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We demonstrate a sub-GHz resolution, fully programmable Fourier-domain pulse shaper capable of generating arbitrary optical pulse patterns for superconducting circuit platforms. This high resolution allows line-by-line pulse shaping of a 1 GHz-spaced comb, and the pulse shaper can accommodate an optical bandwidth as large as 1 THz, which represents the highest resolution programmable line-by-line pulse shaping to our knowledge. Linear optical sampling with a dual-comb system confirms independent control of 1 GHz-spaced optical lines, and the low phase noise of the pulse shaper is characterized. We apply the pulse shaper as an optical drive for an array of Josephson junctions operating at a temperature of 4 K, where cryogenic photodetection of pulse doublets with user-defined separation characterizes the Josephson junction response. Furthermore, we demonstrate a pulse-density modulation pattern of 4 ps duration optical pulses that can serve as the high bandwidth drive of a quantum-based Josephson arbitrary waveform synthesizer. By leveraging the exquisite control, large bandwidth, and low noise of photonics, this represents an important advance toward the realization of high power and high spectral purity AC voltage standards at gigahertz frequencies without requiring 100 GHz bandwidth driving electronics. [ABSTRACT FROM AUTHOR]

1. IntroductionFor the forthcoming redefinition of the kelvin in the International System of Units (SI), an exact numerical value for the Boltzmann constant k in units of joules per kelvin [...]

We show proof of concept of a transmission-mode wavelength filtering device consisting of layered holographically formed polymer dispersed liquid crystal (H-PDLC) cells. H-PDLC cells were fabricated from a thiolene based polymer composite to have transmission notches in the near-IR wavelength range. Wavelength filtering was achieved by stacking four H-PDLC cells with transmission notches spaced at 10 nm intervals. Results show a broad transmission notch spanning the spectral width of the constituent cells. With bias applied to an individual cell within the stack, the transmission notch of the cell inverts and the overall transmission envelope changes shape. Using a transmitted energy sensing device and a lineshape mapping algorithm, spectral content can be determined to a resolution of 0.1 nm for narrow banded signals. Applications for this switchable wavelength filtering device include serial detection of spectral content for telecom data signals or chemical and biological sample identification through absorption or emission spectroscopy. OCIS codes: 090.2890, 160.0160, 300.6190, 310.6860.

We demonstrate a tenfold increase in the amplitude of microwave-frequency waveforms generated by a quantum-defined superconducting voltage source, with an open-circuit signal of 17.56 mV rms at 1.005 GHz. The voltage source is an RF Josephson arbitrary waveform synthesizer (RF-JAWS) that utilizes a circuit that is cooled to 4 K and is composed of an array of 4500 Josephson junctions. These junctions are connected in series along the center conductor of a 50- $\Omega $ superconducting coplanar waveguide transmission line. We introduce a new zero-forcing equalization technique for reducing distortion in drive current pulse patterns. This technique allows an increase in the amplitude of the quantum-based voltage waveforms while suppressing parasitic feedthrough signals to −75 dBc. Synthesizing a two-tone delta–sigma waveform, we monitor an audio-frequency 10-kHz tone of less than 100- $\mu \text{V}$ rms amplitude while simultaneously measuring the 1.005-GHz tone of −28.12-dBm power in a 50- $\Omega $ environment. The two-tone synthesis allows simultaneous verification of correct operation of the voltage source using time-efficient low-frequency measurement techniques as well as slower microwave measurements. [ABSTRACT FROM AUTHOR]

We construct cosmic microwave background lensing mass maps using data from the 2014 and 2015 seasons of observations with the Atacama Cosmology Telescope (ACT). These maps cover 2100 square degrees of sky and overlap with a wide variety of optical surveys. The maps are signal dominated on large scales and have fidelity such that their correlation with the cosmic infrared background is clearly visible by eye. We also create lensing maps with thermal Sunyaev−Zel'dovich contamination removed using a novel cleaning procedure that only slightly degrades the lensing signal-to-noise ratio. The cross-spectrum between the cleaned lensing map and the BOSS CMASS galaxy sample is detected at 10σ significance, with an amplitude of A = 1.02 ± 0.10 relative to the Planck best-fitting Lambda cold dark matter cosmological model with fiducial linear galaxy bias. Our measurement lays the foundation for lensing cross-correlation science with current ACT data and beyond. [ABSTRACT FROM AUTHOR]

