Detector Backaction on the Self-Consistent Bound State in Quantum Point Contacts

TL;DR

This paper investigates how monitoring a bound state in a quantum point contact with a second QPC causes backaction, weakening the bound state, but this effect can be controlled via gate tuning of wavefunction overlap.

Contribution

It demonstrates that detector backaction in coupled QPCs can be both characterized and regulated through wavefunction overlap control.

Findings

Backaction weakens the bound state as the detector QPC approaches.

Wavefunction overlap controls the strength of detector backaction.

Backaction effects are tunable via an additional gate.

Abstract

Bound-state (BS) formation in quantum point contacts (QPCs) may offer a convenient way to localize and probe single spins. In this letter, we investigate how such BSs are affected by monitoring them with a second QPC, which is coupled to the BS via wavefunction overlap. We show that this coupling leads to a unique detector backaction, in which the BS is weakened by increasing its proximity to the detector. We also show, however, that this interaction between the QPCs can be regulated at will, by using an additional gate to control their wavefunction overlap.