A new experiment out of the University of Southern California might have solved one of the toughest problems in quantum computing, and it did so by building a computer inside a diamond...
This new computer isn’t going to be doing your taxes any time soon, but it shows the viability of solidstate quantum computers to lessen decoherence. Put simply, decoherence is a loss of observable information, which is the last thing you want in a computer. Digital computers are incredibly coherent — if you try to add 1 and 1, you will always get 2 — but due to decoherence, a quantum computer could return almost any result. In past liquid and gasbased systems, researchers often had to deal with decoherence as a consequence of using small, efficient particles.
The diamond computer developed at USC makes use of the impurities in the crystalline structure to make up its two quantum bits, or qubits. The CPUs you’ve always used have transistors that can represent data as a 0 or a 1. A qubit can represent a 0 and a 1 at the same time. This is thanks to the quantum property of superposition, and it’s the property that may one day make quantum computers insanely fast.

Researchers used a neutron as one qubit, and an electron as the other. This mismatched pair was used in order to accurately measure the level of decoherence. An electron, being smaller, is capable of faster calculations, but suffers more from decoherence. Neutrons are slower, but much more stable. In the experiment, scientists found that a series of microwave pulses hitting the diamond computer “reset” the particles and reduced data loss through decoherence.
At this point, there is no practical application for a simple quantum computer, and no real world test to show it working. The team at USC was able to prove that they had indeed built a solidstate quantum computer by supplying it with a simple data set, and applying Grover’s algorithm, which is a mathematical proof demonstrating the potential power of quantum computers. Grover’s algorithm states that a quantum computer will be able to find a specified entry in an unsorted list on the first try, every time.
A human trying to do this would have to go down the list checking each entry to see if it was the right one. Going this route, you would on average check half the list before finding the right entry. This diamondencrusted computer was able to find the correct choice on the first try 95% of the time, thus proving that the researchers successfully built a functional quantum computer.
http://news.usc.edu/#!/article/27023...sideadiamond
Still, it's a big step towards the sort of computers we'll be using in the future
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