Thermal noise in digital Josephson devices

Author

Feder, J.D. ; Klein, M. ; Anderson, C.J.

Author_Institution

IBM Thomas J. Watson Res. Center, Yorktown Heights, NY, USA

Volume

3

Issue

1

fYear

1993

fDate

3/1/1993 12:00:00 AM

Firstpage

2760

Lastpage

2764

Abstract

A method of accurately estimating the I/sub 0/ (critical current) of a Josephson junction (JJ) with thermal noise was developed by measuring the effective thermal noise temperature of a JJ. The effective thermal noise temperature of various JJ devices was measured and calculated. The JJ devices evaluated included inductively and resistively coupled logic devices and JJ devices in the presence of various noise sources. The noise sources included room-temperature resistors, switched JJ devices, and JJ devices in the linear I-V region beyond the gap. The R/sub NN/ compensator is shown to result in a noise temperature of about 6 K at an interferometer. The addition of a shunt junction lessens the noise penalty introduced by the compensator. A switched isolation interferometer in a two-input AND gate contributes negligible noise at the injection device. It is also shown that bandwidth connections to room-temperature equipment result in very large excess noise and require special input and output circuits on the chip.<>

Keywords

Josephson effect; critical currents; electron device noise; logic gates; superconducting junction devices; superconducting logic circuits; thermal noise; compensator; critical current; digital Josephson devices; inductively coupled devices; linear I-V region; logic devices; noise sources; resistively coupled; room-temperature resistors; shunt junction; switched isolation interferometer; thermal noise temperature; two-input AND gate; Circuit noise; Critical current; Current measurement; Josephson junctions; Logic devices; Neural networks; Noise measurement; Resistors; Superconducting devices; Temperature;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.233509

Filename

233509