In this article, we characterize the microwave behavior of superconductive circuits for quantum voltage standard applications at 4 K. For that, we develop a cryogenic multiline thru-reflect-line (TRL) calibration procedure to calibrate the microwave measurements at the 4 K on-wafer reference plane. We model superconductive circuits, including a Josephson array transmission line, compare simulated to TRL-calibrated measured results, and find excellent agreement up to 50 GHz. [ABSTRACT FROM AUTHOR]

The uniformity of the barriers in Josephson junctions (JJs) is a critical parameter in determining performance and operating margins for a wide variety of superconducting electronic circuits. We present an automated measurement system capable of measuring individual JJs across a 1 × 1 cm die at both ambient temperature and 4 K. This technique allows visualization of the spatial variation over a large area of the critical electrical properties of the junctions and allows for the direct correlation between room-temperature (RT) resistance and low temperature properties. The critical current variation of NbxSi1-x (x = 15%) barriers is found to be about 2.6% (one standard deviation) for 1024 junctions across an individual die and only weakly correlates with RT resistance measurements. [ABSTRACT FROM AUTHOR]

A study has been performed to understand the effects of magnetic field induced current in Josephson voltage standard (JVS) circuits. Inductive filtering is an essential component in JVS devices for isolation of the microwave and dc bias signals within the circuit. However, currents induced by bias currents flowing in the inductor coil cause undesirable effects in the neighboring junctions. These undesirable effects are amplified as circuits grow in density, with limited die space causing inductors to be placed in close proximity to devices. This paper characterizes critical-current suppression of a junction array, as induced currents are introduced into the circuit under various conditions. Results show that critical current suppression is both a function of inductor magnetic field but also of the coupling to the nearby circuit structure. Design variations explore solutions for rerouting or reducing induced currents. A shield around the inductors proved to be best and most practical for protecting the junction circuit from induced currents. Results from actual JVS devices with shielded low-pass filters confirm the technique. [ABSTRACT FROM AUTHOR]

We describe the implementation of new commercial pulse-bias electronics that have enabled an improvement in the generation of quantum-accurate waveforms both with and without low-frequency compensation biases. We have used these electronics to apply a multilevel pulse bias to the Josephson arbitrary waveform synthesizer and have generated, for the first time, a quantum-accurate bipolar sinusoidal waveform without the use of a low-frequency compensation bias current. This uncompensated 1 kHz waveform was synthesized with an rms amplitude of 325 mV and maintained its quantum accuracy over a 1.5 mA operating current range. The same technique and equipment was also used to synthesize a quantum-accurate 1 MHz sinusoid with a 1.2 mA operating margin. In addition, we have synthesized a compensated 1 kHz sinusoid with an rms amplitude of 1 V and a 2.7 mA operating margin. [ABSTRACT FROM PUBLISHER]

The root-mean-square (rms) output voltage of the National Institute of Standards and Technology (NIST) Josephson arbitrary waveform synthesizer (JAWS) has been doubled from 1 V to a record 2 V by combining two new 1 V chips on a cryocooler. This higher voltage will improve calibrations of ac thermal voltage converters and precision voltage measurements that require state-of-the-art quantum accuracy, stability, and signal-to-noise ratio. We achieved this increase in output voltage by using four on-chip Wilkinson dividers and eight inner/outer dc blocks, which enable biasing of eight Josephson junction (JJ) arrays with high-speed inputs from only four high-speed pulse generator channels. This approach halves the number of pulse generator channels required in future JAWS systems. We also implemented on-chip superconducting interconnects between JJ arrays, which reduces systematic errors and enables a new modular chip package. Finally, we demonstrate a new technique for measuring and visualizing the operating current range that reduces the measurement time by almost two orders of magnitude and reveals the relationship between distortion in the output spectrum and output pulse sequence errors. [ABSTRACT FROM AUTHOR]

