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ダイヤモンドNV–¹³Cハイブリッド量子ビット生成に向けた L-アルギニン分子イオン注入エネルギーの最適化

Ｂｉｓｗａｓ　Ｂｉｓｗａｊｉｔ, P. Balasubramanian, Takenaka Kouta, Fedor Jelezko, Ohshima Takeshi, Onoda Shinobu

Published Sep 8, 2026• 0 citations
OpenAlex

Abstract

The nitrogen-vacancy (NV) centers in diamond, also known as quantum bit operating at room temperature, have been recognized as a leading platform for quantum information and sensing. The electron spin of the NV center, along with the nuclear spins of the incorporated nitrogen atom and the neighboring isotope of carbon-13, act as a hybrid quantum register. By utilizing such quantum resister, quantum error correction, magnetic sensing and quantum teleportation have been demonstrated. Previously, we have developed ion beams of 65 keV adenine (C5N4Hn) containing four nitrogen atoms, 284 keV phthalocyanine (C32N8H18) containing eight nitrogen atoms, and 90 or 100 keV L-arginine (13C6H14 15N4O2) with isotopically enriched 13C and 15N. The implanted molecular ions are designed to dissociate into individual atoms at the surface, then progress through the diamond forming vacancies, halting with a spatial spread (~9±4 nm) for all molecular ions. The implanted nitrogen atoms combined with the vacancies via thermal treatment, forming the NV centers. In this study, we optimized the implantation energy of L-arginine ions to make a strong hyperfine coupling where the distance between NV and 13C is closer. A comparative analysis of the molecular ion energy for creating 15N-13C has been conducted where the resulting hybrid multi-qubits are characterized by pulsed optically detected magnetic resonance (ODMR), Ramsey spectroscopy, XY8 spectroscopy, etc. In the presentation we will explain the NV created by L-arginine implantation.

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Generation and Characterization of NV Quantum Registers Using Isotopically Enriched Molecular Ions

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A nitrogen vacancy (NV) center in diamond is known as a solid-state spin quantum bit (qubit) at room temperature. The fabrication of scalable quantum registers based on NV centers is a long-standing issue. In 2005, spin-spin interaction between NV-N pairs, which were fabricated by N2 ion implantation, was reported. An entanglement between two electron-spin qubits becomes an excellent quantum information processing component, as accomplished by an NV-NV pair with a nanometer-scale distance in 2010 and 2013. More recently,strongly dipolar coupled NV-NV pairs were realized by 14N 30 keV implantationvia nanoholes in PMMA resist mask. The creation yields of NV-NV pairs dramatically improved, and the nanohole implantation had been thought to be the most promising technique to integrate NV centers. However, the problem of the technique is the finite size of nanoholes. The distribution of nitrogen atoms is determined by both ion straggling and nanohole diameter. The scaling of NV centers is stagnant up to two for several years. To overcome the barrier of triple NV centers, our previous research gave a ground-breaking idea of a highly populated NV center complex by introducing a molecular ion implantation technique in 2019. Since the molecular ion is regarded as an idea point source, the distribution of nitrogen atoms is determined by only ion straggling. Therefore, our proposed method is more effective than other implantation techniques including nanohole implantation. Instead of a pure nitrogen cluster which is commonly unstable, the stable organic molecular ions (adenine; C5N5H5) were utilized as the ion source. We successfully implanted C5N4Hn ions into single crystalline diamonds. Three NV centers were integrated, and the dipolar interactions among them were successfully observed. In 2022, we succeeded in creating more than 5 NV centers by phthalocyanine (C32H18N8) ion implantation. The next challenge is the implantation of isotopically enriched molecular ions. The isotopically enriched ion contains 13C and 15N. The implantation of isotopically enriched molecular ions is able to create 15NV-13C hybrid quantum registers. In this presentation, we will show the development of the isotopically enriched molecular ion beam and the characterization of created NV centers by laboratory-built confocal microscopy (CFM) and optically detected magnetic resonance (ODMR).

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Nitrogen-vacancy (NV−) color centers in diamond were created by implantation of 7 keV N15(I=1∕2) ions into type IIa diamond. Optically detected magnetic resonance was employed to measure the hyperfine coupling of single NV− centers. The hyperfine spectrum from NV−15 arising from implanted N15 can be distinguished from NV−14 centers created by native N14(I=1) sites. Analysis indicates 1 in 40 implanted N15 atoms give rise to an optically observable NV−15 center. This report ultimately demonstrates a mechanism by which the yield of NV− center formation by nitrogen implantation can be measured.

