Nanotech advanced

Science advances by leaps and bounds, or sometimes by small steps. Now with new results from a… Science advances by leaps and bounds, or sometimes by small steps. Now with new results from a Pitt research team, those steps can be measured in nanometers.

Pitt researchers have developed a new way to create semiconductor islands smaller than 10 nanometers in diameter – semiconductors that are capable of holding a single electron, according to a University press release.

The creation of these structures, or “dots,” is an important step toward developing a “quantum” computer, which is theoretically capable of performing certain tasks far faster than ordinary computers can.

A nanometer is one billionth of a meter, 1,000 nanometers is a micron and 100 microns is about the width of a single strand of hair.

Jeremy Levy, professor of physics and astronomy at Pitt, said that since quantum computers operate in a unique way, they operate unique programs.

“They can execute programs that cannot be run on other computers,” Levy said.

In order for the quantum computer to be superior to a regular computer, a quantum algorithm for the needed function is required.

Levy explained in an e-mail that the factoring of a 400-digit number into two prime numbers, each 200 digits in size, would take longer than the age of the universe even if all of the computers on the planet worked in concert.

Using a quantum-factoring algorithm, the same task would take seconds or minutes on a quantum computer. The ability of quantum computers to factor large numbers would render useless all of the known encryption schemes used on the Internet, according to Levy.

But why is it so important to isolate a single electron?

Levy said that with ordinary computers, the smallest units of data – called bits and delineated as “0” or “1” – are typically stored using groups of electrons, sometimes 100 or more. A quantum computer would use the spin of single electrons to store information, as opposed to the charge.

Electrons spin on their axis, like a planet. However, unlike a planet, it is possible for electrons to spin in two opposite directions at the same time. This bizarre property allows the electron spin to store “quantum information” and form the basis for a quantum computer, according to Levy.

“This is a case where you have to have a great deal of control of the electrons you’re using,” Levy said.

But when the quantum computer functions at its peak, its speed can be indescribably fast.

The team used an electron beam lithography and nano-engineering workstation – that uses an incredibly focused electron beam – through collaboration with Pittsburgh-based Seagate Technology.

The electron beam can be focused to a diameter of two nanometers, or about twice the distance between two atoms in a solid object.

Levy said that the team has been researching for about four years.

But what is the next step?

“The next step is proving to yourself and others that you have developed a structure capable of confining a single electron,” Levy said.

Other researchers were John Yates Jr., Mellon Professor of Chemistry and Physics at Pitt; former Pitt graduate student Olivier Guise; Joachim Ahner of Pittsburgh’s Seagate Technology; Venugopalar Vaithyanathan of Penn State; and Darrell Schlom of Penn State.