Related topics: entanglement
Quantum information
hideIn quantum mechanics, quantum information is physical information that is held in the "state" of a quantum system. The most popular unit of quantum information is the qubit, a two-level quantum system. However, unlike classical digital states (which are discrete), a two-state quantum system can actually be in a superposition of the two states at any given time.
Quantum information differs from classical information in several respects, among which we note the following:
However, despite this, the amount of information that can be retrieved in a single qubit is equal to one bit. It is in the processing of information (quantum computation) that a difference occurs.
The ability to manipulate quantum information enables us to perform tasks that would be unachievable in a classical context, such as unconditionally secure transmission of information. Quantum information processing is the most general field that is concerned with quantum information. There are certain tasks which classical computers cannot perform "efficiently" (that is, in polynomial time) according to any known algorithm. However, a quantum computer can compute the answer to some of these problems in polynomial time; one well-known example of this is Shor's factoring algorithm. Other algorithms can speed up a task less dramatically - for example, Grover's search algorithm which gives a quadratic speed-up over the best possible classical algorithm.
Quantum information, and changes in quantum information, can be quantitatively measured by using an analogue of Shannon entropy. Given a statistical ensemble of quantum mechanical systems with the density matrix S, it is given by
Many of the same entropy measures in classical information theory can also be generalized to the quantum case, such as the conditional quantum entropy.
For more information about Quantum information, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with quantum information
Researchers Design Triple Quantum Dot for Quantum Information Applications
Nov 30, 2009 |
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(PhysOrg.com) -- While quantum dots have existed since the 1980s, only in the past decade have physicists successfully created lateral few-electron single quantum dots. These quantum dots enable physicists ...
Physicists propose quantum entanglement for motion of microscopic objects
Dec 21, 2009 |
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Researchers at the California Institute of Technology (Caltech) have proposed a new paradigm that should allow scientists to observe quantum behavior in small mechanical systems.
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Digital Quantum Battery Could Boost Energy Density Tenfold
Dec 22, 2009 |
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(PhysOrg.com) -- Physicists theorize that quantum phenomena could provide a major boost to batteries, with the potential to increase energy density up to 10 times that of lithium ion batteries. According to ...
Researcher studies the universe through quantum electrodynamics
Dec 17, 2009 |
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(PhysOrg.com) -- Fundamental constants, such as the standards for length and mass, are a given in our society. However, research has shown that these constants might be changing slightly with the expansion of the universe.
Proposed Spacetime Structure Could Provide Hints for Quantum Gravity Theory
Dec 16, 2009 |
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(PhysOrg.com) -- Spacetime, which consists of three dimensions of space and one time dimension, is such a large, abstract concept that scientists have a very difficult time understanding and defining it. Moreover, ...
Google Collaborates with D-Wave on Possible Quantum Image Search
Dec 15, 2009 |
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(PhysOrg.com) -- Always on the cutting edge of new computing technologies, Google has recently announced that it is investigating the use of quantum computing schemes to achieve faster image recognition rates. ...
Physicists lay the groundwork for cooler, faster computing
Dec 14, 2009 |
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University of Toronto quantum optics researchers Sajeev John and Xun Ma have discovered new behaviours of light within photonic crystals that could lead to faster optical information processing and compact computers that ...
Nanomedicine: ending 'hit and miss' design
Nanotechnology / Bio & Medicine
Dec 08, 2009 |
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(PhysOrg.com) -- One of the promises of nanomedicine is the design of tiny particles that can home in on diseased cells and get inside them. Nanoparticles can carry drugs into cells and tag cells for MRI and other diagnostic ...
Does weak equivalence break down at the quantum level?
Dec 08, 2009 |
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(PhysOrg.com) -- One of the givens in physics is the weak equivalence principle. This principle has been considered solid since Einstein proposed that it is not possible to detect the difference between uniform acceleration ...
New imaging nano-technique to change the way we see disease
Nanotechnology / Bio & Medicine
Dec 08, 2009 |
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(PhysOrg.com) -- New nano-technology being developed by physicists at Macquarie University could help medical professionals better understand and more effectively treat cancer and other diseases.
A see-through surprise: Scientists make solid material transparent to terahertz waves
Dec 07, 2009 |
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Very often in science, the unexpected discovery turns out to be the most significant. Rice University Professor Junichiro Kono and his team weren't looking for a breakthrough in the transmission of terahertz signals, but ...
Super cool atom thermometer
Dec 07, 2009 |
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As physicists strive to cool atoms down to ever more frigid temperatures, they face the daunting task of developing new, reliable ways of measuring these extreme lows. Now a team of physicists has devised ...
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