Phys. Rev. Lett. 76, 3005–3008 (1996)
Bimberg, D., Grundmann, M. & Ledentsov, N. N. Quantum Dot Heterostructures (Wiley, Chichester, 1999)
Young, R. J. et al. Inversion of exciton level splitting in quantum dots. Phys. Rev. B 72, 113305 (2005)
Thompson, R. M. et al. Single-photon emission from exciton complexes in individual quantum dots. Phys. Rev. B 64, 201302 (2001)
Rodt, S. et al. Repulsive exciton-exciton interaction in quantum dots. Phys. Rev. B 68, 035331 (2003)
White, A. G., James, D. F. V., Eberhard, P. H. & Kwiat, P. G. Nonmaximally entangled states: Production, characterization, and utilization. Phys. Rev. Lett. 83, 3103–3107 (1999)
James, D. F. V., Kwiat, P. G., Munro, W. J. & White, A. G. Measurement of qubits. Phys. Rev. A 64, 052312 (2001)
Kwiat, P. G., Barraza-Lopez, S., Stefanov, A. & Gisin, N. Experimental entanglement distillation and ‘hidden’ non-locality. Nature 409, 1014–1017 (2001)
Santori, C., Pelton, M., Solomon, G., Dale, Y. & Yamamoto, Y. Triggered single photons from a quantum dot. Phys. Rev. Lett. 86, 1502–1505 (2001)
Pelton, M. et al. Efficient source of single photons: A single quantum dot in a micropost microcavity. Phys. Rev. Lett. 89, 233602 (2002)
Bennett, A. J., Unitt, D. C., Atkinson, P., Ritchie, D. & Shields, A. J. High performance single photon sources from photolithographically defined pillar microcavities. Opt. Express 13, 50–55 (2005)
Bayer, M. & Forchel, A. Temperature dependence of the exciton homogeneous linewidth in In0.60Ga0.40As/GaAs self-assembled quantum dots. Phys. Rev. B 65, 041308 (2002)
Stevenson, R. M. et al. Magnetic-field-induced reduction of the exciton polarisation splitting in InAs quantum dots. Phys. Rev. B (in the press)
We acknowledge continued support from M. Pepper. This work was partially funded by the EU projects RAMBOQ, QAP and SANDiE, and by the EPSRC through the IRC for Quantum Information Processing.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
About this article
Cite this article
Stevenson, R., Young, R., Atkinson, P. et al. A semiconductor source of triggered entangled photon pairs. Nature 439, 179–182 (2006). https://doi.org/10.1038/nature04446
Advanced Quantum Technologies (2020)
Physical Review B (2020)
In situ wavelength tuning of quantum-dot single-photon sources integrated on a CMOS-processed silicon waveguide
Applied Physics Letters (2020)
Journal of Semiconductors (2020)
Resonance fluorescence of a single semiconductor quantum dot: the impact of a fluctuating electrostatic environment
Semiconductor Science and Technology (2019)