Quantum Computing
Author: Ann Wang and Jim Kadtke
Latest Update: Mar 10th, 2011
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Summary
Quantum mechanics offers another possible successor to silicon in which information is stored and managed using atomic particles. The unusual behavior of matter at the quantum level makes this computational technique revolutionary. For instance, two or more atoms can become “entangled” so that a change in one instantaneously produces a like change in the other, offering the possibility of "teleportation” of information. Because of quantum uncertainty, particles can  coexist in two places simultaneously, and this feature of “superposition” allows a single particle to carry two bits of information -  a "qubit." Some think quantum computing may not be restricted to qubits but could involve a continuous spectrum obtained from phase relationships (http://iopscience.iop.org.  Although the field is struggling to mature, promising advances are occurring each year, and applications are appearing already. Reliable quantum computers may thus be available within one to two decades, with vast scientific and commercial potential.
Selected Adoption & Forecast Data

Commercial quantum computers about 2020
Prof. Jeff Kimble, California Institute of Technology, said: "In the next 20 years, quantum [computing] will radically change commerce." (TechnologyReview Sept/Oct 2009)
Dave Evans, chief futurist at Cisco, predicted: "The first commercial quantum computer will be available by mid-2020." (Sync-blog.com Feb 2010).




EXPERT SURVEY RESULTS
Event Being Forecast: A quantum computer enters the commercial market
 
Forecast Data Analysis
    Mean Std Dev N (# Experts)
Most Likely Year 2024 7 77
Market Size (1-10) 4.3 2.1
Confidence (%) 57 17.4

In addition, 2 experts predicted that this event would never occur; mean confidence: 32%; std. dev.: 33.

 
Frequency Distributions
 Most Likely Year Market Size (1-10) Confidence (%)

TREND ANALYSIS
 
PROS: Trends Driving this Event CONS: Obstacles Opposing this Event
POTENTIAL IS VAST
• The basic unit of quantum computing is a “qubit” - the state of an electron spinning in either clockwise or counterclockwise rotation, representing a 0 or a 1. Because superposition allows atoms to exist in two places simultaneously, altering the state of an electron can produce two qubits, two electrons can produce four, three electrons eight, and twenty electrons could perform a million computations instantaneously. This exponential growth offers the potential of producing infinite processing power and infinite storage. A quantum computer could easily complete in seconds a task that takes a silicon computer billions of years. (Wikipedia: Quantum Computing)
• 
U. of Switzerland researchers altered pairs of entangled electrons in labs 18 kilometers apart, demonstrating that the information sent between entangled electrons must travel 10,000 times the speed of light. (NewScientist 8/12/08) This ability to teleport information at a distance by entangling atoms has kindled a wave of imagination among physicists. David Darling (Teleportation, Wiley, 2005) thinks "Teleportation is going to play a major role in our future." (Space.com 7/8/05)
• It is impossible to observe a quantum state without altering it, so quantum cryptography can detect eavesdropping.
The first computer network protected with quantum computing is up and running at Harvard University, and other systems are being used at the NSA and the Federal Reserve (NewScientist 6/16/04). Conversely, this vast power enables cracking even the most sophisticated encryption codes in a flash. Accenture thinks this could unleash a hacker's "ekiller app. that breaks through security defenses." (NetworkedWorld 11/2008) 
THE TECHNOLOGY IS IMPROVING
The U.S. National Institute of Standards and Technology demonstrated what is being called "The world's first quantum computer." It uses lasers that manipulate super-cold beryllium atoms to store data, display it, and move it around the processor. "We've pulled all the needed components together for the first time", said the project leader. Thus far, accuracy is only 79%, however. (Discover Nov 2009)The NIST also developed an ion trap that can store 12 ions and is easily mass produced. (TechnologyReview 10/19/06)
• D-Wave Systems in Canada claims its Orion is the world's first qauntum computer. It operates using 16 qubits and is expected to have 1000 qubits, enough to do massive tasks. Some scientists doubt if it uses true quantum computing methods, but Seth Lloyd at MIT said "This work is potentially solid." (Discover 6/07)
• Research at the University of Bristol shows quantum computers may soon be able to execute complex calculations. The breakthrough involves a specially designed optical chip to perform what's known as a "quantum walk" with two particles. One of the researchers said: "A quantum computer could, in less than ten years, be performing calculations that are outside the capabilities of conventional computers." ( Gizmag 9/16/2010 )
Prof. Prem Kumar at Northwestern University has developed a quantum routing switch that can move entangled photons while keeping their information intact. Prof. James Franson at the University of Maryland said "a quantum switch could someday allow entangled photons to be shared over long distances. (TechnologyReview 3/22/2011)
• 
Japanese researchers calculated a common signal processing algorithm using a single iodine molecule to store the quantum particles (Phys Rev. Letters, May 2010 ).  Ian Walmsley (University of Oxford) says such an astonishingly high-speed calculation shows a great deal can be gained if physicists can overcome the difficulties in putting single-molecule computation to practical use (APS Physics, May 2010).
• An Australian National University team developed the most efficient quantum memory for light in the world, taking us closer to a future of super-fast computers and communication secured by the laws of physics.  The team used a technique they pioneered to stop and control light from a laser, manipulating electrons in a crystal cooled to -270 degrees Celsius. The unprecedented efficiency and accuracy of the system allows the quantum nature of the light tobe stored, manipulated, and recalled. (ScienceDaily June 2010 )
• Scientists at Bristol University have demonstrated the ability to control individual photons and encode each with one quantum bit, considered "a crucial step toward quantum computing. (EurekaAlert 3/27/08) 
  A university team with an infra-red laser precisely controlled the quantum superpositions of an electron in silicon for the first time. "This is a real breakthrough and has huge potential for the future," explained Prof. Ben Murdin, part of the team. (Gizmag June 2010)
• McGill University physicists developed a system for measuring the energy involved in adding electrons to semi-conductor nanocrystals, also known as quantum dots -- a technology that may revolutionize computing and other areas of science.  Measuring the energy at such infinitesimal levels is an important step in developing a replacement for silicon chip computing, especially quantum computing. (Science Daily May 2010).
• Johannes Gutenberg University physicists have developed a quantum interface which can reliably change quantum states using only light passing through an ultra-thin glass fiber. This is an essential prerequisite for quantum communication, which can be used for secure data transmission via quantum cryptography.   (Science Daily, May 2010)
• The world's first universal programmable quantum computer has been tested.  A team at the National Institute of Standards and Technology (NIST; Boulder, CO) built a quantum computer capable of processing two quantum bits, or qubits. (New Scientist, 15Nov 2009 ) 
• The first quantum register used “spintronics” to increase memory density 1000 times by storing data in the spin of electrons. (Technology Review 4/27/04; NewScientist 10/8/04) Fifty DVDs could be stored on a hard drive the size of a credit card.
•  Canadian researchers have created quantum dots of one atom to control individual electrons for computational purposes at room temperatures. This breakthrough offers the prospect of quantum computers requiring 1,000 times less energy with vastly greater power. (PhysOrg 1/27/08)
• Scientists at Penn State have created a 3D array that holds hundreds of atoms precisely at fixed locations where they can be observed and manipulated. The device was used to hold 250 atoms, more than enough to perform vast computational operations with qubits. (NewScientist 6/17/07) 
• IBM has demonstrated the ability to store one bit on a single atom; in comparison, hard drives use 1 million atoms to store one bit of information. Using this technology, an entire supercomputer could be the size of a speck of dust.(EETimes, 8/30/07) 
APPLICATIONS
• 
 
