NEWS
20.10.2020

The future of bio-medicine?

Researchers from Humboldt University and the Experimental and Clinical Research Center (ECRC) built the first infrared based microscope with quantum light. By deliberately entangling the photons, they succeeded in imaging tissue samples with previously invisible bio-features.

Researchers of the  Emmy Noether Junior Research Group "Nonlinear Quantum Optics" of the physics department and IRIS Adlershof of Humboldt-Universität zu Berlin and of the Experimental and Clinical Research Center (ECRC), a joined institution from Charité – Universitätsmedizin Berlin and Max Delbruck Center for Molecular Medicine in the Helmholtz Association, are featured on the cover of ‘Science Advances’ with their new experiment. For the first time they successfully used entangled light (photons) for microscope images. This very surprising method for quantum imaging with undetected photons was only discovered in 2014 in the group of the famous quantum physicist Anton Zeilinger in Vienna. The first images show tissue samples from a mouse heart.

The team uses entangled photons to image a bio-sample probed by ‘invisible’ light without ever looking at that light. The researchers only use a normal laser and commercial CMOS camera. This makes their MIR microscopy technique not only robust, fast and low noise, but also cost-effective - making it highly promising for real-world applications. This use of quantum light could support the field of biomedical microscopy in the future.

Quantum microscopy of a mouse heart. Entangled photons allow for the making of a high-resolution mid-IR image, using a visible light (CMOS) camera and ultralow illumination intensities. In the picture, absorption (left) and phase information (right) from a region in a mouse heart. The yellow scale bar corresponds to 0.1 mm which is about the width of a human hair.

Current camera detection is unequivocally dominated by silicon based technologies. There are billions of CCD (charge coupled device) and CMOS (complementary metal oxide semiconductor) sensors in digital cameras, mobile phones or autonomous vehicles. These convert light (photons) into electrical signals (electrons). But like our human eyes, these devices cannot see the important mid-IR range. This wavelength range is very important for biological science, containing valuable bio-chemical information that allows researchers to tell different biomolecules apart. The few camera technologies that exist at these crucial wavelengths are very expensive, noisy and subject to export restrictions. That is why the huge potential mid-IR light has for the life sciences so far remained unfulfilled. But researchers have proposed a new solution: “Using a really counterintuitive imaging technique with quantum-entangled photons allows us to measure the influence of a sample on a mid-IR light beam, without requiring any detection of this light” explains Inna Kviatkovsky, the lead author of the study.

There is also no conversion or so-called ‘ghost-imaging’ involved, but the technique relies on a subtle interference effect: first a pair of photons is generated by focusing a pump laser into a nonlinear crystal. This process can be engineered, such that one of the photons will be in the visible range and the other one in the MIR (invisible). The MIR photon probes the sample and is together with the visible photon and the laser sent back to the crystal. Here, quantum interference takes place - between the possibilities of the photon pair being generated on this first pass, and the possibility of not being generated on the first pass, but instead on the second pass through the crystal. Any disturbance, i.e. absorption caused by the sample, will now affect this interference and intriguingly this can be measured by only looking at the visible photons. Using the right optics one can build a mid-IR microscope based on this principle, which the team showed for the first time in their work.

“After a few challenges in the beginning, we were really surprised how well this works on an actual bio-sample.” Kviatkovsky notes. “Also we shine only extremely low powers of mid-IR light on the samples, so low, that no camera technology could directly detect these images.” While this is naturally only the first demonstration of this microscopy technique, the researchers are already developing an improved version of the technique. The researchers envisage a mid-IR microscope powered by quantum light that allows the rapid measurement of the detailed, localized absorption spectra for the whole sample. “If successful this could have a wide range of applications in label-free bio-imaging and we plan to investigate this with our collaboration partners from ECRC”, Dr. Sven Ramelow, group leader at the physics department and IRIS Adlershof of Humboldt-Universität zu Berlin, explains.

