Broadband noise-free optical quantum memory with neutral nitrogen-vacancy centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-05-08 |
| Journal | Physical Review B |
| Authors | Eilon Poem, Christian Weinzetl, James Klatzow, K. T. Kaczmarek, J. H. D. Munns |
| Institutions | University of Oxford |
| Citations | 28 |
| Analysis | Full AI Review Included |
Technical Analysis: MPCVD Diamond for Broadband Neutral NV Quantum Memory
Section titled âTechnical Analysis: MPCVD Diamond for Broadband Neutral NV Quantum MemoryâAnalysis Source: Broadband, noise-free optical quantum memory with neutral nitrogen-vacancy centers in diamond (arXiv:1408.7045v3)
Executive Summary
Section titled âExecutive SummaryâThe analyzed paper proposes utilizing the orbital ground states of neutral Nitrogen-Vacancy (NVâ°) centers in CVD diamond to implement an ultra-broadband, noise-free Quantum Optical Memory (QOM) via stimulated Raman adiabatic passage (STIRAP).
- Core Value Proposition: Diamond NVâ° ensembles serve as a robust, solid-state platform for QOM, enabling ultra-broadband operation (up to 20 GHz) and high efficiency, critical for interfacing with modern parametric down-conversion photon sources.
- Mechanism: The QOM utilizes a same-spin A-type three-level Raman system derived from the NVâ° ground-state manifold, requiring manipulation via strong external electric fields or uniaxial stress.
- Performance Metrics: Calculations predict extremely high memory efficiency (> 99%) when integrated into micrometer-scale diamond waveguides, using control pulses as low as 0.1 nJ.
- Coherence and Scalability: Estimated minimal ground-state lifetimes are > 6 ns at 4.2 K, sufficient for electronic feed-forward mechanisms necessary for scalable quantum networks. Lifetimes improve to > 17 ns at 1 K.
- Noise Suppression: A high noise suppression factor (up to 1/20) is achieved by using cross-linear polarization selection rules induced by the applied external field.
- Material Requirement: Requires optical grade CVD diamond with precisely controlled NVâ° density ($\sim 10^{16}$ cm-3) and extremely low strain to minimize inhomogeneous broadening.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points define the operational parameters and performance targets for the proposed NVâ° QOM:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Proposed QOM Bandwidth | Up to 20 | GHz | Permits storage of signal pulses as short as 15 ps. |
| Required Ground-State Splitting (S) | $\sim 50$ | GHz | Achieved by external electric field or uniaxial stress. |
| Estimated Required E-Field | $\sim 5$ | V/”m | Required to induce 50 GHz splitting. |
| Estimated Uniaxial Stress | $\sim 50$ | MPa | Required to induce 50 GHz splitting. |
| Required NVâ° Density ($n$) | $10^{16}$ | cm-3 | Basis for calculating R $\sim$ 1 (25% efficiency). |
| Calculated Memory Efficiency | > 99 | % | Projected for 1 ”m x 1 ”m x 1 mm waveguide geometry. |
| Minimum Ground-State Lifetime (4.2 K) | > 6 | ns | Limit set by phonon-induced decay rate. |
| Minimum Ground-State Lifetime (1 K) | > 17 | ns | Lower temperature further suppresses phonon coupling. |
| Zero-Field Excited State Energy ($E_{es}$) | 521.4 | THz | Reference energy for the NVâ° center. |
| **Longitudinal SO Coupling ($\lambda_{ | }$)** | $\approx 4.3$ | |
| Low-Temp Inhomogeneous Broadening ($\delta\epsilon$) | $\approx 16$ | GHz | Measured standard deviation of ZPL broadening (5.7 K). |
| Noise Suppression Factor | At most 1/20 | (Unitless) | Achieved with $S = 50$ GHz splitting, even with random strain. |
Key Methodologies
Section titled âKey MethodologiesâThe following is an outline of the experimental methodology proposed to establish the NVâ° QOM:
- Material Selection: Use of optical grade, low-strain CVD diamond hosting an ensemble of neutral Nitrogen-Vacancy (NVâ°) centers.
- Orbital State Manipulation: Application of external DC electric fields (E-field along [100] for standard (001) samples) or compressive uniaxial stress to control the ground-state splitting (S) and acceptance bandwidth.
- Cross-Polarization Control: Implementation of cross-linear polarization selection rules (enabled by the external field) to couple the control field exclusively to one ground state, achieving maximum readout noise suppression.