Siemens is introducing quantum cryptography for commercial use. The service is being offered to Dutch customers at a cost of $82,000 for the equipment plus the cost of two fiber cables - one for the data being sent and the other for the encryption key. In time, it is expected to be provided along with normal telecom services (TechnologyReview 8/28/09). 
•  D-Wave has built a quantum processor comprised of a programmable superconducting integrated circuit with up to 128 flux qubits. The processor is designed to implement a special-purpose adiabatic quantum optimization algorithm as opposed to being operated as a universal gate-model computer.  If true, this is a significant step toward a commercially viable quantum computer.  (Supercond. Sci. Technol. 23, 2010))
INDETERMINACY Because quantum computers utilize the effects of quantum superposition, there are fundamental uncertainties in any atomic interaction.  This means that significant errors are introduced into all calculations, which may be a big engineering hurdle.  For example, the most recent quantum computer developed by NIST has only 79% accuracy for an individual calculation. All computers operate at less than perfect accuracy, but more reliable commercial operations require accuracies far higher. (Science Daily Nov09).  
STABILITY Since quantum computers operate on arrays of individual atoms, it is essential that these atoms can be reliably stored and not destabilized by computational interactions. Some scientists have claimed that such decoherence may be an almost insurmountable problem (New Scientist 6/05). However very recent scientific results in stabilizing even significant arrays of individual atoms are highly promising (see PROs section ).
COMMERCIAL VIABILITY While quantum computers struggle toward commercialization, other less exotic computer technologies continue to make progress.  Moore's law continues to be pushed farther into the future for silicon processors, and other technologies such as optical processors or bio-computers may provide more immediate commercial options with large performance increases. Quantum computers cannot solve any problem that a conventional computer cannot solve, in terms of computational complexity, and continual improvements in memory and speed of conventional computers may erode the significant speed and memory advantages of quantum computers.  The question, therefore, remains whether quantum computers will ever become commercially viable for commonplace applications or whether other cheaper technologies will dominate the market? In a 2006 poll of their membership about the futureof various new technologies, almost 78% of IEEE members doubted that a quantum computer would ever reach the commercial marketplace  (IEEE Spectrum Sept. 2006)
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Public Comments
(Edited and displayed in 1-2 days)
 
Art Shostak (3/26/2008 5:18:48 PM)
R&D hurles are many and costly. Progess, albeit imuch of it is hidden as proprietory, seems slow and uneven. Still, the incentives are golden, and patience and trust in a positive outcome is recommended.
Rupam Shrivastava (3/10/2010 8:11:12 PM)
D-wave, a quantum computing company has made claims of mainstream quantum computing to be as close as 5 year.
Lester Ingber (8/17/2010 8:31:28 AM)
This Summary needs to be corrected and updated: (1) The invocation of the influence of the Heisenberg Principle is distorted. In fact, it likely is not even so relevant as first imagined regarding quantum computing. See: http://www.sciencedaily.com/releases/2010/07/100727082652.htm (2) Quantum computing may not be so restricted to qubits as first imagined. A continuous spectrum may be obtained from phase relationships. See: http://iopscience.iop.org/1367-2630/12/5/053019/fulltext Lester
Lester Ingber (11/25/2010 7:59:18 AM)
The increasing pace of new results in quantum theory is remarkable. For example, a new result by Oppenheim and Wehner (arXiv:1004.2507v1 [quant-ph]) details how the uncertainty principle and non-locality constrain each other. Such results will greatly influence the nature of R&D and money that will be spent building quantum computers.
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