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## Publications

Publications (78)

The quantum-dot cellular automata (QCA) computing paradigm is used to implement Rule 110, a unique one-dimensional cellular automata (CA) that has been proven to be Turing complete. A Turing complete architecture is capable of universal computing, which means that it could be used to implement any arbitrary computation. The optimized design of a si...

Quantum-dot cellular automata (QCA) are a leading example of field-coupled nanocomputing (FCN) devices. All FCN devices rely on local field interactions among nanoscale building blocks that are arranged in patterns to perform useful calculations. Many methods have been introduced to simulate these devices, but not all of those methods are guarantee...

The quantum-dot cellular automata (QCA) computing paradigm presents great promise as a potential strategy for future nanocomputing devices. Perhaps the greatest challenge facing the QCA architecture is finding a robust wire crossing strategy. In this paper, the recently introduced QCA signal distribution grid is extended to carry out generalized su...

Coplanar wire crossing has been a major challenge for quantum-dot cellular automata systems since their development. Several possible solutions have been presented, but they have either relied on non-adjacent cell interactions or have required switching time that scales with the number of inputs or outputs. In this paper, the authors present a sign...

The authors describe a signal distribution network for sequential systems constructed using the Quantum-dot cellular automata (QCA) computing paradigm. This network promises to enable the construction of arbitrarily complex QCA sequential systems in which all wire crossings are performed using nearest neighbor interactions, which will improve the t...

Emerging technologies have attracted a substantial interest in overcoming the physical limitations of CMOS as projected at the end of the Technology Roadmap; among these technologies, quantum-dot cellular automata (QCA) relies on different and novel paradigms to implement dense, low power circuits and systems for high-performance computing. As appl...

A signal distribution network (SDN) for Quantum-dot Cellular Automata (QDCA) devices is described. This network allows the distribution of a set of inputs to an arbitrary number of outputs in any desired order, overcoming the challenges associated with wire crossings that have faced QDCA systems in the past. The proposed signal distribution network...

The work in this paper describes the applicati on of an optimized eigensolver algorithm to produce the kernel calculations for simulating quantum-dot cellular automata (QCA) circuits, an emerging implementation of quantum computing The application of the locally optimal block preconditioned conjugate gradient (LOBPCG) method to calculate the eigenv...

The authors describe a signal distribution network (SDN) for quantum-dot cellular automata (QCA) devices. This network allows the distribution of a set of inputs to an arbitrary number of combinational functions, overcoming the challenges associated with wire crossings that have faced QCA systems for many years. As an additional benefit, the propos...

The authors analyze the effect of stray charges near a line of quantum-dot cellular automata (QCA) cells. Considering both the ground-state polarization and the excitation energy of the system, it is determined that there is a 129-nm-wide region surrounding a QCA wire where a stray charge will cause the wire to fail. This calculation is the result...

The authors present an analysis of the fault tolerant properties and the effects of temperature on an exclusive OR (XOR) gate and a full adder device implemented using quantum-dot cellular automata (QCA) structures. A Hubbard-type Hamiltonian and the Inter-cellular Hartree approximation have been used for modeling, and a uniform random distribution...

The authors describe a geometric layout of quantum-dot cellular automata (QCA) cells and an associated set of clock signals that can be used to implement a programmable array of logic (PAL). PALs are an important category of programmable logic that can be programmed (typically once) to perform a particular sum-of-products Boolean operation. The par...

Quantum-dot cellular automata (QCA) shows promise as a postsilicon CMOS, low-power computational technology. Nevertheless, to generalize QCA for next-generation digital devices, the ability to implement conventional programmable circuits based on nor, and , and or gates is necessary. To this end, we devise a new QCA structure, the QCA matrix multip...

We propose the design of a symmetric ternary current-mode CMOS Schmitt inverter using transmission current-switch theory. This Schmitt inverter can have multiple outputs, and its width of hysteresis can be adjusted as needed. The computer simulation shows that the designed Schmitt inverter has nearly ideal Schmitt characteristics.

We present fault tolerant properties of various quantum-dot cellular automata (QCA) devices. Effects of temperatures and dot displacements on the operation of the fundamental devices such as a binary wire, logical gates, a crossover, and an exclusive OR (XOR) have been investigated. A Hubbard-type Hamiltonian and intercellular Hartree approximation...

Teaching probability and statistics to undergraduate engineering students is a challenge because of the theoretical nature of the topic. There are many advantages to introducing this topic to first-year students. Students who have seen and worked with topics in probability and statistics are more likely to understand these principles when they are...

