Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 17: Quantum Information: Atoms and Ions I

Q 17.8: Vortrag

Dienstag, 9. März 2010, 16:15–16:30, E 214

Generation of macroscopic singlet states in atomic ensembles — •Geza Toth^1,2,3 and Morgan W. Mitchell⁴ — ¹Theoretical Physics, The University of the Basque Country, E-48080 Bilbao, Spain — ²IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain — ³Research Institute for Solid State Physics and Optics, H-1525 Budapest, Hungary — ⁴ICFO, Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona), Spain

We study squeezing of the spin uncertainties by quantum non-demolition (QND) measurement in non-polarized spin ensembles. Unlike the case of polarized ensembles, the QND measurements can be performed with negligible back-action, which allows, in principle, perfect spin squeezing as quantified by [G. Toth et al., Phys. Rev. Lett. 99, 250405 (2007)]. The generated spin states approach many-body singlet states, and contain a macroscopic number of entangled particles, even when individual spin is large. We introduce the Gaussian treatment of unpolarized spin states and use it to estimate the achievable spin squeezing for realistic experimental parameters. Our proposal might have applications for quantum memories storing information in decoherence free subspaces.