In a recent paper in

*Physical Review Letters*, Rice physicists Rui-Rui Du and Ivan Knez describe a new method for making a tiny device called a "quantum spin Hall topological insulator." The device, which acts as an electron superhighway, is one of the building blocks needed to create quantum particles that store and manipulate data.*In his quest to create a "topological insulator," Rice graduate student Ivan Knez spent hundreds of hours modifying tiny pieces of semiconductors in Rice University's clean room.*

Today's computers use binary bits of data that are either ones or
zeros. Quantum computers would use quantum bits, or "qubits," which can
be both ones and zeros at the same time, thanks to the quirks of quantum
mechanics.

This quirk gives quantum computers a huge edge in performing
particular types of calculations, said Du, professor of physics and
astronomy at Rice. For example, intense computing tasks like
code-breaking, climate modeling and biomedical simulation could be
completed thousands of times faster with quantum computers.

"In principle, we don't need many qubits to create a powerful
computer," he said. "In terms of information density, a silicon
microprocessor with 1 billion transistors would be roughly equal to a
quantum processor with 30 qubits."

In the race to build quantum computers, researchers are taking a
number of approaches to creating qubits. Regardless of the approach, a
common problem is making certain that information encoded into qubits
isn't lost over time due to quantum fluctuations. This is known as
"fault tolerance."

The approach Du and Knez are following is called "topological quantum
computing." Topological designs are expected to be more fault-tolerant
than other types of quantum computers because each qubit in a
topological quantum computer will be made from a pair of quantum
particles that have a virtually immutable shared identity. The catch to
the topological approach is that physicists have yet to create or
observe one of these stable pairs of particles, which are called
"Majorana fermions" (pronounced MAH-yor-ah-na FUR-mee-ons).

The elusive Majorana fermions were first proposed in 1937, although
the race to create them in a chip has just begun. In particular,
physicists believe the particles can be made by marrying a
two-dimensional topological insulator -- like the one created by Du and
Knez -- to a superconductor.

Topological insulators are oddities; although electricity cannot flow
through them, it can flow around their narrow outer edges. If a small
square of a topological insulator is attached to a superconductor, Knez
said, the elusive Majorana fermions are expected to appear precisely
where the materials meet. If this proves true, the devices could
potentially be used to generate qubits for quantum computing, he said.

Knez spent more than a year refining the techniques to create Rice's
topological insulator. The device is made from a commercial-grade
semiconductor that's commonly used in making night-vision goggles. Du
said it is the first 2-D topological insulator made from a material that
physicists already know how to attach to a superconductor.

"We are well-positioned for the next step," Du said. "Meanwhile, only
experiments can tell whether we can find Majorana fermions and whether
they are good candidates for creating stable qubits."

The research was funded by the National Science Foundation, Rice
University, the Hackerman Advanced Research Program, the Welch
Foundation and the Keck Foundation.

**From sciencedaily**
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