Monday, July 31, 2006

Timeline of quantum computing

http://en.wikipedia.org/wiki/Timeline_of_quantum_computing

"1970s
1970 - Stephen Wiesner invents conjugate coding.
1973 - Alexander Holevo publishes a paper showing that n qubits cannot carry more than n classical bits of information (a result known as "Holevo's theorem" or "Holevo's bound".
1975 - R. P. Poplavskii publishes "Thermodynamical models of information processing" (in Russian), Uspekhi Fizicheskikh Nauk,115:3, 465–501 which showed the computational infeasibility of simulating quantum systems on classical computers, due to superposition principle.
1976 - Polish mathematical physicist Roman Ingarden, in one of the first attempts at creating a quantum information theory, shows that Shannon information theory cannot directly be generalized to the quantum case, but rather that it is possible to construct a quantum information theory which is a generalization of Shannon's theory.
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1980s
1980 -- Yuri I. Manin, publishes Computable and uncomputable (in Russian), Moscow, Sovetskoye Radio. This work exploits the exponential number of basis states needed to describe the evolution of a quantum system, and discusses the need for a theory of quantum computation that captures the fundamental principles of computation without committing to a physical realization.
1981
Richard Feynman in his talk at the First Conference on the Physics of Computation, held at MIT, observed that it appeared to be impossible in general to simulate an evolution of a quantum system on a classical computer in an efficient way. He proposed a basic model for a quantum computer that would be capable of such simulations.
Tommaso Toffoli introduced the reversible Toffoli gate, which, together with the NOT and XOR gates provides a universal set for quantum computation.
1984 - Charles Bennett and Gilles Brassard employ Wiesner's conjugate coding for distribution of cryptographic keys.
1985 - David Deutsch, at the University of Oxford, described the first universal quantum computer. Just as a universal Turing machine can simulate any other Turing machine efficiently, so the universal quantum computer is able to simulate any other quantum computer with at most a polynomial slowdown.
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1990s
1991 - Artur Ekert invents entanglement based secure communication.
1993 - Dan Simon, at Université de Montréal, invented an oracle problem for which a quantum computer would be exponentially faster than conventional computer. This algorithm introduced the main ideas which were then developed in Peter Shor's factoring algorithm.
1994
Peter Shor, at AT&T's Bell Labs in New Jersey, discovered a remarkable algorithm. It allowed a quantum computer to factor large integers quickly. It solved both the factoring problem and the discrete log problem. Shor's algorithm could theoretically break many of the cryptosystems in use today. Its invention sparked a tremendous interest in quantum computers, even outside the physics community.
In December, Ignacio Cirac, at University of Castilla-La Mancha at Ciudad Real, and Peter Zoller at the University of Innsbruck proposed an experimental realization of the controlled-NOT gate with trapped ions.
1995
Peter Shor and Andrew Steane simultaneously proposed the first schemes for quantum error correction. This is an approach to making quantum computers that can compute with large numbers of qubits for long periods of time. Errors are always introduced by the environment, but quantum error correction might be able to overcome them. This could be a key technology for building large-scale quantum computers that work. These early proposals had a number of limitations. They could correct for some errors, but not errors that occur during the correction process itself. A number of improvements have been suggested, and active research on this continues. An alternative to quantum error correction has been found. Instead of actively correcting the errors induced by the interaction with the environment, special states that are immune to the errors can be used. This approach, known as decoherence free subspaces, assumes that there is some symmetry in the computer-environment interaction.
Christopher Monroe and David Wineland at NIST (Boulder, Colorado) experimentally realize the first quantum logic gate with trapped ions, according to Cirac and Zoller's proposal.
1996 - Lov Grover, at Bell Labs, invented the quantum database search algorithm. The quadratic speedup isn't as dramatic as the speedup for factoring, discrete logs, or physics simulations. However, the algorithm can be applied to a much wider variety of problems. Any problem that had to be solved by random, brute-force search, could now have a quadratic speedup.
1997 - David Cory, Amr Fahmy and Timothy Havel, and at the same time Neil Gershenfeld and Isaac L. Chuang at MIT published the first papers on quantum computers based on bulk spin resonance, or thermal ensembles. The computer is actually a single, small molecule, which stores qubits in the spin of its protons and neutrons. Trillions of trillions of these can float in a cup of water. That cup is placed in a nuclear magnetic resonance (NMR) machine, similar to the magnetic resonance imaging machines used in hospitals. This room-temperature (thermal) collection of molecules (ensemble) has massive amounts of redundancy, which allows it to maintain coherence for several seconds, much better than many other proposed systems.
1998
First working 2-qubit NMR computers demonstrated by Jonathan A Jones and Michele Mosca at Oxford University and at the same time by Isaac L. Chuang at IBM's Almaden Research Center together with coworkers at Stanford University and MIT.
First working 3-qubit NMR computer.
First execution of Grover's algorithm.
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2000s
2000
First working 5-qubit NMR computer demonstrated at the Technical University of Munich.
First execution of order finding (part of Shor's algorithm) at IBM's Almaden Research Center and Stanford University.
First working 7-qubit NMR computer demonstrated at the Los Alamos National Laboratory.
2001 - First execution of Shor's algorithm at IBM's Almaden Research Center and Stanford University. The number 15 was factored using 1018 identical molecules, each containing seven active nuclear spins.
2002 - The Quantum Information Science and Technology Roadmapping Project, involving some of the main participants in the field, laid out the Quantum computation roadmap.
2002 - 11th UK conference on the Foundations of Physics, the Philosophy Centre, University of Oxford, September 9 - 13 sees the exposition of the theory of the Quantum Time Bomb.
2004 - First working pure state NMR quantum computer (based on parahydrogen) demonstrated at Oxford University and University of York.
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2005

