The qubit count of superconducting transmon-based quantum processors is steadily increasing. Some processors are already beyond the 100-qubit scale. In order to keep the development cadence of those quantum processors high, the test time per qubit needs to be strongly reduced from days to hours. Here we present a test time study based on extracting a single-qubit fidelity using a randomized benchmarking protocol. We show that more than a dozen other tune-up steps are required before a randomized benchmarking protocol can be executed on a qubit. En bloc, such a structured workflow leads to a test-time of about 20 mins per qubit. By extrapolating, we find that testing single-qubit fidelities on a hecto-qubit scale quantum chip using the randomized benchmarking protocol would take about 2.5 days. Executing the test protocol is furthermore embedded in a total test cycle that takes into account that a chip needs to be inserted, tested, and retrieved from the system, consisting of a cooldown to 20 mK base temperature and afterwards a warmup to ambient conditions. The whole process of chip testing, starting with insertion and ending with the retrieval of the quantum processor under test is estimated to take about a week. Considering the current state of technology, such a cadence in chip testing can be considered high throughput.
Superconducting resonators and transmission lines are fundamental building blocks of integrated circuits for millimeter-submillimeter (mm-submm) astronomy. Accurate simulation of radiation loss from the circuit is crucial for the design of these circuits because radiation loss increases with frequency, and can thereby deteriorate the system performance. Here, we show a stratification for a 2.5-dimensional method-of-moment simulator Sonnet em that enables accurate simulations of the radiative resonant behavior of submm-wave coplanar resonators and straight coplanar waveguides. The Sonnet simulation agrees well with the measurement of the transmission through a coplanar resonant filter at 374.6 GHz. Our Sonnet stratification utilizes artificial lossy layers below the lossless substrate to absorb the radiation, and we use co-calibrated internal ports for de-embedding. With this type of stratification, Sonnet can be used to model superconducting mm-submm wave circuits even when radiation loss is a potential concern.
DESHIMA 2.0 is an ultra-wideband submillimeter spectrometer based on integrated superconducting microstrip filters and Microwave Kinetic Inductance Detectors (MKIDs). We have successfully demonstrated its ultra-wideband performance in the laboratory. The measured instantaneous frequency coverage with ~300 MKIDs is 225-415 GHz, with a mean filter Q of ~670. The broadband quasi-optical chain of the instrument is characterized by beam patterns across the whole frequency range that are obtained simultaneously by a novel phase-amplitude beam measurement technique. We plan to deploy the instrument on the ASTE telescope for a commissioning and science verification campaign in 2022-2023.
Superconducting resonators and transmission lines are fundamental building blocks of integrated circuits for millimeter-submillimeter astronomy. Accurate simulation of radiation loss from the circuit is crucial for the design of these circuits because radiation loss increases with frequency, and can thereby deteriorate the system performance. Here we show a stratification for a 2.5-dimensional method-of-moment simulator Sonnet EM that enables accurate simulations of the radiative resonant behavior of submillimeter-wave coplanar resonators and straight coplanar waveguides (CPWs). The Sonnet simulation agrees well with the measurement of the transmission through a coplanar resonant filter at 374.6 GHz. Our Sonnet stratification utilizes artificial lossy layers below the lossless substrate to absorb the radiation, and we use co-calibrated internal ports for de-embedding. With this type of stratification, Sonnet can be used to model superconducting millimeter-submillimeter wave circuits even when radiation loss is a potential concern.
The integrated superconducting spectrometer (ISS) enables ultra-wideband, large field-of-view integral-field-spectrometer designs for mm-submm wave astronomy. DESHIMA 2.0 is a single-pixel ISS spectrometer for the ASTE 10-m telescope, designed to observe the 220-440 GHz band in a single shot, corresponding to a [CII] redshift range of z=3.3-7.6. The first-light experiment of DESHIMA, using a 332-377 GHz configuration has shown excellent consistency between the performance derived from on-sky measurements, lab-measurements and the design. Ongoing upgrades towards the octave-bandwidth full system include the development of a filterbank chip with ~350 channels and higher optical efficiency, a wideband quasioptical design, and observing methods for efficiently removing the atmosphere.
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