Response of a cold-electron bolometer in a coplanar antenna system

Kreidel M., Chu X., Balgley J., Antony A., Verma N., Ingham J., Ranzani L., Queiroz R., Westervelt R.M., Hone J., Fong K.C.

The discovery of van der Waals superconductors in recent years has generated a lot of excitement for their potentially novel pairing mechanisms. However, their typical atomic-scale thickness and micrometer-scale lateral dimensions impose severe challenges to investigations of pairing symmetry by conventional methods. We demonstrate an improved technique that employs high-quality-factor superconducting resonators to measure the kinetic inductance—up to one part per million—and loss of a van der Waals superconductor. We analyze the equivalent circuit model to extract the kinetic inductance, superfluid stiffness, penetration depth, and ratio of imaginary and real parts of the complex conductivity. We validate the technique by measuring aluminum and finding excellent agreement in both the zero-temperature superconducting gap as well as the complex conductivity data when compared with BCS theory. We then demonstrate the utility of the technique by measuring the kinetic inductance of multilayered niobium diselenide and discuss the limits to the accuracy of our technique when the transition temperature of the sample, NbSe2 at 7.06 K, approaches our Nb probe resonator at 8.59 K. Our method will be useful for practitioners in the growing fields of superconducting physics, materials science, and quantum sensing, as a means of characterizing superconducting circuit components and studying pairing mechanisms of the novel superconducting states which arise in layered two-dimensional materials and heterostructures. Published by the American Physical Society 2024

Regnier M., Manzan E., Hamilton J., Mennella A., Errard J., Zapelli L., Torchinsky S.A., Paradiso S., Battistelli E., De Bernardis P., Colombo L., De Petris M., D’Alessandro G., Garcia B., Gervasi M., et. al.

Context. Astrophysical polarized foregrounds represent the most critical challenge in cosmic microwave background (CMB) B-mode experiments, requiring multifrequency observations to constrain astrophysical foregrounds and isolate the CMB signal. However, recent observations indicate that foreground emission may be more complex than anticipated. Not properly accounting for these complexities during component separation can lead to a bias in the recovered tensor-to-scalar ratio. Aims. In this paper we investigate how the increased spectral resolution provided by band-splitting in bolometric interferometry (BI) through a technique called spectral imaging can help control the foreground contamination in the case of an unaccounted-for Galactic dust frequency de-correlation along the line of sight (LOS). Methods. We focused on the next-generation ground-based CMB experiment CMB-S4 and compared its anticipated sensitivity, frequency, and sky coverage with a hypothetical version of the same experiment based on BI (CMB-S4/BI). We performed a Monte Carlo analysis based on parametric component separation methods (FGBuster and Commander) and computed the likelihood of the recovered tensor-to-scalar ratio, r. Results. The main result is that spectral imaging allows us to detect systematic uncertainties on r from frequency de-correlation when this effect is not accounted for in the component separation. Conversely, an imager such as CMB-S4 would detect a biased value of r and would be unable to spot the presence of a systematic effect. We find a similar result in the reconstruction of the dust spectral index, and we show that with BI we can more precisely measure the dust spectral index when frequency de-correlation is present and not accounted for in the component separation. Conclusions. The in-band frequency resolution provided by BI allows us to identify dust LOS frequency de-correlation residuals where an imager with a similar level of performance would fail. This creates the possibility of exploiting this potential in the context of future CMB polarization experiments that will be challenged by complex foregrounds in their quest for B-mode detection.

Lemziakov S.A., Karimi B., Nakamura S., Lvov D.S., Upadhyay R., Satrya C.D., Chen Z.-., Subero D., Chang Y.-., Wang L.B., Pekola J.P.

AbstractThe importance and non-trivial properties of superconductor normal metal interfaces were discovered by Alexander Fyodorovich Andreev more than 60 years ago. Only much later, these hybrids have found wide interest in applications such as thermometry and refrigeration, electrical metrology, and quantum circuit engineering. Here we discuss the central properties of such interfaces and describe some of the most prominent and recent applications of them.

Likhachev S.F., Larchenkova T.I.

Sushkov A.O.

In the quest for solving the dark-matter puzzle, quantum engineering strategies for improving detection sensitivity are discussed.

Kalacheva D., Fedorov G., Khrapach I., Astafiev O.

