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"In the whole field of quantum information, there are two different directions: One is quantum computing and the other is quantum communications," said physicist Steve Rolston, who is co-director of the Joint Quantum Institute at the University of Maryland. "If we start with quantum computing, this is the holy grail... The quantum computer is not just a faster regular computer. So far we've only identified a few problems that it's really good at: crunching numbers—which sounds like an arbitrary math problem, but that's how cryptography works—and searching databases."
In other words, a quantum computer is only exceptionally good at a few things—but those few things happen to have major implications for the future of intelligence, surveillance, and security. "That's why the NSA in particular is so interested in quantum computers and would like to have one, and probably would not tell anyone if they did," Rolston told me.
There's some debate over how advanced quantum computing already is. The Canadian startup D-Wave claims to have built a $15 million quantum computer, though many scientists have expressed skepticism about the technology. It still piqued the interest of Google, NASA and the Universities Space Research Association, which teamed up last year to install a D-Wave device in a NASA lab so that researchers can come by and test how it might advance machine learning. Earlier this year D-Wave's CEO was in Washington, D.C., shopping around his company's wares.
Quantum computing's code-cracking potential could undermine encryption protocols that now secure information across any number of networks—the kinds used by financial institutions, government agencies, etc. Quantum computing could also process enormous databases like no computer today.
But quantum communications represents "sort of the flip side," Rolston says. "Because of the laws of quantum mechanics, you can develop ways to communicate with people that are provably secure. It doesn't mean that people can't listen in, but it means you would be able to tell." Here's why: There's this rule in quantum mechanics called the No-Cloning Theorem. Rolston explained it to me like this: "Basically, what that says, is you cannot make an exact copy of an unknown quantum state."
So, think about this theorem in the context of copying—or recording—a tapped phone line. The way we transmit information now, you might bug a phone line you want to secretly record. The people using that phone line won't be able to tell you're listening in, and you end up with a recording of data was transmitted across that line.
But if that data is transmitted as quantum information, the No-Cloning Theorem won't allow a clean recording. It would come out garbled because of the ever-changing value systems assigned to qubits (compared with the reliable 1s and 0s of regular bits).