Decoherence of up to 8-qubit entangled states in a 16-qubit superconducting quantum processor

TL;DR

This study investigates the coherence decay of GHZ entangled states of up to 8 qubits in a 16-qubit superconducting processor, revealing a linear relationship between qubit number and decoherence rate.

Contribution

It provides the first experimental analysis of multi-qubit GHZ state decoherence in a large superconducting quantum processor, highlighting uncorrelated noise effects.

Findings

Decoherence rate increases linearly with the number of qubits.

Coherence decay is consistent with uncorrelated noise across qubits.

GHZ states of up to 8 qubits were successfully characterized.

Abstract

We report on the coherence of Greenberger-Horne-Zeilinger (GHZ) states comprised of up to 8 qubits in the IBM ibmqx5 16-qubit quantum processor. In particular, we evaluate the coherence of GHZ states with $N=1,\ldots,8$ qubits, as a function of a delay time between state creation and measurement. We find that the decay in coherence occurs at a rate that is linear in the number of qubits. This is consistent with a model in which the dominant noise affecting the system is uncorrelated across qubits.