Storage and retrieval of microwave fields at the single-photon level in a spin ensemble
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-08-07 |
| Journal | Physical Review A |
| Authors | CĂ©cile GrĂšzes, Brian Julsgaard, Yuimaru Kubo, Wen-Long Ma, Michael Stern |
| Institutions | Université Paris-Sud, Centre National de la Recherche Scientifique |
| Citations | 57 |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: NV Center Quantum Memory
Section titled âTechnical Analysis and Documentation: NV Center Quantum MemoryâExecutive Summary
Section titled âExecutive SummaryâThis paper reports a crucial step toward realizing a superconducting quantum memory: the single-photon level storage and retrieval of microwave fields using Nitrogen-Vacancy (NV) centers in diamond. This achievement relies heavily on ultra-high purity material engineering, aligning perfectly with 6CCVDâs core capabilities.
- Core Achievement: Storage of microwave pulses at the single-photon level in a spin ensemble memory (1010 NV centers) coupled to a superconducting LC resonator.
- Performance Metric: Successfully retrieved the signal 100 ”s later, achieving an echo efficiency (E) of 0.3%.
- Critical Material: High-purity, isotopically enriched 12C Single Crystal Diamond (SCD) synthesized by HPHT and subjected to electron irradiation and high-temperature annealing.
- Key Limiting Factor Addressed: The use of 99.97% 12C enriched diamond reduced decoherence, enabling a long spin coherence time (T2 = 84 ”s) crucial for robust quantum protocols.
- Engineering Challenge: Precise integration of the diamond onto a Niobium planar lumped-element LC resonator operating at deep cryogenic temperatures (10 mK).
- Future Vision: The demonstrated figures of merit are sufficient to enable the first operational multi-mode quantum memory for superconducting qubits.
Technical Specifications
Section titled âTechnical SpecificationsâThe research hinges on highly specific material and operating parameters, summarized below:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Base Material Purity | 99.97 | % | 12C isotopic enrichment for minimal decoherence |
| NV Center Concentration | 0.4 | ppm | Achieved after 2 MeV irradiation and 1000°C annealing |
| P1 Nitrogen Concentration | 0.6 | ppm | Contributes to spectral diffusion decoherence |
| Stored Signal Power | Average 1 | photon | Demonstrated single-photon level storage sensitivity |
| Maximum Storage Time | 100 | ”s | Retrieval delay via spin-echo techniques |
| Spin Coherence Time (T2) | 84 | ”s | Exponential decay constant, limited by dipolar interactions |
| Echo Efficiency (E) | 0.3 | % | Ratio of recovered energy to absorbed energy |
| Resonator Frequency (Ïr/2Ï) | 2.915 | GHz | Matched to NV transition frequency |
| Resonator Quality Factor (Q) | 650 | N/A | Fixed by coupling to measurement line |
| Operational Temperature | 10 | mK | Dilution cryostat environment for superconductivity |
| Optical Pumping Wavelength | 532 | nm | Used for NV center spin state initialization |
| Zero-Field Splitting (D/2Ï) | 2.88 | GHz | NV electronic ground state (S=1) |
| Magnetic Field (BNV) | 1.74 | mT | Applied along the [110] axis for Zeeman splitting |
Key Methodologies
Section titled âKey MethodologiesâThe success of this experiment is critically dependent on rigorous control over material synthesis, post-processing, and cryogenic integration.
- Diamond Synthesis: Single Crystal Diamond (SCD) was synthesized using the High-Pressure High-Temperature (HPHT) temperature gradient method.
- Isotopic Enrichment: The carbon source was 99.97% 12C-enriched pyrolytic carbon, derived from 12C-enriched methane, resulting in a nominal 13C concentration of 300 ppm.
- NV Conversion: The as-grown diamond, containing 1.4 ppm substitutional nitrogen (P1 centers), underwent 2 MeV electron irradiation at room temperature to create vacancies.
- Annealing: Subsequent annealing for 2 hours at 1000°C optimized the conversion process, yielding the final concentrations of [NV-] = 0.4 ppm and [P1] = 0.6 ppm.
