Control of Cryogenic Memory State Transitions in a Josephson Junction Array
Roland A. Harvey, Zhihua Qu · 2018
Energy efficient cryogenic memory and Josephson junction arrays have the potential of revolutionizing high-performance computing systems based on single flux quantum logic. In this paper, a pulse control is designed to switch among stable equilibrium states of a Josephson junction array. Josephson junction arrays have the ability to store state information at low temperatures and energies, which naturally is useful for cryogenic memory applications. Although typical memory applications involve binary states, as a memory cell, the Josephson junction array has the ability to occupy nonbinary states given the nonlinear nature of the dynamics, which can lead to a reduced number of cells required in practical applications among other advantages. Transitions between states can be achieved through experimental testing for specific transitions, however, there are no known closed-form solutions to arbitrarily transition from one stable state to another. The system dynamics are similar to an array of coupled nonlinear oscillators, for which there is no known analytical solution. By providing an energy-based analysis for the junction array, a lower bound is determined and system trajectories are closely approximated such that the array is capable of transitioning between any desired stable equilibrium states under a Gaussian pulse input.