High sensitivity comparison of potential differences between two Josephson junctions
The experimental and theoretical exactness of the Josephson voltage-frequency relation dUPSILON/dt = (2e/h)V and its relation to the accuracy of quantum electrodynamics, as well as the possible discrepancy between them are discussed. The experiment was designed to compare the electrochemical potential difference between two Josephson junctions by putting them in a DC SQUID configuration, and biasing them on a microwave induced constant-voltage step. On a step, the voltage across the junctions is determined by the applied microwave frequency v through the Josephson relation V = (h/2e) vn, where n is the order of the step. Faraday's law implies that any potential difference ..delta..V around the closed loop has to be sustained by a changing magnetic flux inside the closed loop. Thus under this condition: ((h/2e)/sub 1/ - (h/2e)/sub 2/)vn = dUPSILON/dt, so that any local dependence of the Josephson relation can be measured by monitoring the flux in the DC SQUID. The flux in the DC SQUID was measured by an RF SQUID, coupled to the DC SQUID by a superconducting flux transformer. The use of the RF SQUID and high voltage steps results in very high sensitivity of the measurement. The relative exactness of the Josephson relation between two similar junctions is established to less than one part in 10/sup 17/. This is almost one billion times better than previous results. Measurements were also made on two dissimilar junctions, namely an In microbridge and a Nb-Cu-Nb junction. For those junctions, the relative exactness is established to about two parts in 10/sup 16/. The reduced accuracy is mainly attributed to the lower biasing voltage used. The material and microscopic coupling mechanism dependence of the Josephson relation was shown to be nonexistent at this accuracy.
- Research Organization:
- State Univ. of New York, Stony Brook (USA)
- OSTI ID:
- 5208464
- Country of Publication:
- United States
- Language:
- English
Similar Records
Observation of microwave synchronization of thin film microbridge arrays
Measurement accuracy of macroscopic quantum circuits with RF-biased Josephson junction arrays
Related Subjects
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
COPPER
DATA
ELECTRIC POTENTIAL
ELECTRODYNAMICS
ELECTRONIC EQUIPMENT
ELEMENTS
EQUIPMENT
EXPERIMENTAL DATA
FIELD THEORIES
FLUXMETERS
INFORMATION
JOSEPHSON JUNCTIONS
JUNCTIONS
MEASURING INSTRUMENTS
METALS
MICROWAVE EQUIPMENT
NIOBIUM
NUMERICAL DATA
QUANTUM ELECTRODYNAMICS
QUANTUM FIELD THEORY
SQUID DEVICES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
TIME DEPENDENCE
TRANSITION ELEMENTS