Definition and evolution of quantum cellular automata with two qubits per cell

Studies of quantum computer implementations suggest cellular quantum computer architectures. These architectures can simulate the evolution of quantum cellular automata, which can possibly simulate both quantum and classical physical systems and processes. It is however known that except for the trivial case, unitary evolution of one-dimensional homogeneous quantum cellular automata with one qubit per cell is not possible. Quantum cellular automata that comprise two qubits per cell are defined and their evolution is studied using a quantum computer simulator. The evolution is unitary and its linearity manifests itself as a periodic structure in the probability distribution patterns.Comment: 13 pages, 4 figure

Fundamental Building Blocks for The Design of A Single-electron Nanoelectronic Processor

92-100Nanoelectronics, Single electron, Memory, Fredkin gateA single-electron random access memory array (RAM) and a single-electron universal Fredkin gate are designed and simulated. The universality of the Fredkin gate in combination with the RAM gives the potential of the realization of an elementary single-electron nanoelectronic processor

Current characteristics of defective GNR nanoelectronic devices

The most promising Graphene structures for the development of nanoelectronics and sensor applications are Graphene nanoribbons (GNRs). GNRs with perfect lattices have been extensively investigated in the research literature; however, fabricated GNRs may still suffering from lattice flaws, the possible effect of which, on the operation of the circuitry comprised by GNR based devices, has not attracted significant interest. In this paper, we investigate the effect of lattice defects on the operational behavior of GNRs using the Non-Equilibrium Green's function (NEGF) method combined with tight-binding Hamiltonians targeting to the resulting nanoelectronic devices and circuits functionalities. We focus on butterfly-shaped GNRs, which have been proven to successfully function as switches that can be used as building blocks for simple Boolean gates and logic circuits. Analyses of the most common defects, namely the single and double vacancies, have been adequately performed. The effect of these vacancies was investigated by inserting them in various places and concentrations on the corresponding GNR based nano-devices. The computation results indicate the effect on lattice defects on the important operational device parameters including the leakage current, ION/IOFF and, finally, current density, which will determine the viability of GNR computing circuits.Postprint (published version

MULTIPLE QUANTUM WALKERS ON THE LINE USING HYBRID COINS: A POSSIBLE TOOL FOR QUANTUM SEARCH

In this paper discrete quantum walks with different coins used for odd and even time steps are studied. These coins are called hybrid. The calculation results are compared with the most frequently used coin, the Hadamard transform. Furthermore, quantum walks on the line which involve two or more quantum walkers with hybrid coins are studied. Quantum walks with entangled walkers and hybrid coins are also studied. The results of these calculations show that the proposed types of quantum walks can be used for quantum search, because the walker can be directed towards preferred directions and can also be confined in certain segments of the line

A review of wildland fire spread modelling, 1990-present 3: Mathematical analogues and simulation models

In recent years, advances in computational power and spatial data analysis (GIS, remote sensing, etc) have led to an increase in attempts to model the spread and behvaiour of wildland fires across the landscape. This series of review papers endeavours to critically and comprehensively review all types of surface fire spread models developed since 1990. This paper reviews models of a simulation or mathematical analogue nature. Most simulation models are implementations of existing empirical or quasi-empirical models and their primary function is to convert these generally one dimensional models to two dimensions and then propagate a fire perimeter across a modelled landscape. Mathematical analogue models are those that are based on some mathematical conceit (rather than a physical representation of fire spread) that coincidentally simulates the spread of fire. Other papers in the series review models of an physical or quasi-physical nature and empirical or quasi-empirical nature. Many models are extensions or refinements of models developed before 1990. Where this is the case, these models are also discussed but much less comprehensively.Comment: 20 pages + 9 pages references + 1 page figures. Submitted to the International Journal of Wildland Fir

Quantum gate algorithm for reference-guided DNA sequence alignment

Reference-guided DNA sequencing and alignment is an important process in computational molecular biology. The amount of DNA data grows very fast, and many new genomes are waiting to be sequenced while millions of private genomes need to be re-sequenced. Each human genome has 3.2 B base pairs, and each one could be stored with 2 bits of information, so one human genome would take 6.4 B bits or about 760 MB of storage (National Institute of General Medical Sciences). Today most powerful tensor processing units cannot handle the volume of DNA data necessitating a major leap in computing power. It is, therefore, important to investigate the usefulness of quantum computers in genomic data analysis, especially in DNA sequence alignment. Quantum computers are expected to be involved in DNA sequencing, initially as parts of classical systems, acting as quantum accelerators. The number of available qubits is increasing annually, and future quantum computers could conduct DNA sequencing, taking the place of classical computing systems. We present a novel quantum algorithm for reference-guided DNA sequence alignment modeled with gate-based quantum computing. The algorithm is scalable, can be integrated into existing classical DNA sequencing systems and is intentionally structured to limit computational errors. The quantum algorithm has been tested using the quantum processing units and simulators provided by IBM Quantum, and its correctness has been confirmed.Comment: 19 pages, 13 figure

High Specific Energy Lithium Cells for Space Exploration

The paper discusses development under an ESA TRP activity (Contract No. 4000109879/13/NL/LvH) with a target of high specific energy Lithium-ion cells, capable of operating under low temperature conditions, i.e. −40 °C. Such cells may be encountered in future exploration missions, which do not consider the use of Radioisotope Heater Units. During the activity, ≥1 Ah silicon-based high energy density prototype cells, following components characterization and optimization, were designed, developed, manufactured and tested under room and subzero temperature conditions down to −40 °C. The developed and tested prototype cells exhibited energy density of around 208 Wh/Kg at room temperature under C/10 charge-discharge rate within voltage range of 2.8 V and 4.1 V. Moreover, the prototype cells could retain and deliver more than 75% of their capacity at room temperature upon cycling at −40 °C, demonstrating an energy density of 140 Wh/kg