Alexander Eichler's research while affiliated with Eawag: Das Wasserforschungs-Institut des ETH-Bereichs and other places

... Experimentally, we demonstrate topological flows in a driven microelectromechanical resonator, and reveal an unexpected population-inversion topological transition. Our unique approach paves the way for the exploration of topological effects in quantum circuits 47 , many-body collective phenomena in cold atoms 36,37 , nonlinear phonon networks 55,56 , and nonlinear optics 30 . The classification of the many-body flows in such high-dimensional phasespaces will rely on extensions of Morse-Smale theory 16 . ...

... Going to cryogenic temperatures will increase Q m and at the same time reduce the thermomechanical noise. At the lowest temperature of 640 mK demonstrated with a patterned membrane inside an optical cavity [28], an ideal membrane (low mass and high-Q m ) [55] sensor mode will experience an integrated force of 4×10 −19 N over an integration time of 1 s, corresponding to the force generated by roughly 10 hydrogen spins in the presence of a magnetic field gradient of 5 MT m −1 [59][60][61]. This sensitivity would in principle yield sub-nanometer resolution in three dimensions for typical biological samples [38]. ...

... Our framework captures the topological origin of locking to different drives, over-to under-damped dissipative transitions, and population inversions in the system. We thus pave the path for a comprehensive unveiling of topological effects in nonlinear media [30][31][32][33][34] and in driven-dissipative collective phenomena [35][36][37][38][39][40] . We first recapitulate the topological analysis of vector fields 15,16 . ...

... For J > the spectrum comprises a symmetric (α 1 = α 2 ) and antisymmetric (α 1 = −α 2 ) superposition of the bare cavity modes, split by 2J. Even without memory (τ → 0), coupled cavities can sustain complex dynamics which have drawn great interest in recent years [93,[99][100][101][102][103][104][105][106][107][108][109][110]. Hopf and homoclinic bifurcations and chaos [101,102,105,106], as well as excitability [108], have been numerically shown in the strong-coupling regime (J > ). ...

... The first method is the entanglement-preserving conversion from Fockstate encoding to cat-state encoding. Although there have been studies on two interacting KPOs [46,47], the entanglement between them and its preservation during the conversion have yet to be investigated. Such a conversion suggests the possibility of constructing quantum networks in the cat basis using conventional schemes originally developed for the Fock basis, thereby reducing experimental complexity. ...

... The Q factor measures both radiated acoustic energy and infiltrating thermomechanical noise, with a high Q pivotal in preserving resonator coherence. This is crucial, particularly at room temperature, for observing quantum phenomena 11,12 , advancing quantum technology 13 , and maximizing sensitivity for detecting changes in mass [14][15][16] , force 17,18 , and displacement 1 . High Q is often achieved through "dissipation dilution", a phenomenon originating from the synergistic effects of large tensile stress and high-aspect-ratio, observed both in resonators with macroscopic lengths on the order of centimeters and above 2,19 and resonators with nanometers thicknesses [20][21][22] . ...

... The distributions shown in Fig. 2(d) and (e) are therefore involving only symmetry-broken contributions and can be distinguished from featureless thermal distributions, such as shown in Fig. 2(c), by correlation measurements. The study of the dynamics of tunneling events between the hot spots is an interesting topic [68][69][70][71] that can characterize the DTC lifetime, i.e., the intermediate time under which the system fulfills criterion (ii). ...

... Current quantum hardware platforms use a variety of measurement schemes for electrometry, resulting in a range of achievable bandwidths and measurable sensitivities. Single [26,40] and bulk NV centres [11] utilise resonant pulse schemes on their spin transition frequency and are able to operate at ambient conditions, allowing highly increased flexibility in sensor placement [3]. However, coherence times and coupling strengths limit both the achievable sensitivities and the bandwidth. ...

... Theoretical and applied problems of coupled thermomechanics of materials and structures under nondestructive (opto-thermal) laser excitations are currently attracting growing attention of the scientific and engineering community. This area of research is directly related to the development of a wide range of areas of modern engineering and technology, among which it is necessary to indicate (a) nanooptomechanical signal transmission/processing systems, optoacoustic systems for identifying the geometric and physical characteristics of nano-structures for various purposes [1][2][3][4] and (b) systems for highprecision measurement of various physical quantities and signal processing (nano-and microelectromechanical resonators and sensors) [5][6][7][8][9][10][11][12]. Both classes of systems are based on the use of the unique advantages of laser opto-thermal methods for generating, respectively, acoustic vibrations of submicron heterostructures and low-mode mechanical vibrations of nanoand microsystems. ...

... Dissipation dilution through in-plane strain in silicon nitride [2] can be combined with geometrical patterning to minimize clamping loss through soft clamping [3,4], perimeter modes [5], hierarchical clamping [6,7], and spiderweb designs [8,9]. Such mechanical resonators attain quality factors greater than 10 9 [5,7,8,[10][11][12] at cryogenic temperatures, resulting in exceedingly long coherence times and thermally limited force noise below 100 zN/Hz 1/2 [13]. ...