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Topic: Quantum channel

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In the News (Tue 18 Jun 19)

  Quantum Cryptography
Quantum cryptographic devices typically employ individual photons of light and take advantage of Heisenberg's uncertainty principle, according to which measuring a quantum system in general disturbs it and yields incomplete information about its state before the measurement.
Quantum theory is believed to govern all objects, large and small, but its consequences are most conspicuous in microscopic systems such as individual atoms or subatomic particles.
To construct a quantum channel, one needs a polarizing filter or other means for the sender to prepare photons of selected polarizations and a way for the receiver to measure the polarization of the photons.
dhushara.tripod.com /book/quantcos/aq/qcrypt.htm   (6621 words)

  Channel Data scoops Quantum international channel award
Channel Data has implemented solutions with Quantum's DX-Series to help resellers and their customers deal with today's backup and recovery challenges; requirements for high-performance, high-capacity recovery systems while keeping costs at a minimum.
Quantum's disk-based backup solutions, the DX-30 and DX-100, enable customers to integrate disk in their existing storage environments through the use of tape emulation.
Channel partners also received important information on the company's enhanced channel programmes which include Quantum Alliance (www.quantum-alliance.net) and the Premier VAR partner programme, which Channel Data introduced to the local channel in July.
www.itweb.co.za /office/channeldata/0408020758.htm   (282 words)

 Quantum Information Science
Quantum mechanics is usually taught at the undergraduate and graduate levels as part of the standard physics and chemistry curriculum, but the emphasis is more on applications than on developing a solid comprehension of the subject’s strange and seductive foundations.
Quantum entanglement is a subtle nonlocal correlation among the parts of a quantum system that has no classical analog.
In quantum teleportation, Alice receives a qubit in an unknown state, and destroys it by performing a Bell measurement on that qubit and a member of an entangled pair of qubits that she shares with Bob.
www.nsf.gov /pubs/2000/nsf00101/nsf00101.htm   (13848 words)

 [No title]
Quantum Channel: Is a channel allowing the transmission of quantum states.
That is, the quantum channel is shadowed by a public and classical channel that does not require any privacy but yet does require authentication (not yet implemented) in order to provide security.
For the time being it is achieved through an extra layer of communication between the servers and the quantum data grabber which is a separate application running at each end of the quantum channel and responsible for dealing with specialized hardware.
www.brics.dk /~salvail/qrypto/doc/QuCrypt/qucryptmain.html   (1455 words)

 Quantum Information: Basic Concepts
In fact, some approaches to the foundations of quantum theory (e.g., Ludwig's from the 60ies [Lu83]) are based on the view that Quantum Theory is precisely about the kind of influence transported from a preparing device (the "transmitter") to a measuring device (the "receiver").
In the theory of Quantum Information entanglement is no longer viewed merely as a means to "subtly humiliate the opponents of quantum mechanics" (C.H. Bennett), but as a resource needed to perform otherwise impossible tasks of information processing or computation.
The term "cloning" in the quantum context, coined in a short paper by Wooters and Zurek [WZ82], reflects rather well the idea that there is no blueprint for quantum systems (analogous to a sheep's DNA) from which all its properties could be derived (see the remarks on teleportation).
www.imaph.tu-bs.de /qi/concepts.html   (3109 words)

 Classical information channel - Wikipedia, the free encyclopedia
In quantum teleportation, a classical channel together with a previously prepared entangled quantum state are used to transmit quantum information between two parties.
In quantum cryptography, a classical channel is used along with a quantum channel in protocols for quantum key exchange.
In quantum communication, the information rate of a noisy quantum channel can be increased when used together with a noise-free classical channel.
en.wikipedia.org /wiki/Classical_information_channel   (223 words)

