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.
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.
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.
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.
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 propose a design to realize integrated broadband nonreciprocal microwave isolators and circulators using superconducting circuit elements without any magnetic materials. To obtain a broadband response, we develop a waveguide-based design by temporal modulations. The corresponding compact traveling-wave structure is implemented with integrated superconducting composite right-/left-handed transmission lines. The calculations show that the bandwidth of 580 MHz can be realized over a nonreciprocal isolation of 20 dB in reflections. Such on-chip isolators and circulators are useful for cryogenic integrated microwave connections and measurements, such as protecting qubits from the amplified reflected signal in multiplexed readout.
We report on the design and performance of an on-chip microwave circulator with a widely (GHz) tunable operation frequency.Nonreciprocity is created with a combination of frequency conversion and delay, and requires neither permanent magnets nor microwave bias tones, allowing on-chip integration with other superconducting circuits without the need for high-bandwidth control lines.Isolation in the device exceeds 20 dB over a bandwidth of tens of MHz, and its insertion loss is small, reaching as low as 0.9 dB at select operation frequencies.Furthermore, the device is linear with respect to input power for signal powers up to hundreds of fW (≈10 3 circulating photons), and the direction of circulation can be dynamically reconfigured.We demonstrate its operation at a selection of frequencies between 4 and 6 GHz.
The cryogenic hardware required to build a superconducting-qubit-based quantum computer demands a variety of microwave components. These elements include microwave couplers, filters, amplifiers, and circulators and/or isolators. Traditionally implemented as discrete components, integration of this peripheral hardware, in an effort to reduce overall footprint, thermal load, and added noise, is a key challenge to scaling modern quantum processors with qubit counts climbing over the one hundred plus mark. Ferrite-based microwave isolators, generally employed in the readout chain to decouple qubits and resonators from readout electronics, persist as one of the volumetrically largest devices still utilized as discrete components. Here, we present an alternative two-port isolating integrated circuit derived from the dc superconducting quantum interference device (dc SQUID). Nonreciprocal transmission is achieved using the three-wave microwave-mixing properties of a flux-modulated dc SQUID. We show that when multiple dc SQUIDs are embedded in a multipole admittance-inverting filter structure, the three-wave mixing derived from the flux pumping of the dc SQUIDs can provide directional microwave power flow. For a three-pole filter device, we experimentally demonstrate a directionality greater than 15 dB over a 600-MHz bandwidth.