Abstract

Several research groups have recently observed optical signals using backaction evasion (BAE) techniques that measure a quantum mechanical observable without adding noise to that observable^1,2,3. The goal of such measurements is to achieve quantum optical tapping³ and, ultimately, to carry out quantum nondemolition (QND) measurements of quantum states that leave the quantum state unaltered⁴ A QND measurement can be demonstrated by two successive backaction evasion measurements if losses are negligible for coupling to and from the BAE measurement apparatus, and if propagation losses between the two BAE measurements are negligible.

© 1994 Optical Society of America