QUANTUM NONDEMOLITION MEASUREMENTS OF A QUBIT

摘要

Technique is proposed for performing quantum nondemolition (QND) measurement of coherent oscillations in an individual two-state system. Such a measurement enables direct observation of intrinsic spectrum of these oscillations avoiding the detector-induced dephasing that affects the standard (non-QND) measurements. The suggested scheme can be realized in Josephson-junction systems that combine flux and charge dynamics.