IQI Weekly Seminar

Abstract: Quantum physics holds the promise of enhanced performance in metrology and sensing by exploiting non-classical phenomena such as multiparticle interference. Specific designs for quantum-enhanced schemes need to take into account noise and imperfections present in real-life implementations. This talk will review selected recent results in realistic quantum metrology, starting from interferometric phase estimation with common impairments, such as photon loss, and ending with general scaling laws implied by the geometry of quantum channels. In many situations, although qualitatively improved asymptotic scaling of ideal noise-free protocols is lost, quantum physics can usefully offer performance beyond the standard shot noise limit. As a concrete example, a comparison of the fundamental quantum interferometry bound with the recently achieved sensitivity of the squeezed-light-enhanced GEO600 gravitational wave detector indicates its nearly optimal operation given the present amount of optical loss. Finally, the potential of mode-engineering techniques exploiting multiple degrees of freedom to alleviate deleterious effects induced e.g. by residual distinguishability in multiphoton interference is highlighted.