Accession Number:

ADA379754

Title:

Noise-Mediated Cooperative Behavior and Signal Detection in dc SQUIDs

Descriptive Note:

Professional paper

Corporate Author:

SPACE AND NAVAL WARFARE SYSTEMS CENTER SAN DIEGO CA

Personal Author(s):

• Inichiosa, Mario E.
• Bulsara, Adi R.

Report Date:

1999-08-01

Pagination or Media Count:

14.0

Abstract:

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.

Descriptors:

• *SUPERCONDUCTORS
• *ELECTROMAGNETIC INTERFERENCE
• *QUANTUM ELECTRONICS
• *MAGNETIC DETECTION
• STOCHASTIC PROCESSES
• SIGNAL TO NOISE RATIO
• NONLINEAR DIFFERENTIAL EQUATIONS
• NOISE REDUCTION
• JOSEPHSON JUNCTIONS
• INPUT OUTPUT MODELS
• THERMAL RESISTANCE

Subject Categories:

• Electrical and Electronic Equipment
• Magnetic and Electric Field Detection and Detectors

Distribution Statement:

APPROVED FOR PUBLIC RELEASE