Long-distance excitation of nitrogen-vacancy centers in diamond vian surface spin waves

At a Glance

Metadata	Details
Publication Date	2017-08-02
Journal	arXiv (Cornell University)
Authors	Daisuke Kikuchi, Dwi Prananto, Kunitaka Hayashi, Abdelghani Laraoui, Norikazu Mizuochi
Institutions	Japan Advanced Institute of Science and Technology, Advanced Science Research Center
Citations	55
Analysis	Full AI Review Included

Long-Distance Excitation of NV Centers via Surface Spin Waves: Technical Analysis and 6CCVD Solutions

Executive Summary

This research demonstrates a critical advance in solid-state quantum technology, achieving robust, long-distance spin manipulation of Nitrogen-Vacancy (NV) centers in diamond mediated by Magnetostatic Surface Spin Waves (MSSWs) propagating in an adjacent Yttrium Iron Garnet (YIG) film.

Core Achievement: Demonstrated efficient energy exchange between NV spins and MSSWs, enabling spin manipulation far from the primary microwave (MW) antenna source where the direct MW field is negligible.
Material System: A hybrid architecture combining a high-purity, Type-IIa Single Crystal Diamond (SCD) substrate hosting near-surface NV centers with a polycrystalline YIG disk overlaid with a thin gold (Au) antenna wire.
Performance Metric: An enhancement factor exceeding 100 fold in the effective Rabi field was achieved compared to the calculated direct MW field at a distance of 3.6 mm from the antenna source.
Qubit Control: Time-resolved control was proven through the demonstration of NV spin Rabi oscillations, yielding a period T_R ~2 µs under optimized conditions (90 mW MW power).
NV Preparation: Near-surface NV centers were created via low-energy ion implantation (30 keV) and high-temperature annealing (1000 °C), targeting a depth of 30-40 nm.
Relevance: This work is highly relevant for scalable quantum architectures, wide-bandgap semiconductor qubit processing, and high-sensitivity nanoscale spin sensing, offering a robust, non-cryogenic mechanism for coupling distant qubits.

Technical Specifications

Parameter	Value	Unit	Context
Diamond Crystal Type	<100> Type-IIa	N/A	Host for NV centers (Spin Qubits)
NV Implantation Energy	30	keV	Determines NV depth
NV Implantation Dose	2.0 x 10¹¹	ions/cm²	-
NV Depth (Target)	30-40	nm	Near-surface spins
NV Concentration (Estimated)	0.6	ppm	Inter-NV distance: 60 nm
Annealing Temperature	1000	°C	For NV formation
Annealing Atmosphere	Argon	N/A	-
YIG Disk Thickness	0.4	mm	Ferrimagnetic substrate
YIG Disk Diameter	4	mm	-
External Magnetic Field (H)	212	Oe	Field for resonant FMR/MSSW measurement
Ferromagnetic Resonance (FMR)	1.8	GHz	Lowest resonance peak
MSSW Operating Range	2.0 - 2.8	GHz	Frequencies used for NV coupling
MW Power (Max)	560	mW	Used for ODMR spectra measurement
Rabi Period (T_R)	~2	µs	Observed at 90 mW MW power
Effective Rabi Field (B_eff)	~0.17	Gauss	Achieved at 3.6 mm distance, 90 mW
Enhancement Factor	>100	fold	Ratio of B_eff to calculated direct MW field
Laser Wavelength	532	nm	NV optical initialization and readout

Key Methodologies

The experimental approach focused on creating near-surface NV centers in high-purity diamond and coupling them efficiently to spin waves generated in an adjacent ferrimagnetic insulator (YIG).

Diamond Preparation:
- Acquisition of Type-IIa <100> diamond crystal.
- Creation of NV centers via nitrogen ion implantation (30 keV, 2.0 x 10¹¹ ions/cm²) to generate near-surface spins (30-40 nm depth).
- Post-implantation annealing at 1000 °C for 1 hour in an argon atmosphere to facilitate vacancy migration and NV formation.
Spin Wave Generation Setup:
- A polycrystalline YIG disk (0.4-mm thick, 4-mm diameter) was used as the spin wave propagation medium.
- MSSWs were excited using a MW-driven, thin gold (Au) wire positioned directly on the YIG disk surface.
Hybrid Architecture Assembly:
- The diamond crystal, with the implanted NV surface facing the YIG disk, was placed in direct contact with the YIG.
- An external magnetic field (H) was applied collinear to the Au wire and the <110> direction of the diamond to optimize MSSW propagation perpendicular to H.
Measurement and Detection:
- Optically Detected Magnetic Resonance (ODMR) was performed using a 532 nm laser focused to an ~800 nm spot.
- Measurements were taken at three positions (0, 1.8 mm, 3.6 mm) away from the MW excitation source to quantify coupling distance dependence.
- Rabi oscillations were measured by gradually increasing the duration of the MW pulse while maintaining constant power to demonstrate time control of the NV spin.
Resonance Mapping:
- Microwave absorption spectra of the YIG disk were mapped as a function of frequency (f) and magnetic field (H) to identify FMR and specific MSSW modes (2.0-2.8 GHz).
- NV ODMR spectra were analyzed to identify fluorescence dips corresponding to NV transitions (|m_s = 0> → |m_s = ±1>), ensuring overlap between NV and MSSW frequencies for resonant energy exchange.

