The integration of quantum and classical model is essential for understanding the behaviour of quantum system operating in cryogenic environments. In this work we present a comprehensive simulation framework that combines quantum dots-based Grover-like state generation, cryogenic low noise amplifier (Cryo-LNA) behaviour, and classical LC circuit dynamics. The quantum circuit is simulated using matrix-based operations to evaluate the probability amplitudes of 3 q-bits of quantum state representing Grover-like search behaviour. The performance characteristics of cryo-LNA, including S11 (reflection confection), S21 (Gain), return loss and noise figure are modelled across a wide frequency spectrum to evaluate the amplifier’s behaviour at cryogenic temperature. Additionally, we drive and visualize the classical Lagrangian and Hamiltonian for an LC oscillator, providing insight into energy exchange and time evaluation relevant to superconducting q-bits circuit. The preposed simulation highlights the interplay between quantum signal generation and classical amplifier’s performance, offering a hybrid design approach for quantum hardware system operating at cryogenic condition’s.
The integration of quantum and classical model is essential for understanding the behaviour of quantum system operating in cryogenic environments. In this work we present a comprehensive simulation framework that combines quantum dots-based Grover-like state generation, cryogenic low noise amplifier (Cryo-LNA) behaviour, and classical LC circuit dynamics. The quantum circuit is simulated using matrix-based operations to evaluate the probability amplitudes of 3 q-bits of quantum state representing Grover-like search behaviour. The performance characteristics of cryo-LNA, including S11 (reflection confection), S21 (Gain), return loss and noise figure are modelled across a wide frequency spectrum to evaluate the amplifier’s behaviour at cryogenic temperature. Additionally, we drive and visualize the classical Lagrangian and Hamiltonian for an LC oscillator, providing insight into energy exchange and time evaluation relevant to superconducting q-bits circuit. The preposed simulation highlights the interplay between quantum signal generation and classical amplifier’s performance, offering a hybrid design approach for quantum hardware system operating at cryogenic condition’s.
This work describes a basic interface between solid-state quantum bits (qubits) and classical environments. We describe a multiplexer, a circulator, and a low noise amplifier, designed for cryogenic temperature operation in a 40 nm CMOS technology node. The circuits take advantage of traditional design styles, such as transmission gates, passive LC filters and switches, and recent developments, such as differential noise cancelling with six-port transformers, while exploiting new cryogenic CMOS (cryo-CMOS) modeling for design and verification purposes.
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.
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.
Quantum computing promises to revolutionize our lives, achieving unprecedented computational powers and unlocking new possibilities in drug discovery, chemical simulations and cryptography. The fundamental unit of computation of a quantum computer is the quantum bit (qubit). It can be implemented in a number of technologies, such as superconducting qubits, spin qubits, photonic systems, trapped ions and NV-centers. Solid-state superconducting qubits and spin qubits seem to be the most promising ones, as shown by the recent demonstration of quantum supremacy with a superconducting qubit processor. Such quantum processors, to operate in the quantum regime, require very low temperatures around 10 mK, and they are hence kept inside dilution fridges. The electronics required to read out and control such processors is typically realized by discrete components or bulky scientific instruments at room temperature wired into the dilution fridge. Such approach is only feasible until few (< 100) qubits are handled, but it is not scalable for million-qubit processors required for fault-tolerant operation. In this thesis, readout and control electronics is proposed to be integrated and operated directly at cryogenic temperatures, in close proximity with the qubits and potentially even co-integrated. CMOS technology is advocated for its scalability, compactness and low prototyping cost, to create a comprehensive cryo-CMOS class of fully-integrated transceivers to read out and control solid-state qubits. In particular, the thesis focuses on cryo-CMOS radio-frequency integrated circuits for the readout of silicon quantum computers, looking to integrate the whole readout system, from the quantum layer to the room temperature user interface. Cryogenic CMOS devices are explored first, to lay the foundations of integrated circuit design. The realization of quantum dots in standard CMOS technology is explored as a platform to realize solid-state qubit arrays, demonstrating functionality at 50 mK and good reproducibility. Moreover, the operation of integrated transistors at 50 mK and 4.2 K is explored to understand their basic cryogenic functionality, through characterization and modeling. Then also integrated passives, such as capacitors, inductors and transformers, are studied and modeled at cryogenic temperatures. Then, a fully-integrated readout platform spanning across all the blocks needed for dispersive readout is proposed. A fully-integrated matrix of quantum dots with radio-frequency gate-based readout capabilities is demonstrated along with time- and frequency-multiplexing. This quantum-classical circuit shows all the features for a scalable approach and is the core of the platform following it. A cryogenic CMOS circulator based on a new all-pass filter architecture is demonstrated, to be used as integrated replacement for current bulky counterparts; it allows power reduction, insertion loss and bandwidth enhancement with respect to state-of-the-art integrated circulators. The rest of the front-end is also explored with dedicated test multiplexers, a low noise-amplifier and an oscillator, that are finally merged in a single fully-integrated low-noise receiver with frequency synthesizer operating at 3.5 K for scalable multiplexed readout of silicon qubits. The platform presented in this thesis, across temperature boundaries, carries all the features required for future scalable silicon quantum computing platforms and could therefore form their core.
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.
A fault-tolerant quantum computer with millions of quantum bits (qubits) requires massive yet very precise control electronics for the manipulation and readout of individual qubits. CMOS operating at cryogenic temperatures down to 4 K (cryo-CMOS) allows for closer system integration, thus promising a scalable solution to enable future quantum computers. In this paper, a cryogenic control system is proposed, along with the required specifications, for the interface of the classical electronics with the quantum processor. To prove the advantages of such a system, the functionality of key circuit blocks is experimentally demonstrated. The characteristic properties of cryo-CMOS are exploited to design a noise-canceling low-noise amplifier for spin-qubit RF-reflectometry readout and a class-F2,3digitally controlled oscillator required to manipulate the state of qubits.