Squeezed atomic states and projection noise in spectroscopy

D. J. Wineland, J. J. Bollinger, W. M. Itano, and D. J. Heinzen
Phys. Rev. A 50, 67 – Published 1 July 1994
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Abstract

We investigate the properties of angular-momentum states which yield high sensitivity to rotation. We discuss the application of these ‘‘squeezed-spin’’ or correlated-particle states to spectroscopy. Transitions in an ensemble of N two-level (or, equivalently, spin-1/2) particles are assumed to be detected by observing changes in the state populations of the particles (population spectroscopy). When the particles’ states are detected with 100% efficiency, the fundamental limiting noise is projection noise, the noise associated with the quantum fluctuations in the measured populations. If the particles are first prepared in particular quantum-mechanically correlated states, we find that the signal-to-noise ratio can be improved over the case of initially uncorrelated particles. We have investigated spectroscopy for a particular case of Ramsey’s separated oscillatory method where the radiation pulse lengths are short compared to the time between pulses. We introduce a squeezing parameter ξR which is the ratio of the statistical uncertainty in the determination of the resonance frequency when using correlated states vs that when using uncorrelated states. More generally, this squeezing parameter quantifies the sensitivity of an angular-momentum state to rotation. Other squeezing parameters which are relevant for use in other contexts can be defined. We discuss certain states which exhibit squeezing parameters ξRN1/2. We investigate possible experimental schemes for generation of squeezed-spin states which might be applied to the spectroscopy of trapped atomic ions. We find that applying a Jaynes-Cummings–type coupling between the ensemble of two-level systems and a suitably prepared harmonic oscillator results in correlated states with ξR<1.

  • Received 11 January 1994

DOI:https://doi.org/10.1103/PhysRevA.50.67

©1994 American Physical Society

Authors & Affiliations

D. J. Wineland, J. J. Bollinger, and W. M. Itano

  • Time and Frequency Division, National Institute of Standards Technology, Boulder, Colorado 80303

D. J. Heinzen

  • Physics Department, University of Texas, Austin, Texas 78712

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Vol. 50, Iss. 1 — July 1994

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