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Integrated Quantum Transducer Using NV Color Center in Diamond Nano Device

M. Yoshioka, K. Sato, H. Kurokawa, Y. Sekiguchi, M. Kamata, S. Hachuda, M. Kunii, T. Tamanuki, S. Ishida, H. Matsukiyo, H. Pholsen, Masao Nishioka, S. Ji, H. Otsuki, Kimura Kosuke, Takenaka Kouta, Onoda Shinobu, T. Baba, S. Iwamoto, H. Kosaka

Published Aug 20, 2026• 0 citations
OpenAlex

Abstract

We develop a diamond-based microwave-to-optical transducer to reduce cabling overhead in FTQC. By integrating diamond nanodevices with SiN waveguides, we achieved Purcell enhancement in a dilution refrigerator and verified spin controllability via ODMR, advancing toward scalable quantum interfaces.

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quant-pharXiv:2604.06984•Apr 9, 2026•0 citations

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Connecting cryogenic solid-state quantum processors with room-temperature optical links is a key step toward a scalable quantum computer. This thesis presents two technological advancements toward the realization of a spin-ensemble-based quantum transducer using impurity spins in diamond. First, a low-loss dielectric microwave resonator based on rutile (TiO2) was developed, achieving an internal quality factor of Qint ∼ 104 despite incorporating large optical apertures. Second, an optical Fabry–Pérot cavity was stabilized at millikelvin temperatures with sub-0.1 nm root-mean-square cavity length fluctuations, enabling stable cavity locking to the laser in a dilution refrigerator. These components were integrated into a hybrid resonator enabling spatial mode overlap within a diamond sample containing an ensemble of nitrogen-vacancy centers. Measurements at 10 mK revealed spin coherence times of T1 = 1930 s and T2 = 470 µs, and characterized the inhomogeneous broadening of the optical transition. We estimate the current microwave-to-optical conversion efficiency and discuss potential improvements through device and cavity optimization. This work establishes a platform for spin ensemble-based transducers operating at millikelvin temperatures.

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Efficient interfaces between optical photons and quantum bits are fundamental building blocks for quantum networks and large-scale quantum computers. We demonstrate an integrated platform for scalable quantum optics based on color centers coupled to diamond nanodevices. First, we incorporate nitrogen-vacancy (NV) centers in diamond into hybrid nanophotonic crystal cavities. Despite our progress towards coupling the NV to cavity photons, we find that the NV-cavity interface is limited by the imperfections of the color center's properties and its local environment. We approach this challenge first by characterizing and modifying the diamond surface to reduce the environmental noise affecting the NV optical transition. Subsequently, we develop a new approach that makes use of a quantum emitter with intrinsic protection from this noise: the silicon-vacancy (SiV) center in diamond. We demonstrate that SiV centers introduced through ion implantation feature highly coherent optical transitions, even inside nanostructures. By placing SiV centers inside all-diamond photonic crystal cavities, we achieve strong SiV-photon coupling with a cooperativity of greater than 20. Using this platform, we realize a quantum-optical switch controlled by the spin degree of freedom of a single SiV. By measuring intensity correlations of indistinguishable Raman photons emitted into a single waveguide, we observe a quantum interference effect resulting from the superradiant emission of two probabilistically entangled SiV centers. Finally, we demonstrate controllable photon-mediated interactions between the spin degrees of freedom of two cavity-coupled SiV centers. When the optical transitions of the two SiV centers are tuned into resonance, the coupling of each SiV to the common cavity mode results in a coherent interaction between the two SiVs, leading to the observation of super- and sub-radiant two-SiV states.

Bulletin of the American Physical Society•Mar 9, 2018•0 citations

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Alp Sipahigil, Ruffin E. Evans, Денис Дмитриевич Сукачев +13 more

Efficient interfaces between photons and quantum emitters form the basis for quantum networks and enable optical nonlinearities at the single-photon level. We demonstrate an integrated platform for scalable quantum nanophotonics based on silicon-vacancy (SiV) color centers coupled to diamond nanodevices. By placing SiV centers inside diamond photonic crystal cavities, we realize a quantum-optical switch controlled by a single color center. We control the switch using SiV metastable states and observe optical switching at the single-photon level. Raman transitions are used to realize a single-photon source with a tunable frequency and bandwidth in a diamond waveguide. By measuring intensity correlations of indistinguishable Raman photons emitted into a single waveguide, we observe a quantum interference effect resulting from the superradiant emission of two entangled SiV centers.