- Cryogenic Operation: Maintenance of the diamond sample at liquid helium temperatures (4.2 K or lower) to quench dynamical Jahn-Teller (DJT) distortions and suppress phonon coupling, ensuring necessary coherence times.
- Bandwidth Maximization: Detuning the signal and control pulses far from the broadened optical transition energy (up to 100 GHz detuning) to achieve broadband coupling without significant reduction in Raman coupling efficiency.
- Dephasing Mitigation: Application of picosecond microwave or optical spin-echo pulse sequences to counteract ground-state dephasing induced by random local strain, preserving coherence over the storage period.
- Efficiency Scaling: Integration of the diamond into micro-waveguides (e.g., 1 ”m x 1 ”m x 1 mm) to increase the interaction distance and maintain high control intensity, pushing total memory efficiency beyond 99%.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the specialized MPCVD diamond materials and precision engineering services necessary to replicate and advance this NVâ° quantum memory research. Our expertise directly addresses the challenges of material purity, custom geometry, and integration required for high-fidelity QIP platforms.
Applicable Materials
Section titled âApplicable MaterialsâReplicating this research requires ultra-high purity diamond with controlled defect density. 6CCVD recommends:
| 6CCVD Material | Application Focus | Key Specification Alignment |
|---|---|---|
| Optical Grade Single Crystal Diamond (SCD) | Core QOM platform. Ideal for research requiring minimal inhomogeneous broadening ($\delta\epsilon$ $\approx 16$ GHz) and maximal orbital coherence. | Available in thicknesses from 0.1 ”m up to 500 ”m, allowing precise control over NV layer density and depth. Custom [111] or [001] orientations available. |
| Engineered Polycrystalline Diamond (PCD) | Scalable integration and waveguide fabrication. Necessary for large-area, inch-size substrates (up to 125 mm). | Provides mechanical robustness for integration into complex cryogenic setups and optical chips. |
| Custom Doped SCD | Achieving targeted NVâ° density ($\sim 10^{16}$ cm-3). | We offer precise control over nitrogen/boron incorporation during MPCVD growth to optimize ensemble density, maximizing the relative Raman coupling strength (R). |
Customization Potential
Section titled âCustomization PotentialâThe success of the proposed QOM relies heavily on high-precision fabrication and low-loss interfaces, particularly for waveguide integration.
- Precision Polishing: To minimize scattering losses in the optical transitions and proposed 1 ”m x 1 ”m waveguides, 6CCVD provides SCD polishing down to Ra < 1 nm and large-area PCD polishing down to Ra < 5 nm.
- Custom Dimensions and Etching: To realize the proposed micron-scale waveguides (1 ”m x 1 ”m x 1 mm) or complex sample geometries required for E-field application, we offer high-precision laser cutting and custom wafer dimensions up to 125 mm (PCD).
- Integrated Metalization: The application of transverse electric fields requires reliable electrodes. 6CCVD offers in-house custom metalization services (Ti/Pt/Au, W, Cu, Pd) to deliver turn-key substrates ready for cryogenic and high-voltage testing.
Engineering Support
Section titled âEngineering SupportâThe paper highlights the challenge of random local strain and achieving specific crystal orientations. 6CCVDâs in-house team of PhD material scientists specializes in optimizing MPCVD growth parameters to mitigate these exact challenges:
- Strain Management: Consultation is available on material selection and post-processing (e.g., annealing) to reduce $\delta\epsilon$ and minimize the effects of random local strain on ground-state orbital coherence.
- Material Specification: Our engineering team provides detailed support for material recipe design, ensuring the selected diamond substrate meets the necessary purity, thickness, and doping levels required for highly efficient, broadband NVâ° Quantum Optical Memory projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
It is proposed that the ground-state manifold of the neutral nitrogen-vacancy\ncenter in diamond could be used as a quantum two-level system in a\nsolid-state-based implementation of a broadband, noise-free quantum optical\nmemory. The proposal is based on the same-spin $\Lambda$-type three-level\nsystem created between the two E orbital ground states and the A$_1$ orbital\nexcited state of the center, and the cross-linear polarization selection rules\nobtained with the application of transverse electric field or uniaxial stress.\nPossible decay and decoherence mechanisms of this system are discussed, and it\nis shown that high-efficiency, noise-free storage of photons as short as a few\ntens of picoseconds for at least a few nanoseconds could be possible at low\ntemperature.\n