Orientation-to-alignment conversion and spin squeezing

TL;DR

This paper demonstrates how electric-field-induced orientation-to-alignment conversion in atoms and molecules can produce spin-squeezed states, which are useful for quantum measurement precision enhancements.

Contribution

It establishes a direct connection between orientation-to-alignment conversion and spin squeezing, introducing a method to generate spin-squeezed states via electric fields.

Findings

Electric fields induce orientation-to-alignment conversion in atomic states.

Application of short electric pulses produces spin-squeezed states.

Spin-squeezed states maintain minimum uncertainty with unequal angular-momentum uncertainties.

Abstract

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.