# Stuttgart 2012 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 36: SYPC: From Atoms to Photonic Circuits 1

### Q 36.1: Hauptvortrag

### Donnerstag, 15. März 2012, 10:30–11:00, V47.01

**Quantum Communication: real-world applications and academic research** — •Nicolas Gisin — GAP, University of geneva

Quantum communication is the art of transferring a quantum state from one place, Alice, to another, Zeus. The simplest technique consists in merely sending a system carrying the quantum state, typically a photon, directly from Alice to Zeus. This is basically the way commercial quantum key distribution apparatuses work today, though direct communication is definitively limited to a few hundreds of km due to losses in optical fibers. But there are more sophisticated ways to realize quantum communication, each more fascinating than the other. First, one could exploit 2-photon entanglement and their EPR-like correlations. Next, one could perform quantum teleportation, a mind-boggling 3-photon process. All these have been demonstrated in and outside labs. But the real grand challenge for quantum communication is much more ambitious and fascinating: teleport a quantum state along a chain of sections: from A to B, then from B to C and so on until Y to Z. Moreover, in order to outperform direct communication, the process should be efficient. This requires that the A-B and B-C and * Y-Z entanglements necessary for quantum teleportation, must all be ready before one starts the teleportation processes. This, in turn, implies that the entanglement must be in-between quantum memories located at each node A, B, C, etc, able to hold the quantum state for ms.