Final Report Summary - MASSQ (Massive-Object Quantum Physics)
The ERC-project MassQ was launched to explore quantum physics in the realm of what humans can see with their naked eyes, whose weight they can feel, and whose vibrations they can hear. To this end, a super-polished laser mirror with a mass of 100g was hung with extremely thin wires as a 25cm-long pendulum, whose positions could be precisely monitored with the technology used in gravitational-wave detectors. The setup was isolated from any influences of the environment such as seismic vibrations. It was placed on a self-built seismic isolation platform with a designed suppression of environmental motion by twenty orders of magnitudes at the chosen measurement frequency of 600Hz. A laser interferometer with a squeezed quantum uncertainty of the photon statistics was designed for reading out the 600Hz-overtone motion of the pendulum with a precision at the mechanical zero-point fluctuation. The final goal was to prepare two such mirrors in an Einstein-Podolsky-Rosen (EPR) entangled state. This goal, challenging as it was, has not yet been achieved but is being followed up at Hamburg University. The outcomes of the project so far are mature laser technology at the wavelength of 1550nm for future gravitational-wave (GW) observatories but also for quantum communication networks, a new approach for ultra-low-noise damping of pendulum motion, which might also find applications in future GW observatories, and a passive seismic isolation technology for ultra-high precision measurements.