777 research outputs found
A New Method for Multi-Bit and Qudit Transfer Based on Commensurate Waveguide Arrays
The faithful state transfer is an important requirement in the construction
of classical and quantum computers. While the high-speed transfer is realized
by optical-fibre interconnects, its implementation in integrated optical
circuits is affected by cross-talk. The cross-talk between densely packed
optical waveguides limits the transfer fidelity and distorts the signal in each
channel, thus severely impeding the parallel transfer of states such as
classical registers, multiple qubits and qudits. Here, we leverage on the
suitably engineered cross-talk between waveguides to achieve the parallel
transfer on optical chip. Waveguide coupling coefficients are designed to yield
commensurate eigenvalues of the array and hence, periodic revivals of the input
state. While, in general, polynomially complex, the inverse eigenvalue problem
permits analytic solutions for small number of waveguides. We present exact
solutions for arrays of up to nine waveguides and use them to design realistic
buses for multi-(qu)bit and qudit transfer. Advantages and limitations of the
proposed solution are discussed in the context of available fabrication
techniques
Beyond Binary Search: Parallel In-Place Construction of Implicit Search Tree Layouts.
M.S. Thesis. University of HawaiÊ»i at MÄnoa 2018
Twisted Permutation Codes
We introduce twisted permutation codes, which are frequency permutation
arrays analogous to repetition permutation codes, namely, codes obtained from
the repetition construction applied to a permutation code. In particular, we
show that a lower bound for the minimum distance of a twisted permutation code
is the minimum distance of a repetition permutation code. We give examples
where this bound is tight, but more importantly, we give examples of twisted
permutation codes with minimum distance strictly greater than this lower bound.Comment: 20 page
Infrared Spectroscopy of Quantum Crossbars
Infrared (IR) spectroscopy can be used as an important and effective tool for
probing periodic networks of quantum wires or nanotubes (quantum crossbars,
QCB) at finite frequencies far from the Luttinger liquid fixed point. Plasmon
excitations in QCB may be involved in resonance diffraction of incident
electromagnetic waves and in optical absorption in the IR part of the spectrum.
Direct absorption of external electric field in QCB strongly depends on the
direction of the wave vector This results in two types of
dimensional crossover with varying angle of an incident wave or its frequency.
In the case of QCB interacting with semiconductor substrate, capacitive contact
between them does not destroy the Luttinger liquid character of the long wave
QCB excitations. However, the dielectric losses on a substrate surface are
significantly changed due to appearance of additional Landau damping. The
latter is initiated by diffraction processes on QCB superlattice and manifests
itself as strong but narrow absorption peaks lying below the damping region of
an isolated substrate.SubmiComment: Submitted to Phys. Rev.
Generalized Balanced Tournament Packings and Optimal Equitable Symbol Weight Codes for Power Line Communications
Generalized balance tournament packings (GBTPs) extend the concept of
generalized balanced tournament designs introduced by Lamken and Vanstone
(1989). In this paper, we establish the connection between GBTPs and a class of
codes called equitable symbol weight codes. The latter were recently
demonstrated to optimize the performance against narrowband noise in a general
coded modulation scheme for power line communications. By constructing classes
of GBTPs, we establish infinite families of optimal equitable symbol weight
codes with code lengths greater than alphabet size and whose narrowband noise
error-correcting capability to code length ratios do not diminish to zero as
the length grows
Importance of Symbol Equity in Coded Modulation for Power Line Communications
The use of multiple frequency shift keying modulation with permutation codes
addresses the problem of permanent narrowband noise disturbance in a power line
communications system. In this paper, we extend this coded modulation scheme
based on permutation codes to general codes and introduce an additional new
parameter that more precisely captures a code's performance against permanent
narrowband noise. As a result, we define a new class of codes, namely,
equitable symbol weight codes, which are optimal with respect to this measure
Equivalence of Decoupling Schemes and Orthogonal Arrays
We consider the problem of switching off unwanted interactions in a given
multi-partite Hamiltonian. This is known to be an important primitive in
quantum information processing and several schemes have been presented in the
literature to achieve this task. A method to construct decoupling schemes for
quantum systems of pairwise interacting qubits was introduced by M.
Stollsteimer and G. Mahler and is based on orthogonal arrays. Another approach
based on triples of Hadamard matrices that are closed under pointwise
multiplication was proposed by D. Leung. In this paper, we show that both
methods lead to the same class of decoupling schemes. Moreover, we establish a
characterization of orthogonal arrays by showing that they are equivalent to
decoupling schemes which allow a refinement into equidistant time-slots.
Furthermore, we show that decoupling schemes for networks of higher-dimensional
quantum systems with t-local Hamiltonians can be constructed from classical
error-correcting codes.Comment: 26 pages, latex, 1 figure in tex
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