+++ONLINE COLLOQUIUM+++ DOUBLE FEATURE Dr. Olivier Morin and M.Sc. Fabian Schmid

  • Date: Jul 20, 2021
  • Time: 14:30
  • Speaker: DOUBLE FEATURE Dr. Olivier Morin and M.Sc. Fabian Schmid
  • MPQ, Munich, Germany
  • Location: +++ONLINE KOLLOQUIUM+++
DOUBLE FEATURE Dr. Olivier Morin and M.Sc. Fabian Schmid

Dr. Olivier Morin talks about - "Demonstration of a quantum repeater node“

Quantum repeaters are at the heart of long distance quantum networks. While the main limitation of long distance quantum communication are optical losses, which grow exponentially with distance, the key feature of a quantum repeater lies in the reduction of the effective transmission losses. Although known for about two decades, it remains an experimental challenge to build them. Indeed, the platform used has to show multiple demanding features: efficient light-matter interaction, long coherence time, high fidelity etc. I will present in this colloquium our recent demonstration of a one-node quantum repeater. With the cavity QED arsenal, we actually have all the features needed and can implement the most elementary quantum repeater. Hence, we can observe the losses reduction but also maintain the qubits fidelity to less than 11% errors, a fundamental limit for unconditionally secure communication.

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M.Sc. Fabian Schmid talks about "Towards high-precision spectroscopy of the 1S–2S transition in He+“

Laser spectroscopic measurements on atomic hydrogen provide one of the most precise tests of quantum electrodynamic theory and allow the determination of the Rydberg constant and the proton charge radius. One experimental limitation is that trapping and cooling of atomic hydrogen under conditions suitable for high precision spectroscopy has not yet been achieved. Therefore, these measurements were performed on atomic beams where the thermal motion of the atoms ultimately limits the achievable accuracy.
In this talk, I will report on an experiment we are setting up to perform spectroscopy on the 1S-2S transition in the simplest hydrogen-like ion, He+. Due to their charge, He+ ions can be held near-motionless in the field-free environment of a Paul trap, providing ideal conditions for a high precision measurement. By combining the 1S-2S transition frequency with an accurate value of the helium nuclear charge radius measured by muonic helium spectroscopy, we will be able to make an independent determination of the Rydberg constant. This value will then be compared with the value obtained from hydrogen spectroscopy, serving as one of the most stringent tests of quantum electrodynamics.
The main challenge of the experiment is that driving the 1S-2S transition in He+ requires narrow-band radiation at 61 nm. This lies in the extreme ultraviolet spectral range where no transparent solids and no cw laser sources exist. Our approach is to use two-photon direct frequency comb spectroscopy with an extreme ultraviolet frequency comb. The comb is generated from an infrared high power frequency comb using intracavity high harmonic generation. The spectroscopy target will be a small number of He+ ions which are trapped in a linear Paul trap and sympathetically cooled by co-trapped Be+ ions.


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