Exceptional Point and Cross-Relaxation Effect in a Hybrid Quantum System
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-04-19 |
| Journal | PRX Quantum |
| Authors | Guo-Qiang Zhang, Zhen Chen, Da Xu, Nathan Shammah, Meiyong Liao |
| Institutions | University of Michigan, Beijing Academy of Quantum Information Sciences |
| Citations | 67 |
| Analysis | Full AI Review Included |
Technical Documentation: Exceptional Point in P1 Diamond Hybrid Quantum Systems
Section titled âTechnical Documentation: Exceptional Point in P1 Diamond Hybrid Quantum SystemsâThis document analyzes the recent research on observing an Exceptional Point (EP) in a hybrid quantum system utilizing dense nitrogen (P1) centers in diamond coupled to a coplanar-waveguide (CPW) resonator. This analysis highlights the critical material requirements and demonstrates how 6CCVDâs specialized MPCVD diamond products and engineering services are ideally suited to replicate and advance this cutting-edge quantum research.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrated the experimental observation of an Exceptional Point (EP) in a compact, on-chip hybrid quantum system, offering significant implications for quantum information processing and metrology.
- Core System: Dense nitrogen (P1) centers embedded in Type-1b diamond coupled to a superconducting coplanar-waveguide resonator.
- Key Phenomenon: The EP was observed by precisely tuning the magnon-photon coupling via a microwave drive field, causing the two polariton modes to coalesce.
- Material Requirement: The experiment relies on the specific properties of Type-1b diamond, characterized by dense P1 paramagnetic spin ensembles.
- Novel Finding: The robustness of the EP against driving different spin subensembles convincingly proves the existence and key role of the cross-relaxation effect in P1 centers.
- Technological Impact: This on-chip configuration provides a more compact and tunable platform compared to traditional 3D microwave cavity systems, pushing hybrid quantum systems toward practical applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental setup and results, detailing the physical and operational parameters of the hybrid system.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Operating Temperature | 20 | mK | Cryogenic environment (Dilution refrigerator) |
| Diamond Defect Type | P1 Centers (Dense Nitrogen) | N/A | Main defects in Type-1b diamond |
| Resonator Material | Niobium (Nb) | N/A | 50 nm thick film on oxidized silicon substrate |
| Resonator Frequency ($\omega_c/2\pi$) | 3.093 | GHz | Tuned to s=0 subensemble resonance |
| Effective Coupling ($g_{eff}/2\pi$) | 17.2 ± 0.5 | MHz | Extracted from Rabi splitting |
| Magnon Damping Rate ($\gamma/2\pi$) | 11.9 ± 0.3 | MHz | For s=0 spin subensemble |
| Resonator Decay Rate ($\kappa/2\pi$) | 0.6 ± 0.05 | MHz | Line width of polariton mode |
| EP Drive Power ($P_d$) | â -93.7 | dBm | Power level where polariton modes coalesce |
| **P1 Hyperfine Interaction ($A_{ | }/2\pi$)** | 94 | |
| Static Magnetic Field (B) Orientation | [100] | Crystal Axis | Applied direction |
| Diamond Crystal Orientation | [001] | Crystal Axis | Perpendicular to resonator surface |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized precise material engineering and controlled cryogenic microwave techniques to achieve the EP observation:
- Material Preparation: Type-1b diamond, synthesized under high pressure and high temperature (HPHT), containing dense P1 nitrogen centers, was selected.
- Resonator Fabrication: A coplanar-waveguide (CPW) resonator was fabricated by reactive ion etching a 50 nm Niobium (Nb) film deposited on a thermally oxidized silicon substrate.
- Hybrid System Assembly: The diamond sample was glued onto the CPW resonator. The diamondâs [001] crystal axis was oriented perpendicular to the resonator surface.
- Cryogenic Operation: The hybrid system was placed in a dilution refrigerator and cooled to 20 mK.
- Magnetic Field Alignment: A static magnetic field (B) was applied along the [100] crystal axis to define the spin subensembles.
