Remote State Preparation using Correlations beyond Discord

TL;DR

This paper demonstrates that separable quantum states with certain correlations beyond discord can effectively serve as resources for remote state preparation, expanding the understanding of quantum correlations useful for quantum information processing.

Contribution

It introduces a measure based on correlations in mutually unbiased bases to quantify the usefulness of separable states for RSP, including non-discordant states.

Findings

Non-discordant states with non-vanishing correlations can be useful for RSP.

Higher discord does not necessarily mean higher RSP efficiency.

Simultaneous correlations in mutually unbiased bases are key to resource effectiveness.

Abstract

In recent years, exploring the possible use of separable states as resource for achieving quantum information processing(QIP) tasks has been gaining increasing significance. In this context, a particularly important demonstration has been that non-vanishing discord is the necessary condition for the separable states to be used as resource for remotely preparing any arbitrary pure target state [Nature Physics $8$, $666$ $(2012)$]. The present work stems from our observation that not only resource states with same discord can imply different efficiencies (in terms of average fidelity) of the remote state preparation (RSP) protocol, but also states with higher discord can imply lower RSP efficiency. This, therefore, necessitates identification of the relevant feature of quantum correlations which can appropriately quantify effectiveness of the resource state for the RSP protocol. To this end, for the two-qubit Bell-diagonal states, we show that an appropriate measure of simultaneous correlations in three mutually unbiased bases can serve to quantify usefulness of the resource for the RSP task using entangled as well as separable states, including non-discordant states as resource. In particular, it is revealed that zero-discord states having such non-vanishing measure can be useful for remotely preparing a subset of pure target states. Thus, this work shows that, using separable states, an effective resource for QIP tasks such as RSP can be provided by simultaneous correlations in mutually unbiased bases.