 
Summary: Can a Quantum Nondemolition Measurement Improve the Sensitivity
of an Atomic Magnetometer?
M. Auzinsh,1
D. Budker,2,3,* D. F. Kimball,2
S. M. Rochester,2
J. E. Stalnaker,2
A. O. Sushkov,2
and V.V. Yashchuk4
1
Department of Physics, University of Latvia, 19 Rainis blvd, Riga, LV1586, Latvia
2
Department of Physics, University of California, Berkeley, California 947207300, USA
3
Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley California 94720, USA
4
Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley California 94720, USA
(Received 25 March 2004; published 19 October 2004)
We consider the limitations due to noise (e.g., quantum projection noise and photon shotnoise) on the
sensitivity of an idealized atomic magnetometer that utilizes spin squeezing induced by a continuous
quantum nondemolition measurement. Such a magnetometer measures spin precession of N atomic
