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Optical Materials Express

Proposal for Brillouin microwave-to-optical conversion on a chip [Invited]

Yuan-Hao Yang, Jia-Qi Wang, Xin‐Biao Xu, Ming Li, Yanlei Zhang, Xiaoxuan Pan, Lintao Xiao, W.I. Wang, Guang‐Can Guo, Luyan Sun, Chang‐Ling Zou

Published Sep 12, 2024• 8 citations
Publisher

Abstract

We propose a novel scheme for efficient and low-noise microwave-to-optical quantum transduction based on cavity-enhanced Brillouin interaction between telecom photons and 10 gigahertz phonons on a lithium niobate-on-Sapphire chip. By employing a dual-microring cavity design and tailoring the geometry dispersion, triply-resonant and phase-matching conditions can be achieved for the backward Brillouin process, resulting in strong vacuum coupling strengths between the confined phononic and photonic modes. Our numerical analysis, taking into account the material anisotropy of lithium niobate and sapphire, predicts near-unity internal conversion efficiency with only sub-milliwatt pump power. The unsuspended all-solid-state architecture offers superior mechanical stability and robustness, overcoming a major challenge in piezo-optomechanical systems. Furthermore, the broadband nature of the Brillouin process enables multi-channel conversion, a key advantage over existing approaches. This versatile platform opens up exciting opportunities for scalable quantum processors with hybrid photonic-phononic-superconducting integrated circuits.

