Coherent control of the silicon-vacancy spin in diamond

At a Glance

Metadata	Details
Publication Date	2017-05-30
Journal	Nature Communications
Authors	Benjamin Pingault, David-Dominik Jarausch, Christian Hepp, Lina E. Klintberg, Jonas N. Becker
Institutions	Element Six (United Kingdom), Saarland University
Citations	191
Analysis	Full AI Review Included

Technical Analysis: Coherent Control of the Silicon-Vacancy Spin in Diamond

Documentation Generated for 6CCVD (6ccvd.com) Engineering & Sales Teams based on Pingault et al., Nature Communications, 2017.

Executive Summary

This research successfully demonstrates full coherent control of a single negatively charged Silicon-Vacancy (SiV$^{-}$) electronic spin in diamond, establishing the SiV$^{-}$ center as a highly promising, optically addressable qubit for solid-state quantum technologies.

Coherent Control Established: Demonstrates optically detected magnetic resonance (ODMR) and Rabi oscillations, confirming the ability to coherently drive the SiV$^{-}$ electronic spin using a microwave field.
Key Coherence Metric: Direct measurement of the spin coherence time ($T_{2}^{\ast}$) yields $115 \pm 9$ ns at a cryogenic temperature of $3.6$ K via Ramsey interferometry.
Fundamental Decoherence Mechanism Identified: Analysis of the temperature dependence reveals that spin dephasing and decay are dominated by single-phonon-mediated excitation between the ground state’s orbital branches (split by $50$ GHz).
Operational Timelines: The spin relaxation time ($T_{1, \text{spin}}$) was measured as $350 \pm 11$ ns at $3.5$ K, providing a critical upper bound for subsequent driving pulse sequences.
High Optical Fidelity: The SiV$^{-}$ center maintains its advantage, offering high fluorescence into the zero-phonon line ($\sim 80%$) alongside a ground-state electronic spin ($S = 1/2$).
Hybrid Quantum Interface Potential: The capacity for microwave control, combined with excellent photonic properties, makes the SiV$^{-}$ an ideal candidate for establishing hybrid spin-photon quantum interfaces.

Technical Specifications

Extracted experimental performance metrics and material parameters from the research paper.

Parameter	Value	Unit	Context / Condition
Spin Coherence Time ($T_{2}^{\ast}$)	115 $\pm$ 9	ns	Measured via Ramsey interferometry at 3.6 K
Spin Relaxation Time ($T_{1, \text{spin}}$)	350 $\pm$ 11	ns	Measured at 3.5 K
Bare Rabi Frequency ($\Omega$)	~15	MHz	Consistent with NV centers in similar conditions
ODMR Contrast	~33	%	Relative to peak baseline
Ground State Orbital Splitting ($\Delta E$)	50	GHz	Frequency corresponding to decoherence phonons
Hyperfine Constant ($A_{		}$)	70 $\pm$ 2
Optical Pumping Wavelength	~737	nm	Resonant with the D1 transition
SiV Center Creation Depth	500 $\pm$ 50	nm	Target depth via $^{29}$Si$^{+}$ ion implantation
Operating Temperature	3.5 - 4.3	K	Closed-cycle liquid helium cryostat
External Magnetic Field	0.20 - 0.22	T	Used to lift spin degeneracy

Key Methodologies

A concise, step-by-step summary of the material preparation and experimental control parameters.

Diamond Material Selection: Used high-pressure high-temperature (HPHT) Type IIa bulk diamond, chosen for its high purity, with the surface oriented orthogonally to the [111] crystallographic axis.
SiV Center Creation: SiV centers were generated via ion implantation of isotopically purified $^{29}$Si$^{+}$ ions.
- Implantation Energy: 900 keV, targeting a depth of 500 $\pm$ 50 nm.
- Implantation Dose: Tuned from 10$^{9}$ to 10$^{12}$ ions per cm$^{2}$.
Post-Processing & Activation: The sample was subsequently annealed at 1,000 °C in vacuum for 3 hours, followed by a 1-hour oxidation step in air at 460 °C.
Cryogenic and Magnetic Setup: Single SiV$^{-}$ centers were studied in a closed-cycle liquid helium cryostat (Attodry 1000) at temperatures down to 3.5 K, employing a superconducting coil to apply a vertical magnetic field.
Optical Control: A tunable diode laser ($\sim 737$ nm) delivered optical pulses, regulated by an acousto-optic modulator (AOM) and timed by a delay generator.
Microwave Control (MW): MW pulses were generated by a frequency generator and amplified. The MW signal was radiated onto the sample using a single copper wire (20 $\mu$m diameter) positioned <20 $\mu$m from the SiV$^{-}$.
Measurement Techniques: Used short (500 ns) optical initialization and readout pulses combined with variable duration MW pulses for ODMR and subsequent Ramsey interferometry sequences.

6CCVD Solutions & Capabilities

This research validates the critical role of high-purity, engineered diamond substrates for advancing solid-state quantum technologies. 6CCVD, as an expert MPCVD provider, offers materials and customization services directly addressing the needs identified in this study.

Research Requirement / Challenge	6CCVD Solution & Engineering Advantage
Ultra-High Purity Diamond Substrate (Low NV background, low strain)	Optical Grade SCD (Single Crystal Diamond): 6CCVD grows MPCVD SCD with extremely low intrinsic nitrogen (N) concentration, essential for minimizing background defects and strain, ensuring the stability and high optical yield required for isolated SiV$^{-}$ centers.
Precise Depth Engineering (500 nm implantation target)	Custom Polishing & Surface Finish: We provide SCD wafers with superior polishing (Ra < 1 nm). This low surface roughness is critical for ensuring consistent ion implantation depth and minimizing surface-related decoherence effects.
Scalable Microwave Delivery (Replaces fragile 20 $\mu$m wire)	Integrated Custom Metalization: 6CCVD offers in-house deposition of custom metal stacks (Au, Pt, Ti, W, Cu, Pd) on SCD substrates. We can fabricate robust, scalable on-chip microwave structures (e.g., coplanar waveguides) directly onto the SCD surface, replacing external wiring setups and improving MW coupling strength and uniformity.
Thickness Control for Integration	Precision Thickness Control: We offer SCD wafers from 0.1 $\mu$m up to 500 $\mu$m, and Substrates up to 10 mm thick, providing flexibility for specific device geometries, including integration into photonic crystal cavities or deep-etch structures.
Optimized Crystal Orientation ([111] required)	Custom Growth Orientation: While this work used [111], 6CCVD can grow and supply SCD with precise custom crystallographic orientations, allowing researchers to optimize the alignment of the SiV$^{-}$ symmetry axis relative to the magnetic field for enhanced optical cycling and high-fidelity spin readout.

Engineering Support

This study highlights that achieving longer coherence times requires suppressing phonon interaction, potentially through further orbital splitting via strain engineering, or by developing nanostructures (e.g., photonic crystal cavities) to suppress the phonon density of states.

6CCVD’s in-house PhD team provides comprehensive engineering consultation, specializing in material selection for complex quantum and sensing projects involving SiV$^{-}$, NV$^{-}$, and other color centers. We are equipped to advise on materials optimized for specific post-processing steps (high-temperature annealing, deep etching, and ion implantation).

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

Tech Support

Original Source

DOI: https://doi.org/10.1038/ncomms15579