Entanglement is a fundamental feature of the quantum world and a key resource for quantum
information processing. While the concept of entanglement for distinguishable particles is well
established, its validity for identical particles remains a subject of debate and misconceptions.
In this talk, we resolve this foundational issue: We demonstrate that identical particles do not
form proper subsystems, rendering the concept of entanglement inapplicable to identical
particles in first quantization. However, in second quantization, where the focus shifts from
particles to the inherently distinguishable orbitals, entanglement becomes well-defined. We
then systematically apply this perspective to physics and chemistry. In particular, we show how
quantum phase transitions manifest within this framework and how it provides a deeper
understanding of chemical bonding. Furthermore, we propose a systematic approach to
enhancing wave function methods for strongly correlated electron systems, relevant to both
classical and quantum computing. Altogether, these insights highlight the deep connection
between quantum information and many-body physics, demonstrating fruitful synergies that
can foster the second quantum revolution.
Freeze-in is a well-established mechanism for the early-universe production
of Dark Matter (DM). In the standard freeze-in scenario, a feeble coupling
is required to reproduce the observed DM abundance. Moreover, it typically
assumes zero or negligible initial DM abundance.In this talk, I will
discuss how the mere existence of gravity can lead to non-negligible
initial abundances. I will show how late-time reheating provides a natural
solution to this issue. An advantage of this solution is that it leads to a
regime of Boltzmann-suppressed production. This allows freeze-in to occur
with stronger couplings, opening a new parameter space for well-studied
models such as those with a Z' mediator. Within this framework, I will show
how current and future direct detection experiments play a crucial role in
constraining these models.
In recent years, we have seen major progress in the non-equilibrium control of many-body quantum systems. One tool, which has been applied successfully, is Floquet engineering, i.e. the use of strong time-periodic driving for effectively changing the properties of the system. A prominent example is the realization of effective magnetic fields for charge neutral particles (like atoms in optical lattices or photons in superconducting circuits). Another approach is known as reservoir engineering. Here the system is coupled to a controlled environment, which is designed to either cool the system or to stabilize a non-equilibrium steady state of interest. I will report on recent work, where we combine both approaches in open Floquet systems. One motivation is to use dissipation in order to counteract unwanted heating as it necessarily occurs in Floquet engineered systems, e.g. for the preparation of Floquet engineered topological states of matter. Another motivation is the stabilization of non-equilibrium steady states. Here, I will in discuss ordering away from equilibrium, like driving-induced Bose-condensation.
Efficient retrieval of information is a core operation in the world
wide web, is essential for the sustainance of living organism, and is
a paradigm for optimization algorithms. Inspired by the food search
dynamics of living organisms, we discuss a search on a graph with
multiple constraints where the dynamics is a selforganized process
resulting from the interplay of coherent dynamics and Gaussian noise.
We show that Gaussian noise can be beneficial to the search dynamics
leading to significantly faster convergence to the optimal solution.
We then analyse how these concepts can be extended to quantum
searches, cast in terms of spatial searches on a graph and discuss
whether and when the efficiency of noise-assisted quantum searches can
outperform the one of unitary protocols.
