Suppression of Spin Projection Noise in Broadband Atomic Magnetometry
  Our 2005 Physical Review Letter entitled "Suppression of Spin-Projection Noise in Broadband Atomic Magnetometry" (volume 94, 203002) relied heavily in its claims of experimental quantum-limited performance on the results of a prior publication from our group [1]. In subsequent work we have determined that the results of [1] were incorrect and must therefore retract this Physical Review Letter as well. The authors would like to emphasize that the broadband magnetometry approach taken in our work remains valid, as described in the theoretical paper [2], but we have lost confidence in the calibration procedures employed at the time to establish sensitivity relative to the spin-projection noise level.   [1] JM Geremia, John K. Stockton and Hideo Mabuchi, "Real-Time Quantum Feedback Control of Atomic Spin-Squeezing," Science 304, 270, (2004).   [2] John K. Stockton, JM Geremia, Andrew C. Doherty and Hideo Mabuchi, "Robust quantum parameter estimation: Coherent magnetometry with feedback," Phys. Rev. A 69, 032109, (2004). 
J.M. Geremia, John K. Stockton and Hideo Mabuchi