Realizable Receivers for Discriminating Coherent States near the Quantum Limit

8 11/2013

Friday, 08 Nov. 2013, 11:00 - 12:00

Workgroup Walther Group

Presenter: Si-Hui Tan
Host: P. Walther
Where: Josef-Stefan-Hörsaal, Boltzmanngasse 5, 3rd floor, 1090 Vienna

We propose a receiver, the Sequential Waveform Nulling (SWN) receiver, for discriminating between states of an arbitrary coherent-state ensemble using only auxiliary coherent-state fields, beamsplitters, and non-number-resolving single photon detectors. In particular, it does not require adaptive feedback which has limited the implementation of some known receivers, such as the Dolinar receiver, for large ensembles. We derive the quantum limit on the error probability exponent for discriminating any M multimode coherent-states, which is four times that of a heterodyne receiver, and show that the SWN receiver achieves this limit. As coherent-states are central to applications of laser light, such as quantum communication and imaging, the SWN receiver will be important for these applications as a practical receiver. We demonstrate the performance of the SWN receiver on a 4-Phase-Shift-Key coherent-state ensemble and an image-orientation detection problem, and compare it to the performance of other known coherent-state receivers. Finally, we show a related receiver for discriminating arbitrary multi-copy pure quantum states that achieves the  quantum Chernoff exponent, and does so using only local operations and classical communication.