title: Purification of a single-photon nonlinearity.
abstract: Single photon nonlinearities based on a semiconductor quantum dot in an optical microcavity are a promising candidate for integrated optical quantum information processing nodes. In practice, however, the finite quantum dot lifetime and cavity-quantum dot coupling lead to reduced fidelity. Here we show that, with a nearly polarization degenerate microcavity in the weak coupling regime, polarization pre- and postselection can be used to restore high fidelity. The two orthogonally polarized transmission amplitudes interfere at the output polarizer; for special polarization angles, which depend only on the device cooperativity, this enables cancellation of light that did not interact with the quantum dot. With this, we can transform incident coherent light into a stream of strongly correlated photons with a second-order correlation value up to 40, larger than previous experimental results, even in the strong-coupling regime. This purification technique might also be useful to improve the fidelity of quantum dot based logic gates.
authors: Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
authors: H
authors: H
authors: Snijders
authors: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors: J A
authors: JA
authors: Frey
authors: Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106, USA.
authors: J
authors: J
authors: Norman
authors: Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
authors: M P
authors: MP
authors: Bakker
authors: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors: E C
authors: EC
authors: Langman
authors: Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106, USA.
authors: A
authors: A
authors: Gossard
authors: Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106, USA.
authors: J E
authors: JE
authors: Bowers
authors: Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
authors: M P
authors: MP
authors: van Exter
authors: Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.|Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors: D
authors: D
authors: Bouwmeester
authors: Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
authors: W
authors: W
authors: Löffler