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Research group - Macroscopic Quantum Objects

Illustration of the principle of entanglement generation between two mirrors.

Ultra-stable laser light enables precise distance measurements. Laser interferometers can detect a relative position change of two mirrors that is smaller than a hydrogen nucleus. The sensitivity of laser interferometers is even high enough to detect the quantum mechanical positional uncertainty of a macroscopic object, for instance of a thin membrane with a millimeter diameter. 

A couple of years ago it was theoretically shown that the motion of such a mechanical device can be entangled with reflected laser light. In 2008, this research group showed that ultimately even two such objects in a laser interferometer can become entangled with each other (figure). 

Within QUEST, this research group proposed a new interferometer which is particularly suitable for the observation of the quantum mechanical properties of macroscopic objects: a Michelson-Sagnac interferometer, which is a combination of two well-known interferometer types. It also permits the investigation of partially transmissive objects and enables the application of enhancement resonators, such as power-recycling and signal-recycling resonators. The scientists have already been able to run such an interferometer with a laser power sufficient to observe the positional uncertainty of the membrane inside. The next step will be cooling of the membrane in order to reduce the currently too high Brownian motion of the membrane.