Aeppli leads the Quantum Technologies Group spanning ETH Zurich, EPFL, and PSI. Research directions: (1) Quantum materials imaging — using SLS synchrotron X-rays (including SwissFEL ultrafast pulses) and neutrons at SINQ to image quantum phase transitions, skyrmions, and correlated phases; non-destructive imaging of device structures; (2) Rare-earth quantum magnets and qubits — LiHoF4 as a model quantum system; Er, Pr, and Nd spin qubits in crystals for quantum information and sensing; (3) Semiconductor quantum devices — silicon and germanium nanostructures probed by synchrotron nanoscale X-ray imaging; (4) Van der Waals materials and CDW memory devices. Strong interface with PSI large-scale facilities as unique quantum sensing tools for materials.
Chantler's group is built around the idea that X-ray measurements can be made accurate, not just precise: the X-ray Extended Range Technique (XERT) delivers absolute absorption coefficients at the 0.02 per cent level, which in turn allows XAFS to be used for quantitative structure determination and allows high-accuracy tests of atomic theory. The second thread is precision X-ray spectroscopy of highly charged ions and exotic atoms as a test of bound-state QED, where discrepancies between theory and experiment remain unresolved. Positioned against the established body of NV-ensemble quantum sensing work — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — this is precision measurement at the other end of the electromagnetic spectrum: the methodological common ground with pT/sqrt(Hz) NV ensemble sensing is the obsessive treatment of systematics and absolute calibration that separates a sensitive measurement from an accurate one. Borderline inclusion, kept because the group's core competency is metrology rather than X-ray applications.
Prof. Jacobsen's group develops novel methods, instruments, and analysis approaches for X-ray nanoscale imaging and applies them to biology and environmental science, using the Advanced Photon Source (APS) at Argonne. Directions: (1) Scanning X-ray fluorescence microscopy (SXFM) for organ-wide and nanoscale elemental mapping of metals (zinc, copper, iron) in biological tissues — central to the NIH-funded QE-Map national resource; imaging how metals regulate cellular functions, synaptic zinc signaling, and neurodegenerative disease; (2) X-ray ptychography and coherent diffractive imaging (CDI) for nanoscale biological imaging beyond the diffraction limit with improved dose efficiency; (3) Development of new algorithms, optics (zone plates), and detector systems to push spatial resolution and dose efficiency in X-ray microscopy — including lensless imaging methods and compressed-sensing reconstruction. Joint appointment at Argonne National Laboratory (Argonne Distinguished Fellow); also involved in QE-Map resource with Kozorovitskiy and Hao Zhang (McCormick).
The Stern Group explores fundamental quantum interactions of photons with 2D materials, nano-scale structures, and atoms. Key thrusts: (1) Valley-selective exciton-polaritons in monolayer transition-metal dichalcogenides (MoS₂, MoSe₂, WSe₂) embedded in optical microcavities — hybrid light-matter quasiparticles with valley-selective polarization and cavity-modified dynamics; (2) 2D semiconductor quantum emitters — quantum-dot-like single-photon emitters formed by confinement in TMD nanoribbons and by chemical functionalization/strain engineering of defects; (3) Astrophotonics: collaboration with Argonne National Laboratory and the Australian Astronomical Observatory to design and fabricate silicon ring-resonator photonic circuits for OH sky-background suppression in near-IR astronomical spectrographs; (4) Quantum non-reciprocal photonics in axisymmetric microresonators. Experimental tools: time-resolved spectroscopy, single-photon counting, nanofabrication. DOE Early Career Award; ONR Young Investigator Award; Sloan Research Fellow 2013. Affiliated with Fermilab-Northwestern CAPST.