Controlling a nuclear spin in a nanodiamond

At a Glance

Metadata	Details
Publication Date	2017-09-26
Journal	Physical review. B./Physical review. B
Authors	Helena S. Knowles, Dhiren M. Kara, Mete Atatüre
Institutions	University of Cambridge
Citations	11
Analysis	Full AI Review Included

Technical Documentation & Analysis: Ancilla-Enhanced Quantum Sensing in Nanodiamonds

This document analyzes the research paper “Controlling a nuclear spin in a nanodiamond” to provide technical specifications and align the experimental requirements with the advanced MPCVD diamond solutions offered by 6CCVD.

Executive Summary

This research successfully demonstrates the coherent control of a hybrid electron-nuclear spin system in a nanodiamond, validating the use of proximal dark nuclei (¹³C) as long-lived quantum memory for nanoscale sensing and quantum information.

Quantum Memory Enhancement: Achieved coherent control of a ¹³C nuclear spin coupled to a Nitrogen-Vacancy (NV) center, located approximately 4 Å away.
Coherence Breakthrough: Extracted a nuclear-spin free precession time (T₂*) of 26 µs, representing a 100-fold enhancement over the bare electron spin coherence time in nanodiamonds.
Non-Invasive Sensing: The protocol enables ancilla-enhanced sensing without requiring high static magnetic fields (≥ 0.5T) or high-power radio frequency (RF) excitation, making it ideal for biological and novel material investigations.
Tunable Coupling: Demonstrated a tuneable coupling between the NV electronic spin and the ¹³C nuclear spin, allowing for fast quantum state transfer and initialization.
Scalability to On-Chip Devices: The results confirm that ancilla-based protocols previously limited to bulk diamond can be realized in nanoscale structures, supporting the development of on-chip quantum photonics devices (e.g., waveguides and cavities).

Technical Specifications

The following hard data points were extracted from the experimental results, highlighting the performance metrics achieved using the ¹³C nuclear spin ancilla.

Parameter	Value	Unit	Context
Nuclear Spin Coherence Time (T₂*)	26	µs	100-fold enhancement over electron spin T₂ in nanodiamond.
Nuclear Spin Polarization (p)	15	%	Achieved at room temperature, corresponding to 110 mK spin temperature.
Enhanced ¹³C Precession Frequency (v_0’)	1.6	MHz	Measured at B = 7 mT, 45° to NV axis.
Bare Larmor Frequency (µ_n	B	/h)	5.9
Hyperfine Splitting (v₁)	14.3 ± 1	MHz	Signature of NV-¹³C interaction in ODMR spectrum.
NV Ground State Splitting (D_gs)	2.87	GHz	Intrinsic NV property.
External Magnetic Field (	B	)	~7
¹³C Isotope Concentration	1.1	%	Natural abundance in the nanodiamonds used.
NV-¹³C Separation	~4	Å	Corresponds to one of nine lattice sites.

Key Methodologies

The experiment relied on precise control of the NV electronic spin to manipulate and probe the proximal ¹³C nuclear spin.

Material Basis: Nanodiamonds containing NV centers and natural abundance (1.1%) ¹³C isotopes were utilized. The natural ¹³C concentration ensured an average 1-nm separation, increasing the probability of finding strongly coupled proximal ¹³C atoms.
NV Identification via ODMR: Continuous Wave Optically Detected Magnetic Resonance (ODMR) was employed to identify NV centers coupled to a single proximal ¹³C atom, characterized by a hyperfine-induced splitting (v₁ = 14.3 MHz).
Enhanced Precession Measurement: The NV spin was used as a probe for the oscillating magnetic field created by the precessing ¹³C nuclear spin. Spin echo decay measurements were performed with the external magnetic field (B) oriented 45° from the NV axis, confirming the tuneability and enhancement of the ¹³C precession frequency (v_0’).
Nuclear Spin Polarization: Sequential pulsed optical spin preparation (532 nm laser) and Microwave (MW) rotation (π-pulses) of the NV spin were applied. This protocol utilized the enhanced precession of the ¹³C spin to initialize it, achieving 15% polarization.
Coherence Time Quantification: A pulse sequence involving two MW π-pulses separated by a free interaction time (τ) was used to measure the decay of the nuclear spin oscillations, yielding the T₂* coherence time.

6CCVD Solutions & Capabilities

The successful realization of long-lived quantum memory using ¹³C ancilla spins in nanodiamonds highlights the critical need for high-quality, isotopically controlled diamond substrates. 6CCVD is uniquely positioned to supply the foundational materials required to replicate, scale, and extend this research into commercial quantum devices.

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Isotopic Control for Coherence	Single Crystal Diamond (SCD) with tailored isotopic purity (e.g., < 0.01% ¹³C or enriched ¹³C).	Enables precise control over the nuclear spin bath density. Low ¹³C material maximizes electron spin coherence (T₂) in bulk, while enriched ¹³C material allows for dense, addressable nuclear spin registers.
High-Quality Substrates for Nanoscale Devices	Optical Grade SCD Wafers (up to 500 µm thick) and Polycrystalline Diamond (PCD) Plates (up to 125mm diameter).	Provides ultra-low strain, high-purity starting material essential for creating high-coherence NV centers, whether used as bulk devices or precursors for nanodiamond fabrication.
Integration into Quantum Photonics	Precision Polishing Services: SCD surfaces with roughness R_a < 1 nm. Inch-size PCD polished to R_a < 5 nm.	Critical for minimizing optical scattering losses and maximizing Q-factors when integrating diamond into on-chip quantum devices (e.g., optical cavities and waveguides referenced in the paper).
MW/RF Delivery and Contacting	Custom Metalization: Internal capability for depositing Au, Pt, Pd, Ti, W, Cu layers.	Allows researchers to integrate microwave transmission lines and electrical contacts directly onto the diamond substrate for efficient, localized delivery of the high-frequency pulses required for spin control.
Custom Dimensions for Probes & Devices	Custom Dimensions & Thickness: SCD/PCD plates up to 125mm, thicknesses from 0.1 µm to 10 mm.	Supports the fabrication of diamond membranes, scanning probes, and bulk substrates required for advanced magnetic sensing and quantum computing architectures.

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD growth parameters and post-processing techniques necessary for optimizing NV creation and maximizing spin coherence times. We offer consultation on material selection, nitrogen doping levels, and surface preparation required for ancilla-enhanced magnetic sensing and quantum state storage projects.

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

View Original Abstract

The sensing capability of a single optically bright electronic spin in\ndiamond can be enhanced by making use of proximal dark nuclei as ancillary\nspins. Such systems, so far only realized in bulk diamond, provide orders of\nmagnitude higher sensitivity and spectral resolution in the case of magnetic\nsensing, as well as improved readout fidelity and state storage time in quantum\ninformation schemes. In nanodiamonds, which offer additional opportunities as\nmobile nanoscale sensors, electronic-nuclear spin complexes have remained\ninaccessible. We demonstrate coherent control of a 13C nuclear spin located\n4{\AA} from a nitrogen-vacancy center in a nanodiamond and show quantum-state\ntransfer between the two components of this hybrid spin system. We extract a\nnuclear-spin free precession time of T2* = 26 us, which exceeds the bare\nelectron free precession time in nanodiamond by two orders of magnitude.\n

Tech Support

Original Source

DOI: https://doi.org/10.1103/physrevb.96.115206