Hannover 2020 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 14: Precision Measurements and Metrology

Q 14.2: Talk

Tuesday, March 10, 2020, 11:15–11:30, a310

Complete theory of Ramsey interferometry with squeezing echos — •Marius Schulte, Victor J. Martínez-Lahuerta, Maja S. Scharnagl, and Klemens Hammerer — Institute for Theoretical Physics and Institute for Gravitational Physics (Albert-Einstein-Institute), Leibniz University Hannover

We consider a large class of Ramsey interferometry protocols which are enhanced by squeezing and un-squeezing operations before and after a phase signal is imprinted on the collective spin of N particles. We report an analytical optimization for any given particle number and strengths of (un-)squeezing, including experimentally relevant decoherence processes. This provides a complete characterization of squeezing echo protocols, recovering a number of known quantum metrological protocols as local sensitivity maxima, thereby proving their optimality. We discover a single new protocol. Its sensitivity enhancement relies on a double inversion of squeezing. In the general class of echo protocols, the newly found over-un-twisting protocol is singled out due to its Heisenberg scaling even at strong collective dephasing. arXiv:1911.11801