Computer Science for Education

======Quantum Computation Definition======
According to new calculations, Quantum computing is a theory of quantum mechanics, The basis and principles of quantum computation and quantum algorithms have made possible for the critical speed of calculation beyond the Turing machine model.
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======Fundamental Principle of  Quantum Computation======
superposition and implication of quantum theory had a tremendous computing power. 2 ordinary computer registers can only stored 4 binary number at a certain time(one of 00,01,10,11). while the 2-bit quantum computer qubit registers can store the four numbers at the same time, because each qubit can represent two values. If there are more qubits, computing will be increased exponentially.
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**Superposition Principle**
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Consider a quantum as an electron in a magnetic field. Electronic and magnetic field rotation may be identical or contrast, and it is called spin state and next spin state respectively. Pulse energy by providing the electron spin from one state to another states. For example, Let's assume that we use one unit of laser energy, but what if we can only use half a unit of laser energy to completely eliminate the influence of particles? According to quantum theory, particles will enter the overlapping state, which means that particles are in the two states, each of which shows overlapping qubit state 0 or 1. Therefore, the calculation of the quantum computer is 2^n(n is the number of bits of quantum bits). If a Quantum Computer has 500 qubits, it can do 2 ^ 500 operations in each step. This number is more than the known number of atoms on the planet and even more. This is the true parallel processing. On nowaday's classical computers, the so-called parallel processors can still do only one operation at a time. However, how can these particles interact with each other? It can be done by the quantum implication.
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**Implication Principle**
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Particles (like photons, electrons) interacting at some point have a relationship between each other, leading to the entanglement. This process is called relevance. If we know the entangled state of a particle(up or down),then its companion's rotation will be opposite. Surprisingly, due to cascading phenomenon, no single particle shows the direction of rotation, but they are paired up the spin and down spin state. Rotating particles are determined by the measurement of time and decisions associated with particles, while the related particles are in the opposite direction of rotation. The real phenomenon (Einstein called it "the magic between the acts of a distance") has no suitable theory to explain but simply be accepted. Implicated from the same quantum system, no matter how far the distance between the particles interacting with each other at the same time (it's not limited by the speed of light), No matter how far apart the interaction between particles, they will not entangle with each other until they are separated.
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======The Development of Quantum Computing======

**Early-term Concept**
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Quantum computing concept was first proposed by R. Landauer IBM scientists and C. Bennett in the 70's. They mainly discussed the calculation process, such as free energy, informations and reversibility relationship. In the early '80s, P. Benioff first proposed two energy levels of quantum systems which can be used to simulation figures; later Feynman is also interested in the issue and started studying, and in 1981 in Massachusetts Institute of Technology on the First Conference about Physics of Computation,he gave a lecture to outline the calculation of quantum phenomena to achieve the vision. In 1985,in Oxford University, D. Deutsch proposed quantum Turing machine. The concept of quantum computing started with the basic types of mathematics. However, most of the quantum calculation was limited in the physical nature of computation, while it also stayed in the very abstract level. It hadn't gone further into the development stage of the algorithm.

**Medium-term Development**
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In 1994,in Bell Lab, an applied mathematician P. Shor pointed out that compared to conventional electronic calculator, the use of quantum computation can be in a shorter period of time operating a large integer factorization into prime factors of the product. This conclusion opened a new phase of quantum computing: the laws of quantum computing is different from traditional quantum algorithm which has its usefulness, but not scientists' pocket tricks. Since then, a succession of new quantum algorithms have been proposed, but physicists followed important issues like how to build a real quantum calculator to perform these quantum algorithms. Many quantum systems have been named as the basis for the quantum structure of the calculator, such as photon polarization, cavity quantum electrodynamics(CQED), ion trap and nuclear magnetic resonance(NMR) and so on. With current technology, those in the ion trap and magnetic resonance are most feasible. In fact, NMR has been the first in this race. I. Chuang IBM research team led by the spring of 2002, getting succeeded in containing seven quantum bits using NMR completing N = 15 as the factorization.

**development prospect**
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Quantum computing will be possible to make the computer's computing more powerful than today's computers, but there are still many obstacles. The existence of large-scale quantum computing has issue to improve the accuracy of the necessary difficulties of quantum devices.
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======Links======
http://plato.stanford.edu/entries/qt-quantcomp/
http://www.sciencedaily.com/news/computers_math/quantum_computers/
http://www.howstuffworks.com/quantum-computer.htm
http://en.wikipedia.org/wiki/Quantum_computer
Computer Science for Education

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