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Rare-Earth Quantum Device Project

Sato Shinichiro

Published Oct 1, 2024• 0 citations
OpenAlex

Abstract

Rare-Earth Quantum Device Project aims to develop quantum devices based on gallium nitride (GaN), which has high quality and advanced microfabrication and device technologies, and rare-earth ions (RE3+), which have excellent characteristics as qubits and single photon sources. RE:GaN quantum devices have the potential to realize "electrically controlled single photon sources (SPSs) in the optical communication wavelength band at room temperature," "on-chip quantum entangled light sources," and "real-time diagnostics inside GaN devices by quantum sensing," which have not been achieved to date. Currently, our project studies ion implantation and post thermal annealing for high efficiency optical activation of implanted RE ions in GaN, local atomic structure of implanted RE ions, development of quantum sensing using RE ions in GaN, and enhancement of spontaneous emission of implanted RE ions in GaN by coupling to photonic crystal.

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Photon emission enhancement of lanthanoid ions implanted in gallium nitride nanostructures

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Reliable single-photon sources (SPSs) that provide on-demand single photons are indispensable in the rapidly growing field of quantum technologies. To be maximally useful, they must operate at room temperature, be compatible with mature fabrication processes, and integrate seamlessly with other photonic systems. These requirements have driven research into gallium nitride (GaN)-based photon emitters and devices. Lanthanoid (Ln)-doped GaN exhibits temperature-insensitive, spectrally sharp, and stable visible/near infrared emission. Additionally, Ln-doped GaN leverages a well-developed GaN platform, enabling integration into more complex devices. However, the spontaneous emission rate of Ln ions in the 4f-4f transition is lower than that of other SPS candidates, such as quantum dots. In this study, we present two types of nanostructures that enhance the photon emission of implanted Ln ions in GaN: nanopillar structures and photonic crystal nanocavities. We discuss the mechanisms by which these nanostructures enhance photon emission and explore the future prospects of Ln-doped GaN SPS.

•Mar 1, 2026•0 citations

Roadmap for Rare-earth Quantum Computing

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Several platforms are being considered as hardware for quantum technologies. For quantum computing (QC), superconducting qubits and artificially trapped ions are among the leading platforms, but many others also show promise, e.g. photons, cold atoms, defect centers including Rare-Earth (RE) ions. So far, results are limited to the regime of noisy intermediate scale qubits (NISQ), with a small number of qubits and a limited connectivity, and it is likely that future QC hardware will utilize several existing platforms in different ways. Thus, it currently makes sense to invest resources broadly and explore the full range of promising routes to quantum technology. Rare-earth ions in solids constitute one of the most versatile platforms for future quantum technology. One advantage is good coherence properties even when confined in strong natural traps inside a solid-state matrix. This confinement allows very high qubit densities and correspondingly strong ion-ion couplings. In addition, although their fluorescence is generally weak, cavity integration can enhance the emission greatly and enable very good connections to photonic circuits, including at the telecom wavelengths, making them promising systems for long-term scalability. The primary aim of this roadmap is to provide a complete picture of what components a RE quantum computer would consist of, to describe the details of all parts required to achieve a scalable system, and to discuss the most promising paths to reach it. In brief, we find that clusters of 50-100 single RE ions can act as high fidelity qubits in small processors, occupying only about (10 nm)^3. Due to the high capacity for integration of the RE systems, they be optically read out and connected to other such clusters for larger scalability. We make suggestions for future improvements, which could allow the REQC platform to be a leading one.

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Quantum Nano-photonic Devices Based on Rare-earth Ions

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I present our progress towards developing optical quantum memories based on photonic crystal cavities fabricated in rare-earth-doped crystals. These devices exhibit large spontaneous emission rate enhancement, enabling optical control of single rare-earth ion quantum bits.

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Quantum nano-photonic devices based on rare-earth ions (Conference Presentation)

Andrei Faraon

I present quantum nano-photonic devices based on nanophotonic resonators coupled to rare-earth-ions in crystals. The rare-earth ions exhibit long coherence times on optical transitions, which makes them suitable for optical quantum memories. We demonstrate a high-fidelity nanophotonic quantum memory based on a mesoscopic rare-earth ensemble coupled to a photonic crystal cavity. The nanocavity enables >95% spin polarization for efficient initialization of the atomic frequency comb memory, and time-bin-selective readout via enhanced optical Stark shift of the comb frequencies. Besides ensemble memories, single rare-earth-ions coupled to nano-resonators can be used as single optically addressable quantum bits where the quantum state is mapped on their Zeeman or hyperfine levels with long coherence time. Our solid-state nano-photonic quantum light-matter interfaces can be integrated with other chip-scale photon source and detector devices for multiplexed quantum and classical information processing at the nodes of quantum networks.

