We present a non-magnetic, fully-integrated, superconducting non-reciprocal bandpass filter using spatio-temporal inductance modulation in coupled resonator networks, thus combining the functionalities of a conventional bandpass filter with an isolator. The bandpass filter is based on a capacitively-coupled shunt resonator architecture where the resonators are implemented as a parallel combination of finger capacitors and a chain of 10 SQUIDs which behave as flux-controlled nonlinear inductors. The operation principle of the device has been studied and optimized for non-reciprocal performance using Floquet spectral analysis where the time-modulated SQUIDs are modeled using frequency translational admittance matrices. The bandpass filter is implemented in a single-layer superconducting process. Operating at a base temperature of 20 mK, we measured a low insertion loss of 1.3 dB in the forward direction. In the reverse direction, the measured isolation is as high as +25 dB at the center frequency and >+15 dB across a bandwidth of 250 MHz.
We present a non-magnetic, fully-integrated, superconducting non-reciprocal bandpass filter using spatio-temporal inductance modulation in coupled resonator networks, thus combining the functionalities of a conventional bandpass filter with an isolator. The bandpass filter is based on a capacitively-coupled shunt resonator architecture where the resonators are implemented as a parallel combination of finger capacitors and a chain of 10 SQUIDs which behave as flux-controlled nonlinear inductors. The operation principle of the device has been studied and optimized for non-reciprocal performance using Floquet spectral analysis where the time-modulated SQUIDs are modeled using frequency translational admittance matrices. The bandpass filter is implemented in a single-layer superconducting process. Operating at a base temperature of 20 mK, we measured a low insertion loss of 1.3 dB in the forward direction. In the reverse direction, the measured isolation is as high as +25 dB at the center frequency and >+15 dB across a bandwidth of 250 MHz.
We present a unified approach for designing a diverse range of superconducting non-reciprocal components, including circulators, isolators, and uni-directional amplifiers, based on temporally-modulated coupled resonator networks. Our method leverages standard SQUID-based resonators as building blocks, arranged in various configurations such as series-coupled, wye-connected, and lattice-coupled resonators, to realize a wide range of on-chip non-reciprocal devices. Our theoretical studies demonstrated the effectiveness of the proposed approach, achieving circulators and isolators with near-zero insertion losses and isolation greater than 20 dB, and directional amplifiers with forward gain exceeding 10 dB and reverse isolation greater than 20 dB. To validate our findings, we implemented and measured a series-coupled three-resonator superconducting isolator using a single-layer superconducting process. At a base temperature of 20 mK, our device exhibited insertion loss of 1.3 dB in the forward direction, and isolation of up to 25 dB at the center frequency and greater than 15 dB across a bandwidth of 250 MHz in the reverse direction. Our approach promises to enable the design of a broad range of high-performance non-reciprocal devices for superconducting circuits.
We present a unified approach for designing isolators based on temporally modulated coupled resonator networks. Our method leverages standard superconducting quantum interference device--based resonators as building blocks, arranged in series-coupled resonators to realize a wide range of on-chip nonreciprocal devices. The devices operate by translating microwave power into out-of-band intermodulation products in a direction-dependent way. Our theoretical studies demonstrate the effectiveness of the proposed approach, achieving isolators with near-zero insertion losses and isolation greater than 20 dB. To validate our findings, we implemented and measured a series-coupled three-resonator superconducting isolator using a single-layer superconducting process. At a base temperature of 20 mK, our device exhibited an insertion loss of 1.3 dB in the forward direction and isolation of up to 25 dB at the center frequency and greater than 15 dB across a bandwidth of 250 MHz in the reverse direction. Our approach promises to enable the design of a broad range of high-performance nonreciprocal devices for superconducting circuits.
A superconductor bandpass filter with tunable central frequency in the range of 2-3.5 GHz has been implemented using superconducting quantum interference devices (SQUIDs). The filter is designed using two pi-network resonators connected by a transmission line. Both resonators have a SQUID inductor with a tuning range of 65-200 pH, controlled by current magnetically coupled to the SQUIDs. Over a frequency tunability of 1.5 GHz, the filter has a mid-band insertion loss of 0.5-3.0 dB and corresponding maximum unloaded quality factor of 40. Due to the presence of active elements, tunability of the filter depends on the power of the microwave signal. A maximum power of -52 dBm corresponds to a frequency tuning range of 15%. Spectral measurements by controlling the central frequency of the filter with variable pulsewidth shows that the filter can be tuned at a rate of 120 GHz/mus.
Abstract In quantum information detection, significant interest has recently emerged in replacing conventional ferrite circulators with superconducting magnetic-free nonreciprocal devices. However, superconducting non-reciprocal devices with simpler structures and easier manufacturing processes still require further development. Inspired by conventional microwave circuits, we demonstrate a superconducting nonreciprocal circulator by parametric modulation of three identical, strongly and symmetrically coupled resonators. The circulator requires only three DC superconducting quantum interference devices, achieving an isolation of 20 dB , insertion loss of 0.47 dB , and return loss better than 25 dB over an instantaneous bandwidth of 50 MHz . The center frequency of the circulator is tunable within the range of 4– 8 GHz . Detailed design considerations for the experimental realization of a three-port superconducting circulator are presented, together with simulation results for a four-port circulator. Compared with previously reported superconducting magnetic-free nonreciprocal devices, the proposed circulator features a simpler circuit topology, demonstrating strong potential for scalable superconducting quantum information detection.
Abstract This paper presents a new class of sharp-selectivity low-temperature superconducting filter that incorporates lumped element resonant couplings. Dependent on a novel synthesis approach, the proposed filter exhibits great advantages such as: (1) a very simple in-line topology (without any cross coupling), (2) extremely compact size based on lumped inductor-capacitor (LC) elements, and (3) multiple transmission zeros (TZs) independently generated and controlled (via each resonant coupling). To facilitate the physical implementation, a group of lumped element circuit models are detailed, where series LC units are adopted for both the resonators and the resonant couplings. Considering an in-line topology here, the entire filter layout is then designed by cascading the lumped models one after another. For verification, a 5th-order bandpass filter centered at 5 GHz, with 500 MHz bandwidth and 3 TZs, is designed, simulated, and tested at cryogenic temperature (4.2 K). Moreover, preliminary simulations of the presented filter in series with an on-chip rapid single-flux-quantum microwave pulse generator are discussed for superconducting quantum applications.
The quantum-technology revolution is reshaping computing, sensing, and communication. In magnetometry, recent advances leverage precise control of spin qubits and color centers in solid-state crystals for mesoscopic-scale sensing. Yet at very low temperatures, superconducting sensing technology remains unrivaled because of its non-invasiveness and higher sensitivity. Here we describe a class of superconducting sensors that offers low loss and quantum non-demolition measurement characteristics. We designed and fabricated a superconducting flux-tunable resonator (tRes) in a superconducting chip foundry and matured it to a level that combines the speed of an inductor-capacitor circuit with the flux sensitivity of a superconducting quantum interference device (SQUID) to perform magnetometry at milli-kelvin temperature to investigate targets. We introduce its fundamental functionality readily at MHz magnetic sampling rate, showcase two measurement modalities, and investigate three circuits with gradually increasing complexity to extract target-specific information. The combination of high sensitivity and fast readout characteristics make tRes an attractive and versatile magnetometer.