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In the global quest to develop practical computing and communications devices based on the principles of quantum physics, one potentially useful component has proved elusive: a source of individual particles of light with perfectly constant, predictable, and steady characteristics. Now, researchers at MIT and in Switzerland say they have made major steps toward such a single photon source.
The study, which involves using a family of materials known as perovskites to make light-emitting particles called quantum dots, appears today in the journal Science. The paper is by MIT graduate student in chemistry Hendrik Utzat, professor of chemistry Moungi Bawendi, and nine others at MIT and at ETH in Zurich, Switzerland.
Ability - Photons - Properties - Wavelength - Color
The ability to produce individual photons with precisely known and persistent properties, including a wavelength, or color, that does not fluctuate at all, could be useful for many kinds of proposed quantum devices. Because each photon would be indistinguishable from the others in terms of its quantum-mechanical properties, it could be possible, for example, to delay one of them and then get the pair to interact with each other, in a phenomenon called interference.
"This quantum interference between different indistinguishable single photons is the basis of many optical quantum information technologies using single photons as information carriers," Utzat explains. "But it only works if the photons are coherent, meaning they preserve their quantum states for a sufficiently long time."
Researchers - Sources - Photons - Limitations - Fluctuations
Many researchers have tried to produce sources that could emit such coherent single photons, but all have had limitations. Random fluctuations in the materials surrounding these emitters tend to change the properties of the photons in unpredictable ways, destroying their coherence. Finding emitter materials that maintain coherence and are also bright and stable is "fundamentally challenging," Utzat says. That's because not only the surroundings but even the materials themselves "essentially provide a fluctuating bath that...
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