Josephson junctions, as pivotal components of modern technologies such as superconducting quantum computing, owe their prominence to their unique nonlinear properties at low temperatures. Despite their extensive use in static configurations, the study of dynamic Josephson junctions, under space-time (ST) modulation, remains largely unexplored. This study investigates the interaction and transmission of light through arrays of space-time-modulated (STM) Josephson junctions. A comprehensive mathematical framework is presented to model the propagation of electric and magnetic fields within and beyond these structures. We demonstrate how such dynamic arrays enable unique four-dimensional light manipulation, leading to angular-frequency beam multiplexing through a seamless integration of frequency conversion and beam-splitting functionalities. These advancements open new horizons for electromagnetic field engineering, with far-reaching implications for superconducting quantum technologies, next-generation wireless communications, biomedical sensing, and radar systems.
Josephson junctions, as pivotal components of modern technologies such as superconducting quantum computing, owe their prominence to their unique nonlinear properties at low temperatures. Despite their extensive use in static configurations, the study of dynamic Josephson junctions, under space-time (ST) modulation, remains largely unexplored. This study investigates the interaction and transmission of light through arrays of space-time-modulated (STM) Josephson junctions. A comprehensive mathematical framework is presented to model the propagation of electric and magnetic fields within and beyond these structures. We demonstrate how such dynamic arrays enable unique four-dimensional light manipulation, leading to angular-frequency beam multiplexing through a seamless integration of frequency conversion and beam-splitting functionalities. These advancements open new horizons for electromagnetic field engineering, with far-reaching implications for superconducting quantum technologies, next-generation wireless communications, biomedical sensing, and radar systems.
Josephson junctions, as pivotal components of modern technologies such as superconducting quantum computing, owe their prominence to their unique nonlinear properties at low temperatures. Despite their extensive use in static configurations, the study of dynamic Josephson junctions, particularly under space-time modulation, remains largely unexplored. This study investigates the interaction and transmission of electromagnetic waves through arrays of space-time-modulated Josephson junctions. A comprehensive mathematical framework is presented to model the propagation of electric and magnetic fields within and beyond these structures. We demonstrate how such dynamic arrays enable groundbreaking four-dimensional light manipulation, achieving angular-frequency beam multiplexing through a seamless integration of frequency conversion and beam-splitting functionalities. These advancements open new horizons for electromagnetic field engineering, with far-reaching implications for superconducting quantum technologies, next-generation wireless communications, biomedical sensing, and radar systems.
Abstract We introduce space-time-modulated cryogenic-compatible Josephson metasurfaces as a versatile platform for polychromatic qubit coupling and frequency-selective interactions. These metasurfaces, based on arrays of gated superconductor-semiconductor Josephson field-effect transistors (JoFETs), enable dynamic four-dimensional (space-time) control of microwave fields at millikelvin temperatures. Through spatiotemporal modulation of the critical current density, the metasurface generates controllable Floquet harmonics, facilitating frequency conversion, parametric amplification, and nonreciprocal propagation. Full-wave electromagnetic simulations demonstrate selective excitation and multi-frequency state transitions in superconducting qubit arrays, where a photon emitted at frequency is efficiently redirected into multiple target frequencies to mediate long-range interactions between adjacent and non-adjacent qubits. In the circuit quantum electrodynamics framework, this yields an effective polychromatic Hamiltonian supporting frequency-multiplexed exchange couplings while providing spectral isolation that suppresses crosstalk. The engineered non-Markovian environment arising from the space-time modulation offers pathways to enhance qubit coherence times and entanglement fidelity through information backflow and noise suppression. Fabrication pathways using Al-proximitized InAs quantum wells and cryogenic measurement setups are discussed. This work establishes space-time-modulated Josephson metasurfaces as promising hardware enablers for frequency-selective control, improved connectivity, and robust operation in next-generation superconducting quantum systems.
