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There are differences between the group's demonstrations. For crystals, Tittel's group used thulium-doped lithium niobate, whereas Gisin's group opted for neodymium-doped yttrium silicate. In addition, a different type of laser set-up has favoured Gisin's group, which reports a maximum storage time of some 200 ns at an efficiency of more than 20%; Tittel's group reports a storage time of 7 ns at an efficiency of 2%. On the other hand, the quantum memory of Tittel's group functions at a bandwidth of 5 GHz - some 40 times greater than Gisin's group - which means, potentially, far more information could be sent in the same time.

Engineers at Stevens Institute of Technology have developed a technique to optically modulate the frequency of a laser beam and create a signal that is disrupted significantly less by environmental factors, says Dr. Rainer Martini. The research provides for enhanced optical communications, allowing mobile units not tied to fiber optic cable to communicate in the range of 100 GHz and beyond, the equivalent of 100 gigabytes of data per second. Eventually, the team hopes to extend the reach into the terahertz spectrum. The frequency or amplitude modulation of middle infrared quantum cascade lasers has been limited by electronics, which are barely capable of accepting frequencies of up to 10 GHz by switching a signal on and off.  Marini and his team have developed a method to optically induce fast amplitude modulation in a quantum cascade laser to control the laser's intensity. Their amplitude modulation system employed a second laser to modulate the amplitude of the middle infrared laser, using light to control light. The current detector is only capable of detecting frequencies up to 10 GHz, but Dr. Martini is confident that a new detector will make the system capable of much higher frequencies. With an optical system that is stable enough, satellites may one day convert to laser technology, resulting in a more mobile military and super-sensitive scanners, as well as faster Internet for the masses, says Martini. Ref.: "Optically induced fast wavelength modulation in a quantum cascade laser," Applied Physics Letters, July 7, 2010.

(PhysOrg.com) -- An international team has removed a major obstacle to engineer quantum systems that will play a key role in the computers, communication networks, and even biomedical devices of the future.