Superconducting coplanar-waveguide (CPW) resonators are one of the key devices in circuit quantum electrodynamics (cQED). Their performance can be limited by dielectric losses in the substrate and in the material interfaces. Reliable modeling is required to aid in the design of low-loss CPW structures for cQED. We analyze the geometric dependence of the dielectric losses in CPW structures using finite-element modeling of the participation ratios of the lossy regions. In a practical scenario, uncertainties in the the dielectric constants and loss tangents of these regions introduce uncertainties in the theoretically predicted participation ratios. We present a method for combining loss simulations with measurements of two-level-system-limited quality factors and resonance frequencies of CPW resonators. Namely, we solve an inverse problem to find model parameters producing the measured values. High quality factors are obtainable by properly designing the cross-sectional geometries of the CPW structures, but more accurate modeling and design methods for low-loss CPW resonators are called for major future improvements. Our nonlinear optimization methodology for solving the aforementioned inverse problem is a step in this direction.
Improving the performance of superconducting qubits and resonators generally results from a combination of materials and fabrication process improvements and design modifications that reduce device sensitivity to residual losses. One instance of this approach is to use trenching into the device substrate in combination with superconductors and dielectrics with low intrinsic losses to improve quality factors and coherence times. Here we demonstrate titanium nitride coplanar waveguide resonators with mean quality factors exceeding two million and controlled trenching reaching 2.2 $μ$m into the s…
This white paper presents a single-layer mask, found at https://github.com/Boulder-Cryogenic-Quantum-Testbed/simple-resonator-mask. It is designed for fabrication of superconducting microwave resonators towards 1:1 comparisons of dielectric losses from the metal-substrate interface. Finite-element electromagnetic simulations are used to determine participation ratios of the four major regions of the on-chip devices, as well as to confirm lack of crosstalk between neighboring devices and demonstrate coupling tunability over three orders of magnitude. This mask is intended as an open-source comm…
We developed a novel magnetic coupling module formed of a monolayer superconducting flux concentrator, which is integrated with a coplanar resonator strongly coupled to HTS rf-SQUID. Three types of resonators, including a long stripline resonator between input loop and pick-up loop of the flux concentrator, a complementary split ring resonator (CSRR), and also a spiral shape inside the input loop are explored. The resonance quality factors as well as the coupling to the SQUID of different patterns of these three types of the resonators is evaluated using Finite Element Method (FEM) simulations…
A combination of gap waveguide technology and the traditional coplanar waveguide is studied in detail and demonstrated experimentally for the first time. This novel metamaterial transmission line is presented in three different configurations and offers a broadband operation, low loss, and low dispersion characteristics. Analytical expressions for its characteristic impedance and effective permittivity are provided and validated by Finite Element Method simulations. The loss and dispersion of the line are analyzed with an Eigenmode solver. The proposed line prevents the propagation of substrat…
We present an experimental approach for cryogenic dielectric measurements on ultra-thin insulating films. Based on a coplanar microwave waveguide design we implement superconducting quarter-wave resonators with inductive coupling, which allows us to determine the real part $\varepsilon_1$ of the dielectric function at GHz frequencies and for sample thicknesses down to a few nm. We perform simulations to optimize resonator coupling and sensitivity, and we demonstrate the possibility to quantify $\varepsilon_1$ with a conformal mapping technique in a wide sample-thickness and $\varepsilon_1$-reg…
In this work, we study the development of a coplanar waveguide (CPW) resonator and its use in an electron spin resonance (ESR) spectrometer. The CPW resonator is designed to operate in S-band. It has a short circuit configuration which leads to miniaturization. It is so constructed such that it has a characteristic impedance of 50 ohms. Detailed electromagnetic simulation with a particular emphasis on the excitation of the structure has been performed for this resonator owing to its uniplanar nature. The design parameters and the electromagnetic field distribution are obtained from the simulat…
A strategy aimed at decreasing dielectric loss in coplanar waveguides (CPW) and qubits involves the creation of trenches in the underlying substrate within the gaps of the overlying metallization. Participation of contamination layers residing on surfaces and interfaces in these designs can be reduced due to the change in the effective dielectric properties between the groundplane and conductor metallization. Although finite element method approaches have been previously applied to quantify this decrease, an analytical method is presented that can uniquely address geometries possessing small t…
We report second harmonic generation from a titanium indiffused lithium niobate waveguide resonator device whose cavity length is locked to the fundamental pump laser using an on-chip phase modulator. The device remains locked for more than 5 minutes, producing more than 80\% of the initial second harmonic power. The stability of the system is seen to be limited by DC-drift, a known effect in many lithium niobate systems that include deposited electrodes. The presented device explores the suitability of waveguide resonators in this platform for use in larger integrated networks.
The design and experimental demonstration of a large-area, ultra-high-Q-factor and single-mode operation silicon ring resonator based on a strip silicon photonic waveguide are presented, which is suitable for photon gyroscopic application. Based on these designs, simulation results show that the resonance depth is 0.9979 while the resonator is in an undercoupled state with the coupling length L=2um and coupling gap d=0.2um. For the fabricated resonator, the ultrahigh Q factor of 1.54*106 is experimentally demonstrated, with the free spectrum range (FSR) of 0.036nm and the resonance depth is 0.…
We consider acoustic wave transmission in non axisymmetric waveguide which consists of cylindrical resonator and two semi-infinite cylindrical waveguides whose axes are shifted relative to the resonator axis and each other by azimuthal angle $Δϕ$. We show that for rotation of one of attached waveguides the coupling matrix elements of the eigenmodes of resonator classified by the integer $m$ and propagating mode of the waveguide acquire phase factor $e^{imΔϕ}$. That crucially effect Fano resonances and creates an analog of faucet opening and closing wave flux under rotation of the waveguide. We…
High Q optical resonators are a key component for ultra-narrow linewidth lasers, frequency stabilization, precision spectroscopy and quantum applications. Integration of these resonators in a photonic waveguide wafer-scale platform is key to reducing their cost, size and power as well as sensitivity to environmental disturbances. However, to date, the intrinsic Q of integrated all-waveguide resonators has been relegated to below 150 Million. Here, we report an all-waveguide Si3N4 resonator with an intrinsic Q of 422 Million and a 3.4 Billion absorption loss limited Q. The resonator has a 453 k…
Defect centers are promising candidates for waveguide-integrated silicon light sources. We demonstrate microresonator- and waveguide-coupled photoluminescence from silicon W~centers. Microphotoluminescence measurements indicate wavelengths on-resonance with resonator modes are preferentially coupled to an adjacent waveguide. Quality factors of at least 5,300 are measured, and free spectral ranges closely match expectation. The W~center phonon sideband can be used as a spectral diagnostic for a broader range waveguide-based devices on cryogenic silicon photonic platforms.
