Back to article: "Are Computers Finally Going Quantum?" [1]

## SIDEBAR: WHAT IS A QUANTUM COMPUTER?

*Click to enlarge)*

*Three known types of quantum computers and their applications, generality, and computational power (Flickr/IBM Research [3] CC BY-ND 2.0)*

Classical computers transmit bits of information as electrical pulses encoded numerically as a 0 or a 1. In quantum computers, individual atoms, electrons, or particles of light carry information in quantum bits, or qubits. Following principles of quantum mechanics, these particles can exist in 0, 1, or various probabilities of being either 0 or 1, called superposition. With qubits in superposition and communicating with each other through a property called entanglement, quantum computers can solve a problem by examining multiple solutions simultaneously. The result is extra computing power and speed.

But keeping the "quantumness" in qubits is a big challenge. Multiple qubits need to interact with each other to solve problems in a quantum computer, but any interaction with other particles causes them to lose their quantum states. Once a qubit settles into either a 0 or 1, it acts just like a bit in a classical computer.

As the result of research over the past decade, scientists can now build qubits that remain connected 10,000 times longer than before. But still less than 10 qubits can be fully quantum-ly connected.

In January 2017, the company D-Wave released [4] a quantum computer containing 2,000 qubits. But few of those qubits interact with each other to their full quantum potential. While some quantum behavior may happen on D-Wave’s chip, it’s not providing much extra computing power: the D-Wave computer can solve one problem about as efficiently as a laptop, says John Martinis, at University of California, Santa Barbara.

Engineers built the D-Wave quantum computer specifically to solve a particular problem more efficiently. Martinis, Lieven Vandersypen at TU Delft, and other quantum computer researchers have a different goal: To build a universal quantum computer (see infographic) that could run any quantum algorithm the way our current computers run any standard program. Because those chips utilize all the various types of quantum behavior, the researchers will be able to use all the computational power that Nature will allow, Vandersypen says.

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