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The lack of dense, fast, energy efficient memory has been the main detractor for multiple superconducting digital projects in the past. Recently, fundamental physics research in superconductor-ferromagnet thin-film tunnel structures created a new opportunity to solve this long-standing problem. Superconductivity and ferromagnetism, two deeply antagonistic electronic properties, can co-exist in form of Magnetic Josephson Junctions (MJJs). The superconducting-ferromagnetic MJJs are electrically compatible with traditional superconductor-insulator-superconductor (SIS) Josephson junctions (JJs) used for digital energy-efficient single flux quantum (eSFQ/ERSFQ) circuits. Both MJJ and JJ circuits have similar fabrication process and can be integrated on a single chip. As a result, a combination of MJJs and JJs can be used to form addressable memory cells, energy-efficient memory periphery circuits and programmable logic elements. In this paper, we present the test results of superconductor-insulator-ferromagnet-superconductor (SIFS) MJJs showing their applicability for superconducting spintronic memory and digital circuits.

We have designed and tested at high frequency an RSFQ-based Arithmetic-Logic Unit (ALU), the critical component of an 8-bit RSFQ processor datapath. The ALU design is based on a Kogge-Stone adder and employs an asynchronous wave-pipelined approach scalable for wide datapath processors. The 8-bit ALU circuit was fabricated with HYPRES’ standard 4.5 kA/cm2 process and consists of 7,950 Josephson junctions, including input and output interfaces. In this paper, we present chip design and high-speed test results for the 8-bit ALU circuit.

It is known that the long annular Josephson junction allows to avoid the influence of boundaries and soliton(fluxon)- soliton collisions on the dynamics of soliton chains. With new experimental methods and junction design a fully controlable way of introducing individual solitons into such a system is realized. For the homogeneous junction crossover at high velocities of the fluxon chain is seen and explained in terms of the fluxon bunching. In the periodically modulated junction a new resonant mode called a supersoliton is observed.

We report on the experimental observation of a new resonant mode in a spatially modulated annular Josephson junction with a trapped chain of solitons. We observed voltage steps in the current-voltage characteristics of the junction. These steps appear when the spatial periods of the soliton chain and the junction modulation are incommensurate. The effect is explained in terms of the motion of defects (supersolitons) along the pinned soliton chain, which were found earlier iin numerical simulations by Ustinov [Phys. Lett. A 136 (1989) 155].