Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session P60: Innovations in Measurement ScienceFocus Live
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Sponsoring Units: GIMS Chair: Michael Armstrong, Lawrence Livermore Natl Lab |
Wednesday, March 17, 2021 3:00PM - 3:12PM Live |
P60.00001: High Resolution Near-Field Radiative Heat Transfer Measurements Using Nanomechanical Oscillators. Mathieu Giroux, Chang Zhang, Gengyang Mu, Nikaya Snell, Raphael St-Gelais We report measurement of near-field radiative heat transfer using a new temperature-sensing approach based on nanomechanical oscillators. Silicon nitride membranes are used as sensors by tracking temperature-induced variations of their mechanical resonance frequency. We measure near-field radiative coupling by approaching a room-temperature SiN membrane in extreme proximity with a heated (ΔT=16.1 K) hemispherical BK7-glass surface of 12.7 mm radius. Measurement at distances ranging from 9 µm down to 1200 nm are reported, in good accordance with near-field thermal radiation simulations. Large distance measurements are enabled by the unparalleled temperature-sensing resolution of nanomechanical resonators—5 µK in the present case. The smallest achieved distance is most likely limited by surface contamination for these preliminary measurements. |
Wednesday, March 17, 2021 3:12PM - 3:24PM Live |
P60.00002: Maximum entropy for spectral analysis revisited David Aspnes, Long Van Le, Young Dong Kim For many years the mathematical procedure termed maximum-entropy (M-E) has been used to nominally enhance resolution by sharpening (“whitening”) features in spectra, optical and otherwise. However, details of how it works, and why it fails its primary goal, which is to extrapolate trends in low-order Fourier coefficients into the white-noise region, remain unknown. To solve these problems we re-examine M-E derivations, obtaining a first-order analytic solution that exhibits both properties depending on assumptions made: a correct solution that indeed extrapolates trends, and an incorrect solution that follows from a particular assumption. In the latter case, the first-order solution allows the amount of sharpening to be calculated quantitatively. The results are significant because the correct solution can eliminate Gibbs oscillations that result when high-performance linear filtering is used to reduce noise, thereby allowing spectra to be reconstructed essentially without noise or distortion. Taken together with recently developed methods of eliminating endpoint-discontinuity artifacts, it is now possible to access underlying information essentially unimpeded, thereby changing the way spectra are processed. Examples are given. |
Wednesday, March 17, 2021 3:24PM - 3:36PM Live |
P60.00003: An ultra-stable 1.5 tesla permanent magnet assembly for cryogenic spin qubit experiments Chris Adambukulam, Vikas Sewani, Serwan Asaad, Mateusz T Madzik, Holly G Stemp, Andrea Morello, Arne Laucht The generation of static magnetic fields with flux densities of 0.3 – 1.5 T are key to performing many experiments from the characterisation of materials to providing an energy splitting and quantization axis for a spin qubit. We present a compact permanent magnet assembly capable of operating at mK and generating a magnetic field of up to ~1.5 T across a 7 mm airgap. The assembly, based on the Halbach array, is constructed from neodymium (NdFeB) permanent magnets and the soft magnetic material Supermendur. We demonstrate the operation of a silicon based single atom spin qubit device mounted to the assembly and use the qubit to characterise the assembly. In doing so, we measure an outstanding magnetic field stability of < 1.7 ppb/h. |
Wednesday, March 17, 2021 3:36PM - 3:48PM Live |
P60.00004: Advanced thermal readout techniques for ac voltage metrology Joseph Hagmann, Jason Underwood, Michael J Berilla, Nikolai N Klimov, Stefan Cular One of the most accurate methods for quantifying ac voltage amplitude is to compare the rms amplitude of an ac waveform to an equivalent dc voltage using a device called a multi-junction thermal converter (MJTC). The MJTC produces a dc output voltage in response to the temperature rise from Joule heating due to electrical power dissipation in a resistive heater. The uncertainty of an MJTC measurement is about 1 µV/V (1 ppm) for voltages in the range of 0.5 V to 10 V and frequencies in the range of 40 Hz to 20 kHz. Conventionally, the rise in temperature due to Joule heating is measured on the MJTC by an array of thermocouples. Although well-established, this type of readout suffers is made challenging by the relatively large resistance (~10kΩ) of the thermocouple array, and the low (several mV) thermovoltage. Here, we present our research into alternative measurement techniques based on physical phenomena such as infrared emission in order to achieve improved stability and sensitivity and to extend the voltage and frequency range in which the measurement is accurate, bridging fundamental research with the engineering problems of harnessing useful physics to achieve advanced measurement technology. |
