A scheme for amplifying phase shifts is presented, based on ideal photon number deamplification. For high-sensitivity measurements phase amplification sizeably reduces the bit-error rate and enhances the mutual information retrieved from the measurement. Phase-coherent states preserve their coherence under amplification, and achieve the best amplifier performance. © 1996 The American Physical Society.

• Received 3 July 1996

DOI:https://doi.org/10.1103/PhysRevA.54.4712