Nano-electronic Realizations of Quantum Bits

TL;DR

This paper explores nano-electronic implementations of quantum bits using Josephson junction circuits, comparing charge and flux-based designs for quantum computing, including gate operations and measurement techniques.

Contribution

It introduces and compares two nano-electronic quantum bit designs employing charge and magnetic flux, detailing their operation and read-out methods.

Findings

Elementary quantum gates can be performed with voltage or flux pulses.

Coherence times are sufficient for multiple quantum operations.

Charge read-out is achieved via coupling to a single-electron transistor.

Abstract

Quantum computers could perform certain tasks which no classical computer can perform in acceptable times. Josephson junction circuits can serve as building blocks of quantum computers. We discuss and compare two designs, which employ charge or magnetic flux degrees of freedom to process quantum information. In both cases, elementary single-qubit and two-qubit logic gates can be performed by voltage or flux pulses. The coherence time is long enough to allow a series of such operations. We also discuss the read-out, i.e., a quantum measurement process. In the charge case it is accomplished by coupling a single-electron transistor to the qubit.