The Q-SORT project has successfully created a new generation of electron microscopes - so-called ‘Quantum Sorters’ - that are able to extract previously unavailable information about samples by changing the very concept of measurement.
For decades, both scientists and the wider public have marveled at images produced by electron microscopes. Modern instruments can fire powerful electron beams to form images that have atomic spatial resolution. However, electron microscopes are much more than just imaging tools: they can also be used to study properties such as atomic composition, as well as magnetic, mechanical, structural, and electronic properties of materials.
According to quantum mechanics, the information that can be measured about a single electron is limited and depends on the measurement process. By developing and using a “Quantum Sorter”, we have shown that it is possible to retrieve crucial information that is usually hidden - for example about the symmetry of a scattering object, which is of interest in studies of atomic orbitals, where a specific rotational symmetry provides information about chemical bonds, magnetic states or electronic states.
An important issue in electron microscopy is damage to (or even destruction of) delicate samples, such as proteins, by an incident electron beam. This ‘dose problem’ results in the need to find a trade-off between spatial resolution and sample integrity. In this context, it is significant that a “Quantum Sorter” allows a specific quantity of interest about a sample to be measured optimally.
A “Quantum Sorter” transforms the quantum state of an electron that has probed a sample, thereby maximising the information that can be extracted per incident electron and allowing the measurement of properties of the sample that are not normally accessible. This is a game-changing development in electron microscopy. Q-SORT assessed the benefits of using a “Quantum Sorter” for probing delicate specimens with extremely low damage, for characterising quantum states of plasmonic excitations and for measuring selection rules in atomic transitions excited by beam-sample interactions.
Q-SORT resulted in the development of new devices, in which MEMS technology was used to control and shape the electron wavefunction, as well as to ‘sort’ its quantum states. It required the building of an orbital angular momentum Sorter and demonstrations of its use to provide unprecedented results on the characterisation of atomic transitions, plasmon excitations and protein symmetries.
Applications of the Quantum Sorter to cryo electron microscopy, which is generally used to study biological specimens in the form of a flash-frozen solution, include its use to recognise protein structures and their properties, thereby providing researchers with improved knowledge of how cells, tissues, and viruses function.
Theoretical assessments were performed of different dose-efficient methods. A new approach was demonstrated for the recovery of protein symmetry and orientation using a very limited dose. We also demonstrated experimentally a special Sorter-related method that is referred to as “computational ghost imaging”.
Q-SORT included a comprehensive outreach and dissemination strategy, based on both online and offline engagement. Its objectives were to communicate the Project to the broader public, to spread awareness about excellent EU-funded research, to prime public interest in the underlying physics of the Project, to foster interdisciplinary dialogue between physics and biochemistry, and to promote the project’s results and people in the electron microscopy and quantum science communities.
