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A quantum computer is any device for by Neil Gershenfeld and Isaac L. Chuang - a generally accessible overview of quantum computing and so on. Although quantum computing is still in its infancy, experiments have been carried out in which quantum computational operations were executed on a very small number of Qubit s. Research in both theoretical and practical areas continues at a frantic pace, and many national government and military funding agencies support quantum computing research to develop quantum computers for both civilian and national security purposes, such as Cryptanalysis . Quantum Information Science and Technology Roadmap for a sense of where the research is heading. (See Timeline Of Quantum Computing for details on current and past progress.) If large-scale quantum computers can be built, they will be able to solve certain problems exponentially faster than any of our current classical computers (for example Shor's Algorithm ). Quantum computers are different from other Computers such as DNA Computers and traditional computers based on Transistor s. Some computing architectures such as Optical Computer s may use classical superposition of electromagnetic waves, but without some specifically quantum mechanical resource such as Entanglement , they have less potential for computational speed-up of quantum computers. THE BASIS OF QUANTUM COMPUTING A classical computer has a memory made up of Bit s, where each bit holds either a one or a zero. A quantum computer maintains a sequence of Qubit s. A single qubit can hold a one, a zero, or, crucially, a Superposition of these, allowing for an infinite number of states. A quantum computer operates by manipulating those qubits with (possibly a suite of) Quantum Logic Gate s. An example of an implementation of qubits for a quantum computer would be the use of particles with two quantity ''A'' which is ''conserved'' under time evolution and such that ''A'' has at least two discrete and sufficiently spaced consecutive Eigenvalue s, is a suitable candidate for implementing a qubit. That's because any such system can be mapped onto an effective Spin-1/2 . BITS VS. QUBITS Consider first a classical computer that operates on a 3-bit Register . At any given time, the bits in the register are in a definite state, such as 101. In a quantum computer, however, the qubits can be in a superposition of all the classically allowed states. In fact, the register is described by a Wavefunction : | ||
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| Where The Coefficients A, B, C,, H Are | "http://wwwinformationdelightinfo/information/entry/complex_number" class="copylinks">Complex Number s whose amplitudes squared are the probabilities to measure the qubits in each state- for example, <math>c^2</math> is the probability to measure the register in the state 010 It is important that these numbers are complex, due to the fact that the Phases of the numbers can constructively and destructively interfere with one another this is an important feature for quantum algorithms2 |
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