The Quantum Quest for a Revolutionary Computer

Quantum computing uses strange subatomic behavior to exponentially speed up processing. It could be a revolution, or it could be wishful thinking

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Photograph by Gregg Segal for TIME

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Naturally, a lot of people want one. This is the age of Big Data, and we're burying ourselves in information--search queries, genomes, credit-card purchases, phone records, retail transactions, social media, geological surveys, climate data, surveillance videos, movie recommendations--and D-Wave just happens to be selling a very shiny new shovel. "Who knows what hedge-fund managers would do with one of these and the black-swan event that that might entail?" says Steve Jurvetson, one of the managing directors of Draper Fisher Jurvetson. "For many of the computational traders, it's an arms race."

One of the documents leaked by Edward Snowden, published last month, revealed that the NSA has an $80 million quantum-computing project suggestively code-named Penetrating Hard Targets. Here's why: much of the encryption used online is based on the fact that it can take conventional computers years to find the factors of a number that is the product of two large primes. A quantum computer could do it so fast that it would render a lot of encryption obsolete overnight. You can see why the NSA would take an interest.

But while the theory behind quantum computing is reasonably clear, the actual practice is turning out to be damnably difficult. For one thing, there are sharp limits to what we know how to do with a quantum computer. Cryptography and the simulation of quantum systems are currently the most promising applications, but in many ways quantum computers are still a solution looking for the right problem. For another, they're really hard to build. To be maximally effective, qubits have to exhibit quantum behavior, not just superposition but also entanglement (when the quantum states of two or more particles become linked to one another) and quantum tunneling (just Google it). But they can do that only if they're effectively isolated from their environment--no vibrations, no electromagnetism, no heat. No information can escape: any interaction with the outer world could cause errors to creep into the calculations. This is made even harder by the fact that while they're in their isolated state, you still have to be able to control them. There are many schools of thought on how to build a qubit--D-Wave makes its in the form of niobium loops, which become superconductive at ultra-low temperatures--but all quantum-computing endeavors struggle with this problem.

Since the mid-1990s, scientists have been assembling and entangling systems of a few quantum bits each, but progress has been slow. In 2010 a lab at the University of Innsbruck in Austria announced the completion of the world's first system of 14 entangled qubits. Christopher Monroe at the University of Maryland and the Joint Quantum Institute has created a 20-qubit system, which may be the world's record. Unless, of course, you're counting D-Wave.

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