Quantum Technologies Collaboration at PSI (QTC@PSI)

We have produced ultra-short X-ray FEL pulses at SwissFEL by strongly compressing low-charge electron beams.  Single-shot spectral measurements with only a single mode (see the figure below) indicate a pulse duration well below one femtosecond (detailed analysis on the exact pulse duration is ongoing).

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