Quantum state transfer and conditional phase gate via off-resonant quantum Zeno dynamics
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-09-07 |
| Journal | Optics Communications |
| Authors | Wan-Jun Su, ZhenâBiao Yang, HuaiâZhi Wu |
| Institutions | Fuzhou University |
| Citations | 6 |
| Analysis | Full AI Review Included |
Conditional Phase Gate and Quantum State Transfer using MPCVD NV Diamond
Section titled âConditional Phase Gate and Quantum State Transfer using MPCVD NV DiamondâTechnical Documentation and QIP Material Sourcing Guide
Section titled âTechnical Documentation and QIP Material Sourcing Guideâ6CCVD Analysis Reference: Su, W. J. (2017). Conditional phase gate and quantum state transfer via off-resonant quantum Zeno dynamics. arXiv:1705.04759v1.
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates a highly robust theoretical scheme for fundamental Quantum Information Processing (QIP) primitivesâQuantum State Transfer (QST) and Conditional Phase Gate (CPG)âusing nitrogen-vacancy (NV) centers in diamond coupled to a microcavity quantum bus.
- Core Material: The scheme relies on two individual NV centers embedded in high-quality diamond, interacting with a high-Q microcavity (e.g., microsphere resonator).
- Methodology: Implementation utilizes off-resonant Quantum Zeno Dynamics (QZD) under large detuning ($|\Delta| \gg \Omega$), ensuring the quantum interaction is a virtual-photon process.
- Decoherence Immunity: By preventing population of both the cavity field and the NV center excited levels, the scheme achieves strong immunity against major decoherence sources: cavity decay ($\kappa$) and atomic spontaneous emission ($\gamma$).
- Performance: Achieved optimal fidelity of > 0.998 for QST and high robustness, maintaining > 94.5% fidelity for CPG even in the presence of realistic dissipation.
- Speed: QST operations are projected to be rapid (approximately 200 ns), significantly shorter than the NV centerâs room-temperature decoherence time (known to exceed 600 ”s).
- 6CCVD Relevance: Successful experimental realization requires high-purity Single Crystal Diamond (SCD) wafers with precise NV incorporation and custom geometry for seamless integration into microcavity systems.
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters define the operational regime and expected performance of the QST and CPG protocols based on the numerical simulations and experimental feasibility discussion (Section 6).
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimal QST Fidelity | > 0.998 | N/A | Under ideal conditions ($\Delta/g = 0.5, \Omega/g = 0.05$) |
| Robust CPG Fidelity | 94.5% | N/A | Under high dissipation ($\gamma/g = 0.01, \kappa/g = 0.2$) |
| QST Operation Time | ~200 | ns | Using realistic QED parameters |
| NV Center Coherence Time ($T_{2}$) | > 600 | ”s | Observed room-temperature lifetime [39] |
| Quantum Zeno Detuning Ratio ($\Delta / \Omega$) | 10 | N/A | Based on median values $0.5g / 0.05g$ |
| NV-Cavity Coupling ($g/2\pi$) | 1 | GHz | Feasibility parameter (hundreds of MHz to several GHz) |
| Cavity Leakage Rate ($\kappa/2\pi$) | 0.12 | GHz | Required for high-Q microsphere cavity |
| Spontaneous Decay Rate ($\gamma/2\pi$) | 0.015 | GHz | NV spontaneous decay rate |
| Required Cavity Quality Factor (Q) | > 2 x 106 | N/A | Minimizes photon leakage |
| CPG Sensitivity to Shift Time ($\delta t/t$) | Insensitive | N/A | Optimal fidelity maintained for $\delta t/t \le \pm 0.1$ |
Key Methodologies
Section titled âKey MethodologiesâThe schemes for QST and CPG rely on precise control over NV center energy levels and coupling strengths within a high-Q cavity environment.
- Physical Setup: Two spatially separated NV centers are coupled simultaneously to a single high-Q microcavity (e.g., microtoroidal or microsphere resonator), which functions as the quantum bus.
- NV Qubit Configuration: The NV centers are modeled in a $\Lambda$ configuration, using two ground states ($\vert g \rangle$ and $\vert f \rangle$) and one excited state ($\vert e \rangle$). An ancillary ground state ($\vert i \rangle$) is also utilized.
