Hamburg 2009 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 56: Poster IV
Q 56.40: Poster
Thursday, March 5, 2009, 16:30–19:00, VMP 9 Poster
Coherent state discrimination via a Homodyne-Kennedy Hybrid — •Christian Müller1, Mario Usuga1,2, Christoffer Wittmann1, Masahiro Takeoka3, Ulrik L. Andersen1,2, and Gerd Leuchs1 — 1Max-Planck-Institut für die Physik des Lichts , Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen, Germany — 2Department of Physics, Technical University of Denmark, Building 309, 2800 Lyngby, Denmark — 3National Institute of Information and Communications Technology, 4-2-1 Nukui-Kita, Koganei, Tokyo 184-8795, Japan
We present a novel quantum receiver for the discrimination of a coherent state alphabet consisting of four phase covariant coherent states equally spaced in phase by pi/2. The task of the receiver is to guess the arriving quantum state with minimum error. Our receiver is a hybrid system composed of a homodyne detector and an modified Kennedy detector [1] where the latter one is controlled by the outcome of the former one: The measurement outcome of the homodyne detector reduces the alphabet from four states to two states which are then discriminated with the adapted Kennedy detector. We show that in theory this hybrid receiver surpasses a receiver using heterodyne detection for signal states with average photon numbers larger than about 1.5.
[1] C. Wittmann, M. Takeoka, K.N. Cassemiro, M. Sasaki, G. Leuchs, and U.L. Andersen, Phys. Rev. Lett. 101, 210501 (2008)