Bayesian Frequency Metrology with Optimal Ramsey Interferometry in Optical Atomic Clocks

TL;DR

This paper develops a Bayesian theoretical framework to optimize Ramsey interrogation schemes in optical atomic clocks, balancing sensitivity and robustness against laser noise for next-generation precision timekeeping.

Contribution

It introduces a comprehensive Bayesian approach to identify optimal states and measurement strategies, including variational protocols, for enhanced clock stability.

Findings

Identifies new optimal interrogation schemes for various experimental conditions.

Analyzes trade-offs between entanglement-enhanced sensitivity and noise robustness.

Provides a benchmark based on fundamental Bayesian estimation bounds.

Abstract

Frequency metrology is a cornerstone of modern precision measurements and optical atomic clocks have emerged as the most precise measurement devices. In this progress report, we explore various Ramsey interrogation schemes tailored to optical atomic clocks primarily limited by laser noise. To incorporate frequency fluctuations directly into the theoretical model, we consider a Bayesian framework. In this context, we review fundamental bounds arising in Bayesian estimation theory, which serve as a benchmark throughout this work. We investigate the trade-off between entanglement-enhanced sensitivity and robustness against laser noise in order to identify optimal initial states, measurement schemes and estimation strategies. Beside standard protocols based on coherent spin states, squeezed spin states and GHZ states, we consider variational Ramsey protocols implemented via low-depth quantum circuits based on one-axis twisting operations to approach optimal stability. In particular, we review known and identify new optimal interrogation schemes for a variety of scenarios, including different experimental platforms, ensemble sizes and regimes characterized by a wide range of interrogation durations and dead times. Hence, this work establishes a comprehensive theoretical framework for optimizing Ramsey interrogation schemes, providing guidance for the development of next-generation optical atomic clocks.