Scientists create a single-electron transistor: A big step for quantum computing?

University of Pittsburgh researchers built a single-electron transistor made of oxide-based materials. One day, computers could hold data without an external power source.
Written by Boonsri Dickinson, Contributing Editor

Do you remember the Etch A Sketch drawing toy that lets you draw stuff with huge white buttons? I do. I loved that I could sketch something and then start over again.

In fact, that doodling pad inspired Jeremy Levy to create a sketch-based single-electron transistor. Instead of using the bulky Etch A Sketch buttons to do the trick, Levy used an atomic force microscope to create an electronic device made of wires and transistors - a design that can be wiped away and re-drawn again.

I spoke with Levy, a physicist at the University of Pittsburgh, about his discovery of single-electron transistors.

SmartPlanet: Why is this single-electron transistor important for building quantum computers?

JL: Quantum computers need to be able to control matter at the most fundamental level.

Quantum information is similar to ordinary information in that you have different states of matter representing “0” and “1”.

For a single electron, that could be the spin orientation (“up” or “down”).

So you want to be able to capture single electrons. There are other reasons, but that is a big one.

SmartPlanet: How did you build this super small transistor in the lab?

JL: It is a lot like using “Etch a Sketch” except we use a sharp probe from an “atomic force microscope” to charge the top surface of an oxide-based material. Where we place positive charges on the top surface, negatively charged electrons collect directly underneath. We simply draw a pattern that looks like several wires that are very close to a tiny island. That’s the SketchSET.

SmartPlanet: So basically this transistor could help crunch computer problems much faster?

JL: Maybe. If we can build a quantum computer, then it would be a very powerful computer indeed.

But this device is just one piece of the puzzle.

One property that we found very interesting was the ability of the transistor to be in the “on” or “off” state in the absence of power. That’s due to the ferroelectric property, which is a lot like magnetism in that you can reverse the properties and they switch the transistor on and off.

So it’s like a transistor plus memory. If we can get that to work at room temperature, we wouldn’t need to turn off our computers when we’re not using them.

SmartPlanet: That sounds cool. And it can be used to make new materials?

JL: In a sense, yes. We are trying arrange electrons and these islands in such a way that they have novel properties. In that sense, they are new artificial materials that we want to assemble, dot for dot. We would simply get rid of the wires and just put an array of these tiny islands, so they form a lattice like in a crystal.

SmartPlanet: What kind of materials?

JL: I don’t know what their name would be—perhaps I could sell those rights on eBay! They would be new materials, made with new properties. But they would be designed at the quantum level. It’s a new frontier in science, one that is very active in another community known as “cold atom” physics.

SmartPlanet: Why is oxide-base materials key for SketchSET?

JL: I would say they have properties a lot like semiconductors, but the size that we can control them is much smaller than traditional materials. Also, the interactions between electrons is much stronger. And they have other properties like ferroelectricity and superconductivity.

SmartPlanet: Why is it important that it remain sensitive to an electric change?

JL: Well, charge is one of the ways in which we can sense quantum interactions. So it’s important to be able to measure charge in a sensitive way. That is something that single-electron transistors are especially good at.

SmartPlanet: What are some applications of your discovery?

JL: We’d like to make a quantum computer.

But there is a lot of basic physics to explore, and a lot to learn about quantum mechanics. It’s never quite clear at the time what the most important applications will be. When the transistor was first invented, everyone thought that the “killer app” was the portable hearing aid!

via University of Pittsburgh

Photo: Pitt

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