The two main challenges to operating a programmable Josephson voltage standard (PJVS) on a cryocooler are the available cooling power and the temperature oscillations of the cold head. We overcame these challenges and successfully operated a PJVS circuit on a cryocooler by employing one supercritical helium buffer that damps the temperature oscillations, developing a new cryogenic package that increases the thermal conductivity between the chip and the cold head, and increasing overall device performance with fabrication improvements. A 1.32 mA step width of the quantized voltage produced with all of the subarrays of the PJVS circuit biased was achieved at an operating temperature of 4.3 K. The quantum accuracy of the PJVS is maintained at temperatures up to 4.8 K. This result was obtained with a cryocooler that employs a 3 kW water-cooled compressor to produce at the chip about 270 mW of net cooling power at 4.3 K.11

Contribution of the U.S. government, not subject to copyright. [ABSTRACT FROM PUBLISHER]

A quantum-accurate waveform with an rms output amplitude of 1 V has been synthesized for the first time. This fourfold increase in voltage over previous systems was achieved through developments and improvements in bias electronics, pulse-bias techniques, Josephson junction array circuit fabrication, and packaging. A recently described ac-coupled bipolar pulse-bias technique was used to bias a superconducting integrated circuit with 25 600 junctions, which are equally divided into four series-connected arrays, into the second quantum state. We describe these advancements and present the measured 1 V spectra for 2 Hz and 10 Hz sine waves that remained quantized over a 0.4 mA current range. We also demonstrate a 2 kHz sine wave produced with another bias technique that requires no compensation current and remains quantized at an rms voltage of 128 mV over a 1 mA current range. Increasing the clock frequency to 19 GHz also allowed us to achieve a maximum rms output voltage for a single array of 330 mV. [ABSTRACT FROM PUBLISHER]

We present a comparison of materials for adhering layers of holographically formed polymer dispersed liquid crystal (H-PDLC) films layered in stacks fabricated on common substrates. The results of this study are used in applications that rely on maximization of transmitted light through the layers of H-PDLC. Data is presented by comparing a simulated transmission envelope modeled on the individual H-PDLC cells with the actual stacked transmission spectrum. Additionally, data is presented on the quality of the wavefront of H-PDLC transmission spectrum individually and layered using air and index matching layers. [ABSTRACT FROM AUTHOR]

Transition-edge sensor microcalorimeters with recovery times near 1 μs have become highly desirable in quantum science applications as near-infrared single-photon detectors with photon-number resolving capability. Previously, the recovery times of these devices could be decreased only by changing device material or modifying the superconducting-to-normal transition. We demonstrate a method for improving this speed that uses a normal-metal heat-sink. This demonstration with tungsten devices realizes a factor of 4 decrease in recovery time without significantly affecting energy resolution. Our approach may enable the creation of high-efficiency transition-edge sensors with decay times short enough to operate with 80 MHz pulsed single-photon sources. [ABSTRACT FROM AUTHOR]

We show proof of concept of a real-time reconfigurable photomask fabricated from holographically formed polymer-dispersed liquid crystal (H-PDLC) reflection gratings on etched indium tin oxide patterned electrodes. H-PDLC films were formed using a thiolene based polymer to have a reflection wavelength that modulates 440 nm, the peak sensitivity wavelength of Shipley 1800 series positive photoresist. A working prototype of this adaptable photomask device is shown by comparing patterns formed using the H-PDLC mask and similar patterns formed using a static contact photomask showing that H-PDLC films have the ability to modulate 440 nm light and control the exposure dose of photoresist. [ABSTRACT FROM AUTHOR]

Abstract: We present the case of a 44-year-old lady with an ‘L-shaped’ intermediate cuneiform. Plain radiography did not identify the anomaly but showed osteoarthritic changes in her tarsometatarsal joint. At the time of sugical fusion, an ‘L-shaped’ intermediate cuneiform was observed, preventing the medial cuneiform articulating with the navicular bone. Fusion of the medial through the intermediate, to the navicular bone was successful at resolving her midfoot pain. [Copyright &y& Elsevier]