Wednesday, March 17, 2021 3:48PM - 4:00PM Live |
P60.00005: Second Harmonic Generation using a seeded soft X-ray laser Michael Zuerch, Tobias Helk, Emma Berger, Sasawat Jamnuch, Lars Hoffmann, Adeline Kabacinski, Julien Gautier, Fabien Tissandier, Jean philipe Goddet, Hung-Tzu Chang, Juwon Oh, C Das Pemmaraju, Tod Pascal, Stephane Sebban, Christian Spielmann Nonlinear interactions between light and matter are crucial for widespread applications in physical sciences, life science and engineering. Not only enables the nonlinear response of matter the generation of laser light at virtually any wavelength from Terahertz to X-rays, it is also the basis for nonlinear spectroscopies that enable unique insight into properties and dynamics of matter itself. Most notably, second |
Wednesday, March 17, 2021 4:00PM - 4:12PM Live |
P60.00006: Finite element analysis of transmission loss across a coplanar waveguide-integrated printed circuit board for quantum information science applications Alessandro R Castelli, Neda Forouzani, Chih-Chiao Hung, Timothy P Kohler, Kevin Daniel Osborn, Yaniv J Rosen Quantum information science (QIS) relies heavily on low-loss transmission lines for exciting and measuring myriad quantum devices in the RF bandwidth. However, factors such as impedance mismatches and parasitic mode coupling lead to loss and spurious reflection across a printed circuit board (PCB) array, especially when signal wavelength is comparable to feature size. This talk outlines the various considerations needed when designing a PCB sample box and which optimizations contribute to the achieved performance improvements. We use the ANSYS electronics workbench, HFSS, to investigate the effects of coupler configuration, PCB thickness, dielectric constant, and PCB via pattern on transmission spectra across a transmission line printed on a silicon substrate. We report on common sources of PCB loss, then proceed to detail optimal parameters for < 0.25 dB return loss in the crucial 4-8 GHz bandwidth. These steps lead to favorable simulated PCB performance and can serve as a guide for those designing sample boxes for QIS applications. |
Wednesday, March 17, 2021 4:12PM - 4:24PM Live |
P60.00007: Cryogen-free one hundred microKelvin refrigerator Jiaojie Yan, Jianing Yao, Vladimir Shvarts, Rui-Rui Du, Xi Lin Temperature below 100 μK is achieved in a customized cryogen-free dilution refrigerator with a copper-nuclear demagnetization stage. The lowest temperature of conduction electrons of the demagnetization stage is below 100 μK as measured by a pulsed platinum NMR thermometer and the temperature can remain below 100 μK for over 10 hours. 9 T demagnetization magnetic field and 12 T research magnetic field can be controlled independently, provided by a coaxial room-temperature-bore cryogen-free magnet. |
Wednesday, March 17, 2021 4:24PM - 4:36PM Live |
P60.00008: A Device and Method to Study the Ionic Permeation Properties of Membranes Under Continuously Tuneable, Uniform Pressure Vasumathy Ravishankar, Manu Jaiswal, Sundara Ramaprabhu A well-known material test applied to thin films and membranes, bulge test is limited to measuring only mechanical properties. Further, two different experimental setups are needed to apply pressure and make a measurement. In this work, we describe a modified bulge test, where, one single experimental setup is used to apply a pressure as well as make measurements in-situ. A membrane is clamped at its periphery, with a circular window for measurement, and sandwiched between two liquids. By controlling the extent of immersion of membrane in the liquid below the membrane, differential pressure on the membrane may be controlled. The setup was tested and validated with Nafion, a proton conducting membrane, in a 2-electrode configuration by sandwiching H2SO4-saturated Nafion between liquid gallium. Electro-impedance spectroscopy was used to quantify permeation and frequency dependent response was modelled using equivalent circuits. The resistance of Nafion increased with depth of immersion, indicating decreasing proton permeation. Conductivity was calculated to be ∼6.4 × 10−3 S/cm at equilibrium position, where stress on the membrane is zero. This value matches well with existing literature value for partially hydrated Nafion. |
