Dephasing in a crystal-phase defined double quantum dot charge qubit strongly coupled to a high-impedance resonator

TL;DR

This study demonstrates that charge noise is not the primary factor limiting coherence in a semiconductor nanowire double quantum dot charge qubit strongly coupled to a high-impedance resonator, challenging conventional assumptions.

Contribution

The paper shows that dephasing in this qubit system is dominated by mechanisms other than charge noise, supported by experimental measurements and theoretical modeling.

Findings

Dephasing rates differ by only 10% between sensitive and insensitive points.

Charge noise sensitivity varies by a factor of 5, yet dephasing remains similar.

Charge noise is not the main decoherence source in this qubit system.

Abstract

Dephasing of a charge qubit is usually credited to charge noise in the environment. Here we show that charge noise may not be the limiting factor for the qubit coherence. To this end, we study coherence properties of a crystal-phase defined semiconductor nanowire double quantum dot (DQD) charge qubit strongly coupled to a high-impedance resonator using radio-frequency (RF) reflectometry. Response of this hybrid system is measured both at a charge noise sensitive operation point (with finite DQD detuning) and at an insensitive point (so-called sweet spot with zero detuning). A theoretical model based on Jaynes-Cummings Hamiltonian matches the experimental results well and yields only a 10 % difference in dephasing rates between the two cases, despite that the sensitivity to detuning charge noise differs by a factor of 5. Therefore the charge noise is not the limiting factor for the coherence in this type of semiconducting nanowire qubits.