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Decoherence immunity using Majorana fermions: state of play and possible challenges


The central challenge to harnessing the power of quantum entanglement to do useful tasks is figuring out how to maintain coherences for long periods of time.  As realized by Kitaev a little over a decade ago, one way to do this is to encode quantum information in the wavefunction of particles—so-called non-Abelian anyons—which obey neither Bose nor Fermi statistics.  Since then, there has been an enormous amount of activity devoted to trying to find such particles in the form of Majorana surface states (quasiparticles) of topological superconductors.  In this talk, I will review the theoretical and experimental state of play before raising questions about the current theory orthodoxy, which is based on the mean-field BCS theory of superconductivity and excludes fluctuations—Goldstone modes—which can interact with the Majoranas and modify their properties.