Kinetic Inductance Research Articles

Hybrid α -Ta/ β -Ta lumped element kinetic inductance detectors with photon noise limited sensitivity and stability

The terahertz (THz) band is of immense interest in astronomy as it encompasses significant energy generated following the Big Bang, offering critical insight into processes invisible in other bands, such as the earliest stages of planet, star, and galaxy formation. Kinetic inductance detectors (KIDs) have emerged as a formidable contender in the field of THz astronomy, attributed to their exceptional sensitivity and scalability. In this study, we introduce a kind of KIDs incorporating a lumped element (LE) resonator design, with inductors fabricated on β-Ta film and capacitors on α-Ta film. We characterize the noise of the hybrid α-Ta/β-Ta LEKIDs, achieving an optical noise equivalent power of 8.3 ± 5.7 × 10−19 W/Hz1/2, demonstrating high sensitivity. Additionally, the LEKIDs exhibited stability across multiple thermal cycles. The combination of high sensitivity and stability makes the hybrid LEKIDs promising for the stringent demands of THz astronomy.

Doubling photon-processing power for MKID readout

Scalable platform based on Radio-Frequency System-on-Chip technology can read out twice as many Microwave Kinetic Inductance Detectors as previous systems.

Kinetic inductance current sensor for visible to near-infrared wavelength transition-edge sensor readout

Single-photon detectors based on the superconducting transition-edge sensor are used in a number of visible to near-infrared applications, particularly for photon-number-resolving measurements in quantum information science. To be practical for large-scale spectroscopic imaging or photonic quantum computing applications, the size of visible to near-infrared transition-edge sensor arrays and their associated readouts must be increased from a few pixels to many thousands. In this manuscript, we introduce the kinetic inductance current sensor, a scalable readout technology that exploits the nonlinear kinetic inductance in a superconducting resonator to make sensitive current measurements. Kinetic inductance current sensors can replace superconducting quantum interference devices for many applications because of their ability to measure fast, high slew-rate signals, their compatibility with standard microwave frequency-division multiplexing techniques, and their relatively simple fabrication. Here, we demonstrate the readout of a visible to near-infrared transition-edge sensor using a kinetic inductance current sensor with 3.7 MHz of bandwidth. We measure a readout noise of 1.4pA/Hz\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.4\\,{{{\\rm{pA}}}}/\\sqrt{{{{\\rm{Hz}}}}}$$\\end{document}, considerably below the detector noise at frequencies of interest, and an energy resolution of (0.137 ± 0.001) eV at 0.8 eV, comparable to resolutions observed with non-multiplexed superconducting quantum interference device readouts.

Analysis of Delay and Dynamic Crosstalk in Spatially Arranged Mixed CNT Bundle Interconnects at Different Technology Nodes

In the present nanoscale regime, mixed carbon nanotube bundles (MCBs) are considered to be highly promising interconnect options. This research paper introduces a spatially arranged mixed carbon nanotubes (CNTs) bundle (MCB), wherein single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) occupy equal halves in the MCB. An equivalent single conductor (ESC) model for MCB is employed to analyze the interconnect performances in terms of signal transmission delay and dynamic crosstalk delay at different technology nodes (i.e., 32nm, 22nm, and 16 nm). Encouragingly, a significant reduction in signal transmission delay and dynamic crosstalk induced delay are observed at 32 nm technology node. It is observed that at 32 nm technology node, the propagation delay and crosstalk induced delay significantly improves by 29.40% and 55.53%, respectively, compared to 22 nm technology node and 187.88% and 185.94%, respectively, compared to 16 nm technology node. The improvement in interconnect performances can primarily be attributed to the improvement in the number of conducting channels inside the MCB at 32 nm, which greatly impacted the interconnect parasitics such as quantum resistance, quantum capacitance, kinetic inductance etc.

Absolute Reference for Microwave Polarization Experiments. The COSMOCal Project and its Proof of Concept

Context. The cosmic microwave background (CMB), a remnant of the Big Bang, provides unparalleled insights into the primordial universe, its energy content, and the origin of cosmic structures. The success of forthcoming terrestrial and space experiments hinges on meticulously calibrated data. Specifically, the ability to achieve an absolute calibration of the polarization angles with a precision of <0.°1 is crucial to identify the signatures of primordial gravitational waves and cosmic birefringence within the CMB polarization. Aims. We introduce the COSmological Microwave Observations Calibrator project, designed to deploy a polarized source in space for calibrating microwave frequency observations. The project aims to integrate microwave polarization observations from small and large telescopes, ground-based and in space, into a unified scale, enhancing the effectiveness of each observatory and allowing robust combination of data. Methods. To demonstrate the feasibility and confirm the observational approach of our project, we developed a prototype instrument that operates in the atmospheric window centered at 260 GHz, specifically tailored for use with the NIKA2 camera at the IRAM 30 m telescope. Results. We present the instrument components and their laboratory characterization. The results of tests performed with the fully assembled prototype using a Kinetic Inductance Detectors-based instrument, similar concept of NIKA2, are also reported. Conclusions. This study paves the way for an observing campaign using the IRAM 30 m telescope and contributes to the development of a space-based instrument.

