IEEE Electronic Components and Technology Conference (ECTC)
Tailored Multi-mode, High-Q Superconducting Nb Resonators: Unique Platform for Magnon-Photon Coupling
Muntasir Mahdi, Bhargav Yelamanchili, Archit Shah, Sherman E. Peek, Yuzan Xiong, Andrew Christy, Dan-Chi Nguyen, Tae Hee Kim, Wei Zhang, Michael C. Hamilton
Superconducting resonators have previously been used for magnon-photon coupling, which facilitates quantum information transduction. In this work, we demonstrate robust superconducting Nb resonators that show closely spaced resonances with high quality (Q) factors. The fundamental frequencies ranging from 440 MHz to 668 MHz with second harmonics at 870 MHz and 1.3 GHz, offer extensive frequency coverage. They maintain resonance integrity by exhibiting useful Q-factors for many harmonics, even in magnetic fields up to 1 T at 1.7 K. These resonators provide a versatile platform for investigating magnon-photon interactions in hybrid magnonic systems, overcoming limitations of previous designs and offering the potential for broad frequency coverage and application in quantum information studies.
Superconducting resonators have previously been used for magnon-photon coupling, which facilitates quantum information transduction. In this work, we demonstrate robust superconducting Nb resonators that show closely spaced resonances with high quality (Q) factors. The fundamental frequencies ranging from 440 MHz to 668 MHz with second harmonics at 870 MHz and 1.3 GHz, offer extensive frequency coverage. They maintain resonance integrity by exhibiting useful Q-factors for many harmonics, even in magnetic fields up to 1 T at 1.7 K. These resonators provide a versatile platform for investigating magnon-photon interactions in hybrid magnonic systems, overcoming limitations of previous designs and offering the potential for broad frequency coverage and application in quantum information studies.
Inthe application of quantum information transduction with superconducting (SC) qubits, SC resonators play a phenomenal role in magnon-photon coupled systems. We present NbN (Tc= 10.8 K) superconducting microstrip resonators tailored for hybrid magnon-photon coupled systems. Our resonators exhibit remarkable coupling capability, enabling rigorous probing of magnon-photon interactions. With a fundamental frequency of 1.4 GHz and a second harmonic of 2.8 GHz, these resonators offer extensive frequency coverage, facilitating the identification and characterization of a wide spectral range. It exhibits a strong magnon-microwave photon coupling with a sphere of yttrium iron garnet (YIG). The average gyromagnetic ratio (γ/2π) and coupling strength (g/2π) achieved are 2.7 MHz/Oe and 11.14 MHz, respectively. The NbN SC resonators developed in this work address challenges associated with probing magnon-photon coupling in strong magnetic fields and are expected to serve as a unique platform for studying magnon-photon coupled hybrid devices.
Superconducting resonators are powerful tools widely used in circuit Quantum Electrodynamics [1]. High-quality factors, tunability, and several implemented layouts make them ideal circuital elements for various applications from quantum metrology [2], to quantum computation [3] and quantum information [4]. Here, we report on the simulation and design of superconducting Coplanar Waveguide (CPW) resonators whose resonance frequencies are in the range of 4–8 GHz. Typical properties of superconducting resonators employed in standard transmon qubits can be achieved by designing a λ/4 resonator made by Niobium (Nb) and modeling the capacitive coupling to provide a high-quality factor useful for its future employments in more advanced quantum circuits [5]. Nb gives the advantage of better stability of the superconducting properties of the material against the application of a magnetic field, compared those achievable by Aluminum (Al), thus guaranteeing an additional degree of freedom in the implementation of complex quantum architectures [5]–[7].
