Atom-chip-based generation of entanglement for quantum metrology
Abstract
Atom chips provide a versatile quantum laboratory for experiments with ultracold atomic gases1. They have been used in diverse experiments involving low-dimensional quantum gases2, cavity quantum electrodynamics3, atom-surface interactions4,5, and chip-based atomic clocks6 and interferometers7,8. However, a severe limitation of atom chips is that techniques to control atomic interactions and to generate entanglement have not been experimentally available so far. Such techniques enable chip-based studies of entangled many-body systems and are a key prerequisite for atom chip applications in quantum simulations9, quantum information processing10 and quantum metrology11. Here we report the experimental generation of multi-particle entanglement on an atom chip by controlling elastic collisional interactions with a state-dependent potential12. We use this technique to generate spin-squeezed states of a two-component Bose-Einstein condensate13; such states are a useful resource for quantum metrology. The observed reduction in spin noise of -3.7 ± 0.4 dB, combined with the spin coherence, implies four-partite entanglement between the condensate atoms14; this could be used to improve an interferometric measurement by -2.5 ± 0.6 dB over the standard quantum limit15. Our data show good agreement with a dynamical multi-mode simulation16 and allow us to reconstruct the Wigner function17 of the spin-squeezed condensate. The techniques reported here could be directly applied to chip-based atomic clocks, currently under development18.
- Publication:
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Nature
- Pub Date:
- March 2010
- DOI:
- arXiv:
- arXiv:1003.1651
- Bibcode:
- 2010Natur.464.1170R
- Keywords:
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- Quantum Physics
- E-Print:
- doi:10.1038/nature08988