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Science A Strange(?Quantum) Computer(from NY Times)
2013.03.21 18:09
A Strange Computer Promises Great Speed  Kim Stallknecht for The New York Times Lockheed Martin brought a version of D-Wave’s quantum computer and plans to upgrade it to commercial scale. By QUENTIN HARDY VANCOUVER, British Columbia — Our digital age is all about bits, those precise ones and zeros that are the stuff of modern computer code. But a powerful new type of computer that is about to be commercially deployed by a major American military contractor is taking computing into the strange, subatomic realm of quantum mechanics. In that infinitesimal neighborhood, common sense logic no longer seems to apply. A one can be a one, or it can be a one and a zero and everything in between — all at the same time. It sounds preposterous, particularly to those familiar with the yes/no world of conventional computing. But academic researchers and scientists at companies like Microsoft, I.B.M. and Hewlett-Packard have been working to develop quantum computers. Now, Lockheed Martin — which bought an early version of such a computer from the Canadian company D-Wave Systems two years ago — is confident enough in the technology to upgrade it to commercial scale, becoming the first company to use quantum computing as part of its business. Skeptics say that D-Wave has yet to prove to outside scientists that it has solved the myriad challenges involved in quantum computation. But if it performs as Lockheed and D-Wave expect, the design could be used to supercharge even the most powerful systems, solving some science and business problems millions of times faster than can be done today. Ray Johnson, Lockheed’s chief technical officer, said his company would use the quantum computer to create and test complex radar, space and aircraft systems. It could be possible, for example, to tell instantly how the millions of lines of software running a network of satellites would react to a solar burst or a pulse from a nuclear explosion — something that can now take weeks, if ever, to determine. “This is a revolution not unlike the early days of computing,” he said. “It is a transformation in the way computers are thought about.” Many others could find applications for D-Wave’s computers. Cancer researchers see a potential to move rapidly through vast amounts of genetic data. The technology could also be used to determine the behavior of proteins in the human genome, a bigger and tougher problem than sequencing the genome. Researchers at Google have worked with D-Wave on using quantum computers to recognize cars and landmarks, a critical step in managing self-driving vehicles. Quantum computing is so much faster than traditional computing because of the unusual properties of particles at the smallest level. Instead of the precision of ones and zeros that have been used to represent data since the earliest days of computers, quantum computing relies on the fact that subatomic particles inhabit a range of states. Different relationships among the particles may coexist, as well. Those probable states can be narrowed to determine an optimal outcome among a near-infinitude of possibilities, which allows certain types of problems to be solved rapidly. D-Wave, a 12-year-old company based in Vancouver, has received investments from Jeff Bezos, the founder of Amazon.com, which operates one of the world’s largest computer systems, as well as from the investment bank Goldman Sachs and from In-Q-Tel, an investment firm with close ties to the Central Intelligence Agency and other government agencies. “What we’re doing is a parallel development to the kind of computing we’ve had for the past 70 years,” said Vern Brownell, D-Wave’s chief executive. Mr. Brownell, who joined D-Wave in 2009, was until 2000 the chief technical officer at Goldman Sachs. “In those days, we had 50,000 servers just doing simulations” to figure out trading strategies, he said. “I’m sure there is a lot more than that now, but we’ll be able to do that with one machine, for far less money.” D-Wave, and the broader vision of quantum-supercharged computing, is not without its critics. Much of the criticism stems from D-Wave’s own claims in 2007, later withdrawn, that it would produce a commercial quantum computer within a year. “There’s no reason quantum computing shouldn’t be possible, but people talked about heavier-than-air flight for a long time before the Wright brothers solved the problem,” said Scott Aaronson, a professor of computer science at the Massachusetts Institute of Technology. D-Wave, he said, “has said things in the past that were just ridiculous, things that give you very little confidence.” But others say people working in quantum computing are generally optimistic about breakthroughs to come. Quantum researchers “are taking a step out of the theoretical domain and into the applied,” said Peter Lee, the head of Microsoft’s research arm, which has a team in Santa Barbara, Calif., pursuing its own quantum work. “There is a sense among top researchers that we’re all in a race.” If Microsoft’s work pans out, he said, the millions of possible combinations of the proteins in a human gene could be worked out “fairly easily.” Quantum computing has been a goal of researchers for more than three decades, but it has proved remarkably difficult to achieve. The idea has been to exploit a property of matter in a quantum state known as superposition, which makes it possible for the basic elements of a quantum computer, known as qubits, to hold a vast array of values simultaneously. There are a variety of ways scientists create the conditions needed to achieve superposition as well as a second quantum state known as entanglement, which are both necessary for quantum computing. Researchers have suspended ions in magnetic fields, trapped photons or manipulated phosphorus atoms in silicon. The D-Wave computer that Lockheed has bought uses a different mathematical approach than competing efforts. In the D-Wave system, a quantum computing processor, made from a lattice of tiny superconducting wires, is chilled close to absolute zero. It is then programmed by loading a set of mathematical equations into the lattice. The processor then moves through a near-infinity of possibilities to determine the lowest energy required to form those relationships. That state, seen as the optimal outcome, is the answer. The approach, which is known as adiabatic quantum computing, has been shown to have promise in applications like calculating protein folding, and D-Wave’s designers said it could potentially be used to evaluate complicated financial strategies or vast logistics problems. However, the company’s scientists have not yet published scientific data showing that the system computes faster than today’s conventional binary computers. While similar subatomic properties are used by plants to turn sunlight into photosynthetic energy in a few million-billionths of a second, critics of D-Wave’s method say it is not quantum computing at all, but a form of standard thermal behavior. ■ John Markoff contributed reporting from San Francisco. PUBLISHED MARCH 21, 2013 http://www.nytimes.com/2013/03/22/technology/testing-a-new-class-of-speedy-computer.html |
What does quantum physics have to do with computing? How can a quantum computer work and what makes it different from a traditional computer?
