Decoherence of charge qubit coupled to interacting background charges

TL;DR

This paper demonstrates that short-range Coulomb interactions significantly increase the number of effective fluctuators, revealing a dominant decoherence mechanism for charge qubits previously underestimated by existing theories.

Contribution

It introduces the role of short-range Coulomb interactions in enhancing fluctuator effects, resolving a paradox in decoherence estimations for charge qubits.

Findings

Short-range Coulomb interactions increase effective fluctuators.

Enhanced fluctuator contribution leads to dominant decoherence.

Revised understanding of decoherence mechanisms in charge qubits.

Abstract

The major contribution to decoherence of a double quantum dot or a Josephson junction charge qubit comes from the electrostatic coupling to fluctuating background charges hybridized with the conduction electrons in the reservoir. However, estimations according to previously developed theories show that finding a sufficient number of effective fluctuators in a realistic experimental layout is quite improbable. We show that this paradox is resolved by allowing for a short-range Coulomb interaction of the fluctuators with the electrons in the reservoir. This dramatically enhances both the number of effective fluctuators and their contribution to decoherence, resulting in the most dangerous decoherence mechanism for charge qubits.