Autonomous Multi-Ion Optical Clock with On-Chip Photonics Achieves Stability Using Four Yb+ Ions

The pursuit of portable, precise timekeeping and scalable quantum computing demands increasingly integrated technologies, and a team led by Tharon D. Morrison, Joonhyuk Kwon, and Matthew A. Delaney at Sandia National Laboratories has achieved a significant step forward in this area. They demonstrate a fully autonomous multi-ion optical clock, operating with exceptional stability using an ensemble of yttrium ions. This clock uniquely integrates all necessary optical components onto a single chip, delivering light via on-chip waveguides and automating ion management to maintain performance over extended periods. The achievement represents a crucial move beyond individual component demonstrations, establishing a robust and scalable architecture for future portable atomic clocks and quantum computers.

Autonomous Multi-Ion Clock with Integrated Photonics

This research presents a fully autonomous multi-ion optical clock built on a microfabricated silicon nitride photonic integrated circuit. The system demonstrates a crucial advancement for applications like distributed quantum sensors and scalable quantum computers, simultaneously trapping and cooling up to eight ions. Light is delivered to each ion via a single optical fibre and integrated beam steering elements, simplifying optical setups, reducing system size, and enhancing long-term stability. The clock operates using a specific transition in ytterbium ions, achieving a fractional frequency stability of 2.

8x 10 -18 at one second, with a systematic uncertainty of 1. 1x 10 -17 . This level of precision represents a significant step towards compact, high-performance optical clocks for fundamental physics research and precision metrology. The on-chip integration of light delivery and ion trapping streamlines the system and improves its overall performance.

The team overcame challenges related to maintaining a stable ion population by implementing an automated system for ion shuttling and reloading, mitigating ion loss during continuous clock measurements and ensuring uninterrupted operation. This achievement moves beyond component-level demonstrations, paving the way for fully integrated and robust quantum systems.

Multi-Ion Quantum Clock with Integrated Waveguides

This research details the construction and operation of a highly stable quantum clock using multiple trapped ions, leveraging their collective properties to achieve high precision and stability. A key innovation is the use of integrated waveguides for both ion loading and clock interrogation, alongside a sophisticated system for managing ion loss and replacement. The system confines individual ions within a Paul trap, utilising radio frequency and direct current fields. Integrated waveguides are essential for delivering laser light for ion trapping, cooling, and precise clock interrogation, employing multiple lasers for cooling, tuning to the clock transition frequency, and preparing and detecting quantum states.

The system manages multiple ions simultaneously, tracking each ion’s presence and automatically replacing any that are lost through a sophisticated algorithm and pre-defined shuttling scenarios. A key challenge is the relatively high heating rate of the ions, which limits achievable clock resolution, potentially stemming from imperfections in trap fabrication, charging of the waveguides, and Johnson noise. The clock protocol involves probing the ions with a laser tuned to the clock transition frequency and detecting their state through fluorescence, stabilising the clock frequency with a feedback loop utilising second-order integrators. The algorithm reports ion presence and data every 0. 47 seconds, identifying lost ions based on a lack of fluorescence. Future work will focus on reducing the heating rate, improving trap fabrication, optimising the ion shuttling process, and implementing better control of stray fields, pushing the boundaries of quantum clock technology and demonstrating the potential of integrated waveguides and robust multi-ion management systems.

Integrated Ytterbium Clock Achieves Record Stability

This research demonstrates a fully functional, autonomously operating optical clock built using trapped ytterbium ions and integrated photonic circuits, achieving a fractional frequency instability of 3. 14(5) x 10 -14 /√τ. This represents a significant step towards practical, portable timekeeping devices, overcoming limitations in ion lifetime through automated ion shuttling and reloading, maintaining continuous clock operation during measurements. The team successfully integrated all necessary clock functionalities onto a single chip, paving the way for scalable and deployable atomic clocks and quantum computing architectures.

Measurements confirm that individual trapping sites exhibit minimal frequency differences, ensuring clock accuracy and stability. While acknowledging current limitations stemming from vacuum pressure and heating rates, the researchers highlight potential improvements through the use of more suitable ultra-high vacuum materials and the implementation of side-band cooling techniques. Better optical coupling and conductive coatings on grating windows could further enhance performance by improving contrast and coherence times, establishing a robust platform for future development of highly accurate and versatile quantum technologies.