DID YOU KNOW? DTIC has over 3.5 million final reports on DoD funded research, development, test, and evaluation activities available to our registered users. Click HERE
to register or log in.
Noise-Mediated Cooperative Behavior and Signal Detection in dc SQUIDs
SPACE AND NAVAL WARFARE SYSTEMS CENTER SAN DIEGO CA
Pagination or Media Count:
We study the detection of very weak time-periodic magnetic signals via a double-junction dc Superconducting Quantum Interference Device SQUID. The device, represented by two coupled nonlinear differential equations for the quantum mechanical junction phases, admits of long-time static or oscillatory solutions, the transition being controllable by experimental parameters. Signal detection is optimal when the device is tuned to the onset of the oscillatory solutions i.e., when the minima in the 2D potential function disappear. Modeling the device via a derived input-output transfer characteristic yields a response quantified via the signal-to-noise ratio at the signal frequency in good agreement with recent experiments. We also present some preliminary results pertaining to coupled dc SQUIDs, taking into account the incoherent thermal noise sources in each of the Josephson junctions. As might be expected from previous work, coupling the SQUIDs andor summing their outputs enhances the response to the external signal.
APPROVED FOR PUBLIC RELEASE