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Spectroscopic Theories and First-principles Calculations for Using Rare-Earth Ions Doped in Nanofabricated Materials to Build Quantum Computers: Showcases of RE3+ Doped Y2SiO5

Yau Yuen Yeung, Meng Ju

Without using any trapping lasers, rare-earth (RE) ions can be doped into some nanofabricated materials in form of nanocrystals in a solid state matrix, thus rendering a natural trap for potential application as a quantum computing device. In particular, passive nuclear spin states of RE ions can be utilized as (i) optical quantum memory (with huge density as yielded from nanocrystals), (ii) qubits by encoding in ground hyperfine states and operated as (iii) two-qubit gate when transferring them to active magnetized electronic states. A feasible implementation of qubits is realised by using those doped RE ions whose open-shell (for inner highly shielded $4 f$ shell electrons) energy levels and statevectors are well described by the crystal field (CF) interaction and hyperfine coupling in which the Hamiltonian is composed of various freeion interactions, the CF potential, electronic and nuclear Zeeman effects as well as the hyperfine interaction. For those qubit encoded in the two ground hyperfine states of RE ions, they can have fairly long lifetimes of days and coherence times (from 1.3s for $\mathrm{Er}^{3+}$ to 6 hours for $\mathrm{Eu}^{3+}$) due to the unique spectroscopic properties of RE ions. Because of the recent progress in optical single-ion detection for addressing individual qubits with a specific frequency channel, RE ions could be packed in a solid state 3D matrix at nanometer spacing, hence rendering very high qubit densities for quantum memories. Meanwhile, this configure also leads to strong dipole-dipole interactions (or high connectivity) between qubits which are not nearest neighbors. In this study, Kramers ions like ${ }^{167} \mathbf{E r}$ and ${ }^{171} \mathbf{Y b}$ doped in yttrium orthosilicate ${Y}_{2} {SiO}_{5}$ (YSO) nanocrystals will be investigated as a promising system for quantum computing because of their weak spin bath and possibility for being directly milled in single nanocrystals as nano-resonators. By using the famous Wien2k package to carry out the first-principles calculations, we can obtain the CF parameters and hyperfine constants as well as various electronic properties like energy gap and band structure for those Kramers RE ions doped in YSO. We shall present some essential findings from first-principles calculations to obtain various properties of the ground and excited CF and hyperfine states for those RE ions with an aim to optimize RE ions doping in YSO nanocrystals for quantum memories and qubits, contributing to scalable quantum computing architectures.

IEEE International Conference Nanomaterials: Applications & Properties (NAP)•Sep 8, 2024•0 citations

Engineering mesoscopic coherence between photons and atoms

Mahdi Hosseini, Zongfeng Li, Trevor Kling

Rare earth ions in solids provide a versatile platform for quantum optical information control. Our research focuses on light storage at telecom wavelengths in Erbium-doped crystals, aiming to develop efficient quantum optical memories for applications in quantum communication and computation. Additionally, we design solid-state devices relying on collective atom-atom interactions to enhance light-matter interactions, based on rare-earth photonic devices.

