A wide variety of applications of microwave cavities, such as measurement and control of superconducting qubits, magnonic resonators, and phase noise filters, would be well served by having a highly tunable microwave resonance. Often this tunability is desired in situ at low temperatures, where one can take advantage of superconducting cavities. To date, such cryogenic tuning while maintaining a high quality factor has been limited to $\sim500$ MHz. Here we demonstrate a three-dimensional superconducting microwave cavity that shares one wall with a pressurized volume of helium. Upon pressurization of the helium chamber the microwave cavity is deformed, which results in in situ tuning of its resonant frequency by more than 5 GHz, greater than 60% of the original 8 GHz resonant frequency. The quality factor of the cavity remains approximately constant at $\approx7\times 10^{3}$ over the entire range of tuning. As a demonstration of its usefulness, we implement a tunable cryogenic phase noise filter, which reduces the phase noise of our source by approximately 10 dB above 400 kHz.
Prime-Cam is a first-generation instrument for the Cerro Chajnantor Atacama Telescope-prime (CCAT-prime) Facility. The 850$~$GHz module for Prime-Cam will probe the highest frequency of all the instrument modules. We describe the parameter space of the 850$~$GHz optical system between the F$λ$ spacing, beam size, pixel sensitivity, and detector count. We present the optimization of an optical design for the 850$~$GHz instrument module for CCAT-prime. We further describe the development of the cryogenic RF chain design to accommodate $>$30 readout lines to read 41,400 kinetic inductance detecto…
The ability to achieve strong-coupling has made cavity-magnon systems an exciting platform for the development of hybrid quantum systems and the investigation of fundamental problems in physics. Unfortunately, current experimental realizations are constrained to operate at a single frequency, defined by the geometry of the microwave cavity. In this article we realize a highly-tunable, cryogenic, microwave cavity strongly coupled to magnetic spins. The cavity can be tuned in situ by up to 1.5 GHz, approximately 15% of its original 10 GHz resonance frequency. Moreover, this system remains within…
We describe an instrument which can be used to analyze complex chemical mixtures at high resolution and high sensitivity. Molecules are collisionally cooled with helium gas at cryogenic temperatures (~ 4-7 K), and subsequently detected using chirped pulse microwave spectroscopy. Here we demonstrate three significant improvements to the apparatus relative to an earlier version: (1) extension of its operating range by more than a factor of two, from 12-18 GHz to 12-26 GHz, which allows a much wider range of species to be characterized; (2) improved detection sensitivity owing to use of cryogenic…
ALMA has been operating since 2011, but has not yet been populated with the full suite of intended frequency bands. In particular, ALMA Band 2 (67-90 GHz) is the final band in the original ALMA band definition to be approved for production. We aim to produce a wideband, tuneable, sideband-separating receiver with 28 GHz of instantaneous bandwidth per polarisation operating in the sky frequency range 67-116 GHz. Our design anticipates new ALMA requirements following the recommendations in the 2030 ALMA Development Roadmap. The cryogenic cartridge is designed to be compatible with the ALMA Band …
High-finesse, open-geometry microcavities have recently emerged as a versatile tool for enhancing interactions between photons and material systems, with a range of applications in quantum optics and quantum information science. However, mechanical vibrations pose a considerable challenge to their operation within a closed-cycle cryostat, particularly when spatial tunability and free-space optical access are required. Here, we present the design and characterization of a system that can achieve $\sim$16 pm-rms passive mechanical stability between two high-finesse mirrors while permitting both …
Large arrays of cryogenic detectors, including transition-edge sensors (TESs) or magnetic micro-calorimeters (MMCs), are needed for future experiments across a wide range of applications. Complexities in integration and cryogenic wiring have driven efforts to develop cryogenic readout technologies with large multiplexing factors while maintaining minimal readout noise. One such example is the microwave SQUID multiplexer ($μ$mux), which couples an incoming TES or magnetic calorimeter signal to a unique GHz-frequency resonance that is modulated in frequency. Here, we present a hybrid scheme comb…
We studied noise properties of microwave signals transmitted through the cryogenic resonator. The experiments were performed with the 11.342 GHz sapphire loaded cavity resonator cooled to 6.2 K. Based on the measured transmission coefficient of the cryogenic resonator we computed its noise suppression function. This was done via Monte-Carlo simulations some details of which are discussed in this Letter. Next, we measured technical fluctuations of a signal incident on the cryogenic resonator. Having processed these data with the previously computed noise filtering "template" we inferred noise s…
This paper presents a low noise amplifier for large arrays of silicon photomultipliers (SiPMs) operated in cryogenic environments, especially liquid argon (87 K) and liquid nitrogen (77 K). The goal is for one amplifier to read out a total photosensitive surface of tens of cm$^2$ while retaining the capability to resolve single photoelectron signals. Due to the large capacitance of SiPMs, typically a few nF per cm$^2$, the main contributor to noise is the series (voltage) component. A silicon-germanium heterojunction bipolar transistor (HBT) was selected as the input device of the cryogenic am…
3D-Structured Polyethylene Windows for Low-Loss Transmission in Wideband Cryogenic Terahertz Systems
Chalmers University of Technology（查尔姆斯理工大学）；Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS, Grenoble INP, CROMA（格勒诺布尔阿尔卑斯大学、萨瓦-蒙布朗大学、法国国家科学研究中心、格勒诺布尔理工学院、CROMA）
We present two prescriptions for broadband (~77 - 252 GHz), millimeter-wave antireflection coatings for cryogenic, sintered polycrystalline aluminum oxide optics: one for large-format (700 mm diameter) planar and plano-convex elements, the other for densely packed arrays of quasi-optical elements, in our case 5 mm diameter half-spheres (called "lenslets"). The coatings comprise three layers of commercially-available, polytetrafluoroethylene-based, dielectric sheet material. The lenslet coating is molded to fit the 150 mm diameter arrays directly while the large-diameter lenses are coated using…
