Quantum noise in Josephson junctions and dc SQUIDs

Thesis/Dissertation · Thu Dec 31 23:00:00 EST 1981

OSTI ID:5195355

Koch, R H

The development of a model to predict and understand the effects of quantum noise in the resistively shunted Josephson junction and experimental tests of this model are described. It is shown that the low-frequency spectral density of the voltage noise in a current-biased Josephson junction with critical current I/sub 0/, shunt resistance R, and small capacitance is 2el/sub 0//sup 2/R/sup 3//V in the limit eV >> k/sub B/T(I/I/sub 0/)/sup 2/ and I > I/sub 0/, where V is the voltage and I is the current. The noise arises from zero-point current fluctuations in the shunt resistor that are mixed down from near the Josephson frequency to the much lower measurement frequency. Experimental data are in excellent agreement with these predictions, demonstrating clearly the measurability of zero-point fluctuations and the validity of I>I/sub o/ of the Langevin treatment combined with the Callen-Welton expression for the noise from a resistor. The rounding of the current-voltage characteristic when I

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 5195355
• Country of Publication: United States
• Language: English

Related Subjects

420201 -- Engineering-- Cryogenic Equipment & Devices
656102* -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CURRENTS
DATA
ELECTRIC CURRENTS
ELECTRIC POTENTIAL
ELECTRONIC EQUIPMENT
EQUIPMENT
FABRICATION
FLUCTUATIONS
FLUXMETERS
INFORMATION
JOSEPHSON JUNCTIONS
JUNCTIONS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
NOISE
NUMERICAL DATA
SQUID DEVICES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
TEMPERATURE DEPENDENCE
THEORETICAL DATA
TUNNEL EFFECT
VARIATIONS