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Magnetic sensitivity beyond the projection noise limit by spin squeezing.
R J Sewell1, M Koschorreck, M Napolitano
1ICFO-Institut de Ciencies Fotoniques, Avenida Carl Friedrich Gauss 3, 08860 Castelldefels, Barcelona, Spain. robert.sewell@icfo.es
Physical Review Letters
|February 2, 2013
Summary
Researchers generated spin squeezing and entanglement in Rubidium-87 atoms, achieving quantum nondemolition measurement for enhanced field sensitivity. This breakthrough demonstrates entanglement-enhanced metrology with reduced noise below the projection-noise level.
Area of Science:
- Quantum optics
- Atomic physics
- Quantum metrology
Background:
- Atomic ensembles are sensitive to magnetic fields.
- Quantum entanglement and spin squeezing offer enhanced measurement precision.
- Optical quantum nondemolition measurement is a technique for measuring quantum systems without disturbing their state.
Purpose of the Study:
- To generate spin squeezing and entanglement in a magnetically sensitive atomic ensemble.
- To demonstrate entanglement-enhanced field measurements using this system.
- To achieve noise reduction below the standard quantum limit.
Main Methods:
- Preparation of maximal m(f) = ± 1 Raman coherence in laser-cooled Rubidium-87 atoms.
- Squeezing of the collective spin using synthesized optical quantum nondemolition measurement.
- Measurement of noise in a mixed alignment-orientation variable.
Main Results:
- Generation of spin squeezing and entanglement in the atomic ensemble.
- Observed 3.2 dB of noise reduction and 2.0 dB of squeezing (Wineland criterion).
- Demonstrated enhanced sensitivity in field measurements via alignment-to-orientation conversion.
Conclusions:
- The study successfully generated spin squeezing and entanglement in an atomic ensemble.
- The results imply both entanglement and a metrological advantage.
- Entanglement-enhanced field measurements were demonstrated with significant noise reduction.
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