Parity meter for charge qubits: an efficient quantum entangler

TL;DR

This paper introduces a charge parity meter using double quantum dots and a quantum point contact, enabling entangled state preparation and quantum gate operations through current measurement.

Contribution

It presents a specific implementation of a mesoscopic quadratic quantum measurement device for charge qubits, facilitating entanglement and quantum logic operations.

Findings

Enables entangled state preparation via current measurement

Allows effective decoupling of qubits by controlling the parity meter

Demonstrates applications in Bell's inequality measurement and CNOT gate realization

Abstract

We propose a realization of a charge parity meter based on two double quantum dots alongside a quantum point contact. Such a device is a specific example of the general class of mesoscopic quadratic quantum measurement detectors previously investigated by Mao et al. [Phys. Rev. Lett. 93, 056803 (2004)]. Our setup accomplishes entangled state preparation by a current measurement alone, and allows the qubits to be effectively decoupled by pinching off the parity meter. Two applications of the parity meter are discussed: the measurement of Bell's inequality in charge qubits and the realization of a controlled NOT gate.