Browsing by Author "Sparrow, Chris"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Photonic quantum simulations of coupled PT -symmetric Hamiltonians
    (APS, 2022-01-26) Maraviglia, Nicola; Yard, Patrick; Wakefield, Ross; Carolan, Jacques; Sparrow, Chris; Chakhmakhchyan, Levon; Harrold, Chris; Hashimoto, Toshikazu; Matsuda, Nobuyuki; Harter, Andrew K.; Joglekar, Yogesh N.; Laing, Anthony; Physics, School of Science
    Parity-time-symmetric (PT -symmetric) Hamiltonians are generally non-Hermitian and give rise to exotic behavior in quantum systems at exceptional points, where eigenvectors coalesce. The recent realization of PT -symmetric Hamiltonians in quantum systems has ignited efforts to simulate and investigate many-particle quantum systems across exceptional points. Here, we use a programmable integrated photonic chip to simulate a model composed of twin pairs of PT -symmetric Hamiltonians, with each the time reverse of its twin. We simulate quantum dynamics across exceptional points including two- and three-particle interference, and a particle-trembling behavior that arises due to interference between subsystems undergoing time-reversed evolutions. These results show how programmable quantum simulators can be used to investigate foundational questions in quantum mechanics.
  • Thumbnail Image
    Item
    Simulating the vibrational quantum dynamics of molecules using photonics
    (Nature, 2018) Sparrow, Chris; Martín-López, Enrique; Maraviglia, Nicola; Neville, Alex; Harrold, Christopher; Carolan, Jacques; Joglekar, Yogesh N.; Hashimoto, Toshikazu; Matsuda, Nobuyuki; O'Brien, Jeremy L.; Tew, David P.; Laing, Anthony; Physics, School of Science
    Advances in control techniques for vibrational quantum states in molecules present new challenges for modelling such systems, which could be amenable to quantum simulation methods. Here, by exploiting a natural mapping between vibrations in molecules and photons in waveguides, we demonstrate a reprogrammable photonic chip as a versatile simulation platform for a range of quantum dynamic behaviour in different molecules. We begin by simulating the time evolution of vibrational excitations in the harmonic approximation for several four-atom molecules, including H2CS, SO3, HNCO, HFHF, N4 and P4. We then simulate coherent and dephased energy transport in the simplest model of the peptide bond in proteins—N-methylacetamide—and simulate thermal relaxation and the effect of anharmonicities in H2O. Finally, we use multi-photon statistics with a feedback control algorithm to iteratively identify quantum states that increase a particular dissociation pathway of NH3. These methods point to powerful new simulation tools for molecular quantum dynamics and the field of femtochemistry.