Quantum Technologies Collaboration at PSI (QTC@PSI)

In findings recently published in Nature Photonics, a team including researchers from the UK, the Netherlands and Photon Sciences division head Gabriel Aeppli have investigated multi-photon THz absorption in Si:P. Their studies, using the THz free-electron laser FELIX, discovered a two photon absorption cross-section ten orders of magnitude higher than that of a natural hydrogen atom and may enable new methods in quantum control. In addition to the original publication their findings are also discussed in a 'News and Views' article.

Christopher Mudry and his collaborators have shown theoretically how to construct strongly interacting phases of matter that realize topological order in two-dimensional space by strongly coupling quantum wire. Remarkably, their model supports both Abelian topological order (ATO) and non-Abelian topological order (NATO) with a continuous phase transition separating them. Read the full paper here

Superposition of orbital eigenstates is crucial to quantum technology utilizing atoms, such as atomic clocks and quantum computers, and control over the interaction between atoms and their neighbours is an essential ingredient for both gating and readout. A team of researchers including Photon Science division head Gabriel Aeppli has demonstrated THz laser pulse control of Si:P orbitals using multiple orbital state admixtures, observing beat patterns produced by Zeeman splitting. The beats are an observable signature of the ability to control the path of the electron, which implies we can now control the strength and duration of the interaction of the atom with different neighbours. This could simplify surface code networks which require spatially controlled interaction between atoms. The full article can be read in Nature Communications

A team of researchers including Photon Sciences division head Gabriel Aeppli have demonstrated the first non-destructive imaging of atomically thin nanostructures in silicon. Such structures are the building blocks of quantum devices for physics research and are likely to serve as key components of devices for next-generation classical and quantum information processing. Until now, the characteristics of buried dopant nanostructures could only be inferred from destructive techniques and/or the performance of the final electronic device; this severely limits engineering and manufacture of real-world devices based on atomic-scale lithography. In work recently published in Science Advances, the team use scanning microwave microscopy (SMM) to image and electronically characterize three-dimensional phosphorus nanostructures fabricated via scanning tunneling microscope based lithography.

For the first time, researchers have produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Paul Scherrer Institute, in collaboration with their research partners, published the findings in the journal Nature Communications.

In their recent paper, Distinct Evolutions of Weyl fermion quasiparticles and Fermi arcs with bulk band topology in Weyl semimetals, two MARVEL groups — led by Prof. Ming Shi and Dr Nan Xu at PSI for the experimental part, and with Prof. Oleg Yazyev and Dr Gabriel Autès at EPFL for the theoretical side — joined forces to shed light (and soft X-rays) on the relationship between the bulk band topology in Weyl semimetals and two measurable signatures of Weyl fermion quasiparticles: magneto-transport effects in the bulk, and Fermi arcs on the surface.