It Takes Two to Entangle

Two quantum bits can be far apart but remain correlated via the process of entanglement. How can we exploit this in quantum computing?

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Researchers are still trying to figure out all the ways that we can exploit quantum computing. Everything that is possible using a classical bit — the smallest unit of information on classical computers — is possible with a quantum bit or qubit, but qubits can do even more.

“This is the difference we are trying to exploit,” says Robert Raussendorf, associate professor of physics and astronomy at the University of British Columbia, and researcher at the Stewart Blusson Quantum Matter Institute.

The thing that sets quantum physics apart from classical physics is entanglement, says Raussendorf. He describes it as the universal currency of quantum mechanics.

“Let’s look at what’s called a Bell state,” says Raussendorf. “This is the entangled state of two qubits, and they could be spatially separated. One of the qubits could be on the Earth, the other could be on the moon, and they are very strangely correlated.”

Once entangled, no matter how far apart the qubits are, the information they hold is related.

“I could, for example, measure my qubit on Earth, and once I did my measurement over here, I would know in an instant what the state of the qubit at the moon was,” adds Raussendorf. “So we have these very funny correlations that are implied by entanglement, and that’s the physical ramification of it.”

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Robert Raussendorf obtained his PhD from the Ludwig Maximilians University in Munich, Germany in 2003. From 2003 to 2006, he was a post doctoral fellow at Caltech, and from 2006 to 2007 at the Perimeter Institute for Theoretical Physics in Waterloo, Canada. Raussendorf joined the Department of Physics and Astronomy of the University of British Columbia as Assistant Professor in January 2008 and has been an Associate Professor since 2013. He has been a scholar of the Quantum Information Program of the Canadian Institute for Advanced Research (CIFAR) since 2008 and was a Sloan Research Fellow from 2009 – 2011.

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