One of the most important responsibilities of a university faculty is to design the curriculum that
their students will experience. The design of a first-semester engineering course is an especially
important and challenging responsibility, because it forms the foundation of the students’ future
educational experiences. Many different philosophies...

We present a study of the joint influence of temperature and fabrication defects on the operation of quantum-dot cellular automata (QCA) devices. Canonical ensemble, a Hubbard-type Hamiltonian and the inter-cellular Hartree approximation were used, and a statistical model has been introduced to simulate defects in the QCA devices. Parameters such a...

Emerging technologies have attracted a substantial interest in overcoming the physical limitations of CMOS as projected at the end of the Technology Roadmap; among these technologies, quantum-dot cellular automata (QCA) relies on different and novel paradigms to implement dense, low power circuits and systems for high-performance computing. As appl...

Most applications of distance learning involve an instructor at a central, technology-rich location delivering a virtual classroom experience to students at one or more remote sites. However, there are many occasions when instructors need to be away from campus to attend conferences, perform on-site research projects, or administer off-campus acade...

In an effort to immediately use valuable student feedback from final course evaluations, Valparaiso University's Hesse Learning Resource and Assessment Center has worked with the Department of Electrical and Computer Engineering to optimize the format of the surveys themselves and procedures used to extract key information from those surveys in a t...

We present a numerical study of fault tolerance properties in quantum-dot cellular automata (QCA) devices. A full-basis quantum method is used for calculations of the Hamiltonian, and a statistical model has been introduced to simulate the influence of position defects of the dots within cells on the logical output. Combined effects of temperature...

This paper presents a novel method for the implementation of wire-crossing networks using quantum-dot cellular automata (QCA) cells. Such wire-crossing networks, also called crossbar networks, are an important part of modern programmable logic devices, such as programmable arrays of logic. The crossbar networks are made possible through the use of...

We present a theoretical study of thermal effect in quantum-dot cellular automata (QCA). A quantum statistical model has been introduced to obtain the thermal average of polarization of a QCA cell. We have studied the thermal effect on an inverter, a majority gate and planar arrays of different sizes. The theoretical analysis has been approximated...

As the size and complexity of quantum-dot cellular automata (QCA) digital circuits increase, the amount of time needed to create a QCA layout and then simulate the quasi-adiabatic switching of that layout significantly increases. To help reduce this development time, the same design process methodology that has been applied in developing complement...

Quasi-adiabatically switched quantum-dot cellular automata (QCA) devices present the opportunity to extend our efforts from the implementation of combinational logic devices to more useful sequential logic devices. One very important application of sequential logic is in the recognition of patterns in serial bit streams. This is important, for exam...

We will present numerical results of thermal effect in Quantum-dot
Cellular Automata (QCA). A quantum statistical model has been introduced
to obtain thermal average of polarization of a QCA cell. We will show
change in average polarization with temperature on devices: an inverter,
a majority gate and planar arrays of different sizes. The theoretic...

A theoretical study of thermal effect in QCA is presented. Quantum statistical analysis for average polarization of each cell is done. A computational model has been developed to find all the possible configurations of polarizations in an array of cells. All cells are in one of the two possible eigenstates corresponding to the total Hamiltonian. He...

In distributed computing, a majority of the computing power in a local area network resides in the computers that users directly access. Researchers learned that placing the computational resources as close as possible to the end users prevented a resource bottleneck at the supercomputer, reduced the networking cost, and provided superior service t...

Previous research has shown the viability of fundamental quantum-dot cellular automata (QCA) structures such as binary wires, coplanar wire crossings, inverters, and programmable AND/OR gates. Combining these and other logic devices, we have designed and simulated a regular array of QCA “macrocells,” with each macrocell housing an irregular array o...

We have previously proposed a way of using coupled quantum dots to construct digital computing elements - quantum-dot cellular automata (QCA). Here we consider a different approach to using coupled quantum-dot cells in an architecture which, rather that reproducing Boolean logic, uses a physical near-neighbor connectivity to construct an analog Cel...

Previous research on quantum cellular automata devices has restricted the cells to a single plane. In this paper, a noncoplanar arrangement is considered. These noncoplanar devices are found to be capable of implementing the same logical functions as conventional quantum cellular automata cells, and they typically require 50% of the area required b...

We use hierarchical layout methods to combine fundamental quantum-dot cellular automata (QCA) devices into more complex devices, including a 2-to-1 multiplexer, a 4-to-1 multiplexer, and an eight-function bit-slice arithmetic logic unit (ALU). The ALU unit is implemented using 1245 cells, making it the largest QCA device ever designed and simulated...

