National Institute of Standards and Technology

The Simons Observatory (SO) is a new suite of cosmic microwave background telescopes in the Chilean Atacama Desert with an extensive science program spanning cosmology, Galactic and extragalactic astrophysics, and particle physics. SO will survey the millimeter-wave sky over a wide range of angular scales using six spectral bands across three types of dichroic, polarization-sensitive transition-edge sensor (TES) detector modules: Low-Frequency (LF) modules with bandpasses centered near 30 and 40 GHz, Mid-Frequency (MF) modules near 90 and 150 GHz, and Ultra-High-Frequency (UHF) modules near 220 and 280 GHz. Twenty-five UHF detector modules, each containing 1720 optically-coupled TESs connected to microwave SQUID multiplexing readout, have now been produced. This work summarizes the pre-deployment characterization of these detector modules in laboratory cryostats. Across all UHF modules, we find an average operable TES yield of 83%, equating to over 36,000 devices tested. The distributions of (220, 280) GHz saturation powers have medians of (24, 26) pW, near the centers of their target ranges. For both bands, the median optical efficiency is 0.6, the median effective time constant is 0.4 ms, and the median dark noise-equivalent power (NEP) is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>40 aW<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$/\sqrt{\mathbf {Hz}}$</tex-math></inline-formula>. The expected photon NEPs at (220, 280) GHz are (64, 99) aW<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$/\sqrt{\mathbf {Hz}}$</tex-math></inline-formula>, indicating these detectors will achieve background-limited performance on the sky. Thirty-nine UHF and MF detector modules are currently operating in fielded SO instruments, which are transitioning from the commissioning stage to full science observations.

In the paper, we develop Bayesian inference procedures for the model parameters of the multivariate location-scale model connected to the multivariate Birge ratio method, a novel approach for pooling multivariate measurements together which extends the widely-used univariate Birge ratio method. In particular, the expressions of the joint posterior, the marginal posterior and the conditional posterior distributions are derived. These findings lead to the introduction of the Metropolis–Hastings algorithm and the Gibbs sampler approach for drawing samples from the joint posterior distribution and for conducting Bayesian inference procedures based on the simulated samples. The theoretical findings of the paper are implemented in an empirical illustration by studying the effectiveness of the hypertension treatment. It is found that the anti-hypertension drugs lead to the statistically significant reduction of the systolic and diastolic blood pressure as well as to the reduction of the risk of cardiovascular disease and stroke.

Superconducting microresonators have diverse applications, including microwave kinetic inductance detectors, microwave superconducting quantum interference device multiplexers, and superconducting qubits. Arrays of such devices are typically addressed using microwave frequency combs with probe tones matched to individual device resonances. However, resonator frequency collisions caused by wafer non-uniformity and fabrication variations significantly limit usable device yields. In this Letter, we present a technique that mitigates these frequency collisions without the need for ex post facto processing. By leveraging nonlinear kinetic inductance and persistent current in a superconducting loop, we achieve in situ tuning of individual resonator frequencies within an array during device cooldown, effectively resolving frequency collisions in a way that is both highly flexible and reversible. We successfully demonstrate this technique by tuning a small array of four resonators to both identical frequencies and a uniformly spaced frequency comb. This in situ resonator tuning approach provides a universal solution for improving yield and multiplexing density in large resonator arrays, addressing a critical need for scaling up superconducting detector and qubit systems.

The solid electrolyte interphase (SEI) critically governs the reversibility of sodium metal batteries, through dynamically mediating ion transport and interfacial reactions. However, its kinetic evolution under operating conditions, and how it influences interfacial stability, remains poorly understood. Here, we reveal that the SEI undergoes coupled chemical and mechanical changes during sodium plating and stripping, leading to spatial and temporal heterogeneity that drives interfacial degradation. Synchrotron operando grazing-incidence wide-angle X-ray scattering and soft X-ray absorption spectroscopy capture the sequential formation and dissolution of inorganic SEI phases (NaF, NaH, NaOH, Na2PO3F), accompanied by depth-dependent alterations in organic SEI components. Mesoscale modeling connects this evolving SEI heterogeneity to localized current density fluctuations and stress accumulation at the Na interface, identifying pathways to electrically isolated sodium formation. These findings show that SEI instability fundamentally limits reversibility in sodium metal batteries, and that controlling SEI chemistry–mechanics coupling is essential to achieving its durability.

