Mechanical quanta see the light

Quantum physics is increasingly becoming the scientific basis for a plethora of new "quantum technologies". These new technologies promise to fundamentally change the way we communicate, as well as radically enhance the performance of sensors and of our most powerful computers. One of the open challenges for practical applications is how to make different quantum technologies talk to each other.

Presently, in most cases, different quantum devices are incompatible with one another, preventing these emerging technologies from linking, or connecting, to one another. One solution proposed by scientists is to build nanometer-sized mechanical objects that vibrate back-and-forth, just like a tiny vibrating tuning fork. These "nanomechanical devices" could be engineered such that their vibrations are the mediator between otherwise different quantum systems.

For example, mechanical devices that convert their mechanical vibrations to light could connect themselves (and other devices) to the world's optical fibre networks, which form the Internet. An outstanding challenge in quantum physics has been building a nanomechanical device that convert quantum-mechanical vibrations to quantum-level light, thus allowing one to connect quantum devices to a future quantum Internet.

Researchers led by Simon Gröblacher at TU Delft and Markus Aspelmeyer at the University of Vienna have now realized just such a nanomechanical device. It converts individual particles of light, known as photons, into quantum-mechanical vibrations, known as phonons, and then back again, as reported today in the journal Nature ("Non-classical correlations between single photons and phonons from a mechanical oscillator").