Scalable quantum computing is limited by the dense network of electrical interconnects linking cryogenic quantum processors to room-temperature control electronics. To overcome this bottleneck, considerable effort has focused on cryogenic CMOS electronics and microwave-to-optical transduction, aiming to reduce wiring complexity and thermal loading. Wireless interconnects have recently emerged as a promising complementary approach, yet their compatibility with superconducting quantum hardware remains largely unexplored. Here, we demonstrate the wireless excitation of a superconducting microwave resonator of the type routinely employed for qubit readout, operating at millikelvin temperatures inside a dilution refrigerator. By directly comparing wired and wireless operation within the same cryogenic environment, we show that wireless coupling preserves the intrinsic resonator response while revealing parasitic electromagnetic pathways arising from stray radiation within the cryostat enclosure. These results establish a framework for the co-design of wireless interconnects, cryogenic packaging and superconducting quantum hardware.
Scalable quantum computing is limited by the dense network of electrical interconnects linking cryogenic quantum processors to room-temperature control electronics. To overcome this bottleneck, considerable effort has focused on cryogenic CMOS electronics and microwave-to-optical transduction, aiming to reduce wiring complexity and thermal loading. Wireless interconnects have recently emerged as a promising complementary approach, yet their compatibility with superconducting quantum hardware remains largely unexplored. Here, we demonstrate the wireless excitation of a superconducting microwave resonator of the type routinely employed for qubit readout, operating at millikelvin temperatures inside a dilution refrigerator. By directly comparing wired and wireless operation within the same cryogenic environment, we show that wireless coupling preserves the intrinsic resonator response while revealing parasitic electromagnetic pathways arising from stray radiation within the cryostat enclosure. These results establish a framework for the co-design of wireless interconnects, cryogenic packaging and superconducting quantum hardware.
As quantum computing technology advances, the demand for efficient, scalable, and thermally optimized solutions for qubit control and readout under cryogenic conditions has become increasingly critical. Currently, cryogenic qubit systems rely on numerous coaxial cables and DC wires for readout and control—typically two to three per qubit. Such dense wiring introduces significant engineering challenges, particularly regarding heat dissipation and spatial limitations [1]. To address these issues, wireless approaches have been proposed, offering promising advantages in scalability, thermal load reduction, and efficient quantum state transfer. Although wireless systems eliminate the need for cables, dilution refrigerators (DRs) impose strict spatial constraints, limiting the use of conventional microwave-range wireless components such as horn antennas and dielectric lenses. In addition, the sensitive and enclosed cryogenic environment demands precise beam shaping to prevent unwanted scattering and reflections. Hence, there is a pressing need for a compact and effective wireless solution tailored to such environments. In this study, we present a next-generation wireless communication system specifically designed for cryogenic quantum environments, enabling qubit control and readout at millikelvin temperatures. To achieve optimal signal transmission, we explored and simulated multiple design strategies, addressing challenges such as signal degradation, noise interference, and limited spatial volume within the refrigerator. Our system employs metasurface lens antennas to enhance transmission efficiency while minimizing signal-to-noise ratio (SNR) degradation. Considering the confined geometry of cryogenic setups, we developed two types of compact metalens antennas operating in both the microwave and millimeterwave regimes. Experimental measurements demonstrate more than 20 dB enhancement in wireless transmission, consistent with simulation results. These findings confirm that the proposed system satisfies the stringent requirements of quantum control and readout, making it a promising and practical solution for future quantum computing applications. We will share further details and insights on the metasurface-enabled wireless quantum computing platform at the upcoming conference presentation.
The transition of quantum technologies from laboratory-scale demonstrations to fault-tolerant and deployable systems is increasingly limited by the classical–quantum hardware interface. Although microwave subsystems for several leading quantum-computing platforms have been reviewed previously, the RF-to-terahertz hardware requirements that enable cross-platform maturation remain less systematically addressed. This article critically reviews RF-to-terahertz hardware for quantum technologies, focusing on cryogenic integration, high-density interconnects, and fabrication bottlenecks. Recent experimental efforts from the electronics engineering community are analyzed to identify shared limitations in low-temperature device modeling, thermal management, signal integrity, low-noise amplification, passive microwave structures, control and readout electronics, microwave-to-optical transduction, and scalable packaging. Competing approaches are assessed against common engineering criteria including RF and noise performance, bandwidth, power dissipation and thermal load, integration density, calibration complexity, fabrication reproducibility, and maturity toward scalable deployment. The review argues that future progress is no longer governed only by the optimization of individual components, but by the co-design of materials, devices, interconnects, control architectures, measurement chains, and manufacturing processes. In this framework, scalability, miniaturization, integration density, and reproducibility become central metrics for quantum hardware development. By synthesizing developments across quantum computing, sensing, communication, and networking platforms, this review provides a component-level roadmap for RF, microwave, terahertz, and electronics engineers working toward scalable, manufacturable, and interoperable quantum technology systems.
