Superconductor - Insulator - Superconductor Quasiparticle Tunnel Junctions as Microwave Receivers.

A.S. Clorfeine, Barry N. Taylor

John R. Tucker, M. J. Feldman

Photon-assisted tunneling of electrons through an insulating barrier may be used to detect long-wavelength radiation with a sensitivity approaching the limit imposed by the Heisenberg uncertainty principle. A new generation of ultra-low-noise millimeter-wave receivers, currently being developed for astronomical observation, utilizes the extremely sharp nonlinearity produced by single-electron quasiparticle tunneling between two superconductors in a superconductor-insulator-superconductor (SIS) tunnel junction. At millimeter wavelengths, the quantum energy $\frac{\ensuremath{\hbar}\ensuremath{\omega}}{e}$ may be larger than the voltage width for onset of quasiparticle tunneling in a SIS junction; and under these conditions the absorption of a single photon can cause one additional electron to tunnel through the barrier. Several newly discovered quantum effects become possible in this regime, including power amplification of an incoming signal during the process of frequency down-conversion in a heterodyne receiver. The experimental development of SIS millimeter-wave receivers is reviewed, along with the quantum theory of mixing which predicts their performance.

T. M. Shen, P. L. Richards, R. Harris +1 more

We report the observation of heterodyne mixing in superconductor-insulator-superconductor tunnel junctions with significant conversion gain and with a noise temperature comparable to the photon noise limit. (Double sideband L−1=1.400.14, TM≲1.5 K at 36 GHz.) The mixing arises from the strong nonlinearity in the quasiparticle tunneling currents at voltages comparable to the full energy gap. Gain is observed when the onset of quasiparticle current is sufficiently sharp that quantum effects are important. The observed gain is in good quantitative agreement with calculations based on the work of Tucker. It should make possible the construction of photon-noise-limited microwave heterodyne receivers.

Vasilii Sevriuk, Matti Silveri, Mikko Möttönen

K. H. Gundlach

Takafumi Kojima, Sho Masui, Wenlei Shan +1 more

This paper describes a low-noise microwave amplifier based on up- and down-frequency-conversion processes in quasiparticle superconductor–insulator–superconductor (SIS) tunnel junctions. The SIS amplifier was configured with two SIS frequency-converter modules and a cryogenic millimeter-wave isolator inserted between them. Moreover, a local oscillator (LO) using millimeter-wave attenuators and a phase shifter was considered. This setup allowed the control of individual LO power and differential phase in these SIS frequency converters to optimize the amplifier performance. The SIS amplifier showed noise temperatures as low as 11 K and a 6–8 dB gain from nearly DC to 5 GHz. The attained microwave performance is promising for obtaining large-format arrays, such as multibeam heterodyne receivers. Moreover, this two-frequency-converter concept based on SIS junctions might enable microwave applications, such as wideband non-reciprocal circuits in isolators, gyrators, and circulators, which are essential devices in the quantum computing and radio astronomy fields.