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arXiv:2309.03976

Low-noise amplifier cryogenic testbed validation in a TaaS (Testing-as-a-Service) framework

Brandon Boiko, Eric Zhang, Doug Jorgesen, Sebastian U Engelmann, Grosskopf, Curtis, Ryan Paske

Published Sep 7, 2023• 0 citations
arXivHTMLPDF

Abstract

As quantum computers based on superconducting qubit processors scale, cryogenic microwave components in the qubit control and readout chain must be appropriately tested and qualified to ensure consistent and high-fidelity quantum computation. However, the intersection of superconducting cryogenics and microwave electronics is a new domain with limited technical and commercial expertise. In this paper we validate a TaaS (testing-as-a-service) framework using an organizational workgroup model that consists of (1) a commercial Test House, (2) standard temperature Component Manufacturer, (3) Academic Partner, and (4) System Integrator to demonstrate a scalable model for the qualification of cryogenic microwave components. The goal of this model is to secure the supply chain and support the rapid growth of Quantum Computing (QC) technologies. The component test vehicle presented in this paper is a low-noise amplifier (LNA) which is a crucial component in the cryogenic chain to ensure adequate signal-to-noise of the qubit readout. We devise standard test metrics and protocols by which LNA performance is measured, including key parameters such as gain and flatness, reflection and isolation, operating bandwidth, and noise figure. We present details of the cryogenic testbed customized for LNA qualification, outline test methodologies, and present a suite of standard processes that are used to systematize data collation and reporting. The testbed is validated by reproducing parameters of a pre-characterized LNA. Its value is demonstrated by characterizing a proof-of-concept cryogenic LNA prototype. Finally, we describe the extension of our TaaS framework toward testing at scale for various active and passive cryogenic components used in QC.