Dr. Matthew Sellars of the Laser Physics Centre at the Australian National University in Canberra, Australia slowed down a light pulse to a few hundred meters per second. Slowing the light down allows information to be mapped on the light pulse, like memory in a conventional computer. To slow down the light, the researchers used a silicate crystal mixed with a rare earth metal called praseodymium. [1]
In a paper published in the November issue of the journal Nature Physics, researchers at the Georgia Institute of Technology reported experimental evidence that coherence also extends to the internal spin degrees of freedom in Bose-Einstein condensate atoms.
University of Illinois at Urbana-Champaign scientists demonstrate quantum entanglement of multiple characteristics, potentially allowing multiple qubits per particle.
Two teams of physicists have measured the capacitance of a Josephson junction for the first time. The methods could be used to measure the state of quantum bits in a quantum computer without disturbing the state. PhysicsWeb
In December, the first quantum byte, or qubyte, is announced to have been created by scientists at The Institute of Quantum Optics and Quantum Information at the University of Innsbruck in Austria [2], with the formal paper published in the December 1st issue of Nature.
Harvard University and Georgia Institute of Technology researchers succeeded in transferring quantum information between "quantum memories" -- from atoms to photons and back again.
Scientists at the National Institute of Standards and Technology (NIST) coaxed six atoms into spinning together in two opposite directions at the same time.
A scalable quantum computer chip for atomic qubits was built for the first time by researchers at the University of Michigan, offering hopes for making a practical quantum computer using conventional semiconductor manufacturing technology.
[edit]
2006

HP Labs' Quantum Information Processing Group begins finding ways to use photons, or light particles, for information processing, rather than the electrons used in digital electronic computers today. Their work holds promise for someday developing faster, more powerful and more secure computer networks.
Peter Zoller, from the University of Innsbruck in Austria, discovers method of using cryogenic polar molecules to make stable quantum memories.
Professor Winpenny at Manchester's School of Chemistry for the first time demonstrated how metal-containing rings that show properties necessary to act as qubits can be linked together using both organic and metal-organic fragments.
Researchers at Cambridge University and Toshiba announce a new quantum device that produces entangled photons.
Materials Science Department of Oxford, caged qubit in a buckyball (a Buckminster fullerene particle). This isolates a qubit to some extent, but not quite enough. The next step the researchers took was to apply the so-called ‘bang-bang’ method: the qubit is repeatedly hit with a strong pulse of microwaves which reverses the way in which it interacts with the environment. This allows the state of the qubit to be preserved. Bang-bang: a step closer to quantum supercomputers
Circuits built from high-critical-temperature superconductors might support quantum computing, according to experiments performed by physicists at Chalmers University of Technology (Goteborg, Sweden). Working with a group at Italy's University of L'Aquila, the physicists directly observed macroscopic quantum effects in high-critical-temperature Josephson junctions.
Physicists at The University of Texas at Austin use a laser trap to consistently capture and measure the same small number of atoms.
Researchers at the University of Pittsburgh develop a way to create semiconductor islands smaller than 10 nanometers in scale, known as quantum dots. The islands, made from germanium and placed on the surface of silicon with two-nanometer precision, are capable of confining single electrons.
Ohio University scientists discover how to make coherent light travel between quantum dots, facilitating communication in optical quantum computers.
Researchers from the University of Illinois at Urbana-Champaign use the Zeno Effect, repeatedly measuring the properties of a photon to gradually change it without actually allowing the photon to reach the program, to search a database without actually "running" the quantum computer.
Vlatko Vedral of the University of Leeds and colleagues at the universities of Porto and Vienna found that the photons in ordinary laser light can be quantum mechanically entangled with the vibrations of a macroscopic mirror, no matter how hot the mirror is.
Professor Sam Braunstein at the University of York along with the University of Tokyo and the Japan Science and Technology Agency gave the first experimental demonstration of quantum telecloning. [3]
Professors at the University of Sheffield develop a means to efficiently produce and manipulate individual photons at high efficiency at room temperature. [4]
IBM scientists develop spin-excitation spectroscopy to manipulate the magnetism of individual atoms.
New error checking method discovered. [5]
Method developed to count single electrons. [6]
First 12 qubit quantum computer benchmarked. [7]
Two dimensional ion trap developed for quantum computing. [8]
Seven atoms placed in stable line, a step on the way to constructing a quantum gate, at the University of Bonn. [9]
Scientists learn how to synchronize quantum properties of electrons at ends of a nanotube. [10]"

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