Influence of the Josephson junction on the impedance and noise of a resistive superconductive quantum interference device

Robert Soulen; William Fogle; Jack Colwell; Joshua Cohn; Heikki Seppä

Influence of the Josephson junction on the impedance and noise of a resistive superconductive quantum interference device

Robert Soulen, William Fogle, Jack Colwell, Joshua Cohn, Heikki Seppä

Research output: Contribution to journal › Article › Scientific › peer-review

Abstract

The impedance and noise of a resistive superconductive quantum interference device (R‐SQUID) have been measured as a function of the dc and rf currents applied to it. The Josephson junction was adjustable so that data were also taken for several values of the junction critical current. The results were compared with the predictions of a resistively shunted junction (RSJ) model which takes into account the influence of the Josephson junction on the impedance and noise. The agreement was found to be quite good and demonstrates that the noise in the circuit is well understood. Use of the R‐SQUID as a noise thermometer below 1 K is assessed in terms of corrections due to the RSJ model. It is demonstrated how the dc and rf currents may be adjusted so that the total noise of the R‐SQUID is reduced to within 0.1% of the Johnson noise generated by the resistor alone. Under these conditions, the R‐SQUID may be used as a noise thermometer to determine thermodynamic temperature to this inaccuracy from 6 to 700 mK.

Original language	English
Pages (from-to)	5241-5249
Journal	Journal of Applied Physics
Volume	74
Issue number	8
Publication status	Published - 1993
MoE publication type	A1 Journal article-refereed

Keywords

Josephson junction

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title = "Influence of the Josephson junction on the impedance and noise of a resistive superconductive quantum interference device",

abstract = "The impedance and noise of a resistive superconductive quantum interference device (R‐SQUID) have been measured as a function of the dc and rf currents applied to it. The Josephson junction was adjustable so that data were also taken for several values of the junction critical current. The results were compared with the predictions of a resistively shunted junction (RSJ) model which takes into account the influence of the Josephson junction on the impedance and noise. The agreement was found to be quite good and demonstrates that the noise in the circuit is well understood. Use of the R‐SQUID as a noise thermometer below 1 K is assessed in terms of corrections due to the RSJ model. It is demonstrated how the dc and rf currents may be adjusted so that the total noise of the R‐SQUID is reduced to within 0.1% of the Johnson noise generated by the resistor alone. Under these conditions, the R‐SQUID may be used as a noise thermometer to determine thermodynamic temperature to this inaccuracy from 6 to 700 mK.",

keywords = "Josephson junction",

author = "Robert Soulen and William Fogle and Jack Colwell and Joshua Cohn and Heikki Sepp{\"a}",

year = "1993",

language = "English",

volume = "74",

pages = "5241--5249",

journal = "Journal of Applied Physics",

issn = "0021-8979",

publisher = "American Institute of Physics (AIP)",

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TY - JOUR

T1 - Influence of the Josephson junction on the impedance and noise of a resistive superconductive quantum interference device

AU - Soulen, Robert

AU - Fogle, William

AU - Colwell, Jack

AU - Cohn, Joshua

AU - Seppä, Heikki

PY - 1993

Y1 - 1993

N2 - The impedance and noise of a resistive superconductive quantum interference device (R‐SQUID) have been measured as a function of the dc and rf currents applied to it. The Josephson junction was adjustable so that data were also taken for several values of the junction critical current. The results were compared with the predictions of a resistively shunted junction (RSJ) model which takes into account the influence of the Josephson junction on the impedance and noise. The agreement was found to be quite good and demonstrates that the noise in the circuit is well understood. Use of the R‐SQUID as a noise thermometer below 1 K is assessed in terms of corrections due to the RSJ model. It is demonstrated how the dc and rf currents may be adjusted so that the total noise of the R‐SQUID is reduced to within 0.1% of the Johnson noise generated by the resistor alone. Under these conditions, the R‐SQUID may be used as a noise thermometer to determine thermodynamic temperature to this inaccuracy from 6 to 700 mK.

AB - The impedance and noise of a resistive superconductive quantum interference device (R‐SQUID) have been measured as a function of the dc and rf currents applied to it. The Josephson junction was adjustable so that data were also taken for several values of the junction critical current. The results were compared with the predictions of a resistively shunted junction (RSJ) model which takes into account the influence of the Josephson junction on the impedance and noise. The agreement was found to be quite good and demonstrates that the noise in the circuit is well understood. Use of the R‐SQUID as a noise thermometer below 1 K is assessed in terms of corrections due to the RSJ model. It is demonstrated how the dc and rf currents may be adjusted so that the total noise of the R‐SQUID is reduced to within 0.1% of the Johnson noise generated by the resistor alone. Under these conditions, the R‐SQUID may be used as a noise thermometer to determine thermodynamic temperature to this inaccuracy from 6 to 700 mK.

KW - Josephson junction

M3 - Article

VL - 74

SP - 5241

EP - 5249

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 8

ER -