As the field of superconducting quantum technology progresses beyond single-qubit control, scalable and multifunctional quantum architectures become increasingly vital. A central challenge is integrating fast, controllable superconducting circuits with components that offer longer coherence, richer physics, or new functionalities. Hybrid quantum systems, where superconducting microwave resonators interface with semiconducting or magnetic subsystems, have the capabilities to fulfil this need, yet they face significant engineering obstacles. Conventional superconducting resonator designs struggle under magnetic field biasing and electrostatic gating, both of which are essential for coupling to spin-based, semiconductor, or magnonic elements.This thesis explores solutions to these bottlenecks through the development of magnetic-field-resilient coplanar stripline (CPS) resonators based on thin-film NbTiN. These resonators retain a stable resonance frequency in in-plane magnetic fields up to 1T, can have high kinetic inductance and offer broad geometrical tunability, enabling strong and ultrastrong coupling to charge- and spin-based quantum systems. In the superconducting–semiconductor domain, we demonstrate high-impedance CPS resonators inductively coupled to Josephson junctions hosting Andreev bound states (ABSs), revealing both coherent pair transitions and single-quasiparticle excitations near the ultrastrong coupling regime. This opens the door to fast, gate-tunable qubits based on microscopic ABSs, distinct from conventional macroscopic qubit architectures, and lays the groundwork for spin–photon hybridisation, non-perturbative light–matter interactions, and parity-based quantum logic.In parallel, this work investigates rare-earth iron garnet (ReIG) ferrimagnetic insulators as low-loss spin-wave media compatible with superconducting devices. In sputtered thin-film thulium iron garnet (TmIG) with perpendicular magnetic anisotropy, we observe deterministic spin-orbit torque switching and multiple magnetisation polarity reversals. These properties showcase the attractiveness of TmIG both for low-dissipation magnonic information transport and as magnetic interfaces for superconducting hybrid devices. Taken together, the results of this thesis establish materials, device concepts, and measurement strategies for novel classes of hybrid quantum systems that combine robust superconducting circuitry, electrostatically tunable semiconductor excitations, and industry-scalable magnetic elements and pave the way for next-generation hybrid quantum systems. More broadly, they provide concrete routes to overcoming limitations of existing hybrid platforms and advance the development of versatile, low-dissipation quantum technologies.
Frequency-tunable microwave resonators are in great demand especially in hybrid systems where precise frequency alignment of resonances is required. Here, we present frequency-tunable high-Q superconducting resonators fabricated from thin niobium nitride and niobium titanium nitride films. The resonant frequency is tuned by applying a magnetic field perpendicular to the hole structures in the resonator's inductor wire, whose kinetic inductance is modified by wirelessly induced DC supercurrents. A continuous in situ frequency tuning of over 300 MHz is achieved for a 10 GHz resonator with a moderate magnetic field of 1.2 mT. The planar resonator design and the noncontact tuning scheme greatly ease the fabrication complexity and can be widely applied in many hybrid systems for coupling microwave modes with other forms of excitations such as optical photons, phonons, magnons, and spins.
We report our development on design, fabrication and characterization of various superconducting resonators for quantum device applications. The resonators are developed mainly for superconducting qubit implementation in circuit QED structure, but future application will include photon detectors such as microwave kinetic inductance detectors. First we designed and fabricated half-wavelength coplanar waveguide resonators with niobium thin film on a high resistive silicon wafer, with the fundamental frequencies in the range of 1 to 8 GHz. The loaded quality factors are controlled by the coupling capacitors, and the lower bound of the intrinsic quality factor was measured down to 7 mK in the dilution refrigerator. We have also designed quarter-wavelength resonators and lumped LC resonators coupled to a transmission line, and characterized multiple resonators in a single transmission line. For the 3D transmon qubit application, we designed and fabricated a rectangular box resonator with superconducting aluminum. The intrinsic quality factor of the box resonator exceeds three million at 7 mK. We will also present basic results on the integration of a transmon qubit in the superconducting resonator.
Abstract We systematically study the performance of compact lumped element planar microwave Nb70Ti30N (NbTiN) resonators operating at 5 GHz in external in-plane magnetic fields up to 440 mT, a broad temperature regime from 2.2 K up to 13 K, as well as mK temperatures. For comparison, the resonators have been fabricated on thermally oxidized and pristine, (001) oriented silicon substrates. When operating the resonators in the multi-photon regime at T = 2.2 K, we find internal quality factors Q int ≃ 2 × 105 for NbTiN resonators grown on pristine Si substrates. In addition, we investigate the Q-factors of the resonators on pristine Si substrates at millikelvin temperatures to assess their applicability for quantum applications. We find Q int ≃ 2 × 105 in the single photon regime and Q int ≃ 5 × 105 in the high power regime at T = 7 mK. From the excellent performance of our resonators over a broad temperature and magnetic field range, we conclude that NbTiN deposited on Si (100) substrates, where the surface oxide has been removed, constitutes a promising material platform for electron spin resonance and ferromagnetic resonance experiments using superconducting planar microwave resonators.