Robert Weis

Kirchhoff Institute for Physics

The Kirchhoff Institute for Physics (KIP) is named after a prominent physicist of the 19th Century: Gustav Robert Kirchhoff, who worked in Heidelberg for 21 years. His well-known lectures on experimental and theoretical physics attracted many students. Kirchhoff's ground-breaking research was extraordinarily diverse, spanning electrical, magnetic, optical, elastic, hydrodynamic and thermal processes. His laws for electrical circuits are well-known. At the time he was in Heidelberg, in conjunction with Robert Wilhelm Bunsen, he discovered spectral analysis and its application to solar radiation. In this way, Kirchhoff laid the foundation for modern astrophysics, as well as formulating the laws of thermal radiation, which played a key role in the discovery of quantum physics. The KIP aims to continue in this tradition of diverse scientific research and education.

Physikalisches Kolloquium

23. May 2025 5:00 pm  Nuclear Physics with a laser – the story of Thorium-229

Prof. Dr. Thorsten Schumm, Quantum Metrology group, Atominstitut, TU Wien ,Among all known isotopes, Thorium-229 has the lowest nuclear excited state, only 8.4 eV above the ground state. This so-called “isomer” is accessible to VUV laser excitation and a multitude of applications at the interface of atomic and nuclear physics have been proposed, including a nuclear clock, a gamma laser and a sensitive detector for variations of fundamental constants.more...

News

CQD Colloquium (funded by Structures), given by Dr. Simon Balthasar Jäger, 21. Mai, 4:30 p.m.

Next CQD Colloquium (funded by Structures) will be given by Dr. Simon Balthasar Jäger

 

Please note the place and time: 

 

 

Wednesday, 21th of May at 4:30 p.m., PI, INF 226, K 1-3, Goldbox

 

The main talk will be given by Dr. Simon Balthasar Jäger about:

Quantum technologies using cavity-mediated interactions and dissipation

Abstract:
Coupling atoms to optical cavities allows one to explore collective effects that emerge from strong light-matter interactions. In such setups the cavity mediates long-range atom-atom interactions that can be used to explore many-body effects such as spin squeezing, sub- and superradiance. This is not only of fundamental interest but has also direct applications in quantum technologies. In this talk I will discuss a quantum technology which harnesses such effects: the superradiant laser. This laser operates in a regime where the atomic lifetime exceeds by several orders of magnitude the cavity photon lifetime. As a consequence this laser is extremely robust against cavity length fluctuations which makes it a good candidate for atomic clock applications. I will discuss the theory and the general working principles of this laser and show how it can overcome different forms of broadening and disorder in the atomic ensemble and reach narrow laser linewidths. This is due to a synchronization mechanism of the individual atomic emission amplitudes that is mediated by the cavity. Taking the superradiant laser as a first example I will more generally discuss how cavity modes can be used to engineer tailored interactions and dissipation. Here, I will describe a theory which allows one to integrate out the cavity modes and to obtain effective atom-only Lindblad master equations that describe the atomic dynamics. I will demonstrate the validity of this approach and outline how it can be used to describe networks of interacting and dissipative spins.

The pretalk will be given by Hannes Koeper, KIP, University of Heidelberg.


For information about the CQD Colloquium, please see: https://cqd.uni-heidelberg.de/events/cqdcolloquium

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CQD special seminar, 19.5.25, KIP SR. 02403, given by Victor Gondret, Université Paris-Saclay

Next CQD special seminar will be given by Victor Gondret, Université Paris-Saclay
 

Please note the special place and time: 

When: Monday, the 19th of May, 16:00 p.m.,

Where: KIP, INF 227, SR 2403

He will talk about:

Quasi-particle entanglement in a Bose-Einstein condensate : an acoustic analog of the Dynamical Casimir Effect

Parametric resonance is a recurrent phenomenon in physics, observable at all scales. For example, the vibration of a mirror in a cavity leads to the production of photons, a phenomenon known as the dynamical Casimir effect. In 1831, Faraday observed that a container of water excited vertically in a sinusoidal manner generates patterns with a frequency that is half of the excitation frequency. In the primordial universe, after inflation, parametric oscillations of a field (the inflaton) led to the creation of particles from vacuum, whose thermalization subsequently gave rise to the hot, dense state often associated with the Big Bang.

The growth in the number of quasi-particles (or particles) in the excited mode(s) is triggered by the system’s fluctuations and, due to momentum conservation, quasi-particles are created in pairs in two modes of opposite momentum. At zero temperature, quantum fluctuations initiate this growth, but when the temperature is non-zero, both thermal and quantum fluctuations trigger the growth. In this case, the characteristic signature of quantum vacuum fluctuations is then carried by the entanglement between these modes.

In this seminar, I will report on the experimental observation of the growth and decay of quasi-particle in a  parametrically excited Bose-Einstein condensate. I will also discuss the evolution of two-mode entanglement between the quasi-particles and its subsequent disappearance due to thermalization but also effect beyond Bogolyubov theory.

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Spring is coming!

Butterfly-shaped coordination clusters provide an ideal testbed to study fundamental magnetic properties of mixed lnthanide-transition metal systems. In our recent work, we have added a new family of butterfly-structured molecular magnets to this exciting field...

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