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China Semiconductor Technology International Conference (CSTIC)

Integrated Superconducting Isolator-Circulator-Isolator Device

Rutian Huang, Genting Dai, Jianshe Liu, Wei Chen

Published Jun 20, 2022• 0 citations
Publisher

Abstract

There needs a large quantity of microwave devices like circulators, isolators and quantum noise limited amplifier in the development of scalable superconducting quantum computers. Traditional isolators and circulators have huge size and could induce a high thermal dissipation. This paper designs a kind of on-chip Isolator-Circulator-Isolator (ICI), which is able to act as isolator and circulator synchronous. The ICI is composed of tunable inductor bridge which based on an array of superconducting quantum interference devices (SQUID). It works on the frequency between 4 and 8 GHz, and operation temperature at 20 mK, with isolation exceeds 40 dB and insertion loss less than 3 dB.

DOI
10.1109/cstic55103.2022.9856890

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There needs a large quantity of microwave devices like circulators, isolators and quantum noise limited amplifier in the development of scalable superconducting quantum computers. Traditional isolators and circulators have huge size and could induce a high thermal dissipation. This paper designs a kind of on-chip Isolator-Circulator-Isolator (ICI), which is able to act as isolator and circulator synchronous. The ICI is composed of tunable inductor bridge which based on an array of superconducting quantum interference devices (SQUID). It works on the frequency between 4 and 8 GHz, and operation temperature at 20 mK, with isolation exceeds 40 dB and insertion loss less than 3 dB.
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.
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.
This thesis develops theory for and experimentally demonstrates a new way to break Lorentz reciprocity—the symmetry, in an electrical network, under exchange of source and detector. The approach is based on the sequential application of frequency conversion and delay; as frequency and time are Fourier duals, these operations do not generally commute. We apply this method in the construction of an on-chip superconducting microwave circulator, a critical component for the unidirectional routing of quantum information in superconducting networks. The device requires neither permanent magnets nor microwave control tones, allowing on-chip integration with other superconducting circuits without expensive control hardware. 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 many hundreds of fW (~103 circulating photons), and the direction of circulation can be dynamically reconfigured. We demonstrate its tunability with operation at a selection of frequencies between 4 and 6 GHz. Given the current status of quantum error-correction and architectures for quantum information processing with superconducting circuits, such scalable non-reciprocal devices will almost certainly be necessary for construction of a superconducting quantum computer intended to be more than a proof-of-principle.
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.
Scalable superconducting quantum computation requires fast, high-fidelity readout. Currently, this is assisted through cryogenic amplification of the readout signal. In traditional dispersive readout schemes, the amplifiers that are used to provide high signal-to-noise ratio also generate thermal noise that can decohere the qubits, demanding additional ferrite-based isolators to suppress this noise. Here, we integrate a chip-scale microwave switch, the tunable inductive bridge, into the readout chain of a fixed-frequency transmon. Flux-pulsing the switch, such that it transmits only during the readout, did not make a discernable difference to qubit coherence, residual excited-state population, or readout fidelity metrics. By injecting broadband noise that mimics amplifier thermal photons, we show that the switch suppresses the resulting qubit dephasing by more than 303030~dB, consistent with its independently measured on-off ratio, establishing it as a potential chip-based integrated replacement for readout-chain isolators.
Building large-scale superconducting quantum circuits will require miniaturisation and integration of supporting devices including microwave circulators, which are currently bulky, stand-alone components. Here we report the realisation of a passive on-chip circulator which is made from a loop consisting of three tunnel-coupled superconducting islands, with DC-only control fields. We observe the effect of quasiparticle tunnelling, and we dynamically classify the system into different quasiparticle sectors. When tuned for circulation, the device exhibits strongly non-reciprocal 3-port scattering, with average on-resonance insertion loss of 2 dB, isolation of 14 dB, power reflectance of -11 dB, and a bandwidth of 200 MHz.