The research was funded by Deutsche Forschungsgemeinschaft (DFG) within the Emmy-Noether-Program.

Publication:
Inna Kviatkovsky, Helen M. Chrzanowski, Ellen G. Avery, Hendrik Bartolomaeus, and Sven Ramelow
„Microscopy with undetected photons in the mid-infrared.“
Veröffentlichung: 14. Oktober 2020 in Science Advances Issue 42, p. xxx

15.09.2020

IRIS-Nachwuchsforscher Michael Kathan receives prestigious award for photochemistry

For his outstanding dissertation "Photoswitching Reactivity: From remote-controlled to light-driven chemical systems", Dr. Michael P. Kathan was awarded the Albert Weller Prize on September 14, 2020. This is the second award after the Friedrich Hirzebruch PhD award 2020.

Michael Kathan, born in 1988, studied chemistry at the Free University of Berlin and ETH Zurich, where he dealt with fluorine chemistry and strained aromatics. After completing his master's degree at the Free University of Berlin, he began his doctoral thesis in 2015 in the working group of IRIS member Prof. Stefan Hecht at the Humboldt University in Berlin, funded by the German National Academic Foundation.

Michael Kathan's research focus was on the control of chemical reactivity and adaptive materials with light:
In an innovative way, he used light as a tool to control the course of chemical reactions and to control material properties. The focal point of Michael Kathan's dissertation is the development of the concept of "photo reversal", in which the chemical behavior of molecules can be fundamentally changed by the dosed irradiation with light of different colors. In their justification, the jury emphasized that Kathan had impressively managed to span the spectrum from the physicochemical basics to the manufacture of intelligent materials and new, sustainable concepts that address socially relevant issues. His research opens up access to cost-effective sensor materials that indicate, for example, the freshness of highly perishable foods. The light-controlled assembly and dismantling of plastic materials also promises progress in the area of ​​sustainable recycling of mixtures of different plastic products.

The GDCh and the German Bunsen Society awarded the Albert Weller Prize on September 14, 2020 at the digital 27th Lecture Conference on Photochemistry. This year, the award is shared by two young researchers: in addition to Michael Kathan, it was awarded to Yusen Luo, who did her doctorate at Leibniz-IPHT and the University of Jena and is now a post-doc at the Institute for Chemistry and Pharmacy at the University of Erlangen.

Kathan's research has already resulted in several publications in relevant specialist media. Since completing his dissertation in January 2019, Michael Kathan has been working on molecular motors as a postdoc with Prof. Ben Feringa at the University of Groningen, Netherlands.

We congratulate you!

09.09.2020

The Research Training Group 2575 “Rethinking Quantum Field Theory” starts its work.

The Research Training Group 2575 “Rethinking Quantum Field Theory”, funded by the German Research Foundation (DFG), has started its work. Due to the pandemic, the hiring of the first two cohorts was delayed until autumn 2020. In October, however, the Research Training Group (RTG) will start with 15 doctoral students from 10 countries and two postdocs. The RTG will deal with pressing theoretical questions and key innovations in quantum field theory that go beyond established methods. “Quantum field theory is a highly developed formalism of theoretical physics for the description of interacting many-body systems. Nevertheless, fundamental questions are still open, especially in relation to gravity, and in recent years fascinating, almost revolutionary innovations have emerged here, which are being further researched within the our new graduate school, ”says the spokesman Prof. Dr. Jan Plefka, head of the Quantum Fields and String Theory group at the Institute of Physics. However, the pandemic continues to make work difficult. “Fortunately, we theorists are almost fully operational in the home office with a laptop, paper and pencil, Mathematica and Zoom. What is missing, however, is the spontaneous exchange between us, for example in the common room over coffee or at lunch, where new ideas often arise. Every meeting is now planned. ”All courses, colloquia and seminars of the RTG will also have to be held virtually in the winter semester 2020/21. It is also currently unclear whether the first retreat in November can be held as planned. “The organization is in full swing. The first conference in particular is very important to us, in order to give everyone involved the opportunity to get to know each other in an informal setting, "explains PD Dr. Oliver Bär, the coordinator of the GRK.

