Explore cutting-edge concepts in quantum metrology and vector field sensing through this conference talk by Peter Zoller from the University of Innsbruck. Delivered as part of the Frontiers of Quantum Metrology conference at the Kavli Institute for Theoretical Physics, delve into optimal and variational approaches in quantum metrology. Gain insights into the latest advancements in quantum sensors and their applications in fundamental physics, including dark matter searches and gravitational wave detection. Discover unexpected connections between quantum metrology methods and diverse fields of physics, bridging optics, condensed matter, atomic physics, quantum information, particle physics, and gravitational physics. Benefit from this cross-disciplinary platform that fosters collaboration between theorists and experimentalists, potentially sparking new scientific discoveries and innovative applications in quantum metrology.