Theoretical research in Professor Whaley's group is focused on elucidating and manipulating chemical dynamics in strongly quantum environments. Our current interests lie in i) quantum behavior of nanoscale clusters, and ii) molecular aspects of Quantum Computation.
Clusters present a major challenge to chemistry and physics. These systems are intermediate in size between molecular and bulk, and often display marked finite size scaling of their physical and chemical properties. Too large for conventional 'molecular' techniques, they are also too small for traditional bulk theoretical methods, and therefore require new approaches to be developed for analysis of their energetic, structural and dynamical properties. We study a wide range of clusters in the nanoscale regime, ranging from weakly bound van der Waals aggregates of helium and hydrogen ("quantum clusters") to strongly covalently bound semiconductor clusters. Quantum clusters of helium with 20 - 105 atoms are liquid-like but can display a high degree of local ordering upon addition of molecular species. These clusters provide a novel, gentle environment for ultra-cold, high resolution, molecular spectroscopy which is just beginning to be explored experimentally. Elucidation of the relation between the new chemistry displayed by these clusters and the unusual physical properties of bulk superfluid helium is an important goal. Theoretical methods and algorithms for large scale molecular level calculations are being developed for characterization of factors affecting structure, dynamics, and impurity spectroscopy in these nanoscale quantum matrices. Very different problems are posed by covalently bonded semiconductor clusters of materials such as CdSe or Si, which show bulk lattice structure over the entire size range 10 - 100 Å (50 - 104 atoms) but display strongly size dependent electronic properties. The size scaling of optoelectronic properties are components in the development of a fundamental understanding which may be used to design novel nanocrystalline clusters with interesting device applications.
Quantum information processing employs superposition, entanglement, and probabilistic measurement to encode and manipulate information in very different ways from the classical information processing underlying current electronic technology. Dramatic advances in quantum computational algorithms based on the parallelism resulting from quantum mechanical state evolutions, have led to experimental efforts to implement small scale quantum logic devices. Our theoretical work on decoherence, optimal universal quantum computation, and scalable quantum arrays, seeks to define and facilitate the physical implementation of scalable quantum computations
In the News
The flip side of Heisenberg’s uncertainty principle, the energy time uncertainty principle, establishes a speed limit for transitions between two states. UC Berkeley physical chemists have now proved this principle for transitions between states that are not entirely distinct, allowing the calculation of speed limits for processes such as quantum computing and tunneling.