 Quantum Entanglement and Information (Stanford Encyclopedia of Philosophy)
The puzzle is that the quantum state of the particle pair is inconsistent with the assignment of labels to the particles separately that could be associated with appropriately correlated values for the outcomes of position and momentum measurements.
The unit of quantum information is the ‘qubit’, representing the amount of quantum information that can be stored in the state of the simplest quantum system, for example, the polarization state of a photon.
The impossibility of copying an unknown quantum state, or a state that is known to belong to a set of nonorthogonal states with a certain probability, and the existence of a trade-off relation between information gain and state disturbance, is the basis of the application of quantum information to cryptography.
plato.stanford.edu /entries/qt-entangle   (5625 words)

 Quantum channel capacity - Quantiki   (Site not responding. Last check: 2007-10-14)
A quantum channel is a communication channel which can transmit quantum information, as opposed classical information.
Although classical channels cannot transmit quantum information by themselves, they can be useful in combination with quantum channels.
But the quantum channel will not be able to designate either classical information or quantum information, resulting in using either a classical channel or a quantum channel.
quantiki.org /wiki/index.php?title=Quantum_channel_capacity&...   (113 words)

 OUR RESEARCH - QUANTUM CRYPTOGRAPHY   (Site not responding. Last check: 2007-10-14)
Quantum cryptography provides means for two parties to exchange a enciphering key over a private channel with complete security of communication.
The two legitimate users of the quantum channel test for eavesdropping by revealing a random subset of the key bits and checking (in public) the error rate.
However, the act of detection of one particle of a pair destroys its quantum correlation with the other, and the two parties can easily verify whether this has been done, without revealing the results of their own measurements, by communication over an open channel.
eve.physics.ox.ac.uk /NewWeb/Research/crypto.html   (1268 words)

 CRN | Breaking News | Quantum To Acquire Certance, Bring SDLT And LTO Together
Quantum Wednesday said it plans to acquire Certance, one of three suppliers of tape drives and automation products based on LTO-based technology, in a move that could boost the ailing drive maker's position in the high-end backup space.
The channel is an important and growing part of Quantum's business, Belluzzo said, noting that about 45 percent of Certance's revenue came from the channel.
Speaking before a group of solution providers at the company's annual channel summit in San Diego two weeks ago, Scroop said that Quantum's move to focus on capacity was appropriate given that the push to use disk-based backup subsystems for high-speed backups is accelerating.
www.crn.com /showArticle.jhtml?articleID=50900321   (832 words)

 List of Conferences and Seminars   (Site not responding. Last check: 2007-10-14)
In analogy to classical channels, I propose to define the quantum channel capacity as the maximum rate of *mutual entanglement* processed by the channel (for the transmission and storage of quantum entanglement), which reduces to the maximum mutual information processed by the channel for the transmission of classical data.
Quantum trajectory techniques enable one to replace a Markovian master equation with a stochastic differential equation for a single quantum state in Hilbert space; as such, they are useful as quantum Monte Carlo techniques.
The advantages and disadvantages of quantum trajectory simulations for quantum error correction are discussed, along with the results of simulations for simple and fault-tolerant correction algorithms, and the object-oriented code used to generate the results.
qso.lanl.gov /qc/confsem.html   (2340 words)

 CNET Channel
When Quantum, the world’s leading manufacturer of reliable backup, recovery, and archive solutions, says it is a strong channel company, it doesn’t just pay lip service to the phrase.
An important part of Quantum’s channel mix is direct marketers, companies like CDW, Insight, PC Connection, PC Mall, and Zones, that have transformed their businesses from direct-mail catalogs to web-based portals that sell everything from digital cameras to printers to Quantum’s high-end tape automation and disk-based backup products.
Quantum needed to disseminate product content more effectively throughout the channel and have more influence on how its products were marketed.
www.cnetchannel.com /manufacturers/quantum.aspx   (698 words)

