Measurement of two-qubit states by quantum point contacts

TL;DR

This paper analyzes how quantum point contacts can measure two-qubit states, demonstrating their effectiveness in reading out quantum calculations and detecting entanglement through master equation solutions.

Contribution

It provides a detailed theoretical framework for using quantum point contacts to measure and analyze two-qubit states, including entanglement detection and dephasing effects.

Findings

QPC current can read out two-qubit states and entanglement.

Concurrence decreases with increasing dephasing rate.

Coupled charge qubits can be effectively detected by QPCs.

Abstract

We solve the master equations of two charged qubits measured by two serially coupled quantum point contacts (QPCs). We describe two-qubit dynamics by comparing entangled states with product states, and show that the QPC current can be used for reading out results of quantum calculations and providing evidences of two-qubit entanglement. We also calculate the concurrence of the two qubits as a function of dephasing rate that originates from the measurement. We conclude that coupled charge qubits can be effectively detected by a QPC-based detector.