An electron´s spin--Part II

In Part I of this article, we introduced the notion of encoding binary bit information in the spin polarization of a single electron confined in a quantum dot and placed in a magnetic field. The spin polarization becomes bistable in a magnetic field and the spin can point either parallel to the field or antiparallel to it. These two polarizations encode the classical binary bits 0 and 1. We showed that since the bits can be switched by simply flipping the electron´s spin without physically moving the electron in space and causing a current, the energy dissipated during the bit flip operation could be made very small. In Part II we discuss the notion of using a single electron´s spin as a quantum bit (or qubit) that represents information in quantum computers. Just as spin is superior to charge as a vehicle to host classical bit information in classical computers it turns out that spin is superior to charge to host quantum information as well. That is why spin-based quantum information processing is gradually becoming the staple of scalable solid state versions of quantum computers.