Qubit measurements with a double-dot detector

TL;DR

This paper introduces a double-dot resonant-tunneling detector for qubit measurement, demonstrating improved signal-to-noise ratio and highlighting quantum interference effects that impact measurement accuracy.

Contribution

It proposes a novel double-dot detector for qubits, deriving rate equations, and analyzing quantum interference effects on measurement performance.

Findings

Enhanced signal-to-noise ratio with proper parameter tuning

Quantum interference causes systematic measurement errors

Double-dot detector operates effectively at higher temperatures

Abstract

We propose to monitor a qubit with a double-dot (DD) resonant-tunneling detector, which can operate at higher temperatures than a single-dot detector. In order to assess the effectiveness of this device, we derive rate equations for the density matrix of the entire system. We show that the signal-to-noise ratio can be greatly improved by a proper choice of the parameters and location of the detector. We demonstrate that quantum interference effects within the DD detector play an important role in the measurement. Surprisingly, these effects produce a systematic measurement error, even when the entire system is in a stationary state.