When
Where
Title
Covert Quantum Communication Over Bosonic Channels and Covert Quantum Computing
Abstract
This thesis explores the question of covertness as it pertains to quantum communication and quantum covert computing. What are the fundamental limits of transmitting information over a quantum communication channel, so an all-powerful quantum adversary cannot detect presence of the transmission? Similarly, in the quantum computing regime, what are the limits for an adversarial warden on detecting whether or not computation is being performed within the system?
We establish square-root laws for covert classical and quantum communication over bosonic channels. Specifically, we derive the covert capacity for classical communication over the lossy thermal-noise bosonic channel, and develop practical coding protocols for covert entanglement generation and covert quantum communication over a point-to-point bosonic channel. Building on our previous work on entanglement generation capacity, we provide an upper bound on direct covert quantum communication capacity.
In the final chapter, we introduce the concept of covert quantum computing, providing a formal definition and establish its connection to covert quantum communication theory. We develop a square-root lower bound on the number of spectator qubits an adversary may use to detect computation on superconducting quantum processors that is based on noise models from two-qubit gates and chip topologies. We explore this bound experimentally using IQM's Emerald and Garnet superconducting quantum computers, demonstrating detectable crosstalk signatures in spectator qubits using modified Ramsey experiments.
Please email Jini at jini@optics.arizona.edu or Evan at ejdanderson@arizona.edu for a Zoom link.