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Quantum Computing Might Be Closer Than Previously Thought

A silicon chip housing three qubits — Photo courtesy of IBM

Based on years of work, IBM Research recently announced results suggesting that quantum computing—once thought to be an impossible system—may not be so impossible, after all.

Mark Ketchen, manager of the Physics and Information Group at the Thomas J. Watson Research Center in Yorktown Heights, N.Y., says a quantum computing system that could reduce to seconds the time it takes to solve a problem so complex it would take current, conventional systems billions of years to solve could conceivably be operational in as little as 15 years—well before the 50 years previously cited. It won’t be in the data center around the block, but it is a harbinger of interesting advances to come.

Ketchen’s team works on quantum information, and he’s the principle investigator on a large experimental project working to demonstrate various parts of the technology that would be required to build a quantum computer.

“That’s really what all of the buzz has been about lately—recent advances in that work. We are very early in the process, but it’s very exciting and things are starting to happen,” he says.

To learn more about the topic, IBM Systems Magazine sat down with Ketchen.

Q. Could quantum computing really become viable in 15 years rather than 50 years?
A. Those thoughts refer more to having a system that does something pretty useful—much more than you can do with a conventional computer for certain applications. Commercial systems are probably out another five to 10 or so years after that. The key thing, though, is that this is something that’s a lot closer than we originally anticipated.

Keep in mind this isn’t a general-purpose computer in the way we think of them today. There are specific types of problems that this type of system can do extremely well and others it’s not so appropriate for. If you want to factor a very large number, for example, this is what you want to use. If you want to multiply two numbers together, you’re better off using the systems we have today.

Q. What are the differences between contemporary computers and quantum-based computers?
A. If you look at the logic elements in conventional silicon-based technology, you have a switch and it’s on or off, one or zero. The interesting thing with a quantum system is that it can be in a one or zero state, but it can also be in a superposition state where it’s partially one and partially zero—that’s if you have one such switch.

For a collection of N distinct conventional switches, there are 2N possible combination states, only one in which the entire collection can be at a given time. In quantum mechanics, however, a collection of N quantum bits, or qubits, can at any time be in an extended superposition or entangled state involving components of some or even all of the possible combinations. You then actually need 2N numbers to specify the state that the system is in, which is huge, because that number grows exponentially with N.

Interestingly, this is tied to the fact that if you look at a problem like factoring and you try to do it on a conventional computer, it would take an exponentially longer time to do that calculation as the number of digits increase. If you have a 50-digit number that you need to factor, just do it on a conventional computer. It’s not such a big deal. If you have a thousand-decimal-digit number that you want to factor, it would probably take all of the computers that exist and the age of the universe to do so. In the quantum case, because of this interesting behavior where you have a system where the complexity is actually 2N, if you can figure out how to harness that in some parallel way to do the calculation, then you could leverage this to rapidly solve that very difficult problem. That is what a quantum computer could do.

Jim Utsler, IBM Systems Magazine senior writer, has been covering the technology field for more than a decade. Jim can be reached at

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