# Stuttgart 2012 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 65: SYQM: Quantum limited measurement applications 2

### Q 65.7: Vortrag

### Freitag, 16. März 2012, 16:00–16:15, V47.01

**Quantum State Tomography of Bipartite Bose Condensates** — •Roman Schmied, Caspar Ockeloen, and Philipp Treutlein — Departement Physik, Universität Basel, Schweiz

The quantum-mechanical states of large systems are difficult to measure experimentally because of the exponentially large number of variables involved. Yet in systems of indistinguishable bosons, this number is dramatically reduced, and a tomographic reconstruction of the exchange-symmetric density matrix is feasible even for thousands of particles. We present a practical method for experimentally performing this tomography for two-component Bose–Einstein condensates,^{*} and extend it to the tomographic determination of *correlations* between small numbers of particles within a condensate: such correlations can be stable even when the total atom number fluctuates between experimental runs. The tomographic reconstructions of Wigner functions, Glauber–Sudarshan P-representations, and Husimi-Q distributions on the Bloch sphere are compared.

As an application we present the quantum-state tomography of spin-squeezed states of a two-component ^{87}Rb Bose–Einstein condensate (see also SYQM 1.5).

^{*} R. Schmied and P. Treutlein, New J. Phys. **13**, 065019 (2011)