The authors formulate a new paradigm for computing with cellular automata (CAS) composed of arrays of quantum devices-quantum cellular automata. Computing in such a paradigm is edge driven. Input, output, and power are delivered at the edge of the CA array only; no direct flow of information or energy to internal cells is required. Computing in thi...

This paper presents a collaborative effort to combine a computer architecture lecture course with a computer topics laboratory. This integrated course provided the students with an opportunity to apply VHDL modeling to semester-long projects that illustrated many of the points learned in the lecture course. It also gave the students an opportunity...

We examine an alternative layout geometry for the quantum cellular automata (QCA)
architecture. In the traditional QCA geometry, all of the cells are placed in a single
plane, so that each cell interacts with a particular neighbor only along one of its edges.
By rotating the cells out of the plane, we make it possible for neighbors to interact alon...

We describe a paradigm for computing with interacting quantum
dots, quantum-dot cellular automata (QCA). We show how arrays of
quantum-dot cells could be used to perform useful computations. A new
adiabatic switching paradigm is developed which permits clocked control,
eliminates metastability problems, and enables a pipelined architecture

We describe a paradigm for computing with interacting quantum dots, quantum-dot cellular automata (QCA). We show how arrays of quantum-dot cells could be used to perform useful computations. A new adiabatic switching scheme is developed which permits clocked control, eliminates metastability problems, and enables a pipelined architecture. We discus...

Several practical issues in the development and operation of quantum-dot cellular automata (QCA) cells and systems are discussed. The need for adiabatic clocking of QCA systems and modeling of electrostatic confinement of quantum dots are presented. Experimental data on dot coupling and applications to QCA detectors in a 2-dimensional electron gas...

We examine the dynamic behavior of quantum cellular automata, arrays of artificial quantum‐dot cells that can be used to perform useful computations. The dynamics of the array can be solved directly, retaining the full many‐electron degrees of freedom only for small array sizes. For larger arrays, we develop several approximate techniques for reduc...

A new quantum computing architecture, quantum cellular automata, is
studied. Quantum cellular automata (QCA's) are composed of interacting
quantum dot molecules, each of which contains two electrons. Repulsion
between these two electrons causes these molecules to exhibit bistable
behavior, which allows the encoding of binary information directly in...

We study the operation of quantum cellular automata (QCA) devices in the presence of stray charge. The operation of linear arrays of QCA cells, called binary wires, relies on Coulombic interaction between the cells, which is affected by the presence of such stray charge. The position of the charge determines whether or not the devices function prop...

We discuss the fundamental limits of computing using a new
paradigm for quantum computation, cellular automata composed of arrays
of coulombically coupled quantum dot molecules, which we term quantum
cellular automata (QCA). Any logical or arithmetic operation can be
performed in this scheme. QCA's provide a valuable concrete example of
quantum com...

The behavior of rings of four small‐capacitance tunnel junctions that are charged with two extra electrons is examined. Single electron charging effects result in quantization of charge on the metal electrode islands. To minimize the total electrostatic energy, the electrons localize on opposite electrodes, leading to a charge alignment in one of t...

We examine the possible implementation of logic devices using coupled quantum dot cells. Each quantum cell contains two electrons which interact Coulombically with neighboring cells. The charge distribution in each cell tends to align along one of two perpendicular axes, which allows the encoding of binary information using the state of the cell. T...

The behavior of linear arrays of cells composed of quantum dots is examined. Each cell holds two electrons and interacts Coulombically with neighboring cells. The electrons in the cell tend to align along one of two axes resulting in a cell ‘‘polarization’’ which can be used to encode binary information. The ground‐state polarization of a cell is a...

Model quantum dot cells are investigated as potential building blocks for quantum cellular automata architectures. Each cell holds a few electrons and interacts Coulombically with nearby cells. In acceptable cell designs, the charge density tends to align along one of two cell axes. Thus, a cell ‘‘polarization,’’ which can be used to encode binary...

A simple model quantum dot cell containing two electrons is analyzed as a candidate for quantum cellular automata implementations. The cell has eigenstates whose charge density is strongly aligned along one of two directions. In the presence of the electrostatic perturbation due to a neighboring cell, the ground state is nearly completely aligned (...

Wc investigate the behavior of fcw-clcctron systems consisting of tightly-coupl ed quantum dots. Specifically, wc concentrate on a model cell which consists of five quantum dots occupied by two electrons. The mutual Coulombic repulsion, quantum confinement, and discrete nature of the electronic charge, lead to cell states which exhibit distinct cha...

High schools across the country are participating in a national design competition called FIRST—For Inspiration and Recognition of Science and Technology. Participating schools design and build a robot that must work with a partner robot to complete certain goals more effectively than a competing pair of robots. The purpose of the organization is t...