Is quantum discord a useful resource for remote state preparation

Borivoje Dakić, Yannick Ole Lipp, Xiao‐Song Ma +8 more

Gian Luca Giorgi

The role played by quantum discord in mixed-state computation is widely debated since, in spite of evidence of its importance in creating quantum advantages, even in the absence of entanglement, there are not direct proofs of its necessity in these computational tasks. Recently, the presence of discord was shown to be necessary and sufficient for remote state preparation for a broad class of quantum channels [Daki\ifmmode \acute{c}\else \'{c}\fi{} et al., Nat. Phys. 8, 666 (2012)]. Here, we show that this property is not universal. There are states whose discord cannot be considered as a quantum resource since it has been produced locally that are useful for remote state preparation, and there are bona fide discordant states that are of no help.

Animesh Datta, Vaibhav Madhok

Som Kanjilal, Aiman Khan, Chellasamy Jebarathinam +1 more

In recent years, exploration of the possible use of separable states as a resource to achieve quantum information processing (QIP) tasks has been gaining increasing significance. In this context, a particularly important demonstration has been that nonvanishing discord is the necessary condition for separable states to be used as a resource for remotely preparing any arbitrary pure target state [Nat. Phys. 8, 666 (2012)]. The present work stems from our observation that not only can resource states with the same discord 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. Therefore, this necessitates identification of the relevant feature of quantum correlations that can appropriately quantify the 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 the usefulness of the resource for the RSP task using entangled as well as separable states, including nondiscordant states as a resource. In particular, it is revealed that zero-discord states with such a nonvanishing 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.

Shubhayan Sarkar, Chandan Datta

Shenghang Li, Yixin Chen

Quantum discord and quantum entanglement are resources in some quantum information processing (QIP) models. However, in recent years, the evidence that separable states or classically correlated states can also accomplish QIP is demonstrated. It provides a useful tool since such states are easier to prepare. Quantum coherence is a measure of non-classical correlation, containing entanglement and discord as a subset. Nowadays, it is of interest whether quantum coherence can act as a resource in QIP independently or not, without the help from quantum discord or entanglement. In this paper, we show that quantum correlated coherence(a measure of coherence with local parts removed) is also a kind of quantum resource. It is the sufficient and necessary resource for quantum remote state preparation and quantum teleportation.