Scaling superconducting quantum processors to large qubit counts faces challenges in control-signal delivery, thermal management, and hardware complexity, particularly in achieving microwave signal multiplexing and long-distance quantum information routing at millikelvin temperatures. We propose a space-time modulated Josephson-junction metasurface architecture to generate and multiplex microwave control signals directly at millikelvin temperatures. Theoretical and numerical results demonstrate the generation of multiple frequency tones with controlled parameters, enabling efficient and scalable qubit control while minimizing thermal loads and wiring overhead. We derive the nonlinear wave equation governing this system, simulate beam steering and frequency conversion, and discuss the feasibility of experimental implementation. These results lay the groundwork for a next-generation cryogenic signal-delivery paradigm that may enable scaling of superconducting quantum processors to thousands of qubits without overwhelming limited dilution-refrigerator cooling power.
Precise characterization of individual Josephson junctions (JJs) is essential for developing uniform superconducting JJ arrays, particularly in precision metrology, coherent THz sources, and quantum computing. Conventional electrical approaches are often limited by noise, averaging requirements, and the lack of single-junction resolution in large arrays. Here, we introduce a noninvasive optical modulation technique enabling efficient and selective probing of individual JJ characteristics. By modulating the intensity of a light source at high frequencies (50 kHz), we induce controlled changes in JJ properties and extract I c with high precision using lock-in detection. This method achieves 1% accuracy with only 100 ms of integration, offering comparable precision with substantially reduced acquisition time. Importantly, it enables scalable, parallel superlocalized mapping of JJ arrays through beam steering or multiplexed illumination, allowing identification of local inhomogeneities and defects. Beyond JJs, this approach provides a general framework for spatially resolved probing of emerging quantum materials and devices.
The pursuit of scalable and robust quantum computing necessitates innovative approaches to overcome the inherent challenges of qubit connectivity, decoherence, and susceptibility to noise and crosstalk. Conventional monochromatic qubit coupling architectures, constrained by nearest-neighbor interactions and limited algorithmic flexibility, exacerbate these issues, hindering the realization of practical large-scale quantum processors. In this work, we introduce a paradigm leveraging a space-time-modulated cryogenic-compatible Josephson metasurface to enable polychromatic qubit coupling. This metasurface facilitates frequency-selective interactions, transforming nearest-neighbor connectivity into all-to-all qubit interactions, while significantly enhancing coherence, noise robustness, and entanglement fidelity. Our proposed approach capitalizes on the unique capabilities of space-time-modulated Josephson metasurfaces, including dynamic four-dimensional wave manipulation, nonreciprocal state transmission, and state-frequency conversion, to mediate multi-frequency qubit interactions. By isolating qubit couplings into distinct spectral channels, the cryogenic-compatible metasurface mitigates crosstalk and environmental decoherence, extending coherence times and preserving quantum state fidelity. Full-wave simulations and quantum performance analyses demonstrate a significant enhancement in the operational efficiency of a superconducting qubit array, showcasing improved connectivity, robustness, and entanglement stability. This study establishes the potential of space-time-modulated cryogenic-compatible Josephson metasurfaces as a transformative platform for next-generation quantum computing, addressing critical bottlenecks and paving the way for scalable, high-performance quantum processors.
The Josephson junction (JJ) is the fundamental nonlinear building block of superconducting quantum technologies. Its macroscopic quantum tunneling physics underpins superconducting quantum computing, sensing, and communication, but scaling these platforms to utility-scale architectures places increasingly stringent demands on junction materials, interfaces, and fabrication. Practical quantum computing requires high reproducibility, low power consumption, tunability, a small device footprint, and resilience to noise and defects. This review surveys how advances in materials science, device characterization, and nanofabrication are addressing these challenges and redefining the figures of merit for next-generation JJs. This review also examines the evolution of fabrication strategies, from conventional multi-angle evaporation to foundry-compatible superconducting processes and the integration of emerging junction materials. Progress along these directions will determine how rapidly JJs move from laboratory-scale components to the foundation of industrial-scale quantum processors.