MKIDGen3: Energy-resolving, single-photon-counting microwave kinetic inductance detector readout on a radio frequency system-on-chip.

Microwave Kinetic Inductance Detectors (MKIDs) are superconducting detectors capable of single-photon counting with energy resolution across the ultraviolet, optical, and infrared (UVOIR) spectrum with microsecond timing precision. MKIDs are also multiplexable, providing a feasible way to create large-format, cryogenic arrays for sensitive imaging applications in biology, astronomy, and quantum information. Building large, cryogenic MKID arrays requires processing highly multiplexed, wideband readout signals in real time; this task has previously required large, heavy, and power-intensive custom electronics. In this work, we present the third-generation UVOIR MKID readout system (Gen3), which is capable of reading out twice as many detectors with an order of magnitude lower power, weight, volume, and cost-per-pixel as compared to the previous system. Gen3 leverages the Xilinx RFSoC4x2 platform to read out 2048, 1MHz MKID channels per board. The system takes a modern approach to FPGA design using Vitis High-Level Synthesis to specify signal processing blocks in C/C++, Vivado ML intelligent design runs to inform implementation strategy and close timing, and Python productivity for Zynq to simplify interacting with and programming the FPGA using Python. This design suite and tool flow allows general users to contribute to and maintain the design and positions Gen3 to rapidly migrate to future platforms as they become available. In this work, we describe the system requirements, design, and implementation. We also provide performance characterization details and show that the system achieves detector-limited resolving power in the case of few readout tones and minimal degradation with all 2048 tones. Planned upgrades and future work are also discussed. The Gen3 MKID readout system is fully open-source and is expected to facilitate future array scaling to megapixel-sized formats and increase the feasibility of deploying UVOIR MKIDs in space.

KISS: Instrument Description and Performance

Kinetic inductance detectors (KIDs) have been proven as reliable systems for astrophysical observations, especially in the millimeter range. Their compact size enables them to optimally fill the focal plane, thus boosting sensitivity. The KIDs Interferometric Spectral Surveyor (KISS) instrument is a millimeter camera that consists of two KID arrays of 316 pixels each coupled to a Martin–Puplett interferometer (MPI). The addition of the MPI grants the KID camera the ability to provide spectral information in the 100 and 300 GHz range. In this paper, we report the main properties of the KISS instrument and its observations. We also describe the calibration and data analysis procedures used. We present a complete model of the observed data including the sky signal and several identified systematics. We have developed a full photometric and spectroscopic data analysis pipeline that translates our observations into science-ready products. We show examples of the results of this pipeline on selected sources: the Moon, Jupiter, and Venus. We note the presence of a deficit of response with respect to expectations and laboratory measurements. The detector's noise level is consistent with values obtained during laboratory measurements, pointing to a suboptimal coupling between the instrument and the telescope as the most probable origin for the problem. This deficit is large enough to prevent the detection of galaxy clusters, which were KISS's main scientific objective. Nevertheless, we have demonstrated the feasibility of this kind of instrument in the prospect of other KID interferometers (such as the CONCERTO instrument). In this regard, we have developed key instrumental technologies such as optical conception, readout electronics, and raw calibration procedures, as well as adapted data analysis procedures.

Microwave Kinetic Inductance Detector Made of Molecular Beam Epitaxy (MBE)-Grown MgB2 Film.

We present a MgB2-based Microwave Kinetic Inductance Detector (MKID) featuring a quality factor Qi ~ 105 and noise equivalent power NEP ~ 10-14 W/Hz at 2 K. In comparison to YBCO-based MKIDs, the MgB2 detector shows greater sensitivity to both temperature and magnetic field, a result of its two-gap nature and relatively low critical Hc2 field. Our data indicate that MgB2 is more advantageous for MKID applications at temperatures lower than 3 K.