arXiv:1608.05147•Science•Oct 14, 2016•844 citations
Toward the realization of a large-scale fault-tolerant quantum computer, the development of microwave-to-optical quantum transducers has been actively underway over the past 10 years. Optical connections between refrigerators enable wide-bandwidth, flexible, room-temperature transmission of quantum information, extending the computing capacity of superconducting quantum processors. In this research, we explore the possibility of a diamond color-center-based quantum interface. We report the current status of developments in our fiber-integrated nanophotonic diamond devices.
Chip integration of quantum emitters is a crucial milestone for scalable quantum photonic information processing. Among optically active defect centers for quantum photonics, diamond color centers are promising because of their long spin coherence times and high photon emission rates. However, for a coherent-photon emission, they typically require a cryogenic environment to protect optical coherence from thermal phonons, which makes chip integration challenging. In this paper, we develop a chip-integrated diamond photonic crystal cavity embedding an ensemble of nitrogen-vacancy (NV) centers. We confirm cryogenic operation by observing Purcell enhancement of NV-center emission via an edge-coupled optical fiber. This result demonstrates successful integration of diamond color centers, a photonic crystal cavity, and an optical waveguide-fiber package, representing a key step toward scalable diamond-based quantum communication platforms.
Connecting cryogenic solid-state quantum processors with room-temperature optical links is a key step toward a scalable quantum computer. This thesis presents two technological advancements toward the realization of a spin-ensemble-based quantum transducer using impurity spins in diamond. First, a low-loss dielectric microwave resonator based on rutile (TiO2) was developed, achieving an internal quality factor of Qint ∼ 104 despite incorporating large optical apertures. Second, an optical Fabry–Pérot cavity was stabilized at millikelvin temperatures with sub-0.1 nm root-mean-square cavity length fluctuations, enabling stable cavity locking to the laser in a dilution refrigerator. These components were integrated into a hybrid resonator enabling spatial mode overlap within a diamond sample containing an ensemble of nitrogen-vacancy centers. Measurements at 10 mK revealed spin coherence times of T1 = 1930 s and T2 = 470 µs, and characterized the inhomogeneous broadening of the optical transition. We estimate the current microwave-to-optical conversion efficiency and discuss potential improvements through device and cavity optimization. This work establishes a platform for spin ensemble-based transducers operating at millikelvin temperatures.
Efficient interfaces between optical photons and quantum bits are fundamental building blocks for quantum networks and large-scale quantum computers. We demonstrate an integrated platform for scalable quantum optics based on color centers coupled to diamond nanodevices. First, we incorporate nitrogen-vacancy (NV) centers in diamond into hybrid nanophotonic crystal cavities. Despite our progress towards coupling the NV to cavity photons, we find that the NV-cavity interface is limited by the imperfections of the color center's properties and its local environment. We approach this challenge first by characterizing and modifying the diamond surface to reduce the environmental noise affecting the NV optical transition. Subsequently, we develop a new approach that makes use of a quantum emitter with intrinsic protection from this noise: the silicon-vacancy (SiV) center in diamond. We demonstrate that SiV centers introduced through ion implantation feature highly coherent optical transitions, even inside nanostructures. By placing SiV centers inside all-diamond photonic crystal cavities, we achieve strong SiV-photon coupling with a cooperativity of greater than 20. Using this platform, we realize a quantum-optical switch controlled by the spin degree of freedom of a single SiV. By measuring intensity correlations of indistinguishable Raman photons emitted into a single waveguide, we observe a quantum interference effect resulting from the superradiant emission of two probabilistically entangled SiV centers. Finally, we demonstrate controllable photon-mediated interactions between the spin degrees of freedom of two cavity-coupled SiV centers. When the optical transitions of the two SiV centers are tuned into resonance, the coupling of each SiV to the common cavity mode results in a coherent interaction between the two SiVs, leading to the observation of super- and sub-radiant two-SiV states.
On-chip scalable integration represents a major challenge for practical quantum devices. One particular challenge is to implement on-chip optical readout of spins in diamond. This readout requires simultaneous application of optical and microwave fields along with the efficient collection of fluorescence. These requirements are typically met using bulk optical components and dedicated microwave lines. Here, we experimentally demonstrate an on-chip integrated interface for diamond nitrogen vacancy (NV) spin-state preparation and readout, implemented in a planar single layer with only one patterning step. A nanodiamond with NV centers is positioned inside a v-groove waveguide milled in a thick gold film. The gold film carries the microwave control signal, while the v-groove acts as a fluorescence collector and, potentially, as an integrated pump filter. Hence, the device dimensions and fabrication complexity are substantially reduced. Our approach fosters further development of ultracompact nanoscale quantum sensors and quantum information processing devices on a monolithic platform.
Efficient interfaces between photons and quantum emitters form the basis for quantum networks and enable optical nonlinearities at the single-photon level. We demonstrate an integrated platform for scalable quantum nanophotonics based on silicon-vacancy (SiV) color centers coupled to diamond nanodevices. By placing SiV centers inside diamond photonic crystal cavities, we realize a quantum-optical switch controlled by a single color center. We control the switch using SiV metastable states and observe optical switching at the single-photon level. Raman transitions are used to realize a single-photon source with a tunable frequency and bandwidth in a diamond waveguide. By measuring intensity correlations of indistinguishable Raman photons emitted into a single waveguide, we observe a quantum interference effect resulting from the superradiant emission of two entangled SiV centers.