München 2004 – scientific programme

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Q: Quantenoptik und Photonik

Q 7: Quantenkommunikation

Q 7.6: Talk

Monday, March 22, 2004, 17:45–18:00, HS 101

Measurements for quantum communication using linear optics — •Philippe Raynal, Peter van Loock, and Norbert Lütkenhaus — Institut für Theoretische Physik I, Universität Erlangen-Nürnberg, Staudtstrasse, 7/B1 91058 Erlangen, Deutschland

There is a set of simple criteria to decide whether a given projection measurement can be, in principle, exactly implemented solely by means of linear optics utilizing photon counting or homodyne detections [1]. The linear-optics toolbox includes auxiliary photons and conditional dynamics, i.e., the adjustment of subsequent linear-optics transformations of the conditional states after measuring a first mode. Here we add more tools such as phase-space displacements and squeezing and incorporate them into the criteria. This enables one to treat important measurements for quantum communication in the continuous-variable regime where the signal states have an unfixed and unbounded photon number. We further discuss the extension of our approach to generalized measurements (POVM’s).

[1] P. van Loock, N. Lütkenhaus, PRA (in press), quant-ph/0304057.