March 2020

Abstracts of the QSIT Lunch Seminar, Thursday, March 5, 2020

Nanodiamonds as quantum sensors for biology

Takuya Segawa - Spin Physics and Imaging (Degen group), ETH Zurich

A living cell is a chemical microreactor with nanoscale spatial variations of its physical quantities, such as temperature or pH. Its precise measurements at a high spatial resolution would advance the understanding of intracellular processes.
Nanodiamonds containing Nitrogen-Vacancy centers are promising candidates for in-cell measurements. These defect centers are both, fluorescent and paramagnetic, making a single electron spin detectable using a microscope. Changes of physical quantities in the environment of the nanodiamonds affect the magnetic resonance spectra of the Nitrogen-Vacancy center, turning the nanodiamonds into a quantum sensor.
After a general introduction, we will focus on the quest for very small fluorescent nanodiamonds of only 5 nanometer in size.

Entanglement and (non-)equilibration in quantum many-body systems

Henrik Wilming - Quantum Information Theory (Renner group), ETH Zurich

One of the central applications of current and near-term quantum simulators is to study the out-of-equilibrium dynamics of quantum many-body systems, in particular their equilibration behaviour.
Recently, quantum simulations gave rise to the discovery of a class of non-integrable models showing perfect revivals of the full many-body wavefunction at finite times.
These are associated to the existence of very low-entangled eigenstates throughout the energy spectrum, so-called "quantum many-body scars".
I discuss recent general and rigorous theoretical results connecting the (non-)equilibration properties of quantum many-body systems with the entanglement content of their energy eigenstates.
On the one hand, they show that systems with large amounts of entanglement in energy eigenstates equilibrate to high precision.
On the other hand, they show the existence of quantum-many body scars in any local Hamiltonian giving rise to revivals of simple initial states.

 

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