Abstract We present a model and experimental realization of coplanar superconducting resonators terminated by a shunting kinetic inductance bridge made of ultra-thin Al films. The fabrication process that we propose allows us to create very homogeneous films, which makes them suitable for many applications in quantum devices. Due to the specific properties of the films, the resonators exhibit a Duffing oscillator behavior resulting in bifurcations and interactions between different power sources, which was previously observed in similar systems. Moreover, since the nonlinearity of such a system is concentrated at the bridge, while the wave propagates in a linear environment, it is possible to propose a simple model that accurately describes its behavior. We show that, when resonators are operated within a notch-port architecture, our model has a closed-form solution for the transmission coefficient and allows one to accurately extract parameters of the system, including the kinetic inductance of the bridge and its depairing current. Potential applications of such systems include tunable resonators, photon detectors, bifurcation and parametric amplifiers, as well as a measurement device for studying the properties of thin films.

Moskalev D.O., Zikiy E.V., Pishchimova A.A., Ezenkova D.A., Smirnov N.S., Ivanov A.I., Korshakov N.D., Rodionov I.A.

AbstractThe most commonly used physical realization of superconducting qubits for quantum circuits is a transmon. There are a number of superconducting quantum circuits applications, where Josephson junction critical current reproducibility over a chip is crucial. Here, we report on a robust chip scale Al/AlOx/Al junctions fabrication method due to comprehensive study of shadow evaporation and oxidation steps. We experimentally demonstrate the evidence of optimal Josephson junction electrodes thickness, deposition rate and deposition angle, which ensure minimal electrode surface and line edge roughness. The influence of oxidation method, pressure and time on critical current reproducibility is determined. With the proposed method we demonstrate Al/AlOx/Al junction fabrication with the critical current variation $$(\sigma /\langle {I_{c} } \rangle )$$ ( σ / ⟨ I c ⟩ ) less than 3.9% (from 150 × 200 to 150 × 600 nm2 area) and 7.7% (for 100 × 100 nm2 area) over 20 × 20 mm2 chip. Finally, we fabricate separately three 5 × 10 mm2 chips with 18 transmon qubits (near 4.3 GHz frequency) showing less than 1.9% frequency variation between qubits on different chips. The proposed approach and optimization criteria can be utilized for a robust wafer-scale superconducting qubit circuits fabrication.

Withington S.

Allys E., Arnold K., Aumont J., Aurlien R., Azzoni S., Baccigalupi C., Banday A.J., Banerji R., Barreiro R.B., Bartolo N., Bautista L., Beck D., Beckman S., Bersanelli M., Boulanger F., et. al.

Abstract LiteBIRD the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun-Earth Lagrangian point L2, where it will map the cosmic microwave background (CMB) polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of 2.2 μK-arcmin, with a typical angular resolution of 0.5○ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions and synergies with other projects. Subject Index LiteBIRD cosmic inflation, cosmic microwave background, B-mode polarization, primordial gravitational waves, quantum gravity, space telescope

Pimanov D.A., Frost V.A., Blagodatkin A.V., Gordeeva A.V., Pankratov A.L., Kuzmin L.S.

Electron on-chip cooling from the base temperature of 300 mK is very important for highly sensitive detectors operating in space due to problems of dilution fridges at low gravity. Electron cooling is also important for ground-based telescopes equipped with 3He cryostats being able to function at any operating angle. This work is aimed at the investigation of electron cooling in the low-temperature range. New samples of cold-electron bolometers with traps and hybrid superconducting/ferromagnetic absorbers have shown a temperature reduction of the electrons in the refrigerator junctions from 300 to 82 mK, from 200 to 33 mK, and from 100 to 25 mK in the idle regime without optical power load. The electron temperature was determined by solving heat balance equations with account of the leakage current, sixth power of temperature in the whole temperature range, and the Andreev current using numerical methods and an automatic fit algorithm.

Sikivie P.

In the late 1970's, the axion was proposed as a solution to the Strong CP Problem, i.e. the puzzle why the strong interactions conserve parity P and the product CP of charge conjugation and parity in spite of the fact that the Standard Model of elementary particles as a whole violates those symmetries. The original axion was soon ruled out by laboratory experiments and astrophysical considerations, but a new version was invented which is much more weakly coupled and which evades the laboratory and astrophysical constraints. It was dubbed the invisible" axion. However, the axion cannot be arbitrarily weakly coupled because it is overproduced in the early universe by vacuum realignment in the limit of vanishing coupling. The axions produced by vacuum realignment are a form of cold dark matter today. The axion provides a solution then not only to the Strong CP Problem but also to the dark matter problem. Various methods have been proposed to search for dark matter axions and for axions emitted by the Sun. Their implementation and improvement has led to significant constraints on the notion of an invisible axion. Even purely laboratory methods may place significant constraints on invisible axions or axion-like particles. This review discusses the various methods that have been proposed and provides theoretical derivations of their signals.

