Nanoscale Three-Dimensional Imaging of Integrated Circuits Using a Scanning Electron Microscope and Transition-Edge Sensor Spectrometer.

X-ray nanotomography is a powerful tool for the characterization of nanoscale materials and structures, but it is difficult to implement due to the competing requirements of X-ray flux and spot size. Due to this constraint, state-of-the-art nanotomography is predominantly performed at large synchrotron facilities. We present a laboratory-scale nanotomography instrument that achieves nanoscale spatial resolution while addressing the limitations of conventional tomography tools.

Broadband high-energy resolution hard x-ray spectroscopy using transition edge sensors at SPring-8.

We have succeeded in operating a transition-edge sensor (TES) spectrometer and evaluating its performance at the SPring-8 synchrotron x-ray light source. The TES spectrometer consists of a 240 pixel National Institute of Standards and Technology (NIST) TES system, and 220 pixels are operated simultaneously with an energy resolution of 4 eV at 6 keV at a rate of ∼1 c/s pixel. The tolerance for high count rates is evaluated in terms of energy resolution and live time fraction, leading to an empirical compromise of ∼2 × 10 c/s (all pixels) with an energy resolution of 5 eV at 6 keV.

Configurable error correction of code-division multiplexed TES detectors with a cryotron switch.

The development of a superconducting analog to the transistor with extremely low power dissipation will accelerate the proliferation of low-temperature circuitry operating in the milliKelvin regime. The thin-film, magnetically actuated cryotron switch is a candidate building block for more complicated and flexible milliKelvin circuitry. We demonstrate its utility for implementing reconfigurable circuitry by integrating a cryotron switch into flux-summed code-division SQUID multiplexed readout for large arrays of transition-edge-sensor (TES) microcalorimeters.

Selective-Area Superconductor Epitaxy to Ballistic Semiconductor Nanowires.

Semiconductor nanowires such as InAs and InSb are promising materials for studying Majorana zero modes and demonstrating non-Abelian particle exchange relevant for topological quantum computing. While evidence for Majorana bound states in nanowires has been shown, the majority of these experiments are marked by significant disorder. In particular, the interfacial inhomogeneity between the superconductor and nanowire is strongly believed to be the main culprit for disorder and the resulting "soft superconducting gap" ubiquitous in tunneling studies of hybrid semiconductor-superconductor systems.