Browsing by Subject "quantum systems"

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    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.
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    Theoretical and experimental characterization of non-Markovian anti-parity-time systems
    (Springer, 2023-10-20) Wilkey, Andrew; Suelzer, Joseph; Joglekar, Yogesh N.; Vemuri, Gautam; Physics, School of Science
    Open systems with anti-parity-time (APT) or PT symmetry exhibit a rich phenomenology absent in their Hermitian counterparts. To date all model systems and their diverse realizations across classical and quantum platforms have been local in time, i.e., Markovian. Here we propose a non-Markovian system with anti-PT-symmetry where a single time-delay encodes the retention of memory, and experimentally demonstrate its consequences with two time-delay coupled semiconductor lasers. A transcendental characteristic equation with infinitely many eigenvalue pairs sets our model apart. We show that a sequence of amplifying-to-decaying dominant mode transitions is induced by the time delay in our minimal model. The signatures of these transitions quantitatively match results obtained from four, coupled, nonlinear rate equations for laser dynamics, and are experimentally observed as constant-width sideband oscillations in the laser intensity profiles. Our work introduces a paradigmatic non-Hermitian system with memory, paves the way for its realization in classical systems, and may apply to time-delayed feedback-control for quantum systems.