The role of entanglement in energy-restricted communication and randomness generation

TL;DR

This paper explores how entanglement influences energy-restricted quantum communication and randomness generation, revealing conditions where entanglement is beneficial and assessing security implications in low-energy regimes.

Contribution

It provides a correlation criterion for nonlocal resources, shows entanglement's advantages depend on non-unitary encoding, and evaluates security in low-energy quantum random number generation.

Findings

Entanglement can be non-beneficial for classical tasks under energy constraints.

Advantages of entanglement in quantum communication require non-unitary encoding schemes.

Security of quantum randomness generation remains robust in low-energy regimes.

Abstract

A promising platform for semi-device-independent quantum information is prepare-and-measure experiments restricted only by a bound on the energy of the communication. Here, we investigate the role of shared entanglement in such scenarios. For classical communication, we derive a general correlation criterion for nonlocal resources and use it to show that entanglement can fail to be a resource in standard tasks. For quantum communication, we consider the basic primitive for energy-constrained communication, namely the probabilistic transmission of a bit, and show that the advantages of entanglement only can be unlocked by non-unitary encoding schemes that purposefully decohere the entangled state. We also find that these advantages can be increased by using entanglement of higher dimension than qubit. We leverage these insights to investigate the impact of entanglement for quantum random number generation, which is a standard application of these systems but whose security so far only has been established against classical side information. In the low-energy regime, our attacks on the protocol indicate that the security remains largely intact, thereby paving the way for strengthened security without more complex setups and with negligible performance reductions.