6CCVD Solutions & Capabilities

This research relies on ultra-high-quality diamond material with specific crystallographic orientation and processing characteristics, all of which are core specializations of 6CCVD. Our expertise in MPCVD diamond growth and subsequent engineering allows us to supply materials critical for replicating and advancing this breakthrough in magnonics and quantum computing.

Applicable Materials

Research Requirement	6CCVD Material Solution	Engineering Rationale
High-Purity Host Crystal	Optical Grade SCD (Single Crystal Diamond)	Required for minimizing native nitrogen/defects (Type-IIa equivalent) to ensure optical clarity, high coherence, and maximal NV spin contrast.
Specific Orientation	Custom <100> SCD Wafers	The experiment explicitly required <100> orientation to simplify the analysis of Type A and B NV spin configurations relative to the applied H field. 6CCVD delivers custom-oriented SCD.
Substrate Thickness	SCD Substrates (0.1 µm - 500 µm)	While the NVs are near-surface, 6CCVD can provide the necessary bulk thickness (up to 10 mm substrates) for robust handling and integration into vacuum/confocal setups.
Near-Surface Quality	SCD Polishing (Ra < 1 nm)	Critical for near-surface NVs (30-40 nm depth). Our proprietary polishing ensures ultra-low surface roughness, reducing decoherence caused by surface dangling bonds, vital for maintaining spin coherence in the host surface.

Customization Potential

6CCVD provides end-to-end diamond engineering services necessary to transition this research into scalable device fabrication:

Custom Dimensions and Shaping: While the paper used a small chip, 6CCVD can supply SCD plates/wafers up to 125 mm (PCD) or custom-cut chips necessary for complex hybrid systems. We utilize in-house laser cutting for precise geometry matching to magnonic structures (YIG disks, antennae).
Metalization Integration: The experiment utilized a thin gold (Au) wire antenna. 6CCVD offers extensive in-house metalization services, including deposition of Au, Ti, Pt, Pd, W, and Cu. We can apply custom metal stacks directly onto the diamond surface (or the growth surface) prior to shipment, simplifying the integration of MW antennae and contacts for future device designs.
Post-Processing Readiness: The creation of NVs requires high-temperature annealing (1000 °C). 6CCVD materials are CVD-grown and stable at these temperatures, ensuring material integrity during required post-processing steps like implantation, annealing, and surface treatments.

Engineering Support

This research involves complex interface science between diamond and ferrimagnetic insulators. 6CCVD’s in-house PhD team can assist in material selection and optimization for similar Magnonic Quantum Hybrid projects, focusing on:

Selecting the optimal diamond grade (e.g., nitrogen concentration, initial purity) to achieve the desired NV density or enhance the NV ensemble coherence time.
Advising on surface preparation techniques necessary for direct, high-quality contact with materials like YIG, maximizing MSSW coupling efficiency.
Designing custom diamond features, such as waveguides or integrated electrodes, to interface more effectively with complex magnonic circuits.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Coherent communication over mesoscale distances is a necessary condition for\nthe application of solid-state spin qubits to scalable quantum information\nprocessing. Among other routes under study, one possibility entails the\ngeneration of magnetostatic surface spin waves (MSSW) dipolarly coupled to\nshallow paramagnetic defects in wide-bandgap semiconductors. As an initial step\nin this direction, here we make use of room-temperature MSSWs to mediate the\ninteraction between the microwave field from an antenna and the spin of a\nnitrogen-vacancy (NV) center in diamond. We show that this transport spans\ndistances exceeding 3 mm, a manifestation of the MSSW robustness and long\ndiffusion length. Using the NV spin as a local sensor, we find that the MSSW\namplitude grows linearly with the applied microwave power, suggesting this\napproach could be extended to amplify the signal from neighboring spin qubits\nby several orders of magnitude.\n

Tech Support

Original Source

DOI: https://doi.org/10.7567/apex.10.103004