Covert Entanglement Generation and Secrecy

Quantum communication harnesses the principles of quantum mechanics to enable fundamentally

new forms of information transfer, with applications ranging from secure data transmission

to distributed quantum computing. A central feature of quantum communication is the use of

entanglement, whose generation and distribution are essential for enabling these capabilities.

Privacy is a fundamental aspect of communication: while secrecy guarantees that the transmitted

information remains inaccessible to an adversary, covert communication ensures that

the very act of transmission remains undetectable. These are distinct requirements – covert

communication does not necessarily imply secrecy, and vice versa. The covertness requirement

significantly limits throughput: in the covert setting, the amount of information that can be

transmitted reliably follows a square-root law, allowing only O(√n) (qu)bits over n transmissions.

In this work, we characterize the covert capacity for entanglement generation over a noisy

quantum channel. We begin by analyzing the problem of covert communication of classical

information under a secrecy constraint. We then leverage this result to construct a coding

scheme for covert entanglement generation. Specifically, we establish that O(√n) Einstein-

Podolsky-Rosen (EPR) pairs can be distributed covertly and reliably over n transmissions.

We determine the optimal transmission rates for both covert secrecy and covert entanglement

generation.