A Quantum Information Theoretic Approach to Systems in High Energy Physics

In 1964, the physicist John Stuart Bell initiated a new research field by studying the foundations of quantum mechanics that were otherwise very frowned upon in those days. Until today, many interesting and fruitful directions have emerged and even the first applications are entering the market. In a different field, in particle physics, experiments are achieving ever higher precisions such that the borderline of known physics will soon be reached. This proposed project combines both fields. Its aim is to tackle some of the most fundamental questions of quantum mechanics and to relate them to the most fundamental questions in particle physics. We want to investigate superposition, entanglement and their manifestations at high energies. Former results with meson-antimeson systems have shown that such systems at high energy scales reveal new aspects of the manifestation of the phenomenon entanglement. Obviously, to obtain a full picture of the quantum phenomena and their manifestations one also has to study systems not consisting of ordinary matter and light. We hope to achieve with our project new fascinating insights into the very working of quantum theory for systems at high energy scales and to find feasible experimental tests that will be performed at accelerator facilities. Page 1

The Quantum Theory is certainly the best tested physical theories, maybe because nobody really likes to accomplish the consequences, such as that Schrödinger's cat can be dead and alive simultaneously. Why does the quantum theory apply and where is the border between a quantum world and a classical world? Surprisingly, these are not trivial questions to answer and this project has tackled those questions for systems at high energies. We could show that predictions for such high energetic system are very sensitive to small changes to the standard quantum theory. This we utilized to find upper bounds on possible observables but as well to rule out sets of alternative theories. For example, we have constructed a time operator that was not in contradiction for all common quantum systems, but we could show that for high energetic systems that show a difference between matter and antimatter, there is a difference. And with experimental data we could rule out this time operator. We have also studied collapse theories, which predict a limit between a quantum world and a classical world, and found out that they only work out for very limited options, but surprisingly we could show that collapse models would allow in explaining certain properties in this systems such as the decay and the mass differences in a novel way. We have also studied how gravitation would affect K-meson systems and found that it by no means clear which masses of this system should couple to gravity and in particular, that very different predictions result from such options. Last but not least, we, in junction with colleagues, a new technology for high energetic photons that may allow in deducing via quantum information theoretic methods quantum effects from living human bodies, e.g. detecting cancer via quantum effects. In summary, quantum information theoretic methods allowed us in studying in distinct systems at high energies such as e.g. neutrinos, novel properties and for some cases even to propose new experiments.