Underdamped Josephson junction as a switching current detector

Abstract

We demonstrate the narrow switching distribution of an underdamped Josephson junction from the zero to the finite voltage state at millikelvin temperatures. We argue that such junctions can be used as ultrasensitive detectors of the single photons in the GHz range, operating close to the quantum limit: a given initial (zero voltage) state can be driven by an incoming signal to the finite voltage state. The width of the switching distribution at a nominal temperature of about T = 10 mK was 4.5 nA, which corresponds to an effective noise temperature of the device below 60 mK.

Quantized resonator field coupled to a current-biased Josephson junction in circuit QED

“…After having derived the single-mode Hamiltonian (27), we can choose the realistic parameters [34][35][36]. We assume a Josephson Junction with a zero-coupling critical current I c = 2 µA and a Josephson capacitance C J = 1500 fF together with a 50 Ω-impedance resonator with a bare resonance at 7 GHz.…”

Examples of superconducting technology application: Sensing and interfacing

“…The I-V-measurements at the two temperatures show the same characteristic. Switching current histograms can, if necessary, reveal the slight temperature dependency of the switching current [12]. From these measurements we also determine the critical current density -for a Josephson junction with a size of 20 µm 2 we find a J c of 190 A/cm 2 .…”

Микроволновой Фотонный Детектор

“…Тогда очевидно, что можно вычислить температуру переключения из одного режима в другой (см. например [11])…”

“…Используя соображения, изложенные выше, в VTT (Финляндия) был изготовлен джозефсоновский контакт Nb/AlO/Nb со следующими параметрами: плотность критического тока 30 A/cm 2 , емкость C K = 0.33 pF, со-противление R N = 0.44 k [11]. Образец измерялся в IPHT (Jena, Германия), в рефрижераторе растворения при номинальной температуре 10 mK.…”