4,628 research outputs found
Ground State Spin Logic
Designing and optimizing cost functions and energy landscapes is a problem
encountered in many fields of science and engineering. These landscapes and
cost functions can be embedded and annealed in experimentally controllable spin
Hamiltonians. Using an approach based on group theory and symmetries, we
examine the embedding of Boolean logic gates into the ground state subspace of
such spin systems. We describe parameterized families of diagonal Hamiltonians
and symmetry operations which preserve the ground state subspace encoding the
truth tables of Boolean formulas. The ground state embeddings of adder circuits
are used to illustrate how gates are combined and simplified using symmetry.
Our work is relevant for experimental demonstrations of ground state embeddings
found in both classical optimization as well as adiabatic quantum optimization.Comment: 6 pages + 3 pages appendix, 7 figures, 1 tabl
A demonstration of the utility of fractional experimental design for finding optimal genetic algorithm parameter settings
This paper demonstrates that the use of sparse experimental design in the development of the structure for genetic algorithms, and hence other computer programs, is a particularly effective and efficient strategy. Despite widespread knowledge of the existence of these systematic experimental plans, they have seen limited application in the investigation of advanced computer programs. This paper attempts to address this missed opportunity and encourage others to take advantage of the power of these plans. Using data generated from a full factorial experimental design, involving 27 experimental runs that was used to assess the optimum operating settings of the parameters of a special genetic algorithm (GA), we show that similar results could have been obtained using as few as nine runs. The GA was used to find minimum cost schedules for a complex component assembly operation with many sub-processes
Local spin operators for fermion simulations
Digital quantum simulation of fermionic systems is important in the context
of chemistry and physics. Simulating fermionic models on general purpose
quantum computers requires imposing a fermionic algebra on spins. The
previously studied Jordan-Wigner and Bravyi-Kitaev transformations are two
techniques for accomplishing this task. Here we re-examine an auxiliary fermion
construction which maps fermionic operators to local operators on spins. The
local simulation is performed by relaxing the requirement that the number of
spins should match the number of fermionic modes. Instead, auxiliary modes are
introduced to enable non-consecutive fermionic couplings to be simulated with
constant low-rank tensor products on spins. We connect the auxiliary fermion
construction to other topological models and give examples of the construction
When do young birds disperse? : Tests from studies of golden eagles in Scotland
Peer reviewedPublisher PD
Doppler-Broadening of Light Nuclei Gamma-Ray Spectra
Non-destructive methods of material interrogation are used to locate hidden explosives and thwart terrorism attempts. In one such method materials are bombarded with neutrons which react with the nuclei of the atoms within causing a de-excitation process emitting a gamma-ray. The spectrum displayed by the collection of these gamma-rays gives valuable information regarding the materialās elemental make-up. It has been hypothesized that gamma-rays from neutron-induced gamma-ray reactions on light elements with atomic numbers less than 20, including most of the gamma-rays of interest in explosives detection, are Doppler-broadened. This thesis focuses on the gamma ray spectra from the 4438 keV gamma ray in the 12C (n, nāĪ³) reaction wherein Doppler broadening was investigated. A graphite sample was exposed to 14 MeV neutrons and the 12C gamma ray spectra collected using an HPGe detector positioned at four different angles with respect to the neutron beam; near 00, 450, 900 and 1350. No other experimental parameter was changed. The resultant gamma ray spectra indicated Doppler broadening had occurred
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