QUANTUM-NONDEMOLITION MEASUREMENTS ON A DOUBLE HARMONIC-OSCILLATOR

In the measurements of an oscillator to detect short bursts of gravita tional radiation, one important demand is the ability to use short int egration times in order to decrease the contribution of thermal noise. This requires a strong coupling of the antenna to the measuring appar atus, i.e., a high value of the so-called electromechanical coupling p arameter beta(0). A well-known solution is in the use of a resonant tr ansducer, which entails the observation of a system of two harmonic os cillators. We extend to this system the back-action evasion technique by showing that one can perform a quantum nondemolition measurement on a double harmonic oscillator with essentially the same configuration as for the single one.