Fidelity and Entanglement of a Spatially Extended Linear Three-Qubit Register

TL;DR

This paper investigates how spatial separation affects decoherence and entanglement in a three-qubit system coupled to substrate phonons, revealing that regular spacing maximizes decoherence and that two-qubit entanglement remains unaffected by the third qubit.

Contribution

It provides a detailed analysis of non-Markovian decoherence effects in a spatially extended three-qubit register, highlighting the impact of qubit spacing on coherence and entanglement.

Findings

Decoherence is maximized with regular qubit spacing.

Two-qubit entanglement is unaffected by the third qubit's presence.

Spatial separation influences non-Markovian decoherence effects.

Abstract

We study decoherence of a three-qubit array coupled to substrate phonons. Assuming an initial three-qubit entangled state that would be decoherence-free for identical qubit positions, allows us to focus on non-Markovian effects of the inevitable spatial qubit separation. It turns out that the coherence is most affected when the qubits are regularly spaced. Moreover, we find that up to a constant scaling factor, two-qubit entanglement is not influenced by the presence f the third qubit, even though all qubits interact via the phonon field.