We describe shelving spectroscopy measurement of the 689 nm Sr intercombination line in a microfabricated vapor cell. We demonstrate a linewidth below 200 kHz in a 9 x 14 x 4.4 mm Sr vapor cell, limited primarily by transit time broadening and residual Doppler broadening. This device will be useful for developing compact optical frequency references, as well as for laser pre-stabilization for some quantum computing platforms based on alkaline earth atoms.

Atomic ions can be trapped in vacuum with dc and rf electric potentials generated by surface electrode ion traps, and used as qubits in quantum computing applications. Qubit state preparation and control is usually accomplished with laser light while the qubit state readout is achieved by observing qubit-state-dependent fluorescence from the ion while driving an optical cycling transition. The monolithic integration of optical waveguides and single-photon detectors into the ion trap itself provides both light delivery and fluorescence photon counting capability, offering benefits for scaling in trapped ion quantum computing by eliminating the need for free-space optical access to the trap. One promising candidate for integrated high-fidelity trapped-ion qubit state readout are superconducting nanowire single-photon detectors (SNSPDs). However, the joint integration of photonics and superconducting detectors into ion trap chips presents challenges for their design, fabrication, and operation. In this work, we present our progress on the integration of SNSPDs into linear ion traps with integrated photonics designed for Ca+ qubits.

Abstract Broadband and low-loss superconducting switches can facilitate large-scale quantum information processors and cryogenic detectors by dynamically reconfiguring the connectivity of their circuits. The time dependent connectivity is enabled by the nonlinearity of lossless Josephson junctions, which are often wired into superconducting loops to be controlled by magnetic flux. However, this approach needs a power-consuming constant flux bias and dynamic flux actuation, both of which are hard to isolate from other switches or flux sensitive elements, limiting their integration density. Here, we design and characterize a microwave switch that implements a persistent current bias and direct current actuation to reduce static power consumption, actuation energy and potential crosstalk to other devices. We show that persistent current associated with tens of flux quanta is stable and long-lived, reducing the need for on-the-fly tuning. We further demonstrate that our switch has desirable performance for superconducting-circuit-based quantum information processing, including an off mode with more than 20 dB isolation comparable to commercial ferrite isolators, power handling larger than 100 pW sufficient for resonator readout tones and amplifier pumps, and modulation bandwidth broader than 600 MHz useful for multiplexing schemes.

Ten years ago, we introduced a research program applying high strength combinatorial test methods to vulnerability and fault detection for cybersecurity. This article discusses advances in the field and where these methods may be effective for today’s complex security problems.

Desalination membranes are essential for global freshwater production, yet the performance of conventionally synthesized membranes is limited by the lack of synthetic control over the selective film. Solvent-based polymerization methods result in inhomogeneous density, nodular morphology, and the presence of nanoscale defects that hinder salt and boron selectivities. By employing a vapor-phase synthesis strategy, we circumvent the reliance on solvent interfaces to create compositionally homogeneous, defect-free thin-film composite polyamide membranes with Angstrom-level control over thickness. With a structure and thickness defined with nanoscale precision, we measure previously inaccessible properties of membrane selective layers, including intrinsic water and salt permeabilities, and explore the limits of thickness on membrane performance. Membranes with a 12 nm, vapor-synthesized, selective layer exhibit a two-order-of-magnitude reduction in both salt ions and uncharged boron molecules permeabilities, and a twofold improvement in NaCl selectivity relative to commercial desalination membranes. Mechanistic analysis, supported by theoretical modeling and molecular dynamics simulations, demonstrates that salt permeability increases sharply for films thinner than the Bjerrum length, revealing a physical lower bound on selective-layer thickness. These results establish a high-precision platform for probing and optimizing molecular transport in thin-film composite membranes.