+++ONLINE KOLLOQUIUM+++ DOUBLE FEATURE Dr. Isabel Rabey and Dr. Lorenzo Piroli

Dr. Isabel Rabey talks about: Investigating molecule-molecule collisions in a trap

Dense samples of cold and slow polyatomic molecules provide fascinating research possibilities in both physics and chemistry. Reaching the cold collision regime however, has been a long-standing challenge that we address with a combination of cryogenic buffer-gas cooling, centrifuge deceleration, and electrostatic guiding. Using this technique, we have created one of the brightest sources of cold molecules in the world, with fluxes exceeding 1010/s for molecules with kinetic energies below 1K. The cryofuge source is entirely general, and allows us to study the collisional properties of a range of molecules, including CH3F and ND3.The addition of a microstructured electrostatic trap to the end of the cryofuge allows molecules to be trapped and stored for several seconds, with densities up to 5x107/cm3. In this setup we have observed strong dipole-dipole interactions between these molecules, allowing us to study dipolar relaxation in detail. In addition, we can demonstrate controllability of this effect by tuning the electric field distribution of the trap. Understanding molecular interactions at these low energies is a prerequisite for future experiments, including evaporative cooling of polyatomic molecules.

Dr. Lorenzo Piroli talks about: Quantum Cellular Automata, Tensor Networks, and Area Laws

The concept of causality, stating that physical actions cannot propagate in space at an arbitrary speed, can be captured for qudit systems by the notion of Quantum Cellular Automata (QCA), that are unitary maps preserving locality of observables. In this talk, I will show that QCA can be identified, in any dimension, with tensor network (TN) operators with special contraction properties, making it possible to bound in general the amount of entanglement they can create. I will also discuss the generalization of these results for different classes of non-unitary quantum channels either respecting causality or preserving locality. I will show that, whereas the latter obey an area law for the number of quantum correlations they can create, as measured by the quantum mutual information, the former may violate it, although neither of them can in general be expressed as TN with finite bond dimension.