Quantum Variational Optimization of Ramsey Interferometry and Atomic Clocks

authored by
Raphael Kaubruegger, Denis V. Vasilyev, Marius Schulte, Klemens Hammerer, Peter Zoller

We discuss quantum variational optimization of Ramsey interferometry with ensembles of \(N\) entangled atoms, and its application to atomic clocks based on a Bayesian approach to phase estimation. We identify best input states and generalized measurements within a variational approximation for the corresponding entangling and decoding quantum circuits. These circuits are built from basic quantum operations available for the particular sensor platform, such as one-axis twisting, or finite range interactions. Optimization is defined relative to a cost function, which in the present study is the Bayesian mean square error of the estimated phase for a given prior distribution, i.e. we optimize for a finite dynamic range of the interferometer. In analogous variational optimizations of optical atomic clocks, we use the Allan deviation for a given Ramsey interrogation time as the relevant cost function for the long-term instability. Remarkably, even low-depth quantum circuits yield excellent results that closely approach the fundamental quantum limits for optimal Ramsey interferometry and atomic clocks. The quantum metrological schemes identified here are readily applicable to atomic clocks based on optical lattices, tweezer arrays, or trapped ions.

Institute of Theoretical Physics
Institute of Gravitation Physics
CRC 1227 Designed Quantum States of Matter (DQ-mat)
External Organisation(s)
University of Innsbruck
Austrian Academy of Sciences
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
Physical Review X
Publication date
Publication status
Peer reviewed
ASJC Scopus subject areas
Physics and Astronomy(all)
Electronic version(s)
http://10.48550/arXiv.2102.05593 (Access: Open)
https://doi.org/10.1103/PhysRevX.11.041045 (Access: Open)