Quantum Sensing and Nano Electronics and Photonics•Mar 21, 2025•0 citations
Rare-Earth Quantum Device Project aims to develop quantum devices based on gallium nitride (GaN), which has high quality and advanced microfabrication and device technologies, and rare-earth ions (RE3+), which have excellent characteristics as qubits and single photon sources. RE:GaN quantum devices have the potential to realize "electrically controlled single photon sources (SPSs) in the optical communication wavelength band at room temperature," "on-chip quantum entangled light sources," and "real-time diagnostics inside GaN devices by quantum sensing," which have not been achieved to date. Currently, our project studies ion implantation and post thermal annealing for high efficiency optical activation of implanted RE ions in GaN, local atomic structure of implanted RE ions, development of quantum sensing using RE ions in GaN, and enhancement of spontaneous emission of implanted RE ions in GaN by coupling to photonic crystal.
Reliable single-photon sources (SPSs) that provide on-demand single photons are indispensable in the rapidly growing field of quantum technologies. To be maximally useful, they must operate at room temperature, be compatible with mature fabrication processes, and integrate seamlessly with other photonic systems. These requirements have driven research into gallium nitride (GaN)-based photon emitters and devices. Lanthanoid (Ln)-doped GaN exhibits temperature-insensitive, spectrally sharp, and stable visible/near infrared emission. Additionally, Ln-doped GaN leverages a well-developed GaN platform, enabling integration into more complex devices. However, the spontaneous emission rate of Ln ions in the 4f-4f transition is lower than that of other SPS candidates, such as quantum dots. In this study, we present two types of nanostructures that enhance the photon emission of implanted Ln ions in GaN: nanopillar structures and photonic crystal nanocavities. We discuss the mechanisms by which these nanostructures enhance photon emission and explore the future prospects of Ln-doped GaN SPS.
Several platforms are being considered as hardware for quantum technologies. For quantum computing (QC), superconducting qubits and artificially trapped ions are among the leading platforms, but many others also show promise, e.g. photons, cold atoms, defect centers including Rare-Earth (RE) ions. So far, results are limited to the regime of noisy intermediate scale qubits (NISQ), with a small number of qubits and a limited connectivity, and it is likely that future QC hardware will utilize several existing platforms in different ways. Thus, it currently makes sense to invest resources broadly and explore the full range of promising routes to quantum technology. Rare-earth ions in solids constitute one of the most versatile platforms for future quantum technology. One advantage is good coherence properties even when confined in strong natural traps inside a solid-state matrix. This confinement allows very high qubit densities and correspondingly strong ion-ion couplings. In addition, although their fluorescence is generally weak, cavity integration can enhance the emission greatly and enable very good connections to photonic circuits, including at the telecom wavelengths, making them promising systems for long-term scalability. The primary aim of this roadmap is to provide a complete picture of what components a RE quantum computer would consist of, to describe the details of all parts required to achieve a scalable system, and to discuss the most promising paths to reach it. In brief, we find that clusters of 50-100 single RE ions can act as high fidelity qubits in small processors, occupying only about (10 nm)^3. Due to the high capacity for integration of the RE systems, they be optically read out and connected to other such clusters for larger scalability. We make suggestions for future improvements, which could allow the REQC platform to be a leading one.
I present quantum nano-photonic devices based on nanophotonic resonators coupled to rare-earth-ions in crystals. The rare-earth ions exhibit long coherence times on optical transitions, which makes them suitable for optical quantum memories. We demonstrate a high-fidelity nanophotonic quantum memory based on a mesoscopic rare-earth ensemble coupled to a photonic crystal cavity. The nanocavity enables >95% spin polarization for efficient initialization of the atomic frequency comb memory, and time-bin-selective readout via enhanced optical Stark shift of the comb frequencies. Besides ensemble memories, single rare-earth-ions coupled to nano-resonators can be used as single optically addressable quantum bits where the quantum state is mapped on their Zeeman or hyperfine levels with long coherence time. Our solid-state nano-photonic quantum light-matter interfaces can be integrated with other chip-scale photon source and detector devices for multiplexed quantum and classical information processing at the nodes of quantum networks.
Without using any trapping lasers, rare-earth (RE) ions can be doped into some nanofabricated materials in form of nanocrystals in a solid state matrix, thus rendering a natural trap for potential application as a quantum computing device. In particular, passive nuclear spin states of RE ions can be utilized as (i) optical quantum memory (with huge density as yielded from nanocrystals), (ii) qubits by encoding in ground hyperfine states and operated as (iii) two-qubit gate when transferring them to active magnetized electronic states. A feasible implementation of qubits is realised by using those doped RE ions whose open-shell (for inner highly shielded 4f4 f4f shell electrons) energy levels and statevectors are well described by the crystal field (CF) interaction and hyperfine coupling in which the Hamiltonian is composed of various freeion interactions, the CF potential, electronic and nuclear Zeeman effects as well as the hyperfine interaction. For those qubit encoded in the two ground hyperfine states of RE ions, they can have fairly long lifetimes of days and coherence times (from 1.3s for Er3+\mathrm{Er}^{3+}Er3+ to 6 hours for Eu3+\mathrm{Eu}^{3+}Eu3+) due to the unique spectroscopic properties of RE ions. Because of the recent progress in optical single-ion detection for addressing individual qubits with a specific frequency channel, RE ions could be packed in a solid state 3D matrix at nanometer spacing, hence rendering very high qubit densities for quantum memories. Meanwhile, this configure also leads to strong dipole-dipole interactions (or high connectivity) between qubits which are not nearest neighbors. In this study, Kramers ions like 167Er{ }^{167} \mathbf{E r}167Er and 171Yb{ }^{171} \mathbf{Y b}171Yb doped in yttrium orthosilicate Y2SiO5{Y}_{2} {SiO}_{5}Y2​SiO5​ (YSO) nanocrystals will be investigated as a promising system for quantum computing because of their weak spin bath and possibility for being directly milled in single nanocrystals as nano-resonators. By using the famous Wien2k package to carry out the first-principles calculations, we can obtain the CF parameters and hyperfine constants as well as various electronic properties like energy gap and band structure for those Kramers RE ions doped in YSO. We shall present some essential findings from first-principles calculations to obtain various properties of the ground and excited CF and hyperfine states for those RE ions with an aim to optimize RE ions doping in YSO nanocrystals for quantum memories and qubits, contributing to scalable quantum computing architectures.