One of the major problems in keeping Quantum computers accurate is that there be no Quantum decoherence among the atoms performing the calculations. A major way in which decoherence happens is with heat. If heat interferes with the rotations of the atoms it will cause the probability of errors to increase. Vibrations can also cause quantum decoherence. Ideally, all decoherence would be removed, but there are error rates which can be acceptable which can be done by using forms of quantum error correction.
What D Wave Systems Have Done
D-Wave, founded in 1999, founded by Dr. Geordie Rose was able to obtain over $45 million dollars towards the building of the world's first commercial Quantum computer.
In a Google Talk in 2007, Dr. Geordie Rose delivered a talk on D-Wave's quantum computer. According to Rosen most of the research for a quantum computer, has gone into the quantum gate array model. He stated that although not mature yet, it is the most advanced computer model for quantum computing. D-Wave decided to use superconductors to build their quantum computer. There are many other suggestions of materials that could be used to build a quantum computer. As has been stated in part 1 of this series, the basic thesis of quantum computing is the use of the most basic elements of the universe, subatomic particles, to do computation. This Rosen says, means that almost any material that can be used to produce quantum computation, would be feasible in the building of the computer. Rosen picked superconductors because it is the only materials that you can use in a quantum computer that can actually be built. Also these materials allow you to build larger devices that behave as if they were quantum particles. These materials have been demonstrated to build ultra fast chips (the record being a 777GHz chip by IBM), as well as ultra fast circuitry. Also superconductors do not generate heat when you run electricity through them, which allows you to build very small components without heat worries. This would allow for thermodynamically reversible circuits, the holy grail of computer hardware. Either very large or very small circuits which produce NO HEAT. We provide in the following video D-Wave's own explanation for how an Adiabatic Quantum Computer works. If you cannot see the embedded video, here is the link: http://youtu.be/6BxlolQdI3s.
D-Wave's machines only reach up to 32 qubits so far. In his Google talk of 2007, he predicted they would reach 1,000 qubits by 2008 and a 1,000,000 qubit computer by 2012. According to engadget, this first commercial quantum computer reaches up to 128 qubits.
There are four different models for creating a quantum computer.
1. The Quantum Gate Array Model - This computer model uses a few qubits to create quantum gates, which function like logical gates in traditional computer circuits. For those who do no have any understanding of that logic gates are, we present a rather short video which explains how these logic gates work in traditional electronic circuits. If you cannot see the embedded video, here is the link: http://bit.ly/jEBjtK.
2. The One-Way Quantum Computer Model - This model is based on a paper by Robert Raussendorf and Hans Briegel, published in Nature journal in 2005. This original research has been further pursued by Anton Zellinger at the University of Vienna. As we can best understand this model, photons are entangled into what is called a cluster state. The reason it is called one way is because in the computation process the entanglement of the photons is consumed. This system does not attempt to build logic gates with particles as in the first model. Perhaps some of our readers are not sure as to what entanglement means. We provide this video for those who have either forgotten or not known what entanglement means. If you cannot see the embedded video, here is the link: http://youtu.be/9lOWZ0Wv218.
3. The Topological Quantum Computer Model - this kind of computer is formed by creating a two-dimensional quasiparticle (a combination of a particle and the effect that it has on its environment, which acts as a single unit) called anyons ( a type of particle that only happens in a two-dimensional system) to form braids (a mathematical model which tries to explain how a braiding pattern works) into logical gates. This is a highly technical explanation to the average reader. But suffice it to say that these topological quantum computers (due to their braid patterns) would have less decoherence than other models, thus making them more reliable, without consuming as many resources (electricity, etc.) as other quantum computer models.
|A braid pattern associated with a planar graph|
4. The Adiabatic Quantum Computer Model - This system has been somewhat dealt with earlier. As we understand it, this model accepts more errors in the calculations due to the increased speed of the parameter changes of the matrix. However, they make up for this by taking many readings of the final outcome and coming up with a best probabilistic answer, which when double checked with a normal computer is generally very accurate.
What Can A Quantum Computer Do?
The big push with the quantum computer is to have it emulate intelligence. In this case it would be synthetic intelligence, which has to do with what is called machine learning. Machine learning, which is an attempt by a computer to learn like humans do, is in mathematics called an NP-complete problem. The thought is that these kinds of computers will be able to supply the necessary computing horsepower and speed to be able to achieve this level of intelligence, and if you wish to use the term, consciousness.
We present this video to help you understand on what machine learning and synthetic intelligence. If you cannot see the embedded video, here is the link: http://bit.ly/jhP6DZ
Dr. Rosen elucidates further on Dr. Gildert's statements in our previous post on the critical issues of decoherence, size of the qubits and how the quantum computer that D-Wave has produced should be used. Dr. Rosen sees it as an "accelerator" for certain tasks, at least the beginning. He does not, at this point, see it as an overall replacement for traditional silicon-based computers. Here is his video explanation for those who wish to know more the technical details. If you cannot see the embedded video, here is the link: http://youtu.be/5AhZtuP2SS4.
We provide yet another video explanation of a quantum computer. Marcus Chown, author of the book Quantum Theory Cannot Hurt You: A Guide To The Universe, explains an interesting problem first brought out by physicist David Deutsch. Chown states,
It's very easy to imagine building a quantum computer within maybe twenty years, that can do more calculations simultaneously, than there are particles in the universe. And then you have to ask yourself where is the quantum computer doing the calculations? Your computer can only store a number of a particular size because it has the memory space. Where is the quantum computer doing the calculation if it using more physical resources thant exist in our universe? David Deutsch who is a physicist at the University at Oxford, says that what the quantum computer does is explore parallel realities in parallel universes. So when you set a quantum computer a problem it splits it into multiple copies of itself in parallel realities. They all work on threads of their calculations and they come together again with the answer. So he says that quantum computing is something entirely new under the sun. It's the first thing we've ever invented that explores parallel universes.If you cannot see the embedded video, here is the link: http://youtu.be/wH4BH231d2Y.
There is no question in our minds that the quantum computer holds great promise. It looks to us as if Kurzweil's predictions of the advance of computing processing power is within his timetable. Stay tuned from greater things from D-Wave.