Quantum data hiding in the presence of noise

TL;DR

This paper investigates the limits of quantum data hiding in noisy environments, establishing bounds on the capacity of quantum channels to securely hide classical information under realistic conditions.

Contribution

It introduces the concept of data-hiding capacity for quantum channels, derives upper bounds, and analyzes the limitations of coherent-state encodings in noisy settings.

Findings

Established a regularized upper bound on data hiding capacity.

Proved limitations of coherent-state encodings in noisy channels.

Derived lower bounds for mictodiactic channels.

Abstract

When classical or quantum information is broadcast to separate receivers, there exist codes that encrypt the encoded data such that the receivers cannot recover it when performing local operations and classical communication, but they can decode reliably if they bring their systems together and perform a collective measurement. This phenomenon is known as quantum data hiding and hitherto has been studied under the assumption that noise does not affect the encoded systems. With the aim of applying the quantum data hiding effect in practical scenarios, here we define the data-hiding capacity for hiding classical information using a quantum channel. Using this notion, we establish a regularized upper bound on the data hiding capacity of any quantum broadcast channel, and we prove that coherent-state encodings have a strong limitation on their data hiding rates. We then prove a lower bound on the data hiding capacity of channels that map the maximally mixed state to the maximally mixed state (we call these channels "mictodiactic"---they can be seen as a generalization of unital channels when the input and output spaces are not necessarily isomorphic) and argue how to extend this bound to generic channels and to more than two receivers.