On the Synthesis of Stepwise Quantum Waves Using a SNIS Programmable Josephson Array in a Cryocooler

Abstract

This paper presents recent advances in the application of binary-divided 1 V array, consisting of 8192 intrinsically shunted SNIS overdamped Josephson junctions (JJs), for the synthesis of stepwise waves with quantum accuracy. The maximum output voltage is ensured by opportunely driving the subsections of the SNIS array by means of three states biascurrent setpoints to the Shapiro steps n = 0, ±1 or n = ±2, respectively. Reconfigurable digital modular electronics has been designed to bias individually each of the 13 subsections of the SNIS array. A two-stage closed cycle refrigerator equipped with LF and RF electrical lines is employed for cooling-down the SNIS array for temperatures ranging from 3.6 K to above 7 K. Stepwise sine waves with rms amplitude ranging from 1 V to 2 V using the first (n=1) and second (n=2) Shapiro steps, different temperatures and bias-current setpoints have been synthesized up to the kHz range. The synthesized waves have been recorded and analyzed by a high-precision differential sampling system. We report the results of the first characterizations carried out with the new multi-bit current source and an improved version of the sample holder designed to optimize the heat dissipation of the SNIS array for operation in cryocooler setups.

Determination of the temperature vs power dynamic behavior of a cryocooler via two independent methods in time and frequency domain

“…The two methods presented here are independent and, according to the type of the measurement and to the experimental conditions [1,2], the user can choose the method that better fits his needs. Otherwise, both can be carried out in order to perform a self-consistency check, as presented in Ref.…”

“…This is useful for the design of efficient thermal dampers that are necessary for the thermal stabilization of the device under test Sosso et al [1], Trinchera et al [2]. Two different and independent methods for deriving the cooler dynamic (i.e.…”

Non-Conventional PJVS Exploiting First and Second Steps to Reduce Junctions and Bias Lines

“…A straightforward advancement that can be obtained from the availability of second order Shapiro steps is the increase of the maximum output voltage. This idea has been already exploited for both PJVS [14] and JAWS arrays [15], [16]. In [14], both full-scale voltage V F S and resolution V LSB were doubled using a 13-bit PJVS made by superconductor-normal metal-insulator-superconductor (SNIS) junctions [17].…”

Thermal Performances of an Improved Package for Cryocooled Josephson Standards

“…The PJVS chip used in this experiment was fabricated in cooperation with PTB (Physikalisch-Technische Bundesanstalt) with the Superconductor-Normal-Insulator-Superconductor (SNIS) technology [16], developed for applications in quantum voltage metrology and with peculiar characteristic in terms of reduced temperature dependence of the electrical parameters [17]. Its operation was intensively investigated both in liquid helium and in cryocooler [18], [19]. It is made by 8192 series-connected Nb/Al-AlO x /Nb junctions, which are sub-divided into fourteen individually-biased binary segments.…”