M2CS: A Microwave Measurement and Control System for Large-scale Superconducting Quantum Processors

Abstract As superconducting quantum computing continues to advance at an unprecedented pace, there is a compelling demand for the innovation of specialized electronic instruments that act as crucial conduits between quantum processors and host computers. Here, we introduce a Microwave Measurement and Control System (M2CS) dedicated for large-scale superconducting quantum processors. M2CS features a compact modular design that balances overall performance, scalability and flexibility. Electronic tests of M2CS show key metrics comparable to commercial instruments. Benchmark tests on transmon superconducting qubits further show qubit coherence and gate fidelities comparable to state-of-the-art results, confirming M2CS’s capability to meet the stringent requirements of quantum experiments run on intermediate-scale quantum processors. The compact and scalable nature of our design holds the potential to support over 1000 qubits after upgrade in stability and integration. The M2CS architecture may also be adopted to wider range of scenarios, including other quantum computing platforms such as trapped ions and silicon quantum dots, as well as more traditional applications like microwave kinetic inductance detectors, phased array radar systems.

Path-entangled radiation from a kinetic inductance amplifier

Path-entangled radiation from a kinetic inductance amplifier

Performance of a phonon-mediated kinetic inductance detector at the NEXUS cryogenic facility

Performance of a phonon-mediated kinetic inductance detector at the NEXUS cryogenic facility

Significant contributions of the Higgs mode and impurity-scattering self-energy corrections to the low-frequency complex conductivity in dc-biased superconducting devices

We investigate the complex conductivity of superconductors under a direct-current (dc) bias based on the well-established Keldysh-Eilenberger formalism of nonequilibrium superconductivity. This robust framework allows us to account for the Higgs mode and impurity-scattering self-energy corrections, which are now known to significantly impact the complex conductivity under a bias dc, especially near the resonance frequency of the Higgs mode. The purpose of this paper is to explore the effects of these contributions on the low-frequency complex conductivity relevant to superconducting device technologies. We begin by nonperturbatively calculating the equilibrium Green’s functions under a bias dc, followed by an analysis of the time-dependent perturbative components. This approach enables us to derive the complex conductivity formula for superconductors ranging from clean to dirty limits, applicable to any bias dc strength. We validate our theoretical approach by reproducing known results and experimentally observed features, such as the characteristic peak in σ1 and the dip in σ2 attributed to the Higgs mode. Our calculations reveal that the Higgs mode and impurity-scattering self-energy corrections significantly affect the complex conductivity even at low frequencies (ℏω≪Δ), relevant to superconducting device technologies. Specifically, we find that the real part of the low-frequency complex conductivity, σ1, exhibits a bias-dependent reduction up to ℏω∼0.1, a much higher frequency than previously considered. This finding allows for the suppression of dissipation in devices by tuning the bias dc. Additionally, through the calculation of the imaginary part of the complex conductivity, σ2, we evaluate the bias-dependent kinetic inductance for superconductors ranging from clean to dirty limits. The bias dependence becomes stronger as the mean free path decreases. Our dirty-limit results coincide with previous studies based on the oscillating superfluid density (the so-called slow experiment) scenario. This widely used scenario can be understood as a phenomenological implementation of the Higgs mode into the kinetic inductance calculation, now justified by our calculation based on the robust theory of nonequilibrium superconductivity, which microscopically treats the Higgs-mode contribution. These results highlight the importance of considering the Higgs mode and impurity-scattering self-energy corrections in the design and optimization of superconducting devices under a bias dc. Published by the American Physical Society 2024

Superconducting resonator parametric amplifiers with intrinsic separation of pump and signal tones

Abstract Superconducting resonator parametric amplifiers achieve ultra-low-noise amplification through the nonlinear kinetic inductance of thin-film superconductors. One of the main challenges to the operation of these devices is the separation of the strong pump tone from the signal tone after amplification has been achieved. In this paper, we propose and experimentally demonstrate a pump separation method based on operating a half-wave superconducting resonator amplifier behind a cryogenic circulator. Our pump separation scheme does not involve post-amplification interference, and thereby avoids the delicate phase matching of two different pump paths. We demonstrate the scheme using two-port half-wave resonator amplifiers based on superconducting NbN thin-films. We present measurements of gain profiles and degrees of pump separation for amplifiers having different coupling quality factors. On an amplifier having a coupling quality factor of ~2000, we measured a peak signal gain of 15 dB whilst achieving pump separation of 12 dB. The amplifier was stable for continuous measurements, and the gain drift was measured to be 0.15 dB over an hour. The same amplifier was operated at 3.2 K and achieved a peak signal gain of 11 dB whilst having a pump separation factor of 10.5 dB. The pump separation scheme, and these promising results, will advance the development of superconducting resonator amplifiers as an important technology in quantum sensing.