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Nitrogen-vacancy (NV) centers are point defects in diamond formed by one substitutional nitrogen atom and an adjacent vacancy. Low spectral diffusion is a necessary property for NV centers to be qubit candidates. To characterize differences between naturally formed and ion implanted NV centers, diamond samples were studied that contained both types. The ion implantation process used 15N to be able to differentiate from the 14N naturally formed NV centers. This project focused on identifying the isotope of a single NV center, which is the first step toward understanding differences in their emissive properties. Code was developed to execute, and then automate, the three experiments necessary to identify the isotope of a single NV center: Continuous Wave Optically Detected Magnetic Resonance (CW ODMR), Rabi oscillations, and Pulsed ODMR. The code was implemented on a test sample, where it successfully identified the isotope of several NV centers. The next step in this project is to link the isotope of NV centers to their emissive properties, with a goal of producing reliable qubits for quantum information processing circuits.

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Creating dense and shallow nitrogen-vacancy (NV) ensembles with good spin properties is a prerequisite for developing diamond-based quantum sensors exhibiting better performance. Ion implantation is a key enabling tool for precisely controlling spatial localization and density of NV color centers in diamond. However, it suffers from a low creation yield, while higher ion fluences significantly damage the crystal lattice. In this work, we realize N2+ ion implantation in the 30–40 keV range at high temperatures. At 800 °C, NV's ensemble photoluminescence emission is three to four times higher than room temperature implanted films, while narrow electron spin resonance linewidths of 1.5 MHz, comparable to well-established implantation techniques, are obtained. In addition, we found that ion fluences above 2 × 1014 ions/cm2 can be used without graphitization of the diamond film, in contrast to room temperature implantation. This study opens promising perspectives in optimizing diamond films with implanted NV ensembles that could be integrated into quantum sensing devices.

