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 |
4.7 / 5 (17) |
0
(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 ...
First Bose-Einstein condensation of strontium
Nov 09, 2009 |
4.8 / 5 (10) |
5
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 ...
JQI researchers create entangled photons from quantum dots
Nov 18, 2009 |
4.3 / 5 (8) |
1
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 ...
Search results for quantum information
New imaging nano-technique to change the way we see disease
Nanotechnology / Bio & Medicine
4 hours ago |
5 / 5 (1) |
0
(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
15 hours ago |
4.5 / 5 (17) |
0
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
16 hours ago |
5 / 5 (1) |
0
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 ...
Scientists build 'single-atom transistor'
Dec 06, 2009 |
5 / 5 (29) |
2
(PhysOrg.com) -- Researchers from Helsinki University of Technology (Finland), University of New South Wales (Australia), and University of Melbourne (Australia) have succeeded in building a working transistor, ...
Scientists Create World's Smallest Snowman (w/ Video)
Dec 04, 2009 |
3.5 / 5 (18) |
5
(PhysOrg.com) -- David Cox, a scientist in the Quantum Detection group at the National Physical Laboratory in the UK, is an expert in nanofabrication techniques. Recently, using the tools of his trade and ...
Tahoe faces new development battle: green vs. green
Dec 03, 2009 |
4 / 5 (2) |
0
As snow begins to blanket Lake Tahoe, the region finds itself facing a new kind of development battle: green vs. green.
Researchers create 'synthetic magnetic fields' for neutral atoms
Dec 02, 2009 |
4.9 / 5 (15) |
2
(PhysOrg.com) -- Achieving an important new capability in ultracold atomic gases, researchers at the Joint Quantum Institute, a collaboration of the National Institute of Standards and Technology and the University ...
Researchers Identify Key Molecules in Photosynthesis
Dec 02, 2009 |
5 / 5 (8) |
0
(PhysOrg.com) -- Chemistry professor Harry Frank led an international group of researchers that identified the molecules in algae which direct the organisms to convert sunlight into oxygen. The findings may ...
Spin polarization achieved in room temperature silicon
Nov 27, 2009 |
4.8 / 5 (19) |
0
(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 |
4.2 / 5 (36) |
8
(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 ...
List of search results for quantum information
