AbstractsEngineering

An “effective spin” concept is introduced to underpin the fundamental analogy between two disparate fields of physics – phase coherent transport in mesoscopic systems and spin-based quantum information processing. When coupled with the Bloch sphere concept, this isomorphism allows formulation of transport problems in a language more familiar to researchers in the field of spintronics and quantum computing. We exemplify the synergy between charge tunneling and spin qubit unitary operations by recasting well-known problems of tunneling through a delta scatterer, a resonant tunneling structure, a superlattice structure, and arrays of elastic scatterers, in terms of specific unitary operations (rotations) of a spinor on the Bloch sphere. Furthermore, we examine the potential use of random arrays of elastic scatterers as quantum information processors by calculating the properties of their Shannon entropy under the assumption of phase coherent charge transport. The numerical values of the Shannon entropy average and variance are very sensitive to the nature of the impurities, whether attractive, repulsive, or a combination of both; besides, the inclusion of evanescent modes has a profound influence on the value of the Shannon entropy and its associated signal-to-noise ratio (SNR). In samples with repulsive scatterers, the SNR can be tuned over a wide range by applying a potential through a gate to change the impurity potentials from repulsive to attractive by moving their energy levels with respect to the quasi-Fermi level in the sample.