On the construction of model Hamiltonians for adiabatic quantum computation and its application to finding low energy conformations of lattice protein models

In this report, we explore the use of a quantum optimization algorithm for obtaining low energy conformations of protein models. We discuss mappings between protein models and optimization variables, which are in turn mapped to a system of coupled quantum bits. General strategies are given for constructing Hamiltonians to be used to solve optimization problems of physical/chemical/biological interest via quantum computation by adiabatic evolution. As an example, we implement the Hamiltonian corresponding to the Hydrophobic-Polar (HP) model for protein folding. Furthermore, we present an approach to reduce the resulting Hamiltonian to two-body terms gearing towards an experimental realization.Comment: 35 pages, 8 figure

Precision microwave spectroscopy of the heavy fermion superconductor CeCoIn5

The heavy fermion superconductor CeCoIn5 demonstrates remarkable similarities to the high-Tc cuprates in many of its properties including proximity to antiferromagnetism, quasi-two-dimensionality, d-wave superconductivity, and departures from Fermi liquid behaviour in the normal state. It is also a “high-Tc” superconductor in the context of the heavy fermions. The experimental technique of microwave cavity perturbation has been used to measure the electrodynamics of a single crystal of CeCoIn5 over a range of temperatures, from 80 mK to 35 K, in a dilution refrigerator. Measurements at multiple frequencies required the development of an in-situ technique for the bolometric detection of the surface resistance. This has allowed conductivity spectra to be acquired, resulting in several important results. First, the resolution of an unexplained fractional power law in the penetration depth has been achieved by properly isolating the nodal quasiparticle contribution, revealing a previously unseen linear temperature dependence in CeCoIn5, as expected for a d-wave superconductor. Second, the temperature evolution of the microwave conductivity spectra implies that the effective mass of the quasiparticles continues to change below Tc, hinting that quantum criticality remains important even in the superconducting state. Third, conductivity spectra that are strikingly similar to those from YBa2Cu3O6+y suggest a strong connection in the underlying charge dynamics, as both CeCoIn5 and YBa2Cu3O6+y show a collapse in the quasiparticle scattering rate below Tc. Finally, the spectra indicate the presence of multiband effects