Abstract
It is shown that aresonant transducer is indispensable in a wide range of experimental conditions in order to accomplish optimum matching between a cryogenic antenna and a low-noise amplifier. Noise characteristics of a d.c. SQUID are analyzed and an improved design of a point contact d.c. SQUID is described. Conditions for transducer matching and detectability of a gravitational-wave signal are derived for a system employing a d.c. SQUID. It appears that a d.c. SQUID operating at the quantum-limited sensitivity could be realized in our proposed design and matched to a massive aluminum antenna cooled to 0.05 K by using a resonant superconducting inductive transducer. Presently achievable detector parameters are shown to be sufficient to allow a detection sensitivity corresponding to a resolution of a few photons in the antenna, the ultimate quantum-mechanical limit derived for an antenna instrumented with a linear-motion detector.
Published Version
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