 What is the maximum conductance of a single quantum channel?
for a single quantum channel of the general 1D-Fermi-gas type described in Section 7.2.
We try to encourage more current to pass down a single-mode channel (E) by connecting it to a reservoir via multiple routes (A,B,C,D), as shown in Fig 7.4a, where two routes are used on each side.
This illustrates the inextricable link between thermal Fermi occupation of reservoir states and the universal quantum of conductance.
www.math.dartmouth.edu /~ahb/thesis_html/node99.html   (641 words)

 NIST Quantum Information Networks Overview
The telescopes for the quantum channel are being assembled at the lower left.
Classical and quantum physical link layers have been fully integrated and we have observed the generation of sifted quantum key at rates in excess of 3.5 Mbps over the 730 m free-space link.
The maximum rate at which the boards can sift the quantum channel data was increased by a factor of 30 by implementing all sifting functions in the FPGAs, with communications taking place over the primary classical channel (the timing channel).
math.nist.gov /quantum/overview.html   (2350 words)

 Quantum teleportation - Wikipedia, the free encyclopedia
In quantum information, quantum teleportation, or entanglement-assisted teleportation is a technique that transfers a quantum state to an arbitrarily distant location using a distributed entangled state and the transmission of some classical information.
Assume that this quantum state is not known to Alice and she would like to send this state to Bob.
Quantum telecloning: Captain Kirk's clone and the eavesdropper
en.wikipedia.org /wiki/Quantum_teleportation   (1804 words)

 Peter Shor's Publications
Many of my quantum computing papers have appeared on the Los Alamos preprint server and not have been put here yet, since I don't update this page often enough, or completely---if a paper is available on the preprint server, I don't take the trouble to put it here.
The adaptive classical capacity of a quantum channel, or information capacities of three symmetric pure states in three dimensions.
This paper presents a family of quantum error-correcting codes whose capacity (slightly) exceeds that of random coding for very noisy channels; random codes had previously been conjectured to be optimal.
www-math.mit.edu /~shor/elecpubs.html   (1751 words)

 INI : Abstracts : QIS_FOCUS : Unlocking of a Quantum Channel's Forward Classical Capacity by Classical Communicat   (Site not responding. Last check: 2007-10-14)
Classical back communication does not increase a classical channel's forward capacity, but for quantum channels the situation is more complicated.
We have found channels whose Holevo capacity is almost zero, but whose quantum and classical capacities in the presence of classical back communication are quite large.
The greater complexity of the situation with quantum channels stems from the fundamental difference between entanglement and its closest classical analog, shared secret randomness.
www.newton.cam.ac.uk /programmes/QIS/Abstract3/bennett.html   (133 words)

 Citations: Some estimates of the information transmitted by quantum communication channel - Holevo (ResearchIndex)
Suppose that for each x a quantum state with density matrix x is prepared in a quantum register Z, i.e.
It is worthwhile to mention also that this bound is closely related to the fundamental property of decrease of quantum relative entropy under completely positive maps developed in [Lindblad 1973 1975] and in [Uhlmann 1977] see [Yuen and Ozawa 1993] for history and some generalizations of the....
We consider quantum channel [4] with a finite input alphabet f1; ag and with pure signal states S i = j i i j; i = 1; a.
citeseer.ist.psu.edu /context/192100/0   (2004 words)

 Physics 219 Course Information
Quantum Computation and Quantum Information by Michael Nielsen and Isaac Chuang, will be available in the fall of 2000.
Therefore, since the physical world is fundamentally quantum mechanical, the foundations of information theory and computer science should be sought in quantum physics.
A quantum computer will be much more vulnerable than a conventional digital computer to the effects of noise and of imperfections in the machine.
www.theory.caltech.edu /people/preskill/ph229   (1052 words)

 Special Report on Quantum World - New Scientist
Quantum objects can exist in multiple states and places at the same time, requiring a mastery of statistics to describe them.
Quantum entanglement, a strange property that links particles however far apart they are, may be used to "teleport" information, new research reveals
Attempts to reconcile the theories of general relativity and quantum mechanics, to develop a unified theory of everything, could be boosted by lasers
www.newscientist.com /channel/fundamentals/quantum-world   (1487 words)

