Eur. Phys. J. D 18, 179-190 (2002)
https://doi.org/10.1140/epjd/e20020022

Triggered single photons and entangled photons from a quantum dot microcavity

¹ Quantum Entanglement Project, ICORP, JST, E. L. Ginzton Laboratory, Stanford University, Stanford CA-94305, USA
² Solid-State Photonics Laboratory, Stanford University, Stanford CA-94305, USA
³ Physics Department, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany
⁴ NTT Basic Research Laboratories, Atsugishi, Kanagawa, Japan

Corresponding author: ^a pelton@stanford.edu

Received: 8 July 2001
Revised: 25 August 2001
Published online: 15 February 2002

Abstract

Current quantum cryptography systems are limited by the attenuated coherent pulses they use as light sources: a security loophole is opened up by the possibility of multiple-photon pulses. By replacing the source with a single-photon emitter, transmission rates of secure information can be improved. We have investigated the use of single self-assembled InAs/GaAs quantum dots as such single-photon sources, and have seen a tenfold reduction in the multi-photon probability as compared to Poissonian pulses. An extension of our experiment should also allow for the generation of triggered, polarization-entangled photon pairs. The utility of these light sources is currently limited by the low efficiency with which photons are collected. However, by fabricating an optical microcavity containing a single quantum dot, the spontaneous emission rate into a single mode can be enhanced. Using this method, we have seen 78% coupling of single-dot radiation into a single cavity resonance. The enhanced spontaneous decay should also allow for higher photon pulse rates, up to about 3 GHz.