Designing a Quantum Transducer With Genetic Algorithms and Electron Transport Calculations

          @misc{ pirsa_PIRSA:19070021,
            doi = {10.48660/19070021},
            url = {https://pirsa.org/19070021},
            author = {Ryczko, Kevin},
            keywords = {Condensed Matter},
            language = {en},
            title = {Designing a Quantum Transducer With Genetic Algorithms and Electron Transport Calculations},
            publisher = {Perimeter Institute},
            year = {2019},
            month = {jul},
            note = {PIRSA:19070021 see, \url{https://pirsa.org}}
          }
          

Abstract

The fields of quantum information and quantum computation are reliant on creating and maintaining low-dimensional quantum states. In two-dimensional hexagonal materials, one can describe a two-dimensional quantum state with electron quasi-momentum. This description, often referred to as valleytronics allows one to define a two-state vector labelled by k and k', which correspond to symmetric valleys in the conduction band. In this work, we present an algorithm that allows one to construct a nanoscale device that topologically separates k and k' current. Our algorithm incorporates electron transport calculations, artificial neural networks, and genetic algorithms to find structures that optimize a custom objective function. Our first result is that when modifying the on-site energies via doping with simple shapes the genetic algorithm is able to find structures that are able to topologically separate the valley currents with approximately 90% purity. We then introduce an arbitrary shape generator via a policy defined by an artificial neural network to modify the on-site energies of the nanoribbons. We study the dynamics of the genetic algorithms for both cases. Lastly, we then attempt to physically motivate the solutions by mapping the high dimensional search space to a lower dimensional one that can be better understood.