2019/11/30 by Marius Schulte, Victor J. Martínez-Lahuerta, Maja S. Scharnagl +1 · 1 citation
Physics and Astronomy · #quant-ph #physics.atom-ph
paper · pdf · doi:10.22331/q-2020-05-15-268
published as Quantum 4, 268 (2020) · 11+8 pages, 7 figures, comments welcome! ; accepted version
arxiv created 2020/04/27 · arxiv updated 2020/05/20
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. These results can be applied even when experimentally relevant decoherence processes during the squeezing and un-squeezing interactions are included. Noise between the two interactions is however not considered in this work. This provides a generalized 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.