A quantum computer is a computation device that makes direct use of quantu-mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from digital computers based on transistors. Whereas digital computers require data to be encoded into binary digits (bits}
CERN, European Organisati
each of which is always in one of two definite states (0 or 1), quantum
computation uses qubits (quantum bits), which can be in superpositions of
states. A theoretical model is the quantum Turing machine, also known as the
universal quantum computer. Quantum computers share theoretical similarities
with non-deterministic and probabilistic computers; one example is the ability
to be in more than one state simultaneously.The field of quantum compute was
first introduced by Yuri Manin in 1980 and Richard Feynman in 1982. A
quantum computer with spins as quantum bits was also formulated for use as a quantum
space–time in 1969.But the dreamers chasing this goal — a computer that uses quantum mechanics to
solve problems beyond the scope of classical computers, with unprecedented speed —
were jolted awake by a bucket of cold water Thursday, as research showed Canada’s
leading contribution to the field has so far failed to show its promise.
D-Wave Systems, a company in Burnaby, B.C.,whose shareholders include the
Canadian government, has sold devices it markets as quantum computers to theNational Aeronautics & Space Administration, Google and Lockheed Martin,
making it a major player in the predicted quantum revolution, rivalled only
by BlackBerry billionaire Mike Lazaridis, who has made the quantum computer
the key goal of his investment in Waterloo, Ont.’s “Quantum Valley.”But a paper by Swiss and American scientists in the leading journal
Science shows the D-Wave Two device does not calculate any faster than a classical computer.A quantum computer of just 30 qubits would exceed what classical computers can accurately model, and D-Wave’s device has more than 500. The problem is they last mere nanoseconds, decaying long before the computation is complete.
Handout/D-WaveD-Wave extolling some of the virtues of its quantum technology.
In this case, D-Wave’s qubits lasted about 10 nanoseconds, and the alculation
Prof. Troyer tested takes 20 microseconds — 2,000 times as long.Inside the Black Box The guts of a D-Wave don’t look like any other computer. Instead of metals
etched into silicon, the central processor is made of loops of the metal niobium,
surrounded by components designed to protect quantum computer from heat, vibration, and electromagnetic noise.
Isolate those niobium loops well enough from the outside world and you get a quantum computer,
thousands of times faster than the machine on your desk—or so the company claims. —Cameron Bird.For more details on the sequences of operations used for various quantum
algorithms, see universal quantum computer, Shor’s algorithm, Grover’s algorithm, Deutsch-Jozsa algorithm, amplitude amplification, quantum Fourier transform, quantum gate, quantum adiabatic algorithm and quantum error correction.
The concept of a quantum computer relies on the weird and unique ability of inhabitants of the quantum world — from electrons and photons to non-abelian anyons — to be many things at once. An electron, for example, can spin both clockwise and counterclockwise simultaneously.
A photon can be polarized along two axes. The transistors that serve as ordinary bits can only be in one of two states (denoted 0 or 1), but qubits made from spinning electrons or polarized photons
are mixtures or “superpositions” of 0 and 1, existing in both states simultaneously.link:The Future of Quantum Computing Could Depend on This Tricky Qubit _ Science _ WIRED.htm