Diamond-nitrogen-vacancy electronic and nuclear spin-state anticrossings under weak transverse magnetic fields

At a Glance

Metadata	Details
Publication Date	2016-08-01
Journal	DSpace@MIT (Massachusetts Institute of Technology)
Authors	Hannah Clevenson, Edward Chen, Florian Dolde, Carson Teale, Dirk Englund
Analysis	Full AI Review Included

Technical Documentation and Analysis: Low-Field NV Spin State Control

Based on: Clevenson et al., Diamond-nitrogen-vacancy electronic and nuclear spin-state anticrossings under weak transverse magnetic fields Physical Review A 94.2 (2016)

Executive Summary

This research establishes a new regime for manipulating Nitrogen-Vacancy (NV) quantum systems, centered on the discovery and experimental validation of a Hyperfine Level Anticrossing (LAC) occurring at unprecedentedly weak transverse magnetic fields ($B_{\perp}$).

Novel Low-Field Quantum Control: Verified an electron-nuclear spin flip anticrossing (LAC) in the NV ground state at transverse fields ($B_{\perp} \leq 40$ G), two orders of magnitude lower than previously utilized axial LACs (~500 G to ~1000 G).
Enhanced Sensor Sensitivity: Demonstrated that operation at this anticrossing point yields doubled signal contrast in ESR spectra, directly increasing the sensitivity of continuous-wave (CW) diamond-based sensors.
Tailored NV Hamiltonian: The weak-field regime allows for the suppression of sensitivity to axial magnetic fields, enabling tailored NV centers optimally suited for high-resolution electric field and temperature sensing.
Robust Nuclear Polarization: The low-field LAC is proposed as a novel, highly efficient method for ¹⁴N nuclear spin polarization, requiring fewer pulses and a smaller RF excitation range compared to existing high-field protocols.
Material Requirements: High-quality, epitaxially grown diamond with extremely low intrinsic strain (estimated $\sim3 \times 10^{-5}$) is required to achieve the observed precision in spin state control.
Quantum Memory Potential: The resultant system, combining axial field insensitivity with the utilization of the longer-lived nuclear spin state, presents a strong candidate for diamond-based solid-state atomic memories and gyroscopes.

Technical Specifications

Parameter	Value	Unit	Context
Material System	¹⁴N NV Center	Diamond	Spin-1 electronic ground state coupled to Spin-1 nuclear spin
New LAC Transverse Field	$\leq 40$	G	Regime of interest for electron-nuclear spin flip LAC ($N_{g}$)
Previous LAC Axial Field	~500 to ~1000	G	High-field regime for excited/ground-state level anticrossings
Static Transverse Field ($B_{\perp}$) Max	60	G	Provided by Halbach array (uniformity >99% over 2 cm³)
Axial Field Sweep ($B_{\parallel}$) Max	$\pm 30$	G	Provided by Helmholtz coils
New LAC Coupling Strength ($N_{g}$)	~250	kHz	Measured at $B_{\perp} = 30$ G (Figure 5)
New LAC Center Axial Field ($N_{p}$)	$\pm 0.35$	G	Center axial field at $B_{\perp} = 30$ G
Intrinsic Strain Estimate	~600	kHz	Corresponds to strain splitting of central hyperfine resonance
Required Adiabatic Passage Rate	1 / 225	G/µs	Rate required for 99.99% probability of nuclear spin exchange
Laser Pumping Wavelength	532	nm	Green laser for optical spin polarization and readout

Key Methodologies

The NV ensemble was investigated using high-precision Electron Spin Resonance (ESR) measurements coupled with fine magnetic field control.