Answer: A quantum computer is a computer design which uses the principles of quantum physics to increase the computational power beyond what is attainable by a traditional computer. Quantum computers have been built on the small scale and work continues to upgrade them to more practical models.
How Computers Work
Computers function by storing data in a binary number format, which result in a series of 1s & 0s retained in electronic components such as transistors. Each component of computer memory is called a bit and can be manipulated through the steps of Boolean logic so that the bits change, based upon the algorithms applied by the computer program, between the 1 and 0 modes (sometimes referred to as "on" and "off").
How a Quantum Computer Would Work
A quantum computer, on the other hand, would store information as either a 1, 0, or a quantum superposition of the two states. Such a "quantum bit," called a qubit, allows for far greater flexibility than the binary system.
Specifically, a quantum computer would be able to perform calculations on a far greater order of magnitude than traditional computers ... a concept which has serious concerns and applications in the realm of cryptography & encryption. Some fear that a successful & practical quantum computer would devastate the world's financial system by ripping through their computer security encryptions, which are based on factoring large numbers that literally cannot be cracked by traditional computers within the life span of the universe. A quantum computer, on the other hand, could factor the numbers in a reasonable period of time.
To understand how this speeds things up, consider this example. If the qubit is in a superposition of the 1 state and the 0 state, and it performed an calculation with another qubit in the same superposition, then one calculation actually obtains 4 results: a 1/1 result, a 1/0 result, a 0/1 result, and a 0/0 result. This is a result of the mathematics applied to a quantum system when in a state of decoherence, which lasts while it is in a superposition of states until it collapses down into one state. The ability of a quantum computer to perform multiple computations simultaneously (or in parallel, in computer terms) is called quantum parallelism).
The exact physical mechanism at work within the quantum computer is somewhat theoretically complex and intuitively disturbing. Generally, it is explained in terms of the multi-world interpretation of quantum physics, wherein the computer performs calculations not only in our universe but also in other universes simultaneously, while the various qubits are in a state of quantum decoherence. (While this sounds far fetched, the multi-world interpretation has been shown to make predictions which match experimental results. Other physicists have )
History of Quantum Computing
Quantum computing tends to trace its roots back to a 1959 speech by Richard P. Feynman in which he spoke about the effects of miniaturization, including the idea of exploiting quantum effects to create more powerful computers. (This speech is also generally considered the starting point of nanotechnology.)
Of course, before the quantum effects of computing could be realized, scientists and engineers had to more fully develop the technology of traditional computers. This is why, for many years, there was little direct progress, nor even interest, in the idea of making Feynman's suggestions into reality.
In 1985, the idea of "quantum logic gates" was put forth by University of Oxford's David Deutsch, as a means of harnessing the quantum realm inside a computer. In fact, Deutsch's paper on the subject showed that any physical process could be modeled by a quantum computer.
Nearly a decade later, in 1994, AT&T's Peter Shor devised an algorith that could use only 6 qubits to perform some basic factorizations ... more cubits the more complex the numbers requiring factorization became, of course.
A handful of quantum computers have been built. The first, a 2-qubit quantum computer in 1998, could perform trivial calculations before losing decoherence after a few nanoseconds. In 2000, teams successfully built both a 4-qubit and a 7-qubit quantum computer. Research on the subject is still very active, although some physicists and engineers express concerns over the difficulties involved in upscaling these experiments to full-scale computing systems. Still, the success of these initial steps do show that the fundamental theory is sound.
Difficulties with Quantum Computers
The quantum computer's main drawback is the same as its strength: quantum decoherence. The qubit calculations are performed while the quantum wave function is in a state of superposition between states, which is what allows it to perform the calculations using both 1 & 0 states simultaneously.
However, when a measurement of any type is made to a quantum system, decoherence breaks down and the wave function collapses into a single state. Therefore, the computer has to somehow continue making these calculations without having any measurements made until the proper time, when it can then drop out of the quantum state, have a measurement taken to read its result, which then gets passed on to the rest of the system.
The physical requirements of manipulating a system on this scale are considerable, touching on the realms of superconductors, nanotechnology, and quantum electronics, as well as others. Each of these is itself a sophisticated field which is still being fully developed, so trying to merge them all together into a functional quantum computer is a task which I don't particularly envy anyone ... except for the person who finally succeeds.