Room Temperature Electrically Detected Nuclear Spin Coherence of NV Centres in Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-01-21 |
| Journal | Scientific Reports |
| Authors | Hiroki Morishita, S. Kobayashi, Masanori Fujiwara, Hiromitsu Kato, Toshiharu Makino |
| Institutions | Kyoto University, Japan Science and Technology Agency |
| Citations | 28 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates the successful electrical detection of nuclear spin coherence in Nitrogen-Vacancy (NV) centers in diamond at room temperature, a critical step toward integrated quantum devices.
- Core Achievement: First demonstration of room-temperature electrical detection of 14N nuclear spin coherence in NV centers using the Electrically Detected Electron-Nuclear Double Resonance (EDENDOR) technique.
- Coherence Time: A nuclear spin coherence time (T2(n)) of approximately 0.9 ms was measured at 300 K.
- Limitation: The measured T2(n) is currently limited by the longitudinal relaxation time of the NV electron spins (T1(e) â 1.8 ms).
- Detection Mechanism: The EDENDOR signal is observed as a change in the photocurrent (ÎQ) generated via two-photon ionization by a 532 nm laser.
- Sensitivity Advantage: Electrical detection of electron spin coherence is theoretically predicted to offer approximately three times higher sensitivity than traditional optical techniques.
- Material System: Ensemble NV centers were created in a highly P-doped n-type diamond layer (P-donor concentration ~1018 cm-3) to ensure high electrical conductivity.
- Future Impact: The results pave the way for developing novel, all-electrical, integrated electron- and nuclear-spin-based diamond quantum memories and sensors.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Nuclear Spin Coherence Time (T2(n)) | 0.9 (±0.5) | ms | Measured at room temperature (lower limit). |
| Electron Spin Relaxation Time (T1(e)) | 1.8 (±0.6) | ms | Measured via EDMR technique. |
| 14N Nuclear Spin Resonance Frequency | 3.5 | MHz | EDENDOR signal frequency (transition: |
| NV Electron Rabi Oscillation Frequency | ~4.4 | MHz | Measured with 5 W MW input power. |
| Laser Wavelength | 532 | nm | Used for initialization and two-photon ionization. |
| Laser Power (Photocurrent Generation) | 30 | mW | Used for pEDMR/pODMR measurements. |
| Static Magnetic Field (B0) | ~10 | G | Applied approximately along the [111] direction. |
| Applied Voltage (Photocurrent Detection) | 8 | V | Constant voltage applied across interdigital contacts. |
| P-donor Concentration (n-type layer) | ~1018 | cm-3 | Doping concentration of the CVD-grown diamond layer. |
| NV Center Concentration (Estimated) | 1 x 1015 | cm-3 | Concentration within the detection volume. |
| N+-ion Implantation Dose | 1 x 1015 | cm-2 | Used for creating NV centers. |
| N+-ion Kinetic Energy | 350 | keV | Used for creating NV centers. |
| Diamond Layer Thickness | 10 | ”m | Thickness of the P-doped n-type layer. |
| Interdigital Contact Gap | ~2 | ”m | Gap size between electrical contacts. |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a self-built EDENDOR spectrometer and specially prepared P-doped n-type diamond samples.
Sample Preparation Recipe
Section titled âSample Preparation Recipeâ- Substrate: Type IIa (001) diamond substrate.
- Growth: A 10 ”m thick P-doped n-type diamond layer was synthesized via Chemical Vapour Deposition (CVD), achieving a P-donor concentration of ~1018 cm-3.
- NV Creation: Ensemble NV centers were created via 14N+-ion implantation (350 keV kinetic energy, 1 x 1015 cm-2 dose).
- Annealing: The sample was annealed at 1000 °C for 1 hour under vacuum.
- Contact Fabrication: Interdigital contacts with ~2 ”m gaps were fabricated using electron-beam lithography.
- Metallization: Ti(30 nm)/Pt(30 nm)/Au(100 nm) multi-layers were deposited, followed by annealing at 420 °C in an Argon atmosphere.
EDENDOR Measurement Technique
Section titled âEDENDOR Measurement TechniqueâThe EDENDOR technique was implemented using a pulsed sequence to measure Rabi oscillations and T2(n).
- Initialization: NV electron spins are initialized to the |0> state using a pulsed 532 nm laser.
- Manipulation: Electron spins are manipulated using Microwave (MW) pulses (e.g., Ï-pulse at 2916 MHz). Nuclear spins are manipulated using Radio-Frequency (RF) pulses (e.g., 3.5 MHz).
- Photocurrent Generation: A final 532 nm laser pulse generates a photocurrent via two-photon ionization.
- Detection: The change in photocurrent (ÎQ) is measured by integrating the transient current (ÎI) over time, using a current amplifier and digitizer under a constant 8 V bias.
- T2(n) Measurement: A modified EDENDOR sequence incorporating a nuclear-spin Hahn echo sequence was used to measure the T2(n) decay as a function of the free evolution time (2Ï).
- Noise Mitigation: A phase cycling technique was applied to subtract artifact noises arising from off-resonant MW/RF contributions and laser-power fluctuations.
Commercial Applications
Section titled âCommercial ApplicationsâThis technology is foundational for developing next-generation quantum hardware, particularly where room-temperature operation and integration are critical.
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Quantum Computing and Memory:
- Quantum Registers: Utilizing the NV electron spin for fast manipulation and the 14N nuclear spin for long-term, robust quantum memory (T2(n) â 0.9 ms at 300 K).
- Integrated Qubits: Enabling the fabrication of all-electrical quantum devices that can be integrated into standard semiconductor architectures, eliminating the need for complex, bulky optical readout systems.
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Quantum Sensing:
- Highly Sensitive Magnetometers: Developing room-temperature, highly sensitive magnetic sensors based on NV centers, leveraging the enhanced sensitivity of electrical detection.
- Nanoscale Spectroscopy: Using nuclear spin memory to enable sensor-unlimited nanoscale spectroscopy of small spin clusters.
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Diamond Electronics:
- High-Conductivity Platforms: The use of highly P-doped n-type diamond provides a robust, electrically conductive platform necessary for efficient current detection and integration of quantum components.
- Hybrid Devices: Development of hybrid solid-state devices combining classical diamond electronics with quantum spin functionalities.
View Original Abstract
Abstract We demonstrate electrical detection of the 14 N nuclear spin coherence of NV centres at room temperature. Nuclear spins are candidates for quantum memories in quantum-information devices and quantum sensors, and hence the electrical detection of nuclear spin coherence is essential to develop and integrate such quantum devices. In the present study, we used a pulsed electrically detected electron-nuclear double resonance technique to measure the Rabi oscillations and coherence time ( T 2 ) of 14 N nuclear spins in NV centres at room temperature. We observed T 2 â 0.9 ms at room temperature, however, this result should be taken as a lower limit due to limitations in the longitudinal relaxation time of the NV electron spins. Our results will pave the way for the development of novel electron- and nuclear-spin-based diamond quantum devices.