Optically induced static magnetic field in ensemble of nitrogen-vacancyn centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-05-06 |
| Journal | arXiv (Cornell University) |
| Authors | Farid Kalhor, Noah Opondo, Shoaib Mahmud, Leif Bauer, LiâPing Yang |
| Institutions | Northeast Normal University, Purdue University West Lafayette |
| Citations | 5 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates the generation and measurement of an optically induced effective static magnetic field (Beff) within an ensemble of Nitrogen-Vacancy (NV) centers in bulk diamond, enabling all-optical coherent spin control.
- Core Mechanism: The Beff is generated by the Photonic Spin Density (PSD) of an elliptically polarized, off-resonant optical beam interacting coherently with the NV electronic spin.
- Key Achievement: A maximum Beff of 60 nT was measured at room temperature, corresponding to a coherent spin rotation of approximately 12° on the Bloch sphere.
- Platform Optimization: The experiment utilized bulk, single-crystalline CVD diamond with a planar interface, providing a stable platform suitable for on-chip quantum technologies.
- Sensitivity Enhancement: The Hahn echo pulse sequence was employed, leveraging the second nuclear spin revival (T2 â 42 ”s) to maximize the coherence time and measurement sensitivity against background noise.
- Scaling Law: Beff scales linearly with the optical power of the PSD beam and exhibits an inverse dependence on the detuning (the difference between the laser wavelength and the NV optical transition at 637 nm).
- Decoherence Mitigation: The study characterized off-resonant absorption effects, confirming that wavelengths greater than 785 nm allow high power (up to 20 mW) without significant loss of spin coherence.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Effective Magnetic Field (Beff) | 60 | nT | Achieved in the far-off-resonant regime. |
| Maximum Induced Spin Rotation (Ï) | 12 | ° | Corresponds to Beff = 60 nT. |
| Coherence Time (T2) | 42 | ”s | Optimized using Hahn echo (second revival point). |
| NV Optical Transition Wavelength | 637 | nm | Optical resonance wavelength of the NV center. |
| PSD Laser Wavelength Range Tested | 705 to 818 | nm | Characterized scaling in the far-off-resonant regime. |
| Maximum PSD Power (No Decoherence) | 20 | mW | Observed for λ = 785 nm and 818 nm. |
| Sample Material | CVD Diamond | N/A | Bulk, optical grade, (100) orientation, ensemble NV centers. |
| Antenna Metal Stack | 30 nm Ti / 300 nm Au | nm | Fabricated on the diamond surface via E-beam deposition. |
| Measurement Temperature (Standard) | Room Temperature | K | Most measurements performed at RT (265 K used for 705 nm). |
Key Methodologies
Section titled âKey Methodologiesâ- Sample Preparation: Optical grade diamond plates (4.5 mm x 4.5 mm, (100) orientation) grown by Chemical Vapor Deposition (CVD) were cleaned using piranha/nitric acid and a solvent cleaning procedure (toluene, acetone, isopropanol).
- Antenna Fabrication: Microwave antennas were fabricated on the diamond surface using E-beam lithography (JEOL JBX-8100 FS E beam writer, 30 pA current). The process involved spinning CSAR resist, exposure, development in xylene, and a descum process (Ar/O2 plasma, 110 W).
- Metal Deposition: A Ti/Au stack (30 nm Ti adhesion layer, 300 nm Au) was deposited using an electron beam metal deposition system at a base pressure of 1e-6 Torr, followed by lift-off in acetone.
- Magnetic Field Alignment: A static bias magnetic field was applied normal to the sample surface. This alignment ensures that the projection of the field is equal across all four NV center orientations, leading to uniform spin rotation across the ensemble.
- PSD Generation and Interaction: An elliptically polarized laser beam (PSD beam) was focused onto the NV ensemble. Polarization ellipticity, which determines the PSD magnitude, was controlled using a Quarter-Wave Plate (QWP).
- Coherence Optimization (Hahn Echo): The Hahn echo pulse sequence (Ï/2 - Ï - Ï - Ï - Ï/2) was used to eliminate inhomogeneous broadening caused by background noise (e.g., carbon-13 nuclear spins), maximizing the coherence time to T2 â 42 ”s.
- Beff Measurement (AC Magnetometry): The PSD pulse was applied only during one half of the Hahn echo sequence (either the first Ï or the second Ï). Measurements were performed twice (once for each half) and subtracted to calculate the effective static magnetic field amplitude, eliminating systematic readout errors.
- Decoherence Characterization: Off-resonant absorption effects were quantified by adding the PSD laser to both halves of the Hahn echo sequence (canceling spin rotation) and measuring the loss of contrast (decoherence) as the pulse length (T0) increased.
Commercial Applications
Section titled âCommercial ApplicationsâThe demonstration of all-optical, coherent spin control using PSD in bulk diamond opens avenues for several advanced quantum and sensing technologies:
- Quantum Computing and Qubit Control:
- Enables fast, localized, and all-optical coherent manipulation of NV spin qubits, replacing complex microwave circuitry or bulky static magnets.
- Crucial for scaling up quantum processors based on solid-state spin systems.
- On-Chip Quantum Electrodynamics (QED):
- Provides a mechanism for integrating optical control directly into planar diamond architectures, facilitating compact quantum devices.
- Nanoscale Quantum Sensing:
- Utilizing the NV center as a quantum magnetometer to probe and characterize light fields (specifically PSD) at the nanoscale, useful for studying complex optical phenomena.
- High-Gradient Magnetic Field Generation:
- The PSD effect offers a route to generating high-gradient, localized magnetic fields with ultrafast temporal response, which is essential for rapid spin state initialization and readout.
- Advanced Material Characterization:
- The technique can be adapted to study light-matter interactions and spin dynamics in other wide-bandgap semiconductors or materials hosting color centers.
View Original Abstract
Generation of local magnetic field at the nanoscale is desired for many\napplications such as spin-qubit-based quantum memories. However, this is a\nchallenge due to the slow decay of static magnetic fields. Here, we demonstrate\nphotonic spin density (PSD) induced effective static magnetic field for an\nensemble of nitrogen-vacancy (NV) centers in bulk diamond. This locally induced\nmagnetic field is a result of coherent interaction between the optical\nexcitation and the NV centers. We demonstrate an optically induced spin\nrotation on the Bloch sphere exceeding 10 degrees which has potential\napplications in all optical coherent control of spin qubits.\n