title: Quantum-secure covert communication on bosonic channels.
abstract: Computational encryption, information-theoretic secrecy and quantum cryptography offer progressively stronger security against unauthorized decoding of messages contained in communication transmissions. However, these approaches do not ensure stealth--that the mere presence of message-bearing transmissions be undetectable. We characterize the ultimate limit of how much data can be reliably and covertly communicated over the lossy thermal-noise bosonic channel (which models various practical communication channels). We show that whenever there is some channel noise that cannot in principle be controlled by an otherwise arbitrarily powerful adversary--for example, thermal noise from blackbody radiation--the number of reliably transmissible covert bits is at most proportional to the square root of the number of orthogonal modes (the time-bandwidth product) available in the transmission interval. We demonstrate this in a proof-of-principle experiment. Our result paves the way to realizing communications that are kept covert from an all-powerful quantum adversary.
authors.affiliation: Quantum Information Processing Group, Raytheon BBN Technologies, 10 Moulton Street, Cambridge, Massachusetts 02138, USA.|College of Information and Computer Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Boulat A
authors.initials: BA
authors.lastname: Bash
authors.affiliation: Quantum Information Processing Group, Raytheon BBN Technologies, 10 Moulton Street, Cambridge, Massachusetts 02138, USA.|Amherst College, Amherst, Massachusetts 01002, USA.
authors.forename: Andrei H
authors.initials: AH
authors.lastname: Gheorghe
authors.affiliation: Quantum Information Processing Group, Raytheon BBN Technologies, 10 Moulton Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Monika
authors.initials: M
authors.lastname: Patel
authors.affiliation: Quantum Information Processing Group, Raytheon BBN Technologies, 10 Moulton Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Habif
authors.affiliation: Electrical and Computer Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Goeckel
authors.affiliation: College of Information and Computer Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Don
authors.initials: D
authors.lastname: Towsley
authors.affiliation: Quantum Information Processing Group, Raytheon BBN Technologies, 10 Moulton Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Saikat
authors.initials: S
authors.lastname: Guha