DOI
10.48550/arxiv.2309.03976

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As quantum computers based on superconducting qubit processors scale, cryogenic microwave components in the qubit control and readout chain must be appropriately tested and qualified to ensure consistent and high-fidelity quantum computation. However, the intersection of superconducting cryogenics and microwave electronics is a new domain with limited technical and commercial expertise. In this paper we validate a TaaS (testing-as-a-service) framework using an organizational workgroup model that consists of (1) a commercial Test House, (2) standard temperature Component Manufacturer, (3) Academic Partner, and (4) System Integrator to demonstrate a scalable model for the qualification of cryogenic microwave components. The goal of this model is to secure the supply chain and support the rapid growth of Quantum Computing (QC) technologies. The component test vehicle presented in this paper is a low-noise amplifier (LNA) which is a crucial component in the cryogenic chain to ensure adequate signal-to-noise of the qubit readout. We devise standard test metrics and protocols by which LNA performance is measured, including key parameters such as gain and flatness, reflection and isolation, operating bandwidth, and noise figure. We present details of the cryogenic testbed customized for LNA qualification, outline test methodologies, and present a suite of standard processes that are used to systematize data collation and reporting. The testbed is validated by reproducing parameters of a pre-characterized LNA. Its value is demonstrated by characterizing a proof-of-concept cryogenic LNA prototype. Finally, we describe the extension of our TaaS framework toward testing at scale for various active and passive cryogenic components used in QC.
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Large-scale superconducting quantum computers require massive numbers of high-performance cryogenic low-noise amplifiers (cryo-LNAs) for qubit readout. Here we presented a C-band monolithic microwave integrated circuit (MMIC) cryo-LNA for this purpose. This cryo-LNA is based on a 150 nm gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) process and implemented with a three-stage cascaded architecture, where the first stage adopts careful impedance matching to optimize the noise and return loss. The integration of negative feedback loops adopted in the second and third stages enhances the overall stability. Moreover, the pHEMT self-bias and current multiplexing circuitry structure facilitate the reduction of power consumption and require only a single bias line. Operating at an ambient temperature of 3.6 K and consuming 15 mW, the cryo-LNA demonstrates good performance in the C-band, reaching a minimum noise temperature of 4 K and an average gain of 40 dB. We further benchmarked this cryo-LNA with superconducting qubits, achieving an average single-shot dispersive readout fidelity of 98.3% without assistance from a quantum-limited parametric amplifier. The development of GaAs cryo-LNA diversifies technical support necessary for large-scale quantum applications.
A cryogenic low-voltage, broadband low-noise amplifier(LNA) has been designed for qubit state readout systems. The proposed LNA utilizes passive components for noise cancellation. A tri-coupled transformer is utilized to simultaneously achieve broadband input impedance matching and noise matching. Additionally, it incorporates capacitive feedback and an in-phase transformer to effectively cancel noise. Implemented in 28-nm bulk CMOS technology and verified at 10 K, the LNA achieves a maximum gain of 26.7 dB, a −3-dB bandwidth of 2.2 GHz, a lowest noise temperature (NT) of 25 K, a power consumption of 4.05 mW at 0.6-V supply voltage, and a figure of merit (FoM) of 0.12 dB/mW/ph, which is comparable with the recent works.
Today’s quantum computing systems rely on commercial electronics operating at room temperature in order to perform control and readout operations for qubits [1] –[6]. The qubits operate at cryogenic temperatures; the signals that support control and readout of qubits therefore traverse multiple temperature stages in a dilution refrigerator to enable interaction with the qubits of a quantum computer. For many of the most advanced quantum computers built to date, the control of each individual qubit demands application of a radiofrequency pulse that is precisely calibrated in frequency, amplitude, and phase. Oubit readout demands the amplification of very low amplitude signals that are then post-processed to categorize the state of the qubit being measured. Oubit control electronics are implemented using arbitrary waveform generators (AWGs) of various types. The scalability of such systems is challenged by the need to scale the number of qubit control electronics units linearly with the number of qubits in the system. One approach to mitigating this challenge that is under active exploration is the use of multi-channel AWGs (tailored to the requirements of qubit control) that operate at the 4K stage of a quantum computing system [7] –[10]. Oubit readout electronics are typically implemented using multiple stages of amplification and then DSP-based readout performed at room temperature. In today’s systems, while readout electronics benefits from multiplexing of the readout signals (enabling a single cascade of moderately wideband amplifiers to support the delivery of multiple readout signals to the room-temperature electronics), again, the scalability of this approach is challenged much as is the case with control electronics. One approach to mitigating the readout challenge is the expanded use of cryogenic electronics in the readout chain. Success in the implementation of cryogenic control and readout solutions depends critically on multiple CMOS sub-components; in this paper we focus on SRAM and low noise amplifiers (LNAs). Note that SRAM is critical for both control and readout applications as a mixed-signal solution involving the combination of a custom processor and analog elements is highly desirable in both cases. Further, while the LNA is directly used as an element in the readout chain, a deep assessment of LNA performance and opportunities strongly benefits overall understanding of achievable noise performance in CMOS technologies at cryogenic temperatures and is therefore impoitant in both control and readout contexts.
Microwave devices capable of near-quantum-limited signal processing are essential components in the toolbox of solid-state quantum technologies. The manipulation and readout of single-photon microwave signals through amplifiers, mixers, isolators, etc. must fulfill strict requirements in terms of signal integrity to ensure reliable operation. These active microwave quantum devices operate in complex cryo-electronic setups. This poses challenges to their characterization, since all relevant figures of merit must be expressed at the reference planes of their ports. Even though cryogenic S-parameter calibration is non-trivial, metrological approaches are converging toward rigorous methods. Furthermore, preserving signal integrity must be quantified via absolute noise levels at the ports of the Device Under Test (DUT), requiring an absolute power reference. In this work, we present an in situ noise metrology protocol based on substituting a controllable noise source for the DUT. We motivate this choice by showing that placing the noise source at the DUT input impacts the separability of the calibration from the DUT characteristics. Our proposed architecture combines Planck spectroscopy using a Variable Temperature Stage with Short-Open-Load-Reciprocal scattering-parameter calibration, so that noise and scattering quantities are referred to the same cryogenic reference planes. In this configuration, the readout-chain calibration is separated from the internal dynamics of the DUT. As a demanding use case, we apply the protocol to a Josephson Traveling Wave Parametric Amplifier and extract its gain and input-referred added noise under pump conditions activating multimode nonlinear behavior. This illustrates how our device-agnostic protocol supports portable noise characterization of nonlinear cryogenic microwave devices.
This work presents the design and optimization of a low-noise amplifier (LNA) for qubit readout in cryogenic environments of 3 − 4 K. The proposed LNA achieves wide bandwidth (4 GHz), high gain (47.0 dB), and sufficient linearity (IIP 3 = −34 dBm), while maintaining power consumption below 50 mW, making it suitable for integration into quantum computing systems. The amplifier is based on multi-stage cascode architectures with integrated inductances and impedance-matching techniques to optimize performance for a centre frequency of 5 GHz. While the results demonstrate good performance, there is still room for improvement in the S11parameter and the noise figure (NF ), which could benefit from a more refined transformer model. The proposed design represents a significant step toward integrating high-efficiency readout electronics into quantum computing architectures.