Introduction
Thirty years after first proposals to use spin-squeezed states in spectroscopy, we are now on the cusp of achieving realisations of a gain from entangled states in the next generation of frequency metrology with optical transitions. Entanglement in optical clock transitions has been demonstrated with neutral atoms in optical cavities and with Rydberg atoms in a programmable tweezer array. A gain beyond the quantum projection noise limit was obtained by correlated ensembles in the direct comparison of two spin squeezed optical clocks and in differential frequency measurement between two separate Sr+ ion setups using entangled states. Improving the absolute stability of optimised state-of-the-art atomic clocks with entanglement remains an as yet unachieved goal, and a variety of further steps of a technical and conceptual nature will be necessary to achieve it.
Around this overarching goal, various theoretical questions were investigated during the last funding period in the framework of project A06. Since this project will be terminated the research strand from A06 on theoretical aspects of frequency metrology and precision spectroscopy, as well as the related close and fruitful collaboration with the projects B02, B03, and A07, will be continued within the new project A09.
Objectives
In this research project, our primary focus is to advance the field of atomic clocks and quantum measurements. We aim to explore novel concepts and tools that will lead to the realisation of entanglementenhanced atomic clocks. Our investigations target a number of specific questions and challenges.
- Optimal Metrological Protocols: We will develop protocols that strike the right balance between interro- gation time and decoherence due to laser noise and spontaneous emission
- Quantum Gates for Trapped Ion Clocks: Trapped ion clocks have specific requirements, and we will design quantum gates tailored to meet these needs, enabling entanglement-enhanced protocols
- Exploring Squeezing via QND measurements in Optical Atomic Clocks: Recent experiments have demon- strated entangled states on clock transitions and improved clock comparison with spin squeezing gener- ated by Quantum-Nondemolition (QND) measurements. We will investigate clock protocols with QND measurements for state preparation and for readout, similar to what has been considered before for squeezing based on one-axis-twisting operations as generated with trapped-ion quantum gates.
- Mass defect in clocks and Penning traps: We will extend the ab-initio treatment of the mass defect in ion clocks to develop theoretical frameworks for tailored quantum states of motion in ion crystals, aiming to experimentally test the quantum mechanical nature of the mass defect
Through this research, we aim to push the boundaries of sensitivity and accuracy in atomic clocks, unlocking their potential for applications such as determining fundamental constants, testing general relativity, and enabling real-world applications in gravimetry and inertial navigation. Furthermore, our work will contribute valuable insights into quantum control and measurements with trapped ion and Penning trap systems.
Project leader
30167 Hannover
