Howard Barnum is a theorist in CCS-3 (Information Sciences), who uses tools from physics, computer science, mathematics, and information theory to explore the possibilities and limits of quantum information processing, including quantum cryptography and computing, and to explore the implications of quantum information science for physics, including condensed matter physics and the interpretation of quantum mechanics. He is also developing an understanding of where quantum mechanics gets its greater-than-classical power by investigating information processing in a broad framework for theories that include classical probability theory, quantum theory, and a wide spectrum of other possibilities that can serve as foils to these.
Diego Dalvit of the Theoretical Division investigates quantum electrodynamics of the Casimir interaction in the nano and microscales, such as surface-surface and atom-surface interactions. He is also involved in the study of decoherence for the quantum-classical transition and its effects in the context of quantum optics and cold atomic physics.
Matthew Hastings is a theorist studying entanglement in quantum many-body systems. He has proven several theorems constraining the behavior of these systems, including a higher dimension Lieb-Schultz-Mattis theorem and area laws on the entanglement entropy. Currently he is studying topological order and matrix product states.
Jim Harrington is a theorist in P-21 (Applied Modern Physics) working on protocols and security proofs for quantum key distribution systems, as well as studying fault-tolerant quantum computation with topological and other quantum error-correcting codes. In addition, he has performed simulations of rateless and rate-compatible classical error-correcting codes. Currently, he is also interested in speculative ideas such as analyzing the security of quantum key distribution in the presence of closed timelike curves and the effect of entanglement as a resource in cooperative games.
Wojciech Zurek of the Theoretical Division is known internationally for his seminal contributions to theory of decoherence. His interests also include physics of information, quantum error correction, the transition from quantum to classical, as well as other subjects such as cosmology and dynamics of phase transformations. Zurek, Raymond Laflamme, University of Waterloo, Canada, and Emmanuel (Manny) Knill proposed a strategy to enable error-free quantum computations using quantum gates.