The ILP explores the foundations of light, the foundations of the atomic building blocks of matter, and the interaction of the two. From our findings, we want to develop new useful applications. This is done as part of our activities in the Center for Optical Quantum Technologies, whose building is located next to the ILP.
Ultra-Cold Quantum Gases – We cool dilute clouds of atoms to temperatures that are a million times colder than the empty universe. Under these extreme conditions, atoms turn into matter waves, which can interfere constructively or destructively. We examine for instance how ultra-cold bosonic atom clouds turn into Bose-Einstein condensates, in which the locations of all atoms become indistinguishable. Fermionic atoms need to first pair before the can condense and may form a superfluid. We use condensed systems to explore the physics of solids. Beyond that, further possibilities open up. In ultracold quantum gases, we can freely set the interaction between the atoms, from weak to strong and from attractive to repulsive, in contrast to the solid repulsion between electrons in the solid state. In addition, the effective dimensionality of the systems can be reduced by freezing degrees of freedom. Finally, we can change the densities and potential landscapes almost arbitrarily and dynamically. These possibilities make the research on ultracold quantum gases far-reaching and allow us to create model systems in which we study the physics of strongly correlated matter and high-temperature super conductivity.
Gravitational-Wave Detection – Since 2015, a new kind of observatories, which are based on kilometre-long laser interferometers, have been observing gravitational waves (GWs) from the deep universe. GWs are extremely small and localized oscillations in the size of space-time. They arise, for example, when two black holes merge. The group of Prof. Schnabel has been developing new and more sensitive technologies for the observation of gravitational waves since 2003 (since 2014 at the University of Hamburg). The focus of their work is research and development of extremely low-noise laser light with squeezed quantum uncertainty (squeezed light), low-noise mirror coatings, and signal-enhancing radiation pressure coupling between light and interferometer mirrors. Squeezed light and the low-noise mirror coatings also open new industrial applications.
Quantum entanglement – An excited hydrogen atom can decay into an electron and a proton. An electro-magnetic wave that passes through a nonlinear crystal can decay into two waves of longer wavelengths (energy conservation enforces 1/λ0 = 1/λ1 + 1/λ2). Repeated measurements on such decay products show a particularly strong correlation of the measurement values, but only if the decay products have had no interaction with the environment before. The said correlation is called entanglement. The strength of the correlation is due to the fact that the decay products have no individual properties before the measurement, but only properties relative to each other. We want to use entangled light to realize quantum key distribution for secure communication and to improve laser devices for vibration measurements.
Hybrid quantum systems – In the wake of the rapidly growing worldwide interest in quantum technologies, fundamental changes in many technological areas are expected over the next few years. These include quantum cryptography and quantum communication but also highly sensitive measurement methods based on certain quantum mechanical effects. Hybrid quantum systems, as researched at the Institute of Laser Physics and the Center for Optical Quantum Technologies, pursue the approach of combining and instrumenting different quantum systems and circumventing their respective weaknesses. In the group of Prof. Sengstock an attempt is made to entangle the motion of a 1mm SiN membrane with that of a Bose-Einstein condensate. In the group Prof. Schnabel an attempt is made to realize entanglement between the positions and momenta of two 100g pendulum mirrors with the help of the radiation pressure of laser light. The experiment could provide clues for the interaction of quantum physics and gravitation.
Ultracold Quantum Dynamics – Theoretical simulation of the dynamics of ultra-cold quantum gases and Bose-Einstein condensates allows a deep understanding of the dynamic structure formation in many-body systems. Our focus is on the transport and interaction of ultra-cold atoms with the aim of understanding whether the atoms move independently or whether they exhibit correlations. Strong correlations lead to new quantum mechanical tunnelling processes and to unique collective dynamics of the atoms. The research group ‘Fundamental processes in quantum physics’ (Prof. Schmelcher) develops methods to describe these dynamics and applies them to a variety of many-body systems of bosonic and fermionic nature.
Exotic quantum species and quantum processes – Rydberg atoms are giant atoms created by the absorption of light from usual atoms being close to their ground states. We study the extraordinary properties of these 'super atoms', which can become as big as a virus and have huge dipole moments. From these Rydberg atoms molecules with novel binding mechanisms can be built that possess unique new molecular dynamics and hitherto unknown chemical reactions. Trap-induced processes and non-linear waves (solitons and vortices) in Bose-Einstein condensates are also among our research areas.
Local Symmetries in Wave Mechanics – Symmetries play a fundamental role in nature and in physics. If symmetry is, however, not present in the entire space but different symmetries exist at different locations, many fundamental questions arise. We develop new concepts to describe these so-called local symmetries and apply them to wave-mechanical systems in optics and quantum mechanics.