Quantum microwave-optical interface with nitrogen-vacancy centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-09-29 |
| Journal | Physical review. A/Physical review, A |
| Authors | Bo Li, Fuli Li, Yuan Zhou, Sheng-li Ma, Fuli Li |
| Institutions | Xiâan Jiaotong University |
| Citations | 45 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Quantum Microwave-Optical Interface in Diamond
Section titled âTechnical Documentation & Analysis: Quantum Microwave-Optical Interface in DiamondâThis document analyzes the research paper âQuantum microwave-optical interface with nitrogen-vacancy centers in diamondâ (arXiv:1709.04852v1) to provide technical specifications and align the material requirements with 6CCVDâs advanced MPCVD diamond capabilities.
Executive Summary
Section titled âExecutive SummaryâThis research proposes a highly efficient, coherent quantum interface utilizing Nitrogen-Vacancy (NV) centers in diamond to bridge the gap between microwave and optical quantum domains.
- Core Mechanism: An ensemble of NV centers embedded in diamond acts as a collective spin excitation mode ($\hat{b}$), mediating quantum state transfer between a microwave superconducting coplanar waveguide (CPW) cavity ($\hat{a}_1$) and an optical cavity ($\hat{a}_2$).
- High Fidelity Protocols: Two conversion schemes are analyzed: a sequential Double-Swap protocol and an adiabatic Dark-State protocol (STIRAP-like).
- Performance: Numerical simulations demonstrate high conversion fidelities, reaching up to 0.99 for coherent initial states under realistic decay conditions.
- Robustness: The Dark-State scheme is shown to be extremely robust against collective spin dissipation ($\gamma_s$), as the conversion process evolves within a dark mode decoupled from the spin excitations.
- Material Requirements: Experimental feasibility relies on high-quality diamond substrates hosting a dense, coherent NV ensemble ($1 \times 10^{12}$ centers) and operating at cryogenic temperatures (T $\sim$ 20 mK).
- 6CCVD Value Proposition: Replication and extension of this work require ultra-high purity, low-strain Single Crystal Diamond (SCD) substrates, precisely polished and customized for integration with both microwave and optical resonatorsâa core specialization of 6CCVD.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points and operational parameters are extracted from the analysis of the proposed hybrid quantum device:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Center Ensemble Density | $1 \times 10^{12}$ | centers | Required for enhanced collective coupling ($\sqrt{N}g$) |
| Operating Temperature (T) | $\sim 20$ | mK | Necessary for negligible thermal photon occupation ($N_{1,2} \approx 0$) |
| Microwave CPW Cavity Q Factor | $\sim 10^6$ | N/A | Realistic quality factor for superconducting CPW |
| Optical Cavity Q Factor | $\sim 10^9$ | N/A | High Q factor (e.g., WGM or Fabry-PĂ©rot) |
| Collective Coupling Strength (G) | $\sim 2\pi \times 1$ | MHz | Effective Raman transition rate ($G_1=G_2=G$) |
| Microwave Detuning ($\Delta_1$) | $\sim 2\pi \times 200$ | MHz | Used for adiabatic elimination of excited states |
| Optical Detuning ($\Delta_2$) | $\sim 2\pi \times 100$ | GHz | Used for adiabatic elimination of excited states |
| Microwave Decay Rate ($\kappa_1$) | $0.003G$ ($\sim 2\pi \times 3$ kHz) | N/A (or Hz) | Realistic dissipation rate for CPW cavity |
| Collective Spin Decay Rate ($\gamma_s$) | $0.01G$ ($\sim 2\pi \times 10$ kHz) | N/A (or Hz) | Based on demonstrated NV $T_2 > 100$ ”s |
| Optical Decay Rate ($\kappa_2$) | $0.1G$ ($\sim 2\pi \times 100$ kHz) | N/A (or Hz) | Realistic dissipation rate for high-Q optical cavity |
| Maximum Conversion Fidelity | 0.99 | N/A | Achieved for coherent state $ |
Key Methodologies
Section titled âKey MethodologiesâThe proposed quantum interface relies on the following key steps and physical principles:
- Hybrid Setup Construction: The device integrates an ensemble of NV centers embedded in a diamond sample, placed simultaneously above a superconducting Coplanar Waveguide (CPW) resonator (microwave cavity $\hat{a}_1$) and coupled to an external optical cavity ($\hat{a}_2$).
