Quantum Measurements Performed with a Single-Electron Transistor

TL;DR

This paper proposes a method to perform quantum measurements by coupling a single-electron transistor to a quantum bit, analyzing the system's dynamics to demonstrate a feasible quantum measurement process using current nanotechnology.

Contribution

It introduces a novel approach to quantum measurement using a single-electron transistor coupled to a qubit, with analysis showing its practicality in modern nano-tech conditions.

Findings

Weak influence of the transistor on the qubit without voltage

Time evolution of the density matrix analyzed

Quantum measurement process feasible with current technology

Abstract

Low-capacitance Josephson junction systems as well as coupled quantum dots, in a parameter range where single charges can be controlled, provide physical realizations of quantum bits, discussed in connection with quantum computing. The necessary manipulation of the quantum states can be controlled by applied gate voltages. In addition, the state of the system has to be read out. Here we suggest to measure the quantum state by coupling a single-electron transistor to the q-bit. As long as no transport voltage is applied, the transistor influences the quantum dynamics of the q-bit only weakly. We have analyzed the time evolution of the density matrix of the transistor and q-bit when a voltage is turned on. For values of the capacitances and temperatures which can be realized by modern nano-techniques the process constitutes a quantum measurement process.