A 25-micrometer Single-Photon-Sensitive Kinetic Inductance Detector

We report measurements characterizing the performance of a kinetic inductance detector array designed for a wavelength of 25 microns and very low optical background level suitable for applications such as a far-infrared instrument on a cryogenically cooled space telescope. In a pulse-counting mode of operation at low optical flux, the detectors can resolve individual 25-micron photons. In an integrating mode, the detectors remain photon noise limited over more than 6 orders of magnitude in absorbed power from 70 zW to 200 fW, with a limiting noise equivalent power of 4.6×10−20 W Hz−1 at 1 Hz. In addition, the detectors are highly stable with flat power spectra under optical load down to 1 mHz. Operational parameters of the detector are determined including the efficiency of conversion of the incident optical power into quasiparticles in the aluminum absorbing element and the quasiparticle self-recombination constant. Published by the American Physical Society 2024

The universal gaseous detonation dynamics

The present communication proposes a new scaling approach to unify the dynamics of gaseous detonations subject to wall losses in both the narrow channels and small tubes, by compiling the published experimental data of detonations in 23 different mixtures with a very large range of cellular instabilities. A kinetic induction length Δi,loss can be determined from the detonation velocity deficit and detailed chemistry. In order to take into account the sensitivity of the latter length to post-shock temperature fluctuations (through the reduced activation energy θ), which is a partial and indirect marker of the cellular structure, and to bring out energetics (through the Chapman–Jouguet detonation Mach number MCJ), an effective kinetic length of Δi,loss(MCJ4/θ3) was built and has been shown to collapse the different detonation dynamics of various gaseous mixtures, subjected to wall losses, into a single universal curve for detonation velocity deficits.Novelty and Significance: Scaling analysis of large sets of published data of gaseous detonation experiments in narrow channels and small tubes has been made for 23 different mixtures with varied cellular instabilities and activation energies. The universal dynamics of gaseous detonations subject to wall losses in different mixtures has been achieved, for the first time, by adopting an effective kinetic length by taking into account the effect of both the activation energy and the energetics.

Differential modulation of photosystem II photochemical efficiency in six C4 xero-halophytes.

Xero-halophytes are the salt-tolerant plants of dry habitats that adapt efficient strategies to endure extreme salt and water fluctuations. This study elucidated the adaptations related to PSII photochemistry, photoprotection, and photoinhibition in six C4 xero-halophytes (Atriplex stocksii , Haloxylon stocksii , Salsola imbricata, Suaeda fruticosa, Desmostachya bipinnata , and Saccharum griffithii ) grown in their native habitats. Chlorophyll a fluorescence quenching measurements suggested that S. imbricata and H. stocksii maintained efficient PSII photochemistry by downregulating heat dissipation and keeping a high fraction of open PSII centres that indicates plastoquinone (PQ) pool oxidation. Fluorescence induction kinetics revealed that S. imbricata demonstrated the highest performance index of PSII excitation to the reduction of end electron acceptors. S. fruticosa sustained photochemical efficiency through enhanced dissipation of excess energy and a low fraction of open PSII centres, indicating PQ reduced state. The large light-harvesting antenna size, deduced from the chlorophyll a /b ratio in S. fruticosa apparently led to the superior performance index of PSII excitation to the reduction of intersystem electron carriers. A. stocksii retained more open PSII centres with responsive non-photochemical quenching to safely dissipate excess energy. Despite maintaining the highest pigment contents and stoichiometry, A. stocksii remained lowest in both performance indices. The grass species D. bipinnata and S. griffithii kept fewer PSII centres open during photoinhibition, as evidenced by downregulation of PSII operating efficiency. The results provide insights into the differential modulation of PSII photochemical efficiency through dynamic control of photoprotective energy dissipation, PQ pool redox states, and photoinhibitory shutdown in these xero-halophytes.