Quantum Corp. (NYSE:QTM) is the leading global storage company specializing in backup, recovery and archive.
Quantum Corp., 1650 Technology Drive, Suite 700, San Jose, CA 95110, (408) 944-4000, www.quantum.com.
Quantum and the Quantum logo are trademarks of Quantum Corporation registered in the United States and other countries.
www.quantum.com /AboutUs/PressReleases/index.aspx?FullStory=13   (199 words)

 Europhysics Letters (EPL)
We consider transmission of classical information through a quantum channel from one sender to several receivers.
In contrast to quantum information, classical information carried by two non-orthogonal states of a quantum system can be cloned exactly.
The capacity of the corresponding quantum channel is considered.
www.edpsciences.org /articles/epl/abs/2000/12/6132/6132.html   (141 words)

 INI : Abstracts : QISW04 : Differetial geometry of quantum channel estimation   (Site not responding. Last check: 2007-10-14)
INI : Abstracts : QISW04 : Differetial geometry of quantum channel estimation
Since almost every quantum protocol assumes a priori knowledge of the behavoir of the quantum channel under consideration, there is no doubt that identifying the channel is of fundamental importance in quantum information theory.
In this talk, I will review some recent developments in quantum channel estimation theory, putting emphasis on an active interplay between noncommutative statistics and information geometry.
www.newton.cam.ac.uk /programmes/QIS/Abstract4/Fujiwara.html   (90 words)

 William Wootters
In past years my students and I have studied the classical capacity of a quantum channel and the amount of information one can extract from a single quantum object.
Entanglement is a peculiarly quantum mechanical kind of correlation that has no analogue in classical physics.
It is the essential ingredient in such phenomena as superdense coding, in which any of four possible messages can be transmitted via a single binary quantum object, and teleportation, in which a quantum state is transmitted from one location to another without passing through the intervening space.
www.williams.edu /Physics/wwootters   (766 words)

 CiteULike: Quantum Information Theory   (Site not responding. Last check: 2007-10-14)
Quantum information theory is the study of the achievable limits of information processing within quantum mechanics.
Exploring the rich variety of capabilities allowed by these types of information is the subject of quantum information theory, and of this Dissertation.
Many di erent types of information can be accommodated within quantum mechanics, including classical information, coherent quantum information, and entanglement.
www.citeulike.org /user/kevina/article/680974   (184 words)

 Toshiba maps quantum future | Channel Register
Shields said his team are well on the way to solving this problem, which cuts down both the bit rate that quantum-encrypted fibre can run at, and the distance the signal can travel, limited to around 120km.
Advances in "quantum teleportation" will mean keys can be sent anwhere in the world with complete security.
Before a full-blown quantum crypto industry can emerge, he added, standards will have to be developed so that customers know what they're getting.
www.channelregister.co.uk /2006/04/24/toshiba_quantum   (420 words)

 Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations   (Site not responding. Last check: 2007-10-14)
The method is applied to a specific example of a symmetric N-state quantum channel that frequently appears in the analysis of eavesdropping in quantum key distribution protocols.
The numerical results for the accessible information of this quantum channel are compared with recently published analytical solutions showing excellent agreement.
Furthermore, interesting results concerning the capacity of a symmetric quantum channel are presented.
www.osti.gov /energycitations/product.biblio.jsp?osti_id=20653267   (223 words)

 Free-space quantum channel
For this experiment, our quantum channel was maintained for a total of 40 minutes during which time a coincidence lock found approximately 60000 coincident detection events.
This result is promising for entanglement-based freespace quantum communication in high-density urban areas.
It is also encouraging for optical quantum communication between ground stations and satellites since the length of our free-space link exceeds the atmospheric equivalent.
www.quantum.at /research/quantum-teleportation-communication-entanglement/free-space-quantum-channel.html   (234 words)

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