Material Preparation: An epitaxially grown diamond sample was polished to create a light-trapping waveguide geometry, optimizing the collection of red spin-dependent fluorescence.
Static Field Application: A 60 G static transverse magnetic field ($B_{\perp}$) was applied perpendicular to the NV axis using a Halbach array to lift orientation degeneracy and induce the low-field anticrossing condition.
Fine Field Sweep: Weak axial magnetic fields ($B_{\parallel}$, up to $\pm 30$ G) were applied via Helmholtz coils to sweep across the resonance and confirm the predicted anticrossings.
Spin Polarization and Readout: A 532 nm (green) laser was used for optical spin polarization, and the subsequent spin state was monitored via the red spin-dependent fluorescence collected by a photodetector.
ESR Measurement: Radiofrequency (RF) excitation was applied to induce transitions between the electronic ground state triplet levels ($m_{s} = 0 \leftrightarrow m_{s} = \pm 1$), allowing the energy levels and anticrossing dynamics to be mapped.
Resolution Enhancement: RF excitation power was attenuated by 10 dB in high-resolution scans (Figure 5) to minimize power broadening and resolve the precise electron-nuclear spin flip features.

6CCVD Solutions & Capabilities

6CCVD provides the high-specification, quantum-grade MPCVD diamond materials necessary to replicate, optimize, and extend this critical research into low-field NV quantum control and solid-state memory devices.

Applicable Materials

The foundation of low-field quantum control is high-purity, low-strain diamond. 6CCVD delivers materials tailored for this environment:

Optical Grade Single Crystal Diamond (SCD): Required for high-fidelity quantum experiments. Our MPCVD process ensures extremely low defect density and inherent strain ($< 3 \times 10^{-5}$ typically required) to maximize $T_{2}$ spin coherence times necessary for sensitive magnetic/electric/temperature sensing and robust quantum memories.
Custom Isotope-Doped SCD:
- To replicate the high-contrast conditions proposed in the paper’s Appendix B, 6CCVD offers SCD doped with ¹⁵N precursors (Spin-1/2 nuclear system). This substitution immediately increases sensor contrast by 50% compared to natural ¹⁴N samples.
- For applications requiring nuclear spin polarization demonstrated here, high-purity SCD with controlled ¹⁴N incorporation is available.

Customization Potential

The experimental setup requires non-standard component integration, which 6CCVD supports through comprehensive engineering services:

Service Category	Requirements from Research Paper	6CCVD Capability
Substrate Dimensions	Integration into Halbach array / Helmholtz coil setup and waveguide geometry.	Custom plates/wafers up to 125mm (PCD) or large SCD plates, precision laser cut to specific geometries for device integration.
Surface Finish	Trapping green light and guiding red fluorescence (optical fidelity).	SCD polishing achieving $R_{a} < 1$ nm, ensuring minimal scattering losses and optimal optical coupling for quantum measurements.
Thickness Control	Need for thin layers (ensemble depth control) or robust substrates.	SCD/PCD thickness control from $0.1$ µm up to $500$ µm, with custom substrates available up to $10$ mm thick.
Device Integration	Potential for integrated electric field control (Stark shifts) or electrode geometry.	In-house custom metalization services including Au, Pt, Pd, Ti, W, and Cu, allowing researchers to pattern contacts directly onto the SCD surface for integrated magneto-electric control.

Engineering Support

6CCVD’s in-house PhD engineering team specializes in diamond material optimization for quantum technologies. We can assist engineers and scientists in selecting the ideal growth parameters (e.g., specific nitrogen precursor ratio, orientation, substrate preparation) required to maximize $T_{2}$ times and minimize strain for NV sensing applications and solid-state atomic memory development. Our global logistics team ensures fast, reliable delivery of your custom specifications worldwide (DDU default, DDP available).

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

View Original Abstract

We report on detailed studies of electronic and nuclear spin states in the diamond-nitrogen-vacancy (NV) center under weak transverse magnetic fields. We numerically predict and experimentally verify a previously unobserved NV hyperfine level anticrossing (LAC) occurring at bias fields of tens of gauss—two orders of magnitude lower than previously reported LACs at ∼ 500 and ∼ 1000 G axial magnetic fields. We then discuss how the NV ground-state Hamiltonian can be manipulated in this regime to tailor the NV’s sensitivity to environmental factors and to map into the nuclear spin state.

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Original Source

DOI: None