Miniature Trapped Ion Clock on a Chip – MITICC

Today’s most accurate frequency standards are realized by optical transitions in trapped ions. Laboratory setups have reached relative frequency accuracies below the 10-17 level, owed by the use of an optical transition frequency, a tremendous level of technical noise reduction and exquisite experimental control. There is an academic as well as industrial need for compact atomic clocks with good frequency stabilities: observatories, very-long baseline interferometry, particle accelerators, GPS, telecommunications, all require a stable frequency reference for timekeeping purposes. The current compact atomic clocks are liter-sized with a 10-12 at 1 s relative frequency stability, and the 10-13 level will soon be commercially available. There will be a strong need for even better clocks in the future, and research needs to be undertaken towards this goal. In particular, fundamental physics tests, geodesic measurements, time and frequency distribution for satellite networks would directly benefit from compact clocks with improved frequency stabilities.

The goal of the MITICC project is to design and develop a compact system for single ions trapping, with the mid-term objective of realizing an optical atomic clock with a relative frequency stability of 10-14 or better in a volume of about 100 liters. These performances will be granted both by the use of laser-cooled ions, and by the very high (>10^14 Hz) clock frequency. The experiment will be based on the trapping of Yb+ ions with a micro-fabricated circuit (“chip”). Surface electrodes will generate a trapping potential, localizing the ions a few hundreds of µm from the chip. The chip will be placed face-down on a glass cell pumped to ultra-high vacuum. The ions will be laser-cooled to a temperature of about 1 mK.

The project will include the design and experimental characterization of the trap. Measurements of the trap lifetime, heating rate and coherence time will be performed. The optical transition coherence will be characterized by spectroscopy. Long trapping and coherence times along with low heating rates have not yet been demonstrated for room-temperature, surface-electrode ion traps. Such traps have thus mostly been used for Quantum Information Processing (QIP). A compact ion trapping setup compatible with the demands of Time and Frequency (TF) metrology will benefit to both fields. It will of course have a strong impact in the TF metrology field, but also for a number of applications, including telecommunications, navigation…

A prototype Si chip will be designed and produced as well. It will rely on MEMS (Micro Electro Mechanical Systems) technologies and feature an integrated micro-oven at the back of the chip to supply the neutral Yb atoms. This will further reduce the dimensions of the setup and allow for back-loading of the chip, thus avoiding unwanted coating of surfaces by Yb atoms.

The project will be conducted within the TF department of FEMTO-ST in Besançon. It will benefit from its world-renowned expertise in the fields of metrology and MEMS and from interactions with PIA projects (Programme d’Investissements d’Avenir). The OSCILLATOR-IMP Equipex will allow for phase-noise measurements of oscillators from MHz to optical frequencies. FEMTO-ST is also a kernel partner of the FIRST-TF Labex that coordinates the French TF metrology laboratories and their partners, increasing the TF projects visibility. The chip itself will be produced inside FEMTO-ST technologic central (MIMENTO), which features state-of-the-art microfabrication equipment. The chip design will benefit from the expertise of the Micro Nano Science and Systems (MN2S) department. The MITICC team will also interact with two major actors in the French ion trappers community, the CIML team in Marseille and the IPIQ team in Paris.