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arXiv:2510.06176

An integrated photonic millimeter-wave receiver with sub-ambient noise temperature

Junyin Zhang, Shuhang Zheng, Jiachen Cai, Connor Denney, Zihan Li, Yichi Zhang, Changhao Han, Xin Ou, Gabriel Santamaria-Botello, Tobias J. Kippenberg

physics.opticsquant-phSubmitted Oct 7, 2025• Announced Oct 8, 2025• Revised Nov 1, 2026 (v3)
v1 · Oct 7, 2025v2 · Mar 31, 2026v3 · Nov 1, 2026
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Abstract

Growing demands for timing precision in positioning systems, and resolution in atmospheric sensing and automotive radar, have extended receiver frontends into the millimetre-wave and THz regimes. At these frequencies, the noise performance of field-effect transistors used in low-noise amplifiers degrades rapidly due to parasitic effects, limited carrier mobility, hot electrons, and shot noise. Parametric transducers that couple electromagnetic signals to optical fields can offer quantum-limited sensitivity at room temperature. Electro-optic materials can enable receivers that transduce radiofrequency signals into optical phase shifts. Yet to date, room-temperature receivers using electro-optical detection have not attained a noise figure comparable to the electronic amplifiers. Here we demonstrate a room-temperature cavity electro-optic-based millimetre-wave receiver on a lithium tantalate photonic integrated circuit, achieving an on-chip photon-number transduction efficiency of 10%. The equivalent input-referred receiver-added noise temperatures reach $110\,\mathrm{K}$ on-chip and $202^{+35}_{-33}\,\mathrm{K}$ for the full system at 60.5 GHz, with noise figure matching state-of-the-art V-band electronic low-noise amplifiers. We resolve the thermal noise in cavity electro-optic transducers, showing that the system is limited by thermal photon occupation ($\sim$100) in the millimetre-wave cavity and optical vacuum noise, with no measurable excess noise. Our work demonstrates that integrated photonics can reach state-of-the-art electronic receiver noise performance while offering high-radiofrequency-power survivability and compatibility with remote optical readout. This establishes cavity electro-optics as a low-noise, electromagnetic interference-resilient, chip-scale receiver frontend for millimetre-wave applications, enabling scalable analogue processing in the optical domain.

Comments
Main text: 11 pages, 5 figures; Supplementary information: 45 pages, 52 figures

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Millimeter-wave and terahertz technologies offer new opportunities for high-capacity communications, sensing, and quantum systems, but electronic signal chains above 100 GHz are limited by weak sources, noisy receivers, and lossy interconnects. Photonic approaches mitigate these constraints by enabling chip-scale high-frequency components, yet existing implementations generally retain lossy off-chip electrical or free-space links, hindering dense and compact integration for cryogenic or space-constrained settings. Here, we show a monolithic lithium tantalate photonic chip, termed a signal core, which generates, modulates, routes, and detects continuous-wave signals at discrete frequencies between 100 GHz and 2.5 THz. The architecture integrates high-frequency functional modules on chip and uses exclusively fiber-based optical interfaces. Bidirectional coherent electro-optic conversion enables signal generation, detection, and nanosecond-scale amplitude and phase modulation, while micro-coplanar striplines interconnect the modules into an end-to-end signal chain on a single chip. Our modules achieve single-photon electro-optic coupling rates of g_0/2π=10 kHz and peak drive-power-normalized photon-flux conversion efficiencies of 1.0%/mW for generation and 0.5%/mW for detection. It also operates at 4 K in a dilution refrigerator through the same fiber-only optical links. Together, these capabilities establish an all-photonic platform for millimeter-wave-to-terahertz systems and offer a broadly applicable architecture for applications constrained by electrical-interconnect loss, heat load, and footprint.
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Efficient and stable microwave-optical transduction is a key enabling technology for distributed superconducting quantum computing and heterogeneous quantum networks. Electro-optic transducers based on thin-film lithium niobate (TFLN) have shown strong promise, but demonstrations to date have been limited by various factors such as low frequency bias drift, low efficiency, fabrication complexity, and scalability. Here we demonstrate the first integrated electro-optic microwave-optical transducers realized in thin-film lithium tantalate (TFLT), a material platform offering Pockels nonlinearity comparable to TFLN together with improved bias stability and high-power handling. We fabricate superconducting microwave resonators coupled to tunable photonic-molecule optical resonators using wafer-scale deep ultraviolet lithography, offering high-throughput production of hundreds of devices per wafer. Across six devices we observe coherent bidirectional conversion between C-band optical photons and 4.9-5.5 GHz microwave photons, with measured on-chip efficiencies and inferred single-photon coupling rates g_0/2π ~ 1 kHz consistent with theory. Continuous operation over multiple days is achieved using a static bias field with minimal feedback, demonstrating a major operational advantage. We further characterize optical loss statistics, microwave resonator performance, and optically induced added noise under pulsed pumping, finding less than one added photon for 100 microsecond pulses at the highest measured efficiencies. These results establish TFLT as a scalable and robust electro-optic platform for future quantum interconnects and modular quantum processors.