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Posted: May 23rd, 2012 Efficient and tunable interface for quantum networks ( Nanowerk News ) Quantum computers may someday revolutionize the informationworld. But in order for quantum computers at distant locations tocommunicate with one another, they have to be linked together in anetwork. While several building blocks for a quantum computer havealready been successfully tested in the laboratory, a networkrequires one additonal component: a reliable interface betweencomputers and information channels. In the current issue of thejournal Nature , physicists at the University of Innsbruck report the constructionof an efficient and tunable interface for quantum networks. Quantum technologies promise to redefine the landscape ofinformation processing and communication. We already live in aninformation age, in which vast amounts of data are sent around theworld over optical fibers, but future quantum networks may be manytimes more powerful. These networks will require interfaces thatcan transfer information from quantum processors onto lightparticles (photons). Such interfaces will allow optical fibers totransmit information-bearing photons between remote data registers,which are likely to be composed of quantum dots or ions. In contrast to classical information, quantum information can't becopied without being corrupted. Instead, physicists around theworld are searching for ways to transfer quantum informationbetween matter and light using entanglement, the quantum propertyin which the state of one particle depends on the state of asecond. Now, a research team led by Rainer Blatt, Tracy Northup,and Andreas Stute at the University of Innsbruck's Institute forExperimental Physics has demonstrated the first interface between asingle ion and a single photon that is both efficient and freelytunable. At the core of the experiment lies an optical resonator consistingof two highly reflective mirrors. High efficiency and precision The Innsbruck physicists trap a single calcium ion in a so-calledPaul trap and place it between two highly reflective mirrors. Theyexcite the ion with a laser, thereby generating a photon which isentangled with the ion and which is reflected back and forthbetween the mirrors. Custom tuning of the entanglement between ionand photon is possible by adjusting the frequency and amplitude ofthe laser. This technique has two significant advantages overprevious approaches that have entangled atoms with light: "Theefficiency with which we produce entangled photons is quite highand in principle could be increased to over 99 percent," explainsNorthup. "But above all, what this setup lets us do is generate anypossible entangled state." To this end, the frequency and amplitudeof the laser light are carefully chosen so that target collectivestate of the ion and photon is reached. At the core of theexperiment lies an optical resonator consisting of two highlyreflective mirrors. Photons bounce back and forth up to 25,000times between these mirrors, interacting with the ion, beforeescaping through one mirror into an optical fiber. "Along with anefficient entanglement process, we've demonstrated an entangledquantum state between an atom and a photon with the highestprecision measured to date," explains Andreas Stute. Technology for the future The experiment offers important insights into the interaction oflight and matter and may prove useful in constructing quantumcomputers or a future quantum internet. "Whenever we have totransfer quantum information from processing sites to communicationchannels, and vice versa, we're going to need an interface betweenlight and matter," explains Northup. The researchers are supportedby the Austrian Science Fund and the European Union. Their resultsappear in the May 24 issue of Nature ( "Tunable ion hoton entanglement in an optical cavity" ). We are high quality suppliers, our products such as Active Shutter 3D TV Glasses , DLP Active Shutter 3D Glasses for oversee buyer. To know more, please visits DLP Active Shutter 3D Glasses.
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