Interview for Faculty Position

Spins in semiconductors: Qubits or new bits?

William Coish

University of Waterloo

The traditional march of progress in the semiconductor industry has been toward more and smaller device components. As device sizes decrease, dissipation and quantum effects play a greater role, causing conventional wisdom for device fabrication to break down. This realization has given rise to the field of semiconductor spin electronics (spintronics), where the old-style CMOS charge bit is replaced by tiny magnetic moments (spins), in the hopes that power, size, and speed will all be more favourable in the new model.

A still more ambitious idea is to use the spin-1/2 degree of freedom of a single electron confined to a semiconductor quantum dot as a quantum bit (qubit), the fundamental building block for a quantum computer. A major hurdle to overcome before this goal can be achieved is to understand and control fundamental sources of decoherence that can act on these spins, destroying important information stored in them.

In this talk, I will discuss the physics behind spin-based quantum and classical computing, focussing on the decoherence problem for single spins and how it might be solved. I will also address difficulties associated with quantum control and measurement of spins. These difficulties can be mitigated through a careful microscopic understanding of the associated physical systems and understanding of the quantum measurement process, guided by many new and exciting experimental results.