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 ...
JQI researchers create entangled photons from quantum dots
Nov 18, 2009 |
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To exploit the quantum world to the fullest, a key commodity is entanglement—the spooky, distance-defying link that can form between objects such as atoms even when they are completely shielded from one another. Now, physicists ...
First Bose-Einstein condensation of strontium
Nov 09, 2009 |
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In an international first, scientists from the Institute of Quantum Optics and Quantum Information (IQOQI, Austria) produced a Bose-Einstein condensate of the alkaline-earth element strontium, thus narrowly ...
Search results for quantum information
Spin polarization achieved in room temperature silicon
Nov 27, 2009 |
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(PhysOrg.com) -- A group in The Netherlands has achieved a first: injection of spin-polarized electrons in silicon at room temperature. This has previously been observed only at extremely low temperatures, ...
Explained: The Discrete Fourier Transform
Nov 25, 2009 |
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(PhysOrg.com) -- In 1811, Joseph Fourier, the 43-year-old prefect of the French district of Isčre, entered a competition in heat research sponsored by the French Academy of Sciences. The paper he submitted ...
Straightening messy correlations with a quantum comb
Nov 23, 2009 |
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Quantum computing promises ultra-fast communication, computation and more powerful ways to encrypt sensitive information. But trying to use quantum states as carriers of information is an extremely delicate ...
Visual assistance for cosmic blind spots
Nov 23, 2009 |
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A bit of imagination on the part of a measuring instrument wouldn't be a bad thing. It could help to add data from areas where the instrument is unable to measure. However, it must do so constructively. In ...
More than powerful: German research computer QPACE is the most energy efficient in the world
Nov 20, 2009 |
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At the 2009 Supercomputing Conference in Portland, Oregon, the high-performance computer QPACE (QCD Parallel Computing on the Cell) was recognized today as the most energy-efficient supercomputer in the world.
UCSB physicists move one step closer to quantum computing
Nov 20, 2009 |
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Physicists at UC Santa Barbara have made an important advance in electrically controlling quantum states of electrons, a step that could help in the development of quantum computing. The work is published ...
Using superconducting probes to get a picture of what it's like inside CNTs
Nov 20, 2009 |
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(PhysOrg.com) -- "Carbon nanotubes are exciting for fundamental physics, and for potential technological applications," Nadya Mason tells PhysOrg.com. "However, we are generally limited in the way that we can study them. ...
Small nanoparticles bring big improvement to medical imaging
Nanotechnology / Bio & Medicine
Nov 18, 2009 |
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If you're watching the complex processes in a living cell, it is easy to miss something important—especially if you are watching changes that take a long time to unfold and require high-spatial-resolution ...
Turning heat to electricity... efficiently
Nov 18, 2009 |
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(PhysOrg.com) -- In everything from computer processor chips to car engines to electric powerplants, the need to get rid of excess heat creates a major source of inefficiency. But new research points the way ...
New study confirms exotic electric properties of graphene
Nanotechnology / Nanomaterials
Nov 17, 2009 |
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(PhysOrg.com) -- First, it was the soccer-ball-shaped molecules dubbed buckyballs. Then it was the cylindrically shaped nanotubes. Now, the hottest new material in physics and nanotechnology is graphene: ...
List of search results for quantum information
