Perfect excitation of a matter qubit by a single photon in free space

¹  Max Planck Institute for the Science of Light - Günter-Scharowsky-Str. 1, Bau 24, 91058 Erlangen, Germany, EU
²  Institut für Optik, Information und Photonik, Universität Erlangen-Nürnberg - Staudtstr. 7/B2, 91058 Erlangen, Germany, EU
³  Institut für Angewandte Physik, Technische Universität Darmstadt - 64289 Darmstadt, Germany, EU

Corresponding author: magda.stobinska@mpl.mpg.de

Received: 10 March 2009
Accepted: 17 March 2009

Abstract

We propose a scheme for perfect excitation of a single two-level atom by a single photon in free space. The photon state has to match the time reversed photon state originating from spontaneous decay of a two-level system. Here, we discuss its experimental preparation. The state is characterized by a particular asymmetric exponentially shaped temporal profile. Any deviations from this ideal state limit the maximum absorption. Although perfect excitation requires an infinite amount of time, we demonstrate that there is a class of initial one-photon quantum states which can achieve almost perfect absorption even for a finite interaction time. Our results pave the way for realizing perfect coupling between flying and stationary qubits in free space thus opening a possibility for building scalable quantum networks.