Gordeeva A.V., Pankratov A.L., Pugach N.G., Vasenko A.S., Zbrozhek V.O., Blagodatkin A.V., Pimanov D.A., Kuzmin L.S.

AbstractThe Cosmic Microwave Background (CMB) radiation is the only observable that allows studying the earliest stage of the Universe. Radioastronomy instruments for CMB investigation require low working temperatures around 100 mK to get the necessary sensitivity. On-chip electron cooling of receivers is a pathway for future space missions due to problems of dilution fridges at low gravity. Here, we demonstrate experimentally that in a Cold-Electron Bolometer (CEB) a theoretical limit of electron cooling down to 65 mK from phonon temperature of 300 mK can be reached. It is possible due to effective withdrawing of hot electrons from the tunnel barrier by double stock, special traps and suppression of Andreev Joule heating in hybrid Al/Fe normal nanoabsorber.

Lamagna L., Addamo G., Ade P.A., Baccigalupi C., Baldini A.M., Battaglia P.M., Battistelli E., Baù A., Bersanelli M., Biasotti M., Boragno C., Boscaleri A., Caccianiga B., Caprioli S., Cavaliere F., et. al.

The large-scale polarization explorer (LSPE) is a cosmology program for the measurement of large-scale curl-like features (B-modes) in the polarization of the cosmic microwave background. Its goal is to constrain the background of inflationary gravity waves traveling through the universe at the time of matter-radiation decoupling. The two instruments of LSPE are meant to synergically operate by covering a large portion of the northern microwave sky. LSPE/STRIP is a coherent array of receivers planned to be operated from the Teide Observatory in Tenerife, for the control and characterization of the low-frequency polarized signals of galactic origin; LSPE/SWIPE is a balloon-borne bolometric polarimeter based on 330 large throughput multi-moded detectors, designed to measure the CMB polarization at 150 GHz and to monitor the polarized emission by galactic dust above 200 GHz. The combined performance and the expected level of systematics mitigation will allow LSPE to constrain primordial B-modes down to a tensor/scalar ratio of $$10^{-2}$$ . We here report the status of the STRIP pre-commissioning phase and the progress in the characterization of the key subsystems of the SWIPE payload (namely the cryogenic polarization modulation unit and the multi-moded TES pixels) prior to receiver integration.

Schillaci A., Ade P.A., Ahmed Z., Amiri M., Barkats D., Thakur R.B., Bischoff C.A., Bock J.J., Boenish H., Bullock E., Buza V., Cheshire J., Connors J., Cornelison J., Crumrine M., et. al.

Branches of cosmic inflationary models, such as slow-roll inflation, predict a background of primordial gravitational waves that imprints a unique odd-parity “B-mode” pattern in the Cosmic Microwave Background (CMB) at amplitudes that are within experimental reach. The BICEP/Keck (BK) experiment targets this primordial signature, the amplitude of which is parameterized by the tensor-to-scalar ratio r, by observing the polarized microwave sky through the exceptionally clean and stable atmosphere at the South Pole. B-mode measurements require an instrument with exquisite sensitivity, tight control of systematics, and wide frequency coverage to disentangle the primordial signal from the Galactic foregrounds. BICEP Array represents the most recent stage of the BK program and comprises four BICEP3-class receivers observing at 30/40, 95, 150 and 220/270 GHz. The 30/40 GHz receiver will be deployed at the South Pole during the 2019/2020 austral summer. After 3 full years of observations with 30,000+ detectors, BICEP Array will measure primordial gravitational waves to a precision $$\sigma$$(r) between 0.002 and 0.004, depending on foreground complexity and the degree of lensing removal. In this paper, we give an overview of the instrument, highlighting the design features in terms of cryogenics, magnetic shielding, detectors and readout architecture as well as reporting on the integration and tests that are ongoing with the first receiver at 30/40 GHz.

Anghel D.V., Kuzmin L.S.

We investigate theoretically the possibility of using the cold-electron bolometer (CEB) as a counter for 1-cm-wavelength (30-GHz) photons. To reduce the flux of photons from the environment that interact with the detector, the bath temperature is assumed to be below 50 mK. At such temperatures, the time interval between two subsequent photons of 30 GHz that hit the detector is more than 100 h, on average, for a frequency window of 1 MHz. Such temperatures allow the observation of the physically significant photons produced in rare events, such as axion conversion (or Primakoff conversion) in a magnetic field. We present the general formalism for the detector's response and noise, together with numerical calculations for proper experimental setups. We observe that the current-biased regime is favorable due to lower noise and allows for photon counting at least below 50 mK. For the experimental setups investigated here, the voltage-biased CEBs may also work as photon counters but with less accuracy and, eventually, may require smaller volumes of the normal-metal island.