DOI
10.1364/ome.534817

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We propose a novel scheme for efficient and low-noise microwave-to-optical quantum transduction based on cavity-enhanced Brillouin interaction between telecom photons and 10 gigahertz phonons on a lithium niobate-on-Sapphire chip. By employing a dual-microring cavity design and tailoring the geometry dispersion, triply-resonant and phase-matching conditions can be achieved for the backward Brillouin process, resulting in strong vacuum coupling strengths between the confined phononic and photonic modes. Our numerical analysis, taking into account the material anisotropy of lithium niobate and sapphire, predicts near-unity internal conversion efficiency with only sub-milliwatt pump power. The unsuspended all-solid-state architecture offers superior mechanical stability and robustness, overcoming a major challenge in piezo-optomechanical systems. Furthermore, the broadband nature of the Brillouin process enables multi-channel conversion, a key advantage over existing approaches. This versatile platform opens up exciting opportunities for scalable quantum processors with hybrid photonic-phononic-superconducting integrated circuits.
Coherent transduction of quantum states from the microwave to the optical domain can play a key role in quantum networking and distributed quantum computing. We present the design of a piezo-optomechanical device formed in a hybrid lithium niobate on silicon platform, that is suitable for microwave-to-optical quantum transduction. Our design is based on acoustic hybridization of an ultra-low mode volume piezoacoustic cavity with an optomechanical crystal cavity. The strong piezoelectric nature of lithium niobate allows us to mediate transduction via an acoustic mode which only minimally interacts with the lithium niobate, and is predominantly silicon-like, with very low electrical and acoustic loss. We estimate that this transducer can realize an intrinsic conversion efficiency of up to 35% with <0.5 added noise quanta when resonantly coupled to a superconducting transmon qubit and operated in pulsed mode at 10 kHz repetition rate. The performance improvement gained in such hybrid lithium niobate-silicon transducers make them suitable for heralded entanglement of qubits between superconducting quantum processors connected by optical fiber links.
A scalable hybrid cavity quantum acoustodynamics (QAD) platform is proposed. The architecture integrates superconducting transmon qubits with phononic integrated circuits on a single chip made by a lithium niobate-on-sapphire substrate. The platform supports tightly confined and guided phononic modes in unsuspended waveguides and microring structures, while the superconducting qubits reside on the sapphire substrate. Efficient piezoelectric coupling between the phononic modes and transmon qubits can be achieved using interdigital transducers as part of the qubit’s shunt capacitance. Numerical calculations demonstrate the feasibility of achieving strong coupling between the phononic microring resonator and the transmon qubit. Remarkably, we show that a single pair of interdigital transducer fingers is sufficient to yield a coupling strength of g/2π≈1.3 MHz for the quasi-Love mode. This hybrid cavity QAD platform opens up new opportunities for quantum information processing and the study of novel quantum acoustic phenomena.
We present a resonant electro-optic transducer for efficient conversion between microwave and telecom wavelength photons. Our platform employs a bulk lithium niobate crystal whose large dielectric constant creates wavelength-scale confinement of microwave photons. By incorporating this crystal within a high-finesse Fabry - Perot optical cavity, microwave photons couple to optical photons through the electro-optic effect. We demonstrate the ability to tune our system into triply resonant operation, where microwave photons, optical pump photons, and upconverted optical photons are simultaneously resonant with high quality factor electromagnetic modes of the system. The device achieves photon number conversion efficiency at the percent level, comparable to state-of-the-art devices at room temperature -- sufficient to resolve the thermal occupation of the microwave mode -- while avoiding the noise and loss associated with metal electrodes. These results establish our all-dielectric devices as a promising platform for high-precision sensing of optically detected microwave fields and as a viable route toward single-photon-level microwave - optical quantum transduction.
Achieving efficient microwave–optical transduction is a critical challenge for quantum networks where information is shared optically across disparate microwave systems and for coherent optical detection and manipulation of microwave states. Resonant electro-optic systems are being pursued as a means of efficiently bridging these frequencies. Here, we present a platform that employs a bulk lithium niobate crystal whose large dielectric constant creates wavelength-scale confinement of microwave photons. By incorporating this crystal within a high-finesse Fabry–Pérot optical cavity, microwave photons couple to optical photons through the electro-optic effect. We demonstrate the ability to tune our system into triply resonant operation, where microwave photons, optical pump photons, and upconverted optical photons are simultaneously resonant with high quality factor electromagnetic modes of the system. The device achieves photon-number conversion efficiency at the percent level, comparable to that of state-of-the-art devices at room temperature—sufficient to resolve the thermal occupation of the microwave mode—by taking advantage of the high-power handling, low loss, and low noise of all-dielectric devices. These results establish our all-dielectric devices as a promising platform for high-precision sensing of optically detected microwave fields and as a viable route toward single-photon-level microwave–optical quantum transduction.
Quantum transduction between microwave and optical photons offers the potential to merge the long-range connectivity of optical photons with the deterministic quantum operations of superconducting microwave qubits. A promising approach to achieving this uses an intermediary mechanical mode along with piezo-optomechanical interactions. Traditionally, these transducers are suspended to confine mechanical fields, but this complicates manufacturing and comes with the major challenge of poor thermal anchoring and a trade-off between noise and efficiency. To overcome these issues, we introduce the—to our knowledge—first design of a release-free electro-optomechanical quantum transducer. Our release-free, i.e., non-suspended, design leverages a silicon-on-sapphire platform. It combines release-free lithium niobate electromechanical crystals with silicon optomechanical crystals on a sapphire substrate, optimizing thermal anchoring and microwave and mechanical coherence. Despite departing from the traditional suspended transducer paradigm, our release-free design achieves coupling rates sufficient for quantum-level interactions between microwave photons, phonons, and optical photons. Unconventionally, it utilizes high-wavevector mechanical modes tightly confined to the chip surface. Beyond quantum science and engineering, this platform and its design principles could also propel low-power acousto-optic systems in integrated photonics.
We present a numerical study of the design of a microwave-to-optical quantum converter based on Brillouin backscattering in a single thin-film lithium niobate racetrack resonator. The conversion involves TE0 to TM0 polarization conversion mediated by an even-parity acoustic mode that can be excited by a conventional symmetric interdigital transducer. Co-localization of the optical and acoustic fields within a single resonator enhances their interaction, while the signal is separated from the strong optical pump by propagation direction, polarization, and frequency. Combining full-vector electromagnetic and acoustic calculations with a pulsed entanglement transfer protocol, we obtain a vacuum coupling of g0/2π = 2 kHz for the designed perimeter and show that cooperativity of C = 1 is achieved with a calculated on-chip pump power of approximately 2.94 μW for Qopt = 107 and Qac = 105. Under these assumptions, the protocol enables entanglement transfer from a superconducting qubit to a flying telecom photon, supporting the proposed architecture as a compact platform for integrated quantum transduction.