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We consider the phase stability of a local oscillator (or laser) locked to a cavity-QED system composed of atoms with an ultranarrow optical transition. The atoms are cooled to milli-Kelvin temperatures and then released into the optical cavity. Although the atomic motion introduces Doppler broadening, the standing-wave nature of the cavity causes saturated absorption features to appear, which are much narrower than the Doppler width. These features can be used to achieve an extremely high degree of phase stabilization, competitive with the current state of the art. Furthermore, the inhomogeneity introduced by finite atomic velocities can cause optical bistability to disappear, resulting in no regions of dynamic instability and thus enabling a new regime accessible to experiments where optimum stabilization may be achieved. [ABSTRACT FROM AUTHOR]

We present a practical scheme for measuring completely unknown phases with a precision beyond the shot-noise limit even in the presence of loss. Our scheme consists of sending a sequence of unentangled particles and NOON states through an interferometer and analyzing the measurement outcomes using a Bayesian analysis. We compare our results with two recent schemes [L. Pezzé and A. Smerzi, Europhys. Lett. 78, 30004 (2007); B. L. Higgins et al., Nature (London) 450, 393 (2007)] that are closely related but operate in the lossless regime. We show that our technique outperforms the previous schemes when even a modest amount of loss is present and so may prove to be a valuable technique for making precision measurements beyond the classical limit in a range of practical scenarios. [ABSTRACT FROM AUTHOR]

A correction to the article "Laser stabilization using saturated absorption in a cavity-QED system" is presented.