Physicists from the Institute of Science and Technology Austria (IST Austria) used a mechanical oscillator to produce entangled radiation. According to the research team, this is the first time a mechanical object has been used to create entangled radiation. Beyond its significance for fundamental physics, such a device could someday be used to link sensitive quantum computers with the optical fibers that connect computer networks. Classical computers are typically connected through optical fibers, because optical radiation is robust against disturbances that could corrupt or destroy data. In order to apply this technology to quantum computers, a link that can convert the quantum computer’s microwave photons to optical information carriers, or a device that generates entangled microwave-optical fields as a resource for quantum teleportation, would be required. Such a link or device could serve as a bridge between the room- temperature optical and the cryogenic quantum world. “What we have built is a prototype for a quantum link,” researcher Shabir Barzanjeh said. This is an illustration of a prototype of what may, in the future, serve as a link to connect quantum computers. Courtesy of IST Austria/Philip Krantz, Krantz NanoArt. The device could also be used to improve the performance of gravitational wave detectors, the researchers said. “It turns out that observing such steady-state entangled fields implies that the mechanical oscillator producing it has to be a quantum object,” professor Johannes Fink said. “This holds for any type of mediator and without the need to measure it directly, so in the future our measurement principle could help to verify or falsify the potentially quantum nature of other hard-to-interrogate systems like living organisms or the gravitational field.” In addition to its practical value, the experiment to generate entangled radiation using a mechanical oscillator interested the researchers at a fundamental level. With a length of 30 μm and a composition of about a trillion (1012) atoms, the silicon beam created by the group would be considered large by quantum standards. “The question was: Can one use such a large system to produce nonclassical radiation? Now we know that the answer is yes,” Barzanjeh said. The research was published in Nature (https://doi.org/10.1038/s41586-019-1320-2).