Direct current superconducting quantum interferometers with asymmetric shunt resistors
Abstract
We have investigated asymmetrically shunted Nb/AlAlO_{x}/Nb direct current (dc) superconducting quantum interference devices (SQUIDs). While keeping the total resistance R identical to a comparable symmetric SQUID with R^{1}=R_{1}^{1}+R_{2}^{1}, we shunted only one of the two Josephson junctions with R =R_{1,2}/2. Simulations predict that the optimum energy resolution ɛ and thus also the noise performance of such an asymmetric SQUID can be 34 times better than that of its symmetric counterpart. Experiments at a temperature of 4.2 K yielded ɛ ≈32 ℏ for an asymmetric SQUID with an inductance of 22 pH. For a comparable symmetric device, ɛ =110 ℏ was achieved, confirming our simulation results.
 Publication:

Applied Physics Letters
 Pub Date:
 July 2012
 DOI:
 10.1063/1.4739850
 arXiv:
 arXiv:1207.0082
 Bibcode:
 2012ApPhL.101e2602R
 Keywords:

 aluminium;
 aluminium compounds;
 inductance;
 interferometers;
 niobium;
 resistors;
 SQUIDs;
 superconducting device noise;
 superconductorinsulatorsuperconductor devices;
 85.25.Dq;
 84.32.Ff;
 85.25.Cp;
 Superconducting quantum interference devices;
 Conductors resistors;
 Josephson devices;
 Condensed Matter  Superconductivity
 EPrint:
 5 pages, 4 figures