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.
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.
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).
Abstract A nitrogen vacancy (NV) center in diamond is known as a solid-state spin qubit at room temperature. NV centers coherently coupled by dipole–dipole interactions have a potential to accomplish quantum registers at room temperature. This study reports to develop a phthalocyanine ion implantation technique to fabricate multiple dipole-coupled NV centers. Photon counts and optically detected magnetic resonance spectra show that up to four NV centers were successfully created in a confocal spot. The histogram of photon counts is fitted by a Poisson distribution, and the ratio of multiple NV spots suggests the potential for a five NV centers creation.
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.
Abstract The nitrogen-vacancy (NV) centre in diamond is a premier solid-state defect for quantum information processing and metrology. An integrated diamond quantum device harnesses the collective properties of multiple NV centres, enabling room-temperature quantum computing and sensing. While large-scale devices are poised to fill an important gap in the burgeoning quantum technology landscape, their practical realisation has not been achieved using current top-down fabrication techniques such as ion implantation. Consequently, this necessitates the development of a bottom-up fabrication technique, which is scalable, deterministic, and possesses atomic-scale precision. Informed by existing methods for fabricating phosphorous defect qubits in silicon, we envision a hydrogen depassivation lithography technique for atomically-precise manufacturing of nitrogen-vacancy centres in diamond. This perspective article outlines a viable multi-step procedure for realising scalable fabrication of diamond quantum devices and identifies the key challenges in its development.
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.
Coherently coupled pairs or multimers of nitrogen-vacancy defect electron spins in diamond have many promising applications especially in quantum information processing (QIP) but also in nanoscale sensing applications. Scalable registers of spin qubits are essential to the progress of QIP. Ion implantation is the only known technique able to produce defect pairs close enough to allow spin coupling via dipolar interaction. Although several competing methods have been proposed to increase the resulting resolution of ion implantation, the reliable creation of working registers is still to be demonstrated. The current limitation are residual radiation-induced defects, resulting in degraded qubit performance as trade-off for positioning accuracy. Here we present an optimized estimation of nanomask implantation parameters that are most likely to produce interacting qubits under standard conditions. We apply our findings to a well-established technique, namely masks written in electron-beam lithography, to create coupled defect pairs with a reasonable probability. Furthermore, we investigate the scaling behavior and necessary improvements to efficiently engineer interacting spin architectures.