Applied Physics Letters•Mar 25, 2024•15 citations
The nitrogen-vacancy (NV) centers in diamond, also known as quantum bit operating at room temperature, have been recognized as a leading platform for quantum information and sensing. The electron spin of the NV center, along with the nuclear spins of the incorporated nitrogen atom and the neighboring isotope of carbon-13, act as a hybrid quantum register. By utilizing such quantum resister, quantum error correction, magnetic sensing and quantum teleportation have been demonstrated. Previously, we have developed ion beams of 65 keV adenine (C5N4Hn) containing four nitrogen atoms, 284 keV phthalocyanine (C32N8H18) containing eight nitrogen atoms, and 90 or 100 keV L-arginine (13C6H14 15N4O2) with isotopically enriched 13C and 15N. The implanted molecular ions are designed to dissociate into individual atoms at the surface, then progress through the diamond forming vacancies, halting with a spatial spread (~9±4 nm) for all molecular ions. The implanted nitrogen atoms combined with the vacancies via thermal treatment, forming the NV centers. In this study, we optimized the implantation energy of L-arginine ions to make a strong hyperfine coupling where the distance between NV and 13C is closer. A comparative analysis of the molecular ion energy for creating 15N-13C has been conducted where the resulting hybrid multi-qubits are characterized by pulsed optically detected magnetic resonance (ODMR), Ramsey spectroscopy, XY8 spectroscopy, etc. In the presentation we will explain the NV created by L-arginine implantation.
A nitrogen vacancy (NV) center in diamond is known as a solid-state spin quantum bit (qubit) at room temperature. The fabrication of scalable quantum registers based on NV centers is a long-standing issue. In 2005, spin-spin interaction between NV-N pairs, which were fabricated by N2 ion implantation, was reported. An entanglement between two electron-spin qubits becomes an excellent quantum information processing component, as accomplished by an NV-NV pair with a nanometer-scale distance in 2010 and 2013. More recently,strongly dipolar coupled NV-NV pairs were realized by 14N 30 keV implantationvia nanoholes in PMMA resist mask. The creation yields of NV-NV pairs dramatically improved, and the nanohole implantation had been thought to be the most promising technique to integrate NV centers. However, the problem of the technique is the finite size of nanoholes. The distribution of nitrogen atoms is determined by both ion straggling and nanohole diameter. The scaling of NV centers is stagnant up to two for several years. To overcome the barrier of triple NV centers, our previous research gave a ground-breaking idea of a highly populated NV center complex by introducing a molecular ion implantation technique in 2019. Since the molecular ion is regarded as an idea point source, the distribution of nitrogen atoms is determined by only ion straggling. Therefore, our proposed method is more effective than other implantation techniques including nanohole implantation. Instead of a pure nitrogen cluster which is commonly unstable, the stable organic molecular ions (adenine; C5N5H5) were utilized as the ion source. We successfully implanted C5N4Hn ions into single crystalline diamonds. Three NV centers were integrated, and the dipolar interactions among them were successfully observed. In 2022, we succeeded in creating more than 5 NV centers by phthalocyanine (C32H18N8) ion implantation. The next challenge is the implantation of isotopically enriched molecular ions. The isotopically enriched ion contains 13C and 15N. The implantation of isotopically enriched molecular ions is able to create 15NV-13C hybrid quantum registers. In this presentation, we will show the development of the isotopically enriched molecular ion beam and the characterization of created NV centers by laboratory-built confocal microscopy (CFM) and optically detected magnetic resonance (ODMR).
A nitrogen vacancy (NV) center in diamond is known as a qubit with excellent magneto-optical properties at room temperature. Not only is NV center used for Quantum Information Processing (QIP), it is utilized for quantum sensing. The integrated NV centers in nanometer range have the potential of further improvement of sensitivity, etc. Ion implantation into diamond is known as one of the most popular methods for creating multiple qubits. In 2019, we have reported that the creation of three qubits was realized by implantation of the organic molecular (C5N4Hn) ion containing four nitrogen atoms1). In this study, we successfully developed Phthalocyanine (C32N8H18) ion beam for further integration of NV centers. After implantation and annealing, we succeeded to observe the fluorescence spots from NV centers. Fig. 1. shows schematic diagram of 284 keV-C32N8H18 ion implantation into diamond. Red, black, blue, and gray circles indicate nitrogen, carbon, hydrogen, and vacancy, respectively. Dashed circles indicate the NV centers. The average distance between nitrogen atoms is calculated to be 9±4 nm by SRIM (Stopping and Range In Matter) code. After annealing at 1000 oC for 2 hours in vacuum, the fluorescent image is observed by using home-build confocal laser scanning fluorescent microcopy.
Nitrogen-vacancy (NV−) color centers in diamond were created by implantation of 7 keV N15(I=1∕2) ions into type IIa diamond. Optically detected magnetic resonance was employed to measure the hyperfine coupling of single NV− centers. The hyperfine spectrum from NV−15 arising from implanted N15 can be distinguished from NV−14 centers created by native N14(I=1) sites. Analysis indicates 1 in 40 implanted N15 atoms give rise to an optically observable NV−15 center. This report ultimately demonstrates a mechanism by which the yield of NV− center formation by nitrogen implantation can be measured.
Nitrogen-vacancy (NV) centers are point defects in diamond formed by one substitutional nitrogen atom and an adjacent vacancy. Low spectral diffusion is a necessary property for NV centers to be qubit candidates. To characterize differences between naturally formed and ion implanted NV centers, diamond samples were studied that contained both types. The ion implantation process used 15N to be able to differentiate from the 14N naturally formed NV centers. This project focused on identifying the isotope of a single NV center, which is the first step toward understanding differences in their emissive properties. Code was developed to execute, and then automate, the three experiments necessary to identify the isotope of a single NV center: Continuous Wave Optically Detected Magnetic Resonance (CW ODMR), Rabi oscillations, and Pulsed ODMR. The code was implemented on a test sample, where it successfully identified the isotope of several NV centers. The next step in this project is to link the isotope of NV centers to their emissive properties, with a goal of producing reliable qubits for quantum information processing circuits.
Abstract Quantum information processing requires quantum registers based on coherently interacting quantum bits. The dipolar couplings between nitrogen vacancy (NV) centres with nanometre separation makes them a potential platform for room-temperature quantum registers. The fabrication of quantum registers that consist of NV centre arrays has not advanced beyond NV pairs for several years. Further scaling up of coupled NV centres by using nitrogen implantation through nanoholes has been hampered because the shortening of the separation distance is limited by the nanohole size and ion straggling. Here, we demonstrate the implantation of C5N4Hn from an adenine ion source to achieve further scaling. Because the C5N4Hn ion may be regarded as an ideal point source, the separation distance is solely determined by straggling. We successfully demonstrate the fabrication of strongly coupled triple NV centres. Our method may be extended to fabricate small quantum registers that can perform quantum information processing at room temperature.
Creating dense and shallow nitrogen-vacancy (NV) ensembles with good spin properties is a prerequisite for developing diamond-based quantum sensors exhibiting better performance. Ion implantation is a key enabling tool for precisely controlling spatial localization and density of NV color centers in diamond. However, it suffers from a low creation yield, while higher ion fluences significantly damage the crystal lattice. In this work, we realize N2+ ion implantation in the 30–40 keV range at high temperatures. At 800 °C, NV's ensemble photoluminescence emission is three to four times higher than room temperature implanted films, while narrow electron spin resonance linewidths of 1.5 MHz, comparable to well-established implantation techniques, are obtained. In addition, we found that ion fluences above 2 × 1014 ions/cm2 can be used without graphitization of the diamond film, in contrast to room temperature implantation. This study opens promising perspectives in optimizing diamond films with implanted NV ensembles that could be integrated into quantum sensing devices.