Improving Intrinsic Decoherence in Multi-Quantum-Dot Charge Qubits

TL;DR

This paper investigates how to reduce intrinsic decoherence in multi-quantum-dot charge qubits by analyzing different configurations and their interactions with phonons, showing improved coherence properties over simpler systems.

Contribution

The study introduces new multi-dot charge qubit configurations that exhibit higher quality factors and lower decoherence, enhancing quantum coherence compared to traditional double-dot systems.

Findings

Three-dot ring qubits enable gate operations via voltage tuning.

High-multipole charge configurations reduce decoherence at low frequencies.

Three-dot qubits have significantly higher Q factors than double-dot systems.

Abstract

We discuss decoherence in charge qubits formed by multiple lateral quantum dots in the framework of the spin-boson model and the Born-Markov approximation. We consider the intrinsic decoherence caused by the coupling to bulk phonon modes. Two distinct quantum dot configurations are studied: (i) Three quantum dots in a ring geometry with one excess electron in total and (ii) arrays of quantum dots where the computational basis states form multipole charge configurations. For the three-dot qubit, we demonstrate the possibility of performing one- and two-qubit operations by solely tuning gate voltages. Compared to the proposal by DiVincenzo {\it et al.} involving a linear three-dot spin qubit, the three-dot charge qubit allows for less overhead on two-qubit operations. For small interdot tunnel amplitudes, the three-dot qubits have $Q$ factors much higher than those obtained for double dot systems. The high-multipole dot configurations also show a substantial decrease in decoherence at low operation frequencies when compared to the double-dot qubit.