Frankfurt 2006 – scientific programme

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Q: Quantenoptik und Photonik

Q 40: Quanteninformation III

Q 40.1: Talk

Wednesday, March 15, 2006, 11:10–11:25, HI

Cleaning noisy photons via cross phase modulation — •Michael Nock — Universitätstrasse 10, 78457 Konstanz

∖begin{abstract} We propose a scheme for a heralded generation of a pure single-photon state by post-processing the outputs of imperfect single-photon sources. The latter are modelled by mixtures of the single-photon Fock state $∣1∖rangle$ with the vacuum $∣0∖rangle$, i.e., $∖rho=p∣1∖rangle∖langle 1∣+ (1-p)∣0∖rangle∖langle 0∣$ with $p$ being the probability that the source has produced one photon. Our scheme is based on phase shifts induced by cross phase modulation (XPM) via the nonlinear optical Kerr effect. Recent progress in this area have led to the feasibility of huge phase shifts on the order of $∖pi$ even for light pulses of tiny energies corresponding to that of single photons. Given two imperfect inputs we achieve a success probability of $P_{∖mbox{∖tiny success}}=p^2 ∖sin^2( ∖phi /2)$ with $∖phi$ being the phase shift due to XPM. The success probability can be enhanced to $P_{∖mbox{∖tiny success}}=p(1-∖exp[-∣∖alpha∣^2])$ if one of the inputs is replaced by a strong coherent laser pulse, i.e., a coherent state $∣∖alpha∖rangle$ with $∣ ∖alpha∣∖gg 1$. Combination of several apparatuses of this kind and allowing more inputs increases the success probability arbitrarily close to 1. ∖end{abstract}