A general scheme for information interception in the ping pong protocol

TL;DR

This paper introduces a comprehensive, loss-agnostic eavesdropping scheme applicable to high-dimensional quantum communication protocols, addressing previous limitations and unifying known attack strategies.

Contribution

It provides a new generic, loss-independent eavesdropping scheme for the ping-pong protocol that applies to any dimensionality and unifies existing attack methods.

Findings

The scheme is fully consistent with no-loss assumptions.

It applies to high-dimensional quantum systems.

It encompasses known attacks as special cases.

Abstract

The existence of an undetectable eavesdropping of dense coded information has been already demonstrated by Pavi\v{c}i\'c for the quantum direct communication based on the ping-pong paradigm. However, a) the explicit scheme of the circuit is only given and no design rules are provided, b) the existence of losses is implicitly assumed, c) the attack has been formulated against qubit based protocol only and it is not clear whether it can be adapted to higher dimensional systems. These deficiencies are removed in the presented contribution. A new generic eavesdropping scheme built on a firm theoretical background is proposed. In contrast to the previous approach, it does not refer to the properties of the vacuum state, so it is fully consistent with the absence of losses assumption. Moreover, the scheme applies to the communication paradigm based on signal particles of any dimensionality. It is also shown that some well known attacks are special cases of the proposed scheme.