- Device Integration: The SCD crystal was physically glued onto a planar lumped-element LC resonator, patterned from Niobium thin-film on a silicon substrate. The entire assembly was cooled to 10 mK.
- Quantum Sequence: The system was initialized using 532 nm laser optical pumping (reset pulse). Microwave pulses (Ξ, R) were applied to the spins, followed by homodyne detection of the reflected signal and emitted spin-echo after a delay (2Ï).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply and engineer the advanced diamond materials necessary to replicate, optimize, and scale this single-photon memory technology.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve and extend the 84 ”s coherence time (T2) reported in the paper, researchers require diamond with even tighter control over nitrogen and isotopic purity.
- Recommended Material: High Purity Single Crystal Diamond (SCD) for Optical/Quantum Grade applications. 6CCVD utilizes MPCVD growth techniques, which inherently allow for superior control over background impurities and precise nitrogen incorporation compared to legacy HPHT methods used in the cited research.
- Purity Requirements: We can supply SCD materials with ultra-low native 13C concentrations (< 1 ppm is achievable) and controlled P1 nitrogen concentrations to minimize spectral diffusion, allowing researchers to push T2 coherence times far beyond the demonstrated 84 ”s.
- Boron-Doped Alternatives: For similar experiments involving charge state manipulation or integrated microelectronics, we offer Boron-Doped Diamond (BDD) films capable of serving as highly stable, inert electrodes.
Customization Potential
Section titled âCustomization PotentialâThe integration of the diamond crystal with the superconducting resonator requires specialized processing and dimensional precision. 6CCVD provides in-house engineering solutions critical for successful device fabrication.
| Service | Requirement Satisfied | 6CCVD Advantage |
|---|---|---|
| Custom Dimensions/Shaping | Precise fit onto the planar LC resonator | We provide custom laser cutting and shaping for plates/wafers, ensuring the NV ensemble aligns perfectly with the resonator inductance. Custom dimensions up to 125mm (PCD) and precise SCD substrates available. |
| Material Thickness Control | Optimized microwave coupling | Thicknesses for SCD range from 0.1 ”m to 500 ”m, allowing precise tailoring of the spin ensemble volume for specific collective coupling constants (gens). |
| Ultra-Low Roughness Polishing | Minimizing interface loss | We achieve Ra < 1nm polishing on SCD surfaces, critical for reducing scattering losses and ensuring reliable, high-quality bonding to the Niobium thin-film circuit. |
| Cryogenic-Compatible Metalization | Integrated contacts for future designs | We offer custom thin-film deposition including Au, Pt, Pd, Ti, W, and Cu. This capability is essential for defining integrated RF antennas, ground planes, or contact pads compatible with 10 mK cryogenic environments. |
Engineering Support
Section titled âEngineering SupportâThe research requires highly specialized knowledge in material post-processing (electron irradiation and high-temperature annealing) to achieve the target [NV-] / [P1] ratio. 6CCVDâs in-house PhD team can assist with:
- Material Selection: Guiding the choice between specific isotopic purities (e.g., < 0.1% 13C) and nitrogen concentrations to meet the stringent T2 and collective coupling requirements for quantum memory and qubit coupling projects.
- Process Optimization: Consulting on ideal irradiation doses and annealing protocols necessary to maximize NV creation efficiency while minimizing residual strain or surface damage.
- Integration Challenges: Providing technical specifications for surface preparation and metal adhesion, ensuring optimal performance when coupling diamond films to superconducting (Niobium) or microwave circuitry.
Call to Action: For custom specifications or material consultation concerning NV-based quantum memories, sensors, or superconducting integration, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We report the storage of microwave pulses at the single-photon level in a\nspin-ensemble memory consisting of $10^{10}$ NV centers in a diamond crystal\ncoupled to a superconducting LC resonator. The energy of the signal, retrieved\n$100\, \mu \mathrm{s}$ later by spin-echo techniques, reaches $0.3\%$ of the\nenergy absorbed by the spins, and this storage efficiency is quantitatively\naccounted for by simulations. This figure of merit is sufficient to envision\nfirst implementations of a quantum memory for superconducting qubits.\n