Success Story: Quantum-enhanced gravitational wave detection

Developing the world’s best squeezed-light sources in Hannover has been central to achieving the incredible sensitivity of the current gravitational wave detectors. GEO600 was the first detector to routinely employ non-classical light, and QuantumFrontiers researchers hold the record for the highest degree of fixed-quadrature squeezing (6 dB) in a full-scale gravitational wave detector to date [1]. They built and installed the fixed-quadrature squeezed-light source for Advanced Virgo [2, 3], leading to increased astrophysical reach [4], and provided crucial input to the high-power laser system for aLIGO [5, 6], leading to the detectors’ sensitivity that enabled the first direct detection of gravitational waves and allowed these detectors to operate in unison as part of the global detector network.

To enable future gravitational wave detectors with enhanced sensitivity, poised for making groundbreaking astrophysical and fundamental physics discoveries, QuantumFrontiers researchers have produced frequency-dependent squeezed light without external filter cavities [7], have achieved a noise reduction of over 13 dB at the laser wavelength of 1550 nm [8] and have observed squeezing in higher-order transversal modes. [9] 

These achievements have set the LISA mission on track for a mid-2030s launch, with QuantumFrontiers scientists being responsible for the interferometric detection system, phasemeter development, and noise performance studies. “Beyond LISA” efforts include miniaturising optical sensors [15], developing a torsion balance as a force testbed [16], and mitigating optical noise sources [17].

Finally, principal investigators from QuantumFrontiers play a key role in infrasound GWD using matter-wave interferometry. In the terrestrial VLBAI collaboration, various detector concepts were explored [18] with partners in the USA (MAGIS) and China (ZAIGA). 10-meter-scale prototypes are operationally ready, including the VLBAI facility in Hannover. Under European Laboratory for Gravitation and Atom-interferometric Research (ELGAR), QuantumFrontiers researchers are preparing studies for a pan-European infrastructure for a 3D infrasound GWD antenna, including squeezed atomic sources.