- Four-Level System: The NV center is modeled as a four-level system, utilizing the 3A2 spin-1 ground state triplet ($|a\rangle, |b\rangle, |c\rangle$) and an excited optical state ($|e\rangle$).
- Raman Coupling: Quantum state transfer is achieved via two distinct Raman transitions driven by classical fields ($\Omega_1, \Omega_2$), coupling the NV spins to the microwave and optical cavity modes, respectively.
- Boson Mapping: Under the low excitation limit and large detuning conditions ($|\Delta_i| \gg |\Omega_i|, |g_i|$), the collective spin excitations of the NV ensemble are mapped onto a single bosonic mode ($\hat{b}$) using the Holstein-Primakoff representation.
- Effective Hamiltonian: The system dynamics are described by an effective beam-splitter Hamiltonian composed of two Jaynes-Cummings (JC) interactions, linking $\hat{a}_1 \leftrightarrow \hat{b}$ and $\hat{b} \leftrightarrow \hat{a}_2$.
- Dark-State Conversion (STIRAP): The adiabatic protocol modulates the coupling strengths $G_1(t)$ and $G_2(t)$ in a counterintuitive sequence, forcing the quantum state to evolve through a âspin dark modeâ ($\hat{c}_d$) that is decoupled from the collective spin excitation mode ($\hat{b}$), thereby suppressing spin dissipation ($\gamma_s$).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâReplicating or advancing this high-fidelity quantum interface requires diamond materials engineered to meet stringent quantum coherence, purity, and integration standards. 6CCVD is uniquely positioned to supply the necessary MPCVD diamond components.
Applicable Materials
Section titled âApplicable Materialsâ| Research Requirement | 6CCVD Material Recommendation | Technical Rationale |
|---|---|---|
| High Coherence & Low Strain (Essential for $T_2 > 100$ ”s) | Optical Grade Single Crystal Diamond (SCD) | Ultra-high purity MPCVD growth minimizes intrinsic defects and strain, providing the optimal host lattice for long-lived NV spin coherence. |
| High Density NV Ensemble (Requires controlled N content) | Low-N SCD Substrates | Starting with high-purity, low-nitrogen SCD allows researchers to precisely control NV creation (via implantation/annealing) to achieve the required $1 \times 10^{12}$ center density without compromising coherence. |
Customization Potential for Hybrid Integration
Section titled âCustomization Potential for Hybrid IntegrationâThe integration of diamond into complex microwave (CPW) and optical cavity structures demands precise dimensional control and specialized surface preparation, which 6CCVD provides as standard services:
| Integration Challenge | 6CCVD Customization Capability | Specification Range |
|---|---|---|
| CPW Resonator Integration | Custom Metalization Services | Internal deposition of Au, Pt, Pd, Ti, W, or Cu layers for direct integration with superconducting circuits. |
| Optical Cavity Coupling (WGM/Fabry-PĂ©rot) | Ultra-Precision Polishing | SCD surfaces polished to $R_a < 1$ nm, minimizing optical scattering losses critical for achieving $Q \sim 10^9$ optical cavities. |
| Device Geometry & Thickness | Custom Dimensions and Thickness Control | SCD plates available from 0.1 ”m to 500 ”m thickness, and substrates up to 10 mm, with custom laser cutting for specific cavity footprints. |
| Large-Scale Integration | Large Area Polycrystalline Diamond (PCD) | Wafers up to 125 mm (PCD) available for scaling up quantum device fabrication or thermal management applications. |
Engineering Support
Section titled âEngineering Supportâ6CCVD understands that material quality is paramount for achieving the high fidelities demonstrated in the Dark-State conversion protocol.
- Expert Consultation: 6CCVDâs in-house PhD team specializes in diamond material science for quantum applications. We can assist researchers in selecting the optimal SCD purity, thickness, and surface orientation necessary to maximize NV yield and coherence time for similar Quantum Microwave-Optical Interface projects.
- Global Supply Chain: We offer reliable global shipping (DDU default, DDP available) to ensure your critical materials arrive safely and promptly, regardless of your research location.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We propose an efficient scheme for a coherent quantum interface between microwave and optical photons using nitrogen-vacancy (NV) centers in diamond. In this setup, an NV center ensemble is simultaneously coupled to an optical and a microwave cavity. We show that, by using the collective spin excitation modes as an intermediary, quantum states can be transferred between the microwave cavity and the optical cavity through either a double-swap scheme or a dark-state protocol. This hybrid quantum interface may provide interesting applications in single microwave photon detections or quantum information processing.