TLS noise reduction in microwave kinetic inductance detectors using a parallel plate capacitor with a three-layer dielectric

&lt;p&gt;Over the past two decades, microwave kinetic inductance detectors (MKIDs) have gained exceptional importance in millimeter and sub-millimeter astronomy. MKIDs consist of thin strip resonators capable of detecting changes in the surface impedance of superconductor strips, which result from variations in resonance circuit properties. The principal noise in MKIDs comprises excess frequency noise and two-level system noise. In this paper, we propose a technique to mitigate the effect of two-level system (TLS) noise in MKIDs using a parallel plate capacitor with three layers of high ε dielectrics. To achieve this, we employ three layers of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;, HfO&lt;sub&gt;2&lt;/sub&gt;, and TiO&lt;sub&gt;2&lt;/sub&gt; with equal thickness between the capacitor plates. The experimental results demonstrate a nearly 30% reduction in TLS power spectral density.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;

Impact of Pulse Electric Field Stimulation on Negative Air Ion Release Capacity of Snake Plants

To investigate the effects of pulse electric field stimulation on the photosynthetic electron transport chain and negative air ion (NAI) release capacity of snake plants, the chlorophyll content, fluorescence induction kinetics curve (OJIP curve), chlorophyll fluorescence parameters, and NAI release concentration of snake plants kept under identical greenhouse conditions under different pulse electric field stimulations were compared and analyzed. The experimental results show that (1) after pulse electric field stimulation, the chlorophyll content in treatment group T1 (5 kv) and T2 (7 kv) of snake plants increased by 6.30% and 6.70%, respectively, with significant differences observed between the two treatment groups and the control group (CK). (2) In both treatment groups, the OJIP curve exhibited higher values for the inflection point (I) and peak (P) compared to the origin (O) and inflection point (J) values, with the rising trend in the I–P segment being more gentle than that of the O–J segment. Additionally, the J band was above 0, with the peak value in the T2 group being higher than that in the T1 group. (3) The chlorophyll fluorescence parameters showed fluctuating variations. Specifically, Fm, TRo/CSo, ETo/CSo, and DIo/CSo showed ascending trends in the treatment groups. Fv/Fo, Sm, and ABS/RC exhibited descending trends; Fv/Fm, Vj, ETo/RC, and φEo showed relatively minor changes. The PIabs displayed a decreasing trend. The PItotal in the CK was greater than that in the T1 and T2 groups. (4) After 4 h of pulse electric field stimulation, the NAI concentration increased by 87.60% in the T1 group and by 62.09% in the T2 group, compared to the same measurement taken at 3 h. Pulse electric field impacts the photosynthetic electron transport chain of snake plants, thereby influencing their NAI release capacity. This study aims to elucidate the physiological responses of the chloroplasts in snake plants to pulsed electric field stimulation and to lay the foundation for enhancing the plant’s release of negative air ion concentrations through physical and technological means.

Microwave loss and kinetic inductance of epitaxial TiN films

Abstract Low microwave loss and regulatable kinetic inductance are two key characteristics of superconducting films to manufacture high-performance quantum devices. Epitaxial titanium nitride (TiN) thin films have been found to exhibit significant advantages in these two aspects. In this paper, we investigated into the dielectric loss and kinetic inductance of epitaxial TiN films, which were prepared on both silicon and sapphire substrates with different temperatures. Crystal structure, surface morphology, and superconducting properties were characterized systematically. The radio-frequency response of microwave resonators made of TiN films was studied at low temperatures to extract the information of kinetic inductance and quality factor. We obtained the highest internal quality factor up to 1.6 × 10 6 at single photon regime and achieved a regulation of kinetic inductance exceeding 16 times by altering the substrate and the sputtering temperature of the TiN films. This work not only provides an essential foundation for the precise design and preparation of low-loss TiN resonators for superconducting quantum bits, but also demonstrates TiN film as an excellent material platform with both low microwave loss and high kinetic inductance that can be applied in other fields such as microwave kinetic inductance detectors.

Infrared single-photon detection with superconducting magic-angle twisted bilayer graphene.

The moiré superconductor magic-angle twisted bilayer graphene (MATBG) shows exceptional properties, with an electron (hole) ensemble of only ~1011 carriers per square centimeter, which is five orders of magnitude lower than traditional superconductors (SCs). This results in an ultralow electronic heat capacity and a large kinetic inductance of this truly two-dimensional SC, providing record-breaking parameters for quantum sensing applications, specifically thermal sensing and single-photon detection. To fully exploit these unique superconducting properties for quantum sensing, here, we demonstrate a proof-of-principle experiment to detect single near-infrared photons by voltage biasing an MATBG device near its superconducting phase transition. We observe complete destruction of the SC state upon absorption of a single infrared photon even in a 16-square micrometer device, showcasing exceptional sensitivity. Our work offers insights into the MATBG-photon interaction and demonstrates pathways to use moiré superconductors as an exciting platform for revolutionary quantum devices and sensors.