- Magnon Excitation and Tuning: A microwave drive tone ($\omega_d/2\pi = 3.093$ GHz) was applied for a long duration (3000 s) to ensure the system reached a stationary state, precisely tuning the effective magnon-photon coupling ($g_{eff}$).
- Transmission Measurement: The transmission spectrum ($S_{21}$) was measured using a Vector Network Analyzer (VNA) with a fast, low-power probe signal (approx. 1 fW).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-specification MPCVD diamond materials required to replicate and extend this critical research into hybrid quantum systems. Our capabilities ensure material purity, precise geometry, and integrated fabrication support.
| Research Requirement | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| Material Base: Dense P1 Centers (Type-1b characteristics) | Nitrogen-Doped SCD: We supply high-purity Single Crystal Diamond (SCD) tailored for controlled nitrogen incorporation, essential for creating dense P1 spin ensembles. | Guaranteed material consistency and controlled defect density for reliable quantum ensemble performance and high coupling strength. |
| Crystal Orientation: Precise [001] surface orientation required for magnetic alignment. | Custom Crystal Orientation: 6CCVD provides SCD plates with precise crystallographic orientations (e.g., [001], [111], [110]) necessary for optimal magnetic field alignment and spin coherence. | Maximizes coupling efficiency and ensures experimental repeatability crucial for EP observation. |
| Thickness Control: SCD/PCD thickness required for optimal coupling and integration (0.1”m to 500”m range). | Precision Thickness Control: We offer SCD and PCD wafers with thickness control from 0.1”m up to 500”m, allowing researchers to optimize the volume of P1 centers. | Enables fine-tuning of the collective spin excitation properties (magnon number N) and coupling strength $g$. |
| Surface Quality: Ultra-smooth interface required for low-loss CPW integration. | Ultra-Low Roughness Polishing: SCD surfaces polished to Ra < 1nm; Inch-size PCD polished to Ra < 5nm. | Minimizes microwave loss and ensures intimate, low-defect contact when gluing diamond to the superconducting resonator. |
| On-Chip Integration: Small, custom-sized diamond sample for compact system. | Custom Dimensions & Laser Cutting: We provide plates/wafers up to 125mm (PCD) and offer custom laser cutting services for precise geometries required for on-chip CPW integration. | Facilitates compact, high-performance device fabrication and rapid prototyping. |
| Future Integration: Need for metal contacts (e.g., Ti/Pt/Au for ohmic contacts or alternative resonator designs). | In-House Metalization Services: We offer custom deposition of Au, Pt, Pd, Ti, W, and Cu, crucial for superconducting or resistive contacts on diamond substrates. | Streamlines device fabrication by providing integrated material and metalization solutions under one roof. |
6CCVDâs in-house PhD team specializes in material selection and optimization for hybrid quantum systems, including those utilizing NV and P1 centers. We offer comprehensive engineering support to ensure your diamond substrate meets the stringent requirements for high-coherence, low-loss quantum experiments.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping (DDU default, DDP available) ensures prompt delivery worldwide.
View Original Abstract
Exceptional points (EPs) are exotic degeneracies of non-Hermitian systems, where the eigenvalues and the corresponding eigenvectors simultaneously coalesce in parameter space, and these degeneracies are sensitive to tiny perturbations on the system. Here, we report an experimental observation of the EP in a hybrid quantum system consisting of dense nitrogen (P1) centers in diamond coupled to a coplanar-waveguide resonator. These P1 centers can be divided into three subensembles of spins and cross relaxation occurs among them. As a new method to demonstrate this EP, we pump a given spin subensemble with a drive field to tune the magnon-photon coupling in a wide range. We observe the EP in the middle spin subensemble coupled to the resonator mode, irrespective of which spin subensemble is actually driven. This robustness of the EP against pumping reveals the key role of the cross relaxation in P1 centers. It offers a novel way to convincingly prove the existence of the cross-relaxation effect via the EP.