Prof. Dr. Gabriel Aeppli

Head of Photon Science Division (PSD)
 

Paul Scherrer Institute
Forschungsstrasse 111
5232 Villigen PSI
Switzerland


Gabriel Aeppli is professor of physics at ETH Zürich and EPF Lausanne, and head of the Photon Science Division of the Paul Scherrer Institut. All of his degrees are from MIT and include a BSc in Mathematics and Electrical Engineering, and MSc and PhD in Electrical Engineering. A large fraction of his career was in industry, where, starting as a work-study student at IBM and after his PhD moving to Bell Laboratories and then NEC, he worked on problems ranging from liquid crystals to magnetic data storage. He was subsequently co-founder and director of the London Centre for Nanotechnology and Quain Professor at University College London. Aeppli also cofounded the Bio-Nano Consulting Company, of which he remains a non-executive director. He is a frequent advisor to numerous private and public entities worldwide (including China, Australia, Europe and the US) engaged in the funding, evaluation and management of science and technology. Honors include the Mott Prize of the Institute of Physics (London), the Oliver Buckley prize of the American Physical Society, the Néel Medal/International Magnetism Prize of the International Union of Pure and Applied Physics, and election to the (US) National Academy of Sciences, the American Academy of Arts and Sciences, and the Royal Society (London).
Aeppli’s scientific research is currently focused on the applications of nanotechnology and photon science to biomedicine and quantum information processing. Projects include the development of optical and microwave tools for medical diagnostics and pharmacology, where we are interested in new drug-target and antibody-antigen binding assays. We pay particular attention to obtaining specific, quantitative results, as well as to ease of use and (eventual) low cost for our engineered systems. Photons are also at the heart of efforts to control and read out quantum states in solids, including especially silicon, for which we exploit coherent, tunable pulses of THz radiation from a free electron laser. Our most recent work (2015) describes the electrical detection of coherent orbital superpositions in a commercial silicon wafer. A related topic is adiabatic quantum computing, where calculations are performed by mapping problems onto networks of bits, and then relaxing the networks via quantum mechanics. This procedure is most easily modeled in the limits of very large networks using magnets (although programmable medium size networks containing of order 1000 bits are now being implemented using superconducting junctions), where the bits correspond to Ising spins with either up or down magnetization, and quantum mechanics is introduced via a “transverse” field, which allows tunneling between the up and down states.

Viral Lasers for Biological Detection , Paul A. Dalby, John M. Ward and Gabriel Aeppli, Nature Communications volume 10, Article number: 3594 (2019 The polymerase chain reaction (PCR) underpins much of biomedical detection because of both its remarkable chemical amplification and specificity as well as the ubiquity of genetic material. There is no equivalent technique for detecting particular proteins, meaning that immunoassays are much less powerful. We show here that by using a viral chromophore in solution as a lasing medium, new types of biomedical assays become possible. In particular, a viral load measurement and a mix-and-measure immunoassay (detecting a phage antibody) are demonstrated, both with sensitivities orders of magnitude beyond what can be achieved with conventional fluorescence. Additionally, the on-off character of lasing can be exploited for digital medicine.

Giant multiphoton absorption for THz resonances in silicon hydrogenic donors , M. A. W. van LoonN. StavriasNguyen H. Le, K. L. Litvinenko, P. T. GreenlandC. R. PidgeonK. SaeediB. RedlichG. Aeppli, B. N. Murdin, Nature Photonics volume 12, pages179–184 (2018) The non-linear absorption, due to N photons,  of Rydberg atoms scales as the dielectric constant ε to the power 6N and inversely as the effective mass m*of the bound electron to the power 4N. Thus there should be an enormous enhancement when such atoms exist in the effective medium provided by a semiconductor such as silicon, for which ε10 and m* 0.3. We have observed this large effect (orders of magnitude larger than for atoms in vacuum) for Si using THz radiation from a free electron laser, thus opening a new avenue for quantum control in a solid state system.

Coherent superpositions of three states for phosphorous donors in silicon prepared using THz radiation, Chick, Steven, Stavrias, N., Saeedi, K., Redlich, B., Greenland, P. T., Matmon, G., Naftaly, M., Pidgeon, C. R., Aeppli, G. and Murdin, B, Nature Communications 8, 16038 (2017) Superposition of orbital eigenstates is crucial to quantum technology utilising 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. The simplest coherent wavefunction control uses a 2-eigenstate admixture, but more control over the spatial distribution of the wavefunction can be obained by increasing the number of states in the wavepacket. Here we demonstrate THz laser pulse control of Si:P orbitals using multiple orbital state admixtures, 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, and we propose an architecture that might take advantage of this.

Nondestructive imaging of atomically thin nanostructures buried in silicon, Georg Gramse, Alexander Kölker, Tingbin Lim, Taylor J. Z. Stock, Hari Solanki, Steven R. Schofield, Enrico Brinciotti, Gabriel Aeppli, Ferry Kienberger and Neil J. Curson, Science Advances, 28 Jun 2017, Vol. 3, no. 6, e1602586, DOI: 10.1126/sciadv.1602586 It is now possible to create atomically thin regions of dopant atoms in silicon patterned with lateral dimensions ranging from the atomic scale to micrometers. These structures are likely also to serve as key components of devices for next-generation classical and quantum information processing. Until now, their characteristics could only be inferred from destructive techniques and/or final electronic device performance; this severely limits engineering and manufacture based on atomic-scale lithography. Here, we use scanning microwave microscopy to image and electronically characterize three-dimensional phosphorus nanostructures fabricated via scanning tunneling microscope–based lithography.

High-resolution non-destructive three-dimensional imaging of integrated circuits, Mirko Holler, Manuel Guizar-Sicairos, Esther H. R. Tsai, Roberto Dinapoli, Elisabeth Müller, Oliver Bunk, Jörg Raabe & Gabriel Aeppli, Nature 543, 402–406, 16 March 2017, doi:10.1038/nature21698  Modern nanoelectronics has advanced to a point at which it is impossible to image entire devices and their interconnections non-destructively because of their small feature sizes and the complex three-dimensional structures resulting from their integration on a chip. Here we demonstrate that X-ray ptychography—a high-resolution coherent diffractive imaging technique—can create three-dimensional images of integrated circuits of known and unknown designs with a lateral resolution in all directions down to 14.6 nanometres. Our experiments represent a major advance in chip inspection and reverse engineering over the traditional destructive electron microscopy and ion milling techniques.

Fast diffusion of water nanodroplets on graphene, Ming Ma, Gabriele Tocci, Angelos Michaelides & Gabriel Aeppli, Nature Materials 15, 66–71 (2016), doi:10.1038/nmat4449 Diffusion across surfaces generally involves motion on a vibrating but otherwise stationary substrate. Here, using molecular dynamics, we show that a layered material such as graphene opens up a new mechanism for surface diffusion whereby adsorbates are carried by propagating ripples in a motion similar to surfing. For water nanodroplets, we demonstrate that the mechanism leads to exceedingly fast diffusion that is 2–3 orders of magnitude faster than the self-diffusion of water molecules in liquid water. We also reveal the underlying principles that regulate this new mechanism for diffusion and show how it also applies to adsorbates other than water, thus opening up the prospect of achieving fast and controllable motion of adsorbates across material surfaces more generally.

Quantum phase transitions in transverse field spin models: from statistical physics to quantum information, Amit Dutta, Gabriel Aeppli, Bikas K. Chakrabarti, Uma Divakaran, Thomas F. Rosenbaum, Diptiman Sen (v3) Cambridge University Press, Cambridge, 2015. ISBN: 9781107068797