Pages 5-6: Nanotechnology - Quantum Computers and Other Tiny Machines

Quantum physics theorist Eduardo Mucciolo examines quantum dots—nano-scale devices that may one day form the building blocks of quantum computers.

Imagine a computer that could be used to crack nearly any encrypted access code in the blink of an eye. What if that same machine could search a database, amazingly fast, even when the search term is not quite spelled correctly? These are two tasks that a quantum computer could make possible. Quantum computers promise to create a revolution—just as transistors did half a century ago. Although they do not yet exist, Eduardo Mucciolo and his colleagues are working to turn quantum computation into reality.

How Do Quantum Computers Work?
The power of a quantum computer comes from exploiting the peculiar behavior of matter at very small scales—at nano, molecular, atomic, or even sub-atomic sizes. In a typical, non-quantum computer the smallest unit of information is called a bit, and each bit can be either a 1 or a 0. In quantum computing, the smallest unit of information is the quantum bit or qubit, and it can be a 1, 0, or anything in between! This means that qubits have the potential to store much more information than conventional bits. Also, a key feature of quantum computers is their ability to perform many identical steps in parallel by operating on entangled arrays of qubits. This means very fast—almost instantaneous—data processing.

Quantum Computer work at UCF
Researchers from all over the world are trying to create the components that will comprise quantum computers, and they are using several different methods. Some groups are trying to trap and manipulate atoms with lasers, while others are examining ways to use the magnetism found in atoms’ nuclei. Mucciolo and his colleagues are working with quantum dots.

Quantum dots are tiny devices that hold and manipulate electrons. They are made with a super pure version of the same material used in cellular phone transistors. When used for quantum computing, quantum dots are made to trap a series of electrons, like beads on a string, and each electron acts as a qubit. The information “jumps” from electron to electron when they are brought close together, a process that also entangles the qubits. As the states of the electrons are manipulated and information is moved around, computations are performed.

While Mucciolo’s colleagues Albert Chang (Duke University) and Charles Marcus (Harvard University) are busy creating quantum dot qubits in the lab, he uses theory and numerical simulations to understand the devices’ properties. He is looking ahead, trying to predict whether quantum dots will encounter physical limitations that prevent their use in quantum computing.

Quantum dots do have limitations. In collaboration with Harold Baranger (also at Duke University), Mucciolo has shown that even feeble vibrations and minuscule electric fluctuations in the substrate material can spoil quantum computation. Quantum dot qubits will have to be kept extremely cold and isolated, which in turn will make their operation even more challenging.

Because this theoretical work may be seen as an attempt too invalidate quantum dots’ usefulness, Mucciolo likens himself and his colleagues to unpopular guys that no one wants to invite to their party. Nonetheless, this type of research seems quite prudent. Other devices, such as atomic traps, evolved rapidly and were successfully used for some rudimentary quantum computation, but complex operation and high cost have shown them to be less attractive for large-scale applications. That is where quantum dots, based on semiconductor materials and more accessible technology, may step in.

“We are trying to play the role of the devils’ advocate,” Mucciolo says, “and ask, ‘can quantum dots survive in this game, even though they have all these limitations? Are there ways around?’”

So far, Mucciolo is optimistic. Although his work with Baranger has uncovered some potential problems in the use of quantum dots, they hope to help Chang, Marcus, and other experimentalists to optimize the design and operation of their qubits. It will still be many years before quantum computers exist, but with dedicated researchers, like Eduardo Mucciolo, Harold Baranger, Albert Chang, and Charles Marcus, quantum computers may become a reality during our lifetimes.

Undergraduate Nanotech Studies

Quantum computers are just one type of nanomachine. In the near future, nanotechnology will be found in many, many places—from electronics to medicine. Nanoscience and nanotechnology are interdisciplinary fields that involve the study of materials at the atomic scale. By understanding how to manipulate atoms and molecules, it is possible to create machines that have some pretty unique properties and diverse applications.

UCF is one of only a handful of universities that offers a bachelor’s degree in nanoscience and nanotechnology, and it is the first university in the nation to offer the degree as a Liberal Studies program track. The composite program comprises six primary disciplines and fifteen minors. Nanoscience and nanotechnology students specialize in science and engineering subjects and are encouraged to apply their general learning to science and technology at the nano scale.

Nanoscience and nanotechnology blur the existing lines between many disciplines. For example, researchers from optics, engineering, chemistry, physics, biology, the NanoCenter, the Advanced Materials Processing and Analysis Center, and the Florida Solar Energy Center are involved in UCF’s nanotechnology research. Their work ranges from the development of nanodevices to the use of nanoparticles for multifunctional applications, and this diversity of research makes the university’s nanotechnology research unique.

The planning and development for this program is sponsored by a $100,000 National Science Foundation grant, entitled “NUE: An Interdisciplinary Undergraduate Program in Nanoscience and Nanotechnology.” Participating faculty include Sudipta Seal, Aniket Bhattacharya, Otto Phanstiel, Craig Siders, Aldrin Sweeney, and Elliot Vittes.

Want to know more?
Physics website: www.physics.ucf.edu
Liberal Studies website: www.cas.ucf.edu/liberal_studies
Eduardo Mucciolo, mucciolo@physics.ucf.edu

Physics in Films

Popular films are featured in a new series of general education physics courses offered at the University of Central Florida. The idea to organize a science class around films came from Assistant Professor of Physics Costas Efthimiou and Physics Chair Ralph A. Llewellyn. They were motivated to create the classes when they learned that nearly 50% of all Americans do not know simple science facts, such as how long the Earth takes to orbit the sun or whether dinosaurs and humans lived at the same time. Efthimiou and Llewellyn also found that, in addition to a lack of knowledge, many students lack interest in science. To combat indifference, while giving students a good education, the two professors developed the “Physics in Film” course. The course uses Hollywood movies to introduce the science behind mechanics, fluids, sound, thermodynamics, electricity, and magnetism. During each course, the instructor shows scenes from popular films and discusses their fundamental physics principles. For example, Efthimiou discusses the law of gravity as it is (mis)used in “Independence Day,” and he explains conservation of momentum by using “Tango and Cash.” Efthimiou and Llewellyn are currently writing a “Physics in Films” textbook, for which the preliminary edition is expected in 2007. o

Want to know more?
Costas Efthimiou, costas@physics.ucf.edu
Ralph A. Llewellyn, ral@physics.ucf.edu
Physics in Films article from PhysicsWeb: http://physicsweb.org/articles/news/8/4/11

QUEST 2005

DATE
Spring 2005

CONTACT
Sae Schatz
Arts & Sciences
Academic Promotions
407-823-5164
sae@cs.ucf.edu

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