Operation of a quantum dot in the finite-state machine mode: single-electron dynamic memory

TL;DR

This paper demonstrates a quantum dot-based single-electron dynamic memory device that operates as a finite-state machine, with fast writing times and long retention, modeled through charge state dynamics and gate pulse control.

Contribution

It introduces a novel quantum dot memory system modeled via master equations, showing controllable charge state transitions and practical operation parameters.

Findings

Memory retention times in the millisecond range.

Fast writing times in the nanosecond range.

Controlled charge state transition asymmetry.

Abstract

A single electron dynamic memory is designed based on the non-equilibrium dynamics of charge states in electrostatically-defined metallic quantum dots. Using the orthodox theory for computing the transfer rates and a master equation, we model the dynamical response of devices consisting of a charge sensor coupled to either a single and or a double quantum dot subjected to a pulsed gate voltage. We show that transition rates between charge states in metallic quantum dots are characterized by an asymmetry that can be controlled by the gate voltage. This effect is more pronounced when the switching between charge states corresponds to a Markovian process involving electron transport through a chain of several quantum dots. By simulating the dynamics of electron transport we demonstrate that the quantum box operates as a finite-state machine that can be addressed by choosing suitable shapes and switching rates of the gate pulses. We further show that writing times in the ns range and retention memory times six orders of magnitude longer, in the ms range, can be achieved on the double quantum dot system using experimentally feasible parameters thereby demonstrating that the device can operate as a dynamic single electron memory.