News tagged with quantum information
Physicists store short movies in an atomic vapor
The storage of light-encoded messages on film and compact disks and as holograms is ubiquitous---grocery scanners, Netflix disks, credit-card images are just a few examples. And now light signals can be stored ...
May 29, 2012 |
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Research group creates longer lived and more efficient quantum memory
(Phys.org) -- One of the main sticking points to creating a true quantum computer capable of performing meaningful work, is the problem of storing quantum state information in memory. Recent efforts have resulted in highly ...
May 30, 2012 |
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Two stopped light pulses interact with each other
(Phys.org) -- For the first time, physicists have experimentally demonstrated the interaction of two motionless light pulses. Because the stopped light pulses have a long interaction time, it increases the ...
May 08, 2012 |
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'Metamaterials,' quantum dots show promise for new technologies
(Phys.org) -- Researchers are edging toward the creation of new optical technologies using "nanostructured metamaterials" capable of ultra-efficient transmission of light, with potential applications including ...
May 24, 2012 |
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Efficient and tunable interface for quantum networks
(Phys.org) -- Quantum computers may someday revolutionize the information world. But in order for quantum computers at distant locations to communicate with one another, they have to be linked together in ...
May 23, 2012 |
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A magnetic approach to lattices
(Phys.org) -- JQI experimentalists under the direction of Ian Spielman are in the business of using lasers to create novel environments for neutral atoms. For instance, this research group previously enticed ...
May 22, 2012 |
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Keeping it together: Protecting entanglement from decoherence and sudden death
(PhysOrg.com) -- Decoherence can be metaphorically seen as a quantum fall from grace: When quantum bits, or qubits, are in superposition – such as a single qubit simultaneously having both 1 and 0 values ...
Feb 27, 2012 |
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Researchers engineer molecular magnets to act as long-lived qubits
(PhysOrg.com) -- Some physicists today are investigating the possibility of using molecular magnets as information storage units in future quantum computers. Molecular magnets are molecules whose magnetic ...
Mar 21, 2012 |
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Quantum no-hiding theorem experimentally confirmed for first time
(PhysOrg.com) -- In the classical world, information can be copied and deleted at will. In the quantum world, however, the conservation of quantum information means that information cannot be created nor destroyed. ...
Mar 07, 2011 |
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Proposed experiment offers new way to generate macroscopic entanglement
(PhysOrg.com) -- In the development of quantum information processing, one of the key requirements is achieving quantum entanglement. But recently, physicists have been investigating other forms of quantum correlations besides ...
Jan 05, 2012 |
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Physicists build first single-photon router
(PhysOrg.com) -- By demonstrating that an artificial atom embedded in a transmission line can route a single photon from an input port to one of two output ports, physicists have built the first router working ...
Aug 22, 2011 |
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Physicists take steps toward delivering quantum information to the home
(PhysOrg.com) -- Today, fiber optics technology transports information in the form of classical data to homes and businesses. But researchers are currently working on ways to combine quantum data with the ...
Jul 18, 2011 |
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Simplifying the process of detecting genuine multiparticle entanglement
(PhysOrg.com) -- The ability to entangle particles is considered essential for a number of experiments and applications. While we have seen evidence for quantum entanglement, it is still difficult to detect ...
May 20, 2011 |
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Reducing noise in quantum operation at room temperature
(PhysOrg.com) -- "A quantum memory is a crucial component of future quantum information processing technologies. Among these technologies, a quantum communications system based on light will enable vastly improved performance ...
Aug 23, 2011 |
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Quantum eavesdropper steals quantum keys
(PhysOrg.com) -- In quantum cryptography, scientists use quantum mechanical effects to encrypt and then communicate confidential information. Although quantum cryptography codes are unbreakable in principle, even the best ...
Jun 20, 2011 |
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Quantum information
In 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.
