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Computing by the atom

Computers that grow ever faster require creators who are ever more inventive.

The inventors have done well so far, boosting individual processors by fabricating tinier and tinier components, networking hundreds of thousands of processors together, and commandeering specialized devices such as graphics processing units to act as accelerators.

Each approach works, but each has its limits, and only revolutionary approaches will allow the pace of progress to continue.

One promising strategy is quantum computing, systems that rely on the strange behavior of nature’s tiniest particles. ORNL quantum computer scientist Travis Humble is committed to bringing this technology to scientific computing. 

Humble is also winner of an Early Career Research Program award from DOE’s Office of Science. The award will support his efforts to promote the creation of quantum processing units, GPU-like accelerators based on quantum physics.

Quantum computing gets its promise from physical properties found only at the nanoscale. One is superposition, which allows a particle to be in more than one contradictory state at the same time (pointing both up and down, for instance). Another is entanglement, in which two or more particles are connected, so changes in one are reflected by the others.

These properties open up enormous possibilities for computing if they can be harnessed. While the fundamental building block of traditional computing, the bit, has only two possible values (“0” or “1”), the building block of quantum computing—known as a quantum bit, or qubit (pronounced “CUE-bit”)—can have a value of “0” or “1” or both simultaneously. In addition, multiple qubits can be entangled so a change to one will also change the others.

“When you flip a penny, it can be heads or tails,” Humble explained. “But in the quantum world, when you flip a penny, it can be heads, tails, or a superposition of these states. Extending to the case of two pennies, they can again each be heads or tails. But a pair of quantum pennies can be entangled, so they will stay correlated even when flipped again and again.

“There is this idea that we can build a computer that basically uses individual atoms to do computation. As soon as you do that, the physics of the atoms makes it possible to do things that you can’t do with normal computers. My job is to try to figure out how to make that work.”

Humble’s road to quantum computing began when he left the premed track, after realizing he didn’t like the sight of blood. (“That was an important point,” he joked.) Instead, he focused on theoretical chemistry, earning a bachelor’s degree from the University of North Carolina at Wilmington and a Ph.D. from the University of Oregon.

He came to ORNL in 2005 as an Intelligence Community Postdoctoral Research Fellow and eventually joined ORNL’s staff in the Computer Science and Mathematics Division. 

“At the moment I’m focused on pulling together everybody at the lab that I can find to work on quantum computing, because I really think it’s the type of goal that the lab is made for. It has so many disciplines that are required, and ORNL is one of the best places that I know of to find that diversity.”

Eventually, he said, quantum computers will be an everyday reality, and he will be able to go back to focusing on theoretical chemistry.

“In 20 years I see myself solving problems using quantum computers as opposed to solving the problem of quantum computers. That’s what I think would be ideal. I’m willing to put my money on that, because I believe it’s worth it.”

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