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ENLIGHTEN (Jurnal Bimbingan dan Konseling Islam)

Metasurface for Wireless Quantum Computation

Zhong, Mingyan, Al-Taai, Qusay, Stanley, Manoj, Barr, Kristopher, Brennan, Jack, Rossi, Alessandro, Ridler, Nick, Weides, Martin, Li, Chong

Published Nov 18, 2025• 0 citations
OpenAlex

Abstract

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.

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Optics Express•Jan 9, 2024•11 citations
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.
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.
Since superconducting quantum computers use microwave signals to control and readout their qubits, microwave transmission lines and circuits that can be used under cryogenic conditions are required. For microwave transmission lines, thermal insulation is essential to enhance wiring density and to prevent parasitic heating that can lead to increased computational errors. Thus, here we design and characterize a scalable, thermally insulated microwave transmission line. The transmission line designed for superconducting qubit readout at 5 GHz band achieves both thermal insulation and low loss, by employing resonator-based impedance matching in a microstripline structure. A flexible cable including eight planar transmission lines was designed, fabricated and characterized using S-parameter measurement, demonstrating low crosstalk below 40dB and signal attenuation of -23.5±0.07dB; this coincides with electromagnetic simulations. These microwave properties remained stable across a wide temperature range from room temperature down to 4 K, including steep gradients. The integration of chip attenuators further reduces thermal noise and protects sensitive cryogenic components. Our approach offers a promising solution for compact, high-density microwave wiring using flat cables under thermal gradients, necessary for large scale quantum computing.
Current control techniques for cryogenically cooled qubits are realized with coaxial cables, posing multiple challenges in terms of cost, thermal load, size, and long-term scalability. Emerging approaches to tackle this issue include cryogenic CMOS electronics at 4 K, and photonic links for direct qubit control. In this paper, we propose a multiplexed all-passive cryogenic high frequency direct detection control platform (cryo HFDD). The proposed classical interface for direct qubit control utilizes optical or sub-THz bands. We present the possible tradeoffs of this platform, and compare it with current state of-the-art cryogenic CMOS and conventional coaxial approaches. Weassess the feasibility of adopting these efficient links for a wide range of microwave qubit power levels. Specifically, we estimate the heat load to achieve the required signal-to-noise ratio SNR considering different noise sources, component losses, as well as link density. We show that multiplexed photonic receivers at 4 K can aggressively scale the control of thousands of qubits. This opens the door for low cost scalable quantum computing systems.
Engineering research in quantum computing is geared towards building a ”useful” quantum computer; usefulness here refers to the capability of solving computation problems that hold significant value in commercial applications, but are currently impossible to do in reasonable time-frames using classical algorithms. This is fundamentally a problem of scale – problems that can be solved by few-qubit processors can also be readily simulated by classical supercomputers in realistic time-frames, but as these problems grow in complexity, quantum computers are believed to be able to provide an exponential speedup over their classical counterparts, the so-called quantum advantage. However, scaling quantum computers presents many challenges due to the need to perform complex signal control and data processing at nanosecond time scales on fragile quantum systems that need stringent degrees of isolation from the environment for the computations to be carried out with high fidelity. Some of the most promising implementations of experimental-grade quantum computers are maintained in cryogenic environments due to the fact that at low enough temperatures noise processes due to random thermal excitations can be minimized. However, the control and measurement of quantum processors is currently done by systems at room temperature, whose connections to the cryogenic environment present thermal loading that will need to be addressed as these processors scale and their IO requirements to co-processors grow in complexity. As such, one possible path to scaling co-processing capabilities without compromising the quantum processor’s performance is the partial or complete integration of the co-processor in the cryo-environment. Several works describe systems that aim to do just that; and ”Cryo-CMOS” has become an important research subspace. This thesis aims to add to the current advancements in this field, specifically in the area of qubit measurements. It culminates in the implementation of a radio receiver that leverages the advantages of BiCMOS technology in cryo-environments to measure the state of a superconducting transmon-based qubit while strapped to a 4K stage in a dilution refrigerator. Critically, we demonstrate that low-noise amplification, down-conversion, and demodulation can all be done in the cryo-environment on a constrained power budget, with high fidelity comparable to a state-of-the-art (InP-HEMT LNA-based) qubit readout system, when preceded by a high-gain, quantum-noise-limited Josephson parametric amplifier.
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).
With the rapid development of superconducting quantum computing and the implementation of surface code, large-scale quantum computing is emerging as an urgent demand. In a superconducting computing system, the qubit is maintained in a cryogenic environment to avoid thermal excitation. Thus, the transmission of control signals, which are generated at room temperature, is needed. Typically, the transmission of these signals to the qubit relies on a coaxial cable wiring approach. However, in a large-scale computing system with hundreds or even thousands of qubits, the coaxial cables will pose great space and heat load to the dilution refrigerator. Here, to tackle this problem, we propose and demonstrate a direct-modulation-based optical transmission line. In our experiment, the average single-qubit XEB error and control error are measured as 0.139% and 0.014% separately, demonstrating the feasibility of the optical wiring approach and paving the way for large-scale superconducting quantum computing.