- Off-Resonant Coupling:
- The $\vert g \rangle \leftrightarrow \vert e \rangle$ transition is coupled to the cavity field with coupling strength $g$.
- The $\vert f \rangle \leftrightarrow \vert e \rangle$ transition is driven by a classical microwave field with Rabi frequency $\Omega$.
- A large detuning ($\Delta$) is maintained between the NV transitions and the cavity mode ($|\Delta| \gg g$ and $|\Delta| \gg \Omega$).
- Quantum Zeno Dynamics (QZD): The large detuning and coupling conditions enforce the system evolution within a closed quantum Zeno subspace (spanned by $\vert gf \rangle \vert 0 \rangle_c$ and $\vert fg \rangle \vert 0 \rangle_c$), effectively freezing unwanted transitions.
- Virtual-Photon Interaction: Due to the large detuning, the interaction becomes a virtual-photon process. The excited states of the NV centers and the cavity field are not populated, which provides the primary robustness against decay mechanisms.
- Gate Implementation:
- QST: Achieved by selecting an interaction time $tâ$ such that $(\Omega^{2}/\Delta)tâ = \pi$, resulting in the transfer of an arbitrary state from NV1 to NV2.
- CPG: Implemented by modifying the phases ($\phi_1, \phi_2$) of the classical driving fields over a total interaction period $T = 2\pi\Delta/\Omega^{2}$, inducing a geometric phase shift $\pi$.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful realization of solid-state QIP protocols based on NV centers, as proposed in this paper, critically depends on the quality and dimensional precision of the diamond material. 6CCVD is uniquely positioned to supply the requisite components for this advanced research.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this quantum Zeno research, researchers require diamond substrates engineered for minimal decoherence and maximal NV center fidelity.
- Optical Grade Single Crystal Diamond (SCD): Essential for QIP due to its high purity, necessary for maximizing the electron spin coherence time ($T_{2} > 600\ \text{”s}$).
- Recommendation: Ultra-low nitrogen concentration SCD (Type IIa equivalent or better), ideally isotopically purified ${}^{12}\text{C}$ material, to minimize parasitic decoherence from substitutional nitrogen ($P1$ centers) and ${}^{13}\text{C}$ nuclear spins.
- Custom NV Layering: We offer precise growth of SCD layers with tailored NV density (via in-situ nitrogen doping or post-growth implantation) confined close to the surface for efficient coupling to microcavity evanescent fields.
Customization Potential
Section titled âCustomization PotentialâExperimental implementation of this scheme requires integrating diamond components with high-Q microresonators (e.g., microsphere cavities [34]). This necessitates precise dimensional control and geometric features.
| Research Requirement | 6CCVD Capability | Benefits for QIP |
|---|---|---|
| Nanocavity Integration | Custom Thinning & Polishing: SCD plates down to 0.1 ”m thickness. | Enables the creation of high-Q diamond nanopillars or waveguides via subsequent etching. |
| Microresonator Coupling | Custom Dimensions: Wafers/plates up to 125mm size, allowing for standardized processing. | Provides scalable, uniform QIP substrates. |
| Precise Geometry | Laser Cutting & Shaping: Custom shapes and precise geometric features. | Necessary for creating cantilevers or small diamond chips for placement near micro-resonator equators (critical for evanescent coupling). |
| Electrical Contact (Future Steps) | Metalization Services (Au, Pt, Ti, Pd): In-house capability for custom contact layouts. | Supports electrical manipulation of NV states or integration into superconducting hybrid systems (as referenced in [35]). |
| Surface Quality | Precision Polishing: Surface roughness $R_a < 1\ \text{nm}$ (SCD) on the growth face. | Crucial for minimizing surface defects that can introduce decoherence or reduce optical coupling efficiency. |
Engineering Support
Section titled âEngineering SupportâThe robust fidelity achieved in this off-resonant QZD scheme hinges on achieving strict material and coupling specifications ($g, \kappa, \gamma$). 6CCVDâs in-house PhD material science team understands these constraints. We provide expert consultation to select the optimal diamond grade, doping, orientation, and surface termination required for similar quantum computing, QST, and CPG projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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