So far, the most sophisticated quantum computations have been performed in 'ion trap' systems, with up to eight entangled qubits. But physicists believe that the long-term future of this field lies with solid-state computations; that is, in processors made from solid state electronics (or all-electronic devices that look and feel more like regular microprocessors), as opposed to atomic particles. This has not been possible using solid-state qubits until now because the qubits only lasted about a nanosecond. Now these qubits can last a microsecond (a thousand times longer), which is enough to run simple algorithms.
The most recent results showing very low decoherence for magnetic molecule qubits was recently published in Nature International Weekly Journal of Science by a team of researchers from the Vancouver-based company D-Wave Systems. D-Wave has performed a technique called quantum annealing, which could provide the computational model for a quantum processor.
Dr. Suzanne Gildert, PhD from the University of Birmingham, experimental physicist, and quantum computer programmer (now working at D-Wave Systems), says that with quantum annealing, decoherence is not a problem.
According to Gildert, D-Wave uses Natural Quantum Computing (NQC) to build its quantum computers, which is very different from the traditionally proposed schemes. "Some quantum computing schemes try to take ideas from regular computing — such as logic operations — and make 'quantum' versions of them, which is extremely difficult. Making 'quantum' versions of computing operations is a very delicate process. It's like trying to keep a pencil standing on its end by placing it on a block of wood, and then moving the block around to try to balance the whole thing. It's almost impossible. You have to constantly work hard to keep the pencil (i.e., the qubits) in the upright state. Decoherence is what happens when the pencil falls over," Gildert says.
"In our NQC approach, which is more scalable and robust, we let the pencil lie flat on the wood instead, and then move it around. We're computing by allowing the pencil to roll however it wants to, rather than asking it to stay in an unusual state. So we don't have this same problem of bits of information 'decohering' because the state we are trying to put the system into is what nature wants it to be in (that's why we call it Natural QC)."
But Jim Tully, vice president and chief of research, semiconductors and electronics at Gartner Research, says that what D-Wave is doing is not really quantum computing.
Tully says, "A sub-class of quantum computing has been demonstrated by D-Wave Systems that is referred to as quantum annealing, which involves superposition, but does not involve entanglement and is not; therefore, 'true' quantum computing. Quantum annealing is potentially useful for optimization purposes, specifically for the purposes of finding a mathematical minimum in a dataset very quickly."
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