Femptovoltmeter (10-15 Volt) based on a double Josphson junction resistive interferometer
Abstract
A voltmeter of sensitivity $$2 \times 10^{ - 15} V/\sqrt {Hz} \left( {2 fV/} \right)\sqrt {Hz} $$ is based on direct conversion of the voltage to be measured into a frequency according to the Josephson voltage-frequency relation. Selfpumped parametric amplification in a d.c. biased loop containing two Josephson junctions and a measuring resistanceRs=4.7×10-9Ω amplifies the femptovolt level voltages acrossRs to microvolt levels that can be observed with a room temperature amplifier. The sensitivity of the femptovoltmeter is determined by Johnson-Nyquist noise voltages at 4.2 K in the 4.7×10-9 Ω resistance.
- Publication:
-
Zeitschrift Angewandte Mathematik und Physik
- Pub Date:
- March 1978
- DOI:
- Bibcode:
- 1978ZaMP...29..359U
- Keywords:
-
- Electrical Resistivity;
- Interferometers;
- Josephson Junctions;
- Voltmeters;
- Direct Current;
- Electrical Measurement;
- Squid (Detectors);
- Instrumentation and Photography;
- Mathematical Method;
- Josephson Junction;
- Direct Conversion;
- Noise Voltage;
- Parametric Amplification