Study of coherent population trapping and AC Stark effect in ensembles of NV-centers in diamond at room temperature in microwave range
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-01-01 |
| Journal | Оптика и спектроскопия |
| Authors | Р. А. Ахмеджанов, Л. А. Гущин, I. V. Zelensky, Mitrofanova T.G., В. А. Низов |
| Institutions | Institute of Applied Physics, Kazan Scientific Center |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research investigates quantum interference effects—specifically Coherent Population Trapping (CPT) and the AC Stark effect (Autler-Townes)—in ensembles of Nitrogen-Vacancy (NV) centers in diamond using microwave control at room temperature.
- Core Achievement: Successful implementation and observation of CPT and AC Stark effects using microwave transitions between the ground state spin sublevels of NV-centers.
- Mechanism (Λ-Scheme): The required three-level Lambda (Λ) scheme was realized by mixing electron spin and nitrogen nuclear spin sublevels, enabled by applying a small external magnetic field (~35 G) angled at 75° to the NV axis.
- Material Platform: Experiments utilized a low-concentration (1014 cm-3) 7 µm thick CVD diamond layer, confirming the viability of this material for complex quantum control.
- CPT Performance: A narrow CPT resonance dip was measured in the fluorescence profile, exhibiting a linewidth of approximately 200 kHz, determined by the relaxation rate between the lower levels.
- AC Stark Demonstration: The Autler-Townes splitting was observed by tuning a strong microwave drive field both off-resonance (causing transition shifts) and on-resonance (causing splitting) relative to the probe transition.
- Control Requirements: High microwave power (up to 16 W) was necessary to achieve Rabi frequencies (10-15 kHz) sufficient for observing CPT in the weaker, nuclear spin-changing transitions.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV-Center Concentration | ~1014 | cm-3 | Estimated concentration in the CVD layer. |
| Diamond Layer Thickness | 7 | µm | Grown on an HPHT substrate. |
| Operating Temperature | Room | Temperature | All experiments conducted at ambient conditions. |
| Laser Pumping Wavelength | 532 | nm | Used for optical polarization and fluorescence detection. |
| Maximum Microwave Power | Up to 16 | W | Supplied via a high-power amplifier. |
| External Magnetic Field (B) | ~35 | G | Applied at ~75° to the NV axis to mix spins. |
| Nuclear Spin Splitting (Q) | 4.95 | MHz | Zero-field splitting between specific nuclear spin sublevels. |
| CPT Linewidth (Measured) | ~200 | kHz | Determined by the relaxation rate between the lower Λ-scheme levels. |
| Estimated Rabi Frequency (CPT) | 10-15 | kHz | For nuclear spin changing transitions (required for CPT). |
| ODMR Frequency Range | 2830 - 2870 | MHz | Typical range for ground state spin transitions. |
Key Methodologies
Section titled “Key Methodologies”The experiment relied on Optically Detectable Magnetic Resonance (ODMR) combined with precise microwave control to induce and measure quantum interference effects.
- Sample Fabrication: A 7 µm diamond layer with a low NV-center concentration (approx. 1014 cm-3) was grown via Chemical Vapor Deposition (CVD) on an HPHT substrate.
- Magnetic Field Alignment: A small external magnetic field (~35 G) was applied using a coil. The field was oriented at a large angle (~75°) relative to the NV-center axis to mix the electron and nitrogen nuclear spins, thereby making the nuclear spin-changing transitions allowed for the Λ-scheme.
- Optical Pumping and Detection: A 532 nm laser (hundreds of mW) was used for spin polarization and excitation. Spin-dependent fluorescence was collected using a confocal microscope setup and measured by a photomultiplier tube (PMT).
- Microwave Delivery: Two microwave generators (probe and drive fields) were combined, amplified up to 16 W, and delivered to the sample via a 3 mm diameter loop antenna pressed against the diamond surface.
- CPT Implementation: The Λ-scheme utilized the |0>s|0>I → |-1>s|-1>I (probe) and |0>s|-1>I → |-1>s|-1>I (drive) transitions. The probe frequency was scanned while the drive frequency was fixed, and the resulting narrow dip in the fluorescence profile was recorded.
- AC Stark Effect Implementation: The drive field was applied to a strong, direct transition. The probe field was then used to scan either the same transition (to observe the Mollow triplet structure) or a different transition sharing a common lower level (to directly measure the splitting of the “dressed states”).
Commercial Applications
Section titled “Commercial Applications”The successful demonstration of robust quantum control phenomena (CPT and AC Stark) in NV-centers at room temperature validates this platform for next-generation quantum technologies.
- Quantum Magnetometry and Sensing: NV-centers are leading candidates for high-sensitivity magnetic field, electric field, and temperature sensing. CPT techniques can be used to narrow resonance linewidths, significantly improving sensor precision and sensitivity.
- Quantum Information Processing (QIP): The nuclear spin sublevels used in the CPT Λ-scheme serve as long-lived quantum memory registers (qubits). CPT provides a mechanism for robust, coherent transfer and storage of quantum states.
- Microwave Quantum Devices: The ability to control microwave absorption via EIT/CPT principles can be leveraged to create novel microwave filters, switches, and slow-light devices operating at ambient conditions.
- Compact Atomic Clocks: The narrow CPT resonance feature (200 kHz linewidth) can serve as a stable frequency reference, enabling the development of miniature, robust frequency standards and clocks based on solid-state defects.
- Solid-State Quantum Electrodynamics (QED): The AC Stark effect measurements provide fundamental insight into the interaction between strong electromagnetic fields and solid-state quantum systems, crucial for engineering quantum circuits.
View Original Abstract
We study coherent population trapping and AC Stark effect using microwave transitions between the sublevels of the ground state of the NV-center. Sublevels with different projections of the nuclear spin of the nitrogen atom are used to implement the -scheme. Dependence of the characteristics of the coherent population trapping dip on the control field frequency and intensity is studied. Various schemes for observing the AC Stark effect are considered. Keywords: NV-center, coherent population trapping, AC Stark.