Last updated 23/06/2025
International mobility condition: applicants must have been living out of France at least 2 of the last 3 years.
Atomic
clocks are vital components for many applications in our modern
society, such as the operation of GPS and the synchronization of
telecommunication networks. Clocks are also used to bolster
investigations of fundamental physical phenomena, such as the
detection of low-frequency gravitational waves. Recently, a new
type of clock has been proposed: the active clock using
superradiant lasing. Instead of shining a very stable laser onto
ultracold atoms to probe the atom resonance frequency (and thus
measure time), the clock would operate by letting the atoms
themselves emit light. Much like in a laser, cold atoms would be
prepared in an excited state, then placed between two mirrors
forming a cavity. The atoms then coherently emit light into the
cavity mode. However, unlike a traditional laser, the light
frequency will mostly be set by the atoms themselves, and not by
the cavity. The light coherence will be set by a collective
synchronization of the atomic dipoles with each other - a
process called superradiance. Thus, in addition to its
significance as a new clock architecture, this system is
interesting from a fundamental point of view: it is an example
of an open-dissipative system in which correlations of quantum
nature may naturally arise.
We
have built a prototype for such a cold-atom-based superradiant
laser. We want to tackle the unresolved issue of sustaining
continuously a superradiant emission, thus harnessing its full
potential as a clock. Our design is based on an effusive beam of
strontium atoms inside a vacuum chamber, slowed, cooled, guided
continuously up to an optical cavity, there to emit light in a
superradiant fashion. The construction of the apparatus is
completed, and we expect to acquire full control over the atomic
velocity distribution in the next few months. The internship
will thus be devoted to characterizing the signs of collective
interaction between atoms and cavity (i.e., performing
cavity-enhanced spectroscopy), and searching for superradiance
signals in beat note spectroscopy. Throughout the PhD project,
we will investigate the light properties to understand how the
emitters synchronize their oscillations, and how the light
coherence is related to correlations between all atomic
emitters. Our experiment will have the unique capability to
explore several distinct superradiant emission regimes, that
will be identified through the spectral and correlation
properties of the light and of the atoms. In collaboration with
metrology experts both from LPL and the QuRIOUS consortium, we
will contribute to assessing the metrological interest (i.e.,
“performance” criteria to act as a clock) of atomic-beam
continuous superradiant lasers.
The
QuRIOUS doctoral network program:
This PhD thesis is part of the Marie Sklodowska-Curie doctoral
training network QuRIOUS, just recently funded by the European
Union. This program will train 15 young scientists to become
Europe’s future quantum technology leaders. To do so, the
network assembles an outstanding and experienced group of
scientists and innovators from academia, EU metrology
institutes, and industry, with world-class expertise in
practical quantum technologies. The new doctoral students will
be trained at the universities of Amsterdam, Birmingham,
Copenhagen, Toruń, Vienna and Innsbruck, and at the National
Center for Scientific Research in France (CNRS – in Paris,
Villetaneuse and Besançon) and the National Metrology Institute
of Italy; in close collaboration with the industry partners
Menlo Systems (Germany), NKT Photonics (Denmark), and QUBIG
(Germany). Eleven further associated partners throughout Europe
are also involved in the training network.
References:
[1] H. Liu et. al., Rugged mHz-Linewidth Superradiant Laser Driven by a Hot Atomic Beam,
Phys. Rev. Lett. 125,
253602 (2020). https://arxiv.org/abs/2009.05717
Superradiant laser team:
Benjamin Pasquiou, CNRS research engineer
Bruno Laburthe-Tolra, CNRS researcher
Martin Robert-de-Saint-Vincent, CNRS researcher
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