Scientists have created a working quantum computer inside a diamond that includes protection against 'decoherence,' noise that prevents it from functioning properly.
Researchers of the University of Southern California, Iowa State University, University of California, Santa Barbara, and Delft University of Technology in the Netherlands used the diamond to create a protocol for controlling quantum information.
Although the tiny system is not very powerful and only has two qubits, it shows the viability of producing functioning solid-state quantum computers.
Instead of using electrons as the qubits, researchers used nitrogen nuclei, from the diamond’s imperfections. The spin in a rogue nitrogen nucleus became the first qubit, with an electron in a second flaw forming the second.
Although a nucleus is a slower qubit than an electron, it is much more stable.
Electrons are smaller than nuclei and perform computations much more quickly, but they fall victim more quickly to decoherence, scientists noted.
“A nucleus has a long decoherence time - in the milliseconds,” said Professor Daniel Lidar of the University of Southern California. “You can think of it as very sluggish.”
Traditional computer bits can encode either a one or a zero but qubits can encode a one and a zero at the same time. This property, called superposition, along with the ability of quantum states to “tunnel” through energy barriers, will someday allow quantum computers to perform optimization calculations much faster than traditional computers.
"It's a little like time travel" because switching the direction of rotation time-reverses the inconsistencies in motion as the qubits move back to their original position, added Lidar.
The team demonstrated their novel computer’s quantum operation by seeing how closely it matched Grover's algorithm, a test consisting of a search of an unsorted database.
“This demonstration of performing a quantum algorithm at the subatomic level with single spins suggests a pathway to build increasingly complex quantum machines, using qubit control protocols that circumvent the expected limitations from real materials,” explained David Awschalom of the University of California, Santa Barbara.