4 research outputs found
Quantised Bulk Conductivity as a Local Chern Marker
A central property of Chern insulators is the robustness of the topological
phase and edge states to impurities in the system. Despite this, Chern number
cannot be straightforwardly calculated in the presence of disorder. Recently,
work has been done to propose a local analog of the Chern number, called local
markers, that can be used to characterise disordered systems. However, it was
unclear whether the proposed markers represented a physically-measurable
property of the system. Here we propose a local marker starting from a physical
argument, as a local cross-conductivity measured in the bulk of the system. We
find the explicit form of the marker for a non-interacting system of electrons
on the lattice and show that it corresponds to existing expressions for the
Chern number. Examples are calculated for a variety of disordered and amorphous
systems, showing that it is precisely quantised to the Chern number and robust
against disorder.Comment: 10 pages, 9 figure
An Exact Chiral Amorphous Spin Liquid
Topological insulator phases of non-interacting particles have been
generalized from periodic crystals to amorphous lattices, which raises the
question whether topologically ordered quantum many-body phases may similarly
exist in amorphous systems? Here we construct a soluble chiral amorphous
quantum spin liquid by extending the Kitaev honeycomb model to random lattices
with fixed coordination number three. The model retains its exact solubility
but the presence of plaquettes with an odd number of sides leads to a
spontaneous breaking of time reversal symmetry. We unearth a rich phase diagram
displaying Abelian as well as a non-Abelian quantum spin liquid phases with a
remarkably simple ground state flux pattern. Furthermore, we show that the
system undergoes a finite-temperature phase transition to a conducting thermal
metal state and discuss possible experimental realisations.Comment: 5 pages, 3 figure
Temporal mode transformations by sequential time and frequency phase modulation for applications in quantum information science
14 pagesControlling the temporal mode shape of quantum light pulses has wide ranging application to quantum information science and technology. Techniques have been developed to control the bandwidth, allow shifting in the time and frequency domains, and perform mode-selective beam-splitter-like transformations. However, there is no present scheme to perform targeted multimode unitary transformations on temporal modes. Here we present a practical approach to realize general transformations for temporal modes. We show theoretically that any unitary transformation on temporal modes can be performed using a series of phase operations in the time and frequency domains. Numerical simulations show that several key transformations on temporal modes can be performed with greater than 95% fidelity using experimentally feasible specifications.National Science Foundation (1620822); Defence Science and Technology Laboratory (DSTLX-100092545); Horizon 2020 Framework Programme (665148)