The graduate college is supported by 13 principal investigators and includes all working groups in theoretical particle physics at the Institute of Physics. Further cooperation partners are the Max Planck Institute for Gravitational Physics and the Helmholtz Center DESY. “The scientific breadth is what makes the GRK so attractive. It offers young academics many opportunities to think outside the box of their own project, "explains deputy spokesman Prof. Dr. Agostino Patella." It is the stated aim of the RTG to train doctoral candidates comprehensively and broadly, and thus to provide an ideal basis for a career in science. "

Quantum field theory as the unification of quantum mechanics and special relativity represents one of the main intellectual achievements of the last century. These theoretical advances, closely connected with experimental observations, led to the standard model of elementary particle physics. With the experimental discovery of the Higgs boson in 2012, we now have an empirically validated and mathematically consistent theory up to the highest energy scales. Nevertheless, a series of terrestrial experiments, as well as the astrophysically proven existence of dark matter and energy, indicate that the Standard Model cannot be the final theory of nature. At the same time, pressing theoretical questions such as the structure of quantum gravity, the hierarchy problem or the discovery of dualities between different quantum field theories force established formulations to be reconsidered. More recently, crucial innovations have been achieved in quantum field theory that have led to a serious rethinking of its basic principles. These include new methods of perturbation theory, dualities and hidden symmetries, the prominent role of effective field theories, modern methods for scattering amplitudes and the gradient flow in lattice field theory. The further development of these methods and concepts of modern quantum field theory – or simply the rethinking quantum field theory -represent the common basis of this graduate school. These demands result in a challenging qualification program that is based on the current state of research.

More information can be found here.

05.09.2020

New junior research group “Exploring the landscape of string theory flux vacua using exceptional field theory” as part of the Emmy-Noether-Programme of the German Research Foundation

Since August Dr. Emanuel Malek has been establishing a junior research group on “Exploring the landscape of string theory flux vacua using exceptional field theory” at the Physics Department of the Humboldt-Universität zu Berlin. His group will receive more than 1.2 million euros in funding over 6 years from the Emmy-Noether-Programme of the German Research Foundation. After finishing his doctoral studies at the University of Cambridge in 2014, Dr. Malek spent one year as a Postdoctoral Fellow at the University of Cape Town, followed by a three-year-long stay as a Research Fellow at the Ludwig Maximilian University Munich. He subsequently worked at the Max-Planck-Institute for Gravitational Physics in Potsdam for two years. At Humboldt-Universität zu Berlin, Dr. Malek will continue his work on the field of theoretical physics and closely collaborate with Prof. Dr. Jan Plefka, Prof. Dr. Matthias Staudacher and Dr. Olaf Hohm, all of whom are members of IRIS Adlershof.

Dr. Malek’s research group will develop new computational tools that allow us to obtain predictions from string theory for our universe. String theory is based on the idea that all matter is composed of tiny vibrating strings and is our best attempt at unifying the gravitational force with quantum mechanics. A key prediction of string theory is that the universe contains six additional spatial dimensions, on top of the three spatial dimensions we observe daily. While these extra dimensions are too small to be observed directly, their shape determines the particles and forces that we experience in our 3-dimensional universe. However, a large class of shapes for the extra dimensions, so-called flux compactifications, have long evaded a systematic study due to the lack of the right mathematical framework. By using and developing the new mathematical techniques of Exceptional Field Theory, Dr. Malek’s research group will, for the first time, systematically investigate the possible shapes of string theory’s extra dimensions, especially flux compactifications. The insights gained from this research are crucial for testing string theory experimentally in the future.

IRIS Adlershof wishes Dr. Malek much success in obtaining these goals and is looking forward to a fruitful collaboration.