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Research projects in our group

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The Quantum Metrology group currently follows two research topics: (1) the search for physics beyond the standard model using precision measurements in the field of quantum optics, and (2) the development of optical clocks and related technologies.

Both research lines are extremely exciting.

Both are very timely and at the forefront of current research.

And both build on our most favorite platform, alkaline-earth atoms.

Our research is structured into four different projects: 

 

The quMercury project: Quantum gases for a measurement of the atomic EDM of mercury

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The Universe contains substantially more matter than antimatter. What is the reason for this imbalance, why does Nature favor matter over antimatter? This is one of the most challenging problems in fundamental physics, and we are taking a new approach to tackle this problem. The matter/antimatter imbalance is connected to a quantity named electric dipole moment (EDM): a small deformation of the charge distribution of fundamental particles. The current best measurements of this EDM have been performed with gases of mercury atoms at room temperature.

Now, we will take this experiment to the quantum world: we will prepare quantum-degenerate Fermi gases of mercury as the basis of our measurements, which shall improve measurement sensitivity by two orders of magnitude. Ultracold samples of mercury have not yet been studied, so the preparation of Bose-Einstein Condensates (BECs) and Degenerate Fermi Gases is the first step along this road. These systems can also be employed as platforms for novel schemes of quantum simulation and hold the potential to improve the world’s best optical clocks. All of the cooling transitions in mercury are in the UV range 185 and 254 nm), where quite a bit of development in laser technology will be required.

Welcome to the challenge of setting up one of the world’s leading experiments for quantum simulations and EDM measurements! 

 

The CalciumClock project: Robust clocks for application outside the lab

 03_Logo_CalciumClock_rgb.pngThe world’s finest optical clocks reach a stunning fractional uncertainty in the 10-19 range: they would be off by less than a millisecond when operated over the age of the Universe. Equally impressive, they are sensitive to the gravitational redshift in the Earth’s gravitational field that corresponds to a height difference of about 1 cm.

The usage of these dedicated optical clocks with a performance in the 10-19 range is certainly limited to very few metrology labs. For industrial applications (e.g. timekeeping or synchronization of networks), a performance comparable to hydrogen masers (fractional uncertainty in the 10-16 range) would be sufficient.

In this project, we aim to develop rugged and small optical clocks with an uncertainty in the 10-16 range, to be employed outside a quantum optics laboratory. A number of such clocks will be connected via the existing telecom infrastructure to form a network of phase-stabilized network nodes.

We chose beam clocks of alkaline-earth metal atoms as the platform for our devices. Such clocks, using calcium as the atomic species (linewidth 370 Hz) have been pioneered by the NIST group, and we will follow their footsteps. To test their performance, we will put one of these clocks into an elevator: based purely on the gravitational redshift, we will use the reading of the clock to tell at which floor the elevator is.

The transition wavelength in calcium is at 657 nm, far away from the infra-red wavelength used in telecommunication. We will use wavelength conversion in nonlinear crystals to convert light at infra-red wavelength to the visible wavelength range.

On this project, we cooperate with the Max Planck Institute for Radio Astronomy (MPIfR) to explore the suitability of these clocks for the synchronization of arrays of radio telescopes, as well as with the geodesy people from the University of Bonn. The development of such clocks is perfectly aligned with the current Quantum Flagship initiative of the European Union. 

The OT4Q project: Optical technologies for quantum computation

 

The ML4Q collaboration is a recently established network between the universities of Aachen, Cologne, and Bonn, as well as the FZ Jülich. The acronym "ML4Q" means Light and Matter for Quantum Communication, so that's what this project is about: the development of concepts and devices for future quantum computing. Within this Cluster of Excellence, we will develop optical technologies required for large-area communication, for example wavelength conversion at the single-photon level, which is required to link platforms operating at different wavelengths.

Also, we investigate the element Zinc as candidate for very robust and compact optical clocks, which might then be used for network synchronization. 

   

 

The Pulsars&Clocks project: Linking pulsars and optical clocks

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Pulsars are neutron stars in our galaxy that rotate at a very stable frequency, sending out radiowaves that can be detected on Earth as pulses. The arrival time of these pulses is perturbed by various effects, such as processes in the neutron star itself, the orbit of Earth around the sun, and even gravitational waves! Thus, measuring the arrival times of the pulses very precisely allows us to study all these effects. Time-keeping is currently limited by the performance of the maser used for this purpose, and we investigate ways to improve the maser performance through updates from an optical clock.

In addition, we search for ways in which the extreme long-term stability of pulsars (after all, they have been rotating already for many million years) can utilized to improve the long-term stability of optical clocks, which tend to drift away after some time. 

 

 

 

 

Startup funding for these research projects is provided by the University of Bonn, the European Union (ERC Starting Grant 2017), the SFB/TR 185 “OSCAR”, and the Deutsche Forschungsgemeinschaft (DFG).

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