1106.3538 (S. M. Rochester et al.)

Orientation-to-alignment conversion and spin squeezing    [PDF]

S. M. Rochester, M. P. Ledbetter, T. Zigdon, A. D. Wilson-Gordon, D. Budker

The relationship between orientation-to-alignment conversion (a form of
atomic polarization evolution induced by an electric field) and the phenomenon
of spin squeezing is demonstrated. A "stretched" state of an atom or molecule
with maximum angular-momentum projection along the quantization axis possesses
orientation and is a quantum-mechanical minimum-uncertainty state, where the
product of the equal uncertainties of the angular-momentum projections on two
orthogonal directions transverse to the quantization axis is the minimum
allowed by the uncertainty relation. Application of an electric field for a
short time induces orientation-to-alignment conversion and produces a
spin-squeezed state, in which the quantum state essentially remains a
minimum-uncertainty state, but the uncertainties of the angular-momentum
projections on the orthogonal directions are unequal. This property can be
visualized using the angular-momentum probability surfaces, where the radius of
the surface is given by the probability of measuring the maximum
angular-momentum projection in that direction. Brief remarks are also given
concerning collective-spin squeezing and quantum nondemolition measurements.

View original: http://arxiv.org/abs/1106.3538