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Laser-cooled ion source for an ultrahigh-precision single NV center creation

Hosaka Koichi, Iizawa Masatomi, Seiji Hosoya, Kashiwagi Hirotsugu, Yuri Yosuke, Miyawaki Nobumasa, Ishii Yasuyuki, Shimada Hiroyuki, Yamagata Ryohei, Satoh Takahiro, Saito Yuuichi, Onoda Shinobu, Narumi Kazumasa, Kento Muroo, K. Ito, H. Okamoto

Published Jul 24, 2024• 0 citations
OpenAlex

Abstract

Deterministic ion implantation and color-center creation methods at the nanometer scale provide a route towards scalable quantum information processing. For this purpose, we have developed an inherently deterministic single-ion implantation method based on a linear Paul trap (LPT) as a single-ion source since the laser-cooling technique can be applied to the trap system to obtain ultralow-emittance ions and manipulate single ions one by one . Doubly charged nitrogen ions (N2+) produced in a sputter ion source is introduced into the LPT and sympathetically cooled with laser-cooled calcium ions (Ca+). Both the sputter ion source and the LPT chamber are elevated to +50kV for the 100keV-implantation of doubly charged single ions into a grounded diamond crystal.

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arXiv:1902.05308•Physical Review Letters•Sep 4, 2019•72 citations
Deterministic ion implantation and color-center creation methods at the nanometer scale provide a route towards scalable quantum information processing. For this purpose, we have developed an inherently deterministic single-ion implantation method based on a linear Paul trap (LPT) as a single-ion source since the laser-cooling technique can be applied to the trap system to obtain ultralow-emittance ions and manipulate single ions one by one . Doubly charged nitrogen ions (N2+) produced in a sputter ion source is introduced into the LPT and sympathetically cooled with laser-cooled calcium ions (Ca+). Both the sputter ion source and the LPT chamber are elevated to +50kV for the 100keV-implantation of doubly charged single ions into a grounded diamond crystal.
Nitrogen-vacancy (NV) centers in diamond are gaining attention as room-temperature quantum bits, with potential applications in quantum sensing, quantum information processing, and quantum communication. Precise positioning of NV centers is crucial for creating efficient single-photon sources using optical resonators and quantum memories for quantum interface, etc. Generally, broad ion beam implantation through nanohole fabricated by electron beam lithography has been widely used for precise creation of NV centers. There are several reports of deterministic NV creation by using pulsed fs- or ps-laser irradiations. In addition, focusing ion beam implantation provides a route towards scalable quantum information processing [3-6]. In this study, we are developing an inherently deterministic single-ion implantation method based on a linear Paul trap (LPT) as a single-ion source, since the laser-cooling technique can be applied to the trap system to obtain ultralow-emittance ions and manipulate single ions one by one. The QST system uses doubly charged ions cooled with calcium ions, allowing 100 keV ion implantation in diamond.
Abstract A detailed simulation study is conducted to explore the possibility of transporting a single ion precisely along a particular design orbit. As a practically useful example, we consider nitrogen ions sympathetically cooled with ultracold calcium ions produced in a linear Paul trap (LPT) by the Doppler laser-cooling technique. A single nitrogen almost completely frozen in the laboratory frame is extracted from the LPT by manipulating the axial potential barriers. A similar idea was recently implemented by Groot-Berning et al. [New J. Phys. 23, 063067 (2021)] to create nitrogen-vacancy centers in diamond as a platform for some important quantum technologies. We here perform systematic 3D simulations taking a standard LPT structure into account and figure out the necessary conditions to achieve the ultrahigh-precision irradiation of a single nitrogen onto any target. In addition to the string Coulomb crystal used in the previous work above, we show that even the shell crystalline structure can be employed for our purpose. When several specific conditions are satisfied, a normalized root-mean-squared emittance of ejected nitrogen ions can be made of the order of 10−16 m·rad in transverse dimensions perpendicular to the design orbit.
Ion implantation is an accelerator technology essential for creating defects or introducing impurities into materials. A research and development study is currently underway at QST Takasaki Institute toward ultrahigh-precision single-ion implantation based on laser-cooling techniques. To achieve this, we incorporate a linear Paul trap as an ultracold single-ion source, where trapped ions can be cooled to the order of mK or even “Coulomb-crystallized” by Doppler laser cooling. In our scheme, N or Si ions, useful for ion implantation to create color centers, are sympathetically cooled down to the mK range through Coulomb collisions by co-trapping them with laser-cooled Ca ions. Then, the ions are extracted selectively from the trap to be accelerated and focused through a 50-kV electrostatic bipotential lens system. We aim to focus the ions on the order of 10 nm for ultrahigh-precision implantation. The implantation system has already been assembled, and the commissioning is currently underway to enable ion extraction using a Coulomb crystal and focusing extracted cold ions. We present the status of system development and outline the scheme for selective ion extraction and nanobeam focusing based on multiparticle simulations.
Ion implantation is an accelerator-based technology used to create defects and introducing impurities into solid materials. A research and development study is currently underway toward ultrahigh-precision single-ion implantation using laser-cooling techniques at Takasaki Institute, National Institutes for Quantum Science and Technology. To achieve this, we incorporate a linear Paul trap as an ultracold single-ion source, where trapped ions can be made “Coulomb-crystallized” through Doppler laser cooling. In our scheme, nitrogen or silicon ions, useful for ion implantation to create color centers in materials, are sympathetically cooled through Coulomb collisions by co-trapping them with laser-cooled calcium ions to form a two-component crystal. These cold ions are then selectively extracted from the trap to be accelerated and focused through a 50-kV electrostatic bipotential-lens system. Our goal is to achieve beam focusing for ultrahigh-precision implantation on the order of 10 nm. The implanter system has already been assembled, and the commissioning is currently ongoing to enable single-ion extraction using a Coulomb crystal. In these proceedings, we describe the scheme for selective ion extraction and nanobeam focusing based on multiparticle simulations and briefly report recent progress in system implementation.
Abstract Nitrogen vacancy (NV) centers in diamond are a platform for several important quantum technologies, including sensing, communication and elementary quantum processors. In this letter we demonstrate the creation of NV centers by implantation using a deterministic single ion source. For this we sympathetically laser-cool single N 2 + 15 molecular ions in a Paul trap and extract them at an energy of 5.9 keV. Subsequently the ions are focused with a lateral resolution of 121(35) nm and are implanted into a diamond substrate without any spatial filtering by apertures or masks. After high-temperature annealing, we detect the NV centers in a confocal microscope and determine a conversion efficiency of about 0.6%. The 15NV centers are characterized by optically detected magnetic resonance on the hyperfine transition and coherence time.
Single dopant atoms or dopant-related defect centers in a solid state matrix are of particular importance among the physical systems proposed for quantum computing and communication, due to their potential to realize a scalable architecture compatible with electronic and photonic integrated circuits. Here, using a deterministic source of single laser-cooled Pr^{+} ions, we present the fabrication of arrays of praseodymium color centers in yttrium-aluminum-garnet substrates. The beam of single Pr^{+} ions is extracted from a Paul trap and focused down to 30(9) nm. Using a confocal microscope, we determine a conversion yield into active color centers of up to 50% and realize a placement precision of 34 nm.