Josephson Junctions and Single Electron Tunneling Physics

PROGRAMMABLE JOSEPHSON VOLTAGE STANDARD (PJVS) AT 10 VOLT LEVEL

The PJVS system is based on ‘Quantum Phenomena’ (Josephson effect) given by the relation
2eVn = nhf
where n = 0, ± 1, 2 ±, ± 3, ---,       Vn= quantized voltage;            f = frequency of irradiation;                  h= Planck’s constant ;  e = electron charge
This forms the basis for standard of the unit of ‘Volt’ in India at par to the international level. The uncertainty in measurement of Zener Reference Standards is ± 350 nV at k=2 (inclusive of noise of Zener) at 10V level as per the ISO/IEC 17025:2005.
The salient features of the system are :
  • The non-hysteretic Josephson tunnel junctions made up of Nb electrodes and NbxSi1-x barriers.
  • The 10 V chip contains a total of 256,116 Josephson junctions organised in stacks of three junctions and distributed into 32 microwave coplanar waveguide lines.
  • The voltage steps are stable, have superior immunity to noise and have rapid settling time
10 V - PJVS at NPL-India, established in the collaboration with NIST, USA
The I-V curve of a single junction with the microwave power set to equalize the current range of each of the n = {−1, 0, and +1} steps
Photograph of a 10 V-PJVS chip (NIST,USA ) Operating frequency 18-22 GHz picture.2
(a). I-V curves for 23 subarrays
(b). Step flatness test at 18.645 GHz and 0.00 dBm. The array configuration is nnnnnnnnnnnnnnnpppppppp starting from subarray 1 and ending at subarray 23. “0” represents the zero step, “n” the negative step and “p” the positive step. The total array output is 0.000 231 331 5 V, measured by the system nanovoltmeter on 1 mV range.
(a)
(b)
Sub-Division Member:

Head:

Dr. V N Ojha
vnojha@nplindia.org

Scientist:

Mrs. Sandhya Malikaar Patel
patelsm@nplindia.org

Technical Assistant:

Shri Anish Mahaveer Bhargava

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