Spin Dynamics and Quantum Information Processing in the Solid State
Our group is primarily concerned with understanding electron and nuclear spin dynamics in semiconductors and engineering quantum states for information processing and sensing applications. Our experimental program combines quantum optics with electron-spin resonance, materials engineering, and nanofabrication. We are focused on developing experimental tools and uncovering new systems that could expand the technological impact of quantum coherence in the solid state. Certain point defects in semiconductors, such as the nitrogen vacancy center in diamond or the neutral divacancy in silicon carbide, exhibit long-lived spin coherence that persist up to room temperature. Harnessing these defects as atomic-scale probes of electromagnetic fields promises to lead to nanoscale nuclear magnetic resonance, new tools for bio-sensing, and a better understanding of semiconductor electronics.
The fundamental quantum-mechanical nature of spin makes it an ideal candidate for use as a quantum bit, the basic unit of information in a quantum computing architecture. Individual spins may be initialized, coherently controlled, and read out using a variety of optical and electronic techniques. In particular, point defects in crystals have many analogous properties to atoms trapped in vacuum, including localized electronic states and sharp optical and spin transitions. In certain defects, electronic spin states are insulated from lattice dynamics, leading to long quantum coherence times that persist even up to room temperature.
Spintronics, the storage and transport of electronic spins in semiconductor devices may revolutionize the electronic device industry, with spin based transistors, memories, and opto-electronic devices replacing their charge-based counterparts. For instance, giant and tunnel magnetoresistance effects are already used in modern hard drives, and non-volatile spin-logic devices are being studied for inclusion in future computers. Ultimately, spintronics could bring practical logic and memory down to the single electron spin level.
The exchange couplings present in magnetically-doped semiconductors are orders of magnitude larger in energy than the spin-orbit and hyperfine interactions, and the interactions between carriers and magnetic ions in magnetic semiconductors may be engineered through heterostructures grown with molecular beam epitaxy.
Spin phenomena may be quantified to a striking degree of precision using a variety of optical and electronic techniques that enable one to probe spin dynamics as a function of time and space.