04-10-2012, 12:34 AM
http://phys.org/news/2012-04-quantum-bui...l#firstCmt
Quote:Diamonds are forever – or, at least, the effects of this diamond on quantum computing may be. A team that includes scientists from USC has built a quantum computer in a diamond, the first of its kind to include protection against "decoherence" – noise that prevents the computer from functioning properly.
Quote:Though solid-state computing systems have existed before, this was the first to incorporate decoherence protection – using microwave pulses to continually switch the direction of the electron spin rotation.
"It's a little like time travel," Lidar said, because switching the direction of rotation time-reverses the inconsistencies in motion as the qubits move back to their original position.
Quote:The test is a search of an unsorted database, akin to being told to search for a name in a phone book when you've only been given the phone number.
Sometimes you'd miraculously find it on the first try, other times you might have to search through the entire book to find it. If you did the search countless times, on average, you'd find the name you were looking for after searching through half of the phone book.
Mathematically, this can be expressed by saying you'd find the correct choice in X/2 tries – if X is the number of total choices you have to search through. So, with four choices total, you'll find the correct one after two tries on average.
A quantum computer, using the properties of superposition, can find the correct choice much more quickly. The mathematics behind it are complicated, but in practical terms, a quantum computer searching through an unsorted list of four choices will find the correct choice on the first try, every time.
Though not perfect, the new computer picked the correct choice on the first try about 95 percent of the time – enough to demonstrate that it operates in a quantum fashion.
They have been applying it to fiber-optic internet (eg, my internet is 4 threads) and of course, processor cores for computers.