Superconductor-insulator-superconductor quasiparticle junctions as microwave photon detectors

Abstract

The strong nonlinearity of the quasiparticle tunneling current in superconductor-insulator-superconductor junctions near the full-gap voltage 2Δ/e can be used for direct detection of microwave signals. Measurements at 36 GHz yielded a current responsivity of 3500 A/W, which is within a factor of 2 of the quantum-limited value e/∇ω. The measured NEP of 2.6±0.8×10−16 W/,Hz1/2 is the lowest value reported to date and can probably be improved significantly. The experimental results are compared with both the standard classical analysis and photon-assisted tunneling theory.

Superconducting components for infrared and millimeter-wave receivers

“…The first experimental test of an SIS direct detector [36] showed excellent agreement with the quantum theory. The current responsivity of 3.6x103A/W was within a factor 2 of the quantum-limited value e/Mw at 36 GHz.…”

“…In these experiments, the shot noise was measured with amplifiers at 50 MHZ· and 1.4 GHz which were designed for use as IF amplifiers for heterodyne mixers and found to agree with theory. The NEP was deduced to be 2.6x1o-16WHz-1/2 at 36 GHz [36], which is essentially equal to the performance of a millimeter wave astronomical radiometer based on the 3He-cooled composite bolometer. In the usual radiometric applications the signal is modulated at some low frequency 1<f<100 Hz.…”

Coherent revival of tunneling

“…Tunneling phenomena by a driving field have been considered in many different contexts in chemistry 3,4,11 and physics including photonassisted tunneling (PAT) 1,2,5,10,12-22 , coherent destruction of tunneling (CDT) 6,23,24 , dynamical localization 9 , and coherent quantum ratchets 25,26 . For example, PAT has been widely explored in superconductor-insulatorsuperconductor tunnel junctions 1,12 , semiconductor nanostructures 13,14 , quantum dots 15,16 , superlattices 17 , and molecular junctions 10,[18][19][20][21][22] . CDT has been experimentally observed in an Er:Yb-doped glass 7 and in cold atoms within a double-well potential 8 .…”

Observation of quantum susceptance in superconducting tunnel junctions

“…The current responsivity Sr(ro) of the SIS direct detector is given by3 (7) where Pro= Iro V ro/2 is the coupled RF power. Because the reactive quasi panicle response function lKK does not appear in Eq.…”

“…Experimental evidence for this quantum conductance has been well established and it has been utilized in SIS quasiparticle direct detection. 7 The quantum susceptance BQ(C.O), which is the imaginary part of Y(w), should be related to GQ(C.O) through a Kramers-Kronig transform. as is required for any causal.…”