Today's hundred-qubit quantum computers require a dramatic scale up to millions of qubits to become practical for solving real-world problems. Although a variety of qubit technologies have been demonstrated, scalability remains a major hurdle. Superconducting (SC) qubits are one of the most mature and promising technologies to overcome this challenge. However, these qubits reside in a millikelvin cryogenic dilution fridge, isolating them from thermal and electrical noise. They are controlled by a rack-full of external electronics through extremely complex wiring and cables. Although thousands of qubits can be fabricated on a single chip and cooled down to millikelvin temperatures, scaling up the control and readout electronics remains an elusive goal. This is mainly due to the limited available cooling power in cryogenic systems constraining the wiring capacity and cabling heat load management. In this article, we focus on scaling up the number of XY-control lines by using cryogenic RF-photonic links. This is one of the major roadblocks to build a thousand qubit superconducting QC. We will first review and study the challenges of state-of-the-art proposed approaches, including cryogenic CMOS and deep-cryogenic photonic methods, to scale up the control interface for SC qubit systems. We will discuss their limitations due to the active power dissipation and passive heat leakage in detail. By analytically modeling the noise sources and thermal budget limits, we will show that our solution can achieve a scale up to a thousand of qubits. Our proposed method can be seamlessly implemented using advanced silicon photonic processes, and the number of required optical fibers can be further reduced by using wavelength division multiplexing (WDM).
Current superconducting quantum computers (QC) rely on a brute-force scaling approach where quantum chips operating at the millikelvin stage inside dilution refrigerators are connected to room-temperature electronics via an ever-increasing number of signal wires. In order to drastically scale up such systems without facing refrigeration challenges, these quantum interface electronics need to be integrated at cryogenic temperatures, ideally at the same stage as qubits. In this paper, we show that, by employing energy-efficient digital superconducting microchips based on single flux quantum (SFQ) technology, all essential functions to operate a full stack quantum computer can be integrated at 10 mK. They include digital qubit charge control and magnetic flux control for single- and two-qubit gates, as well as digital qubit readout.
For superconducting quantum processors, microwave signals are delivered to each qubit from room-temperature electronics to the cryogenic environment through coaxial cables. Limited by the heat load of cabling and the massive cost of electronics, such an architecture is not viable for millions of qubits required for fault-tolerant quantum computing. Monolithic integration of the control electronics and the qubits provides a promising solution, which, however, requires a coherent cryogenic microwave pulse generator that is compatible with superconducting quantum circuits. Here, we report such a signal source driven by digital-like signals, generating pulsed microwave emission with well-controlled phase, intensity, and frequency directly at millikelvin temperatures. We showcase high-fidelity readout of superconducting qubits with the microwave pulse generator. The device demonstrated here has a small footprint, negligible heat load, great flexibility to operate, and is fully compatible with today's superconducting quantum circuits, thus providing an enabling technology for large-scale superconducting quantum computers.
The rapid development of superconducting quantum hardware is expected to run into substantial restrictions on scalability because error correction in a cryogenic environment has stringent input-output requirements. Classical data centres rely on fibre-optic interconnects to remove similar networking bottlenecks. In the same spirit, ultracold electro-optic links have been proposed and used to generate qubit control signals, or to replace cryogenic readout electronics. So far, these approaches have suffered from either low efficiency, low bandwidth or additional noise. Here we realize radio-over-fibre qubit readout at millikelvin temperatures. We use one device to simultaneously perform upconversion and downconversion between microwave and optical frequencies and so do not require any active or passive cryogenic microwave equipment. We demonstrate all-optical single-shot readout in a circulator-free readout scheme. Importantly, we do not observe any direct radiation impact on the qubit state, despite the absence of shielding elements. This compatibility between superconducting circuits and telecom-wavelength light is not only a prerequisite to establish modular quantum networks, but it is also relevant for multiplexed readout of superconducting photon detectors and classical superconducting logic.