Direct estimation of decoherence rates

TL;DR

This paper proposes a simple experimental method to directly measure the decoherence rate of a quantum channel using two copies, eliminating the need for full process tomography and prior basis knowledge.

Contribution

It introduces a novel experimental approach for directly estimating nonlinear decoherence parameters without complete process characterization.

Findings

The method allows direct measurement of the average decoherence rate.

It requires only two copies of the channel and a simple two-valued measurement.

No prior knowledge of the decoherence basis is necessary.

Abstract

The decoherence rate is a nonlinear channel parameter that describes quantitatively the decay of the off-diagonal elements of a density operator in the decoherence basis. We address the question of how to experimentally access such a nonlinear parameter directly without the need of complete process tomography. In particular, we design a simple experiment working with two copies of the channel, in which the registered mean value of a two-valued measurement directly determines the value of the average decoherence rate. No prior knowledge of the decoherence basis is required.