Wednesday, March 17, 2021 4:36PM - 5:12PM Live |
P60.00009: Recent advances in the fabrication, performance and application of superconducting sources of THz-radiation. Invited Speaker: Ulrich Welp Electromagnetic radiation in the THz-frequency range is attracting increased interest due to a wide range of potential applications in medical diagnostics, high-bandwidth communication, security and defense, nondestructive evaluation, spectroscopy and other fields. In general, these applications would benefit from compact sources of continuous wave radiation. Here, I will review recent progress in superconducting sources of THz-radiation whose operation is based on the Josephson effect. Two successful approaches have emerged: a) Flux Flow Oscillators (FFO) based on artificial Niobium or Niobium nitride Josephson junctions that have been deployed as local oscillators and operate at frequencies in excess of 600 GHz, b) stacks of so-called Intrinsic Josephson junctions (IJJ) in highly-layered high-temperature superconductors such as Bi2Sr2CaCu2O8-d. In the latter, the synchronization of a large number of IJJ by means of a cavity resonance enables emission powers of 0.6 mW. Emission frequencies approaching 2 THz and operation at temperatures above 77 K have been achieved. Applications in imaging and spectroscopy have successfully been demonstrated. Finally, I will describe ongoing efforts in device packaging, heat management and attempts to fabricate devices on epitaxial Bi2Sr2CaCu2O8-d films. |
Wednesday, March 17, 2021 5:12PM - 5:48PM On Demand |
P60.00010: Impact of the Josephson Arbitrary Waveform Synthesizer in electrical metrology and physics Invited Speaker: Jason Underwood The recent redefinition of the SI was motivated in part by the success of quantum-based electrical standards, such as those based on the Josephson effect. Quantum standards enable the direct realization of physical quantities that are traceable to fundamental constants, invariant with respect to time, and in some cases, readily disseminated. In addition to speeding the metrological shift away from artifacts, quantum standards may usher in new measurement capabilities or profoundly reduce measurement uncertainties. One such standard for ac voltage measurements, the Josephson Arbitrary Waveform Synthesizer, or JAWS, generates quantum-accurate output waveforms by precisely controlling the timing and polarity of single flux quanta created by arrays of Josephson junctions. A JAWS is capable of synthesizing pure tones with residual distortion as low as parts in 109. Amplitude and phase accuracies are less than a part in 106 at audio frequencies. These capabilities are being employed to advance measurement science in a range of applications from the Smart Grid to modern wireless radio infrastructure to fundamental impedance metrology. In this talk I will discuss the capabilities and limitations of the JAWS, as well as highlight a few case studies where the JAWS’ accuracy and stability may impact research in condensed matter physics and remote sensing. |
Wednesday, March 17, 2021 5:48PM - 6:00PM On Demand |
P60.00011: Quantitative assessment of linear noise-reduction filters for spectroscopy Long Van Le, Young Dong Kim, David Aspnes Linear noise-reduction filters used in spectroscopy must strike a balance between reducing noise and preserving lineshapes, the two conflicting requirements of interest. Here, we quantify this tradeoff by capitalizing on Parseval’s Theorem to cast two measures of performance, mean-square error (MSE) and noise, into reciprocal- (Fourier-) space (RS). The resulting expressions are simpler and more informative than those based in direct- (spectral) space. These results provide quantitative insight not only into the effectiveness of different linear filters, but also information as to how they can be improved. Surprisingly, the rectangular (“ideal” or “brick wall”) filter is found to be nearly optimal, a consequence of eliminating distortion in low-order Fourier coefficients where the major fraction of spectral information is contained. Using the information provided by the RS version of MSE, we develop a version that is demonstrably superior to the brick-wall and also the Gauss-Hermite filter, its former nearest competitor. |
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