IN two previous notes1, Prof. Max Born and I have shown that one can obtain a theory of superconductivity by taking account of the fact that the interaction of the electrons with the ionic lattice is appreciable only near the boundaries of Brillouin zones, and particularly strong near the corners of these. This leads to the criterion that the metal should be superconductive if a set of corners of a Brillouin zone is lying very near the Fermi surface, considered as a sphere, which limits the region in the momentum space completely filled with electrons.

On the theory of superconductivity

Optical resonance and two-level atoms

High-quality superconducting tunnel junctions operating above liquid nitrogen temperatures can be fabricated with a focused beam of helium ions that directly writes tunnel barriers in a cuprate superconductor.

Nano Josephson superconducting tunnel junctions in YBa2Cu3O7–δ directly patterned with a focused helium ion beam

Cortical lamina-dependent blood volume changes in human brain at 7 T

The predictions of Moore's law are considered by experts to be valid until 2020 giving rise to "post-Moore's" technologies afterwards. Energy efficiency is one of the major challenges in high-performance computing that should be answered. Superconductor digital technology is a promising post-Moore's alternative for the development of supercomputers. In this paper, we consider operation principles of an energy-efficient superconductor logic and memory circuits with a short retrospective review of their evolution. We analyze their shortcomings in respect to computer circuits design. Possible ways of further research are outlined.

Beyond Moore's technologies: operation principles of a superconductor alternative.

The concept of creating an element base for superconducting quantum neural networks based on only a single flux qubit is presented. The behavior of the activation function is analyzed for different variants of the “quantum neuron” implementation (based on three-contact, two-contact, and five-contact interferometers), and the conditions at which this activation function is close to a sigmoid curve are determined. The prospects of using energy-efficient upgrades to the rapid single-flux-quantum logic to control the transfer and activation functions when operating a quantum neural network based on the proposed elements are discussed.

A neuron based on a single flux qubit

Splitting circuits for SFQ-pulse driver based on SQIF

We suggest principal solution for implementation of bi-SQUIDs on the basis of bicrystalline technology for high-temperature Josephson junctions.

Design Issues of High Temperature Superconducting Bi-SQUID

We introduce Superconductive Quantum Arrays (SQAs) and propose to use these structures as active Electrically Small Antennas (ESA). Several prototypes of the active ESA were fabricated using Nb process with critical current density 4.5 kA/cm2 and experimentally evaluated. The magnetic field to voltage transfer function linearity up to 70 dB was measured, and transfer factor dV/dB up to 6.5 mV/{\mu}T was observed for the ESA prototype containing 560 cells.

Active Electrically Small Antenna Based on Superconducting Quantum Array

We present an analysis of noise characteristics of bi-SQUID through its voltage response and compare to characteristics of dc SQUID in the open loop configuration. The additional Josephson junction in bi-SQUID gives an additional source of fluctuations, changes transfer function, nonlinear dynamics and nonlinear noise spectrum transformation. These result in different input noise level versus applied magnetic flux.

http://ieeexplore.ieee.org/iel7/6598362/6604250/06604308.pdf

Igor I. Soloviev

Papers

A neuron based on a single flux qubit

Splitting circuits for SFQ-pulse driver based on SQIF

Design Issues of High Temperature Superconducting Bi-SQUID

Active Electrically Small Antenna Based on Superconducting Quantum Array

Bi-SQUID noise simulation