Quantum-information processing on nitrogen-vacancy ensembles with the local resonance assisted by circuit QED
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-06-24 |
| Journal | Physical Review A |
| Authors | MingâJie Tao, Ming Hua, Qing Ai, FuâGuo Deng |
| Institutions | Beijing Normal University |
| Citations | 44 |
| Analysis | Full AI Review Included |
Hybrid Quantum Systems: High-Fidelity Quantum Logic Gates using NV Ensembles in 6CCVD Single Crystal Diamond
Section titled âHybrid Quantum Systems: High-Fidelity Quantum Logic Gates using NV Ensembles in 6CCVD Single Crystal DiamondâDocument ID: 6CCVD-TD-QUANTUM-NV-150302376v1 Source Publication: arXiv:1503.02376v1 (Tao et al.) Application Focus: High-Fidelity Quantum Computing, Hybrid Circuit QED, Cluster State Generation
Executive Summary
Section titled âExecutive SummaryâThis paper presents a robust, fast, and high-fidelity scheme for quantum information processing utilizing a hybrid system coupling Nitrogen-Vacancy (NV) center ensembles (NVEs) in diamond with high-Q superconducting Transmission Line Resonators (TLRs) and Superconducting Phase Qubits (SPQs). The stability and performance of this device hinge entirely on the use of high-coherence diamond substrates.
- Core Architecture: The scheme links two distant NVEs, each coupled to a TLR, via a tunable SPQ acting as a quantum data bus.
- Performance Metrics: Achieved simulated fidelity of 99.65% for quantum state transfer (QST) in 70.60 ns, and 98.23% for a controlled-phase (c-phase) gate in 93.87 ns.
- Methodological Advantage: Utilizes local resonant interaction between the NVE and the TLR (not global resonance), allowing for significantly shorter operation times compared to previous proposals.
- Material Criticality: The enhanced robustness stems directly from the long spin coherence time (T2 ~ 10-3 s) of NVEs in diamond, significantly outlasting the superconducting qubit coherence time (~ 10-5 s).
- Scalability Demonstrated: The c-phase gate acts as a universal building block, enabling the theoretical construction of scalable 1D and 2D cluster states for one-way quantum computation.
- 6CCVD Relevance: Replication and advancement of this research require ultra-high-purity, low-defect Single Crystal Diamond (SCD) substrates, a core specialization of 6CCVDâs MPCVD capabilities.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Quantum State Transfer (QST) Fidelity | 99.65 | % | Within 70.60 ns operation time |
| C-Phase Gate Fidelity | 98.23 | % | Within 93.87 ns operation time |
| NVE Zero-Field Splitting (Dgs/2Ï) | 2.88 | GHz | Key NV transition frequency |
| SPQ/TLR Transition Frequency (Ï/2Ï) | 1.3 to 1.4 | GHz | Simulated resonant operating frequency |
| NVE-TLR Coupling Strength (g1,2/2Ï) | 16, 20 | MHz | Local coupling regime |
| SPQ-TLR Coupling Strength (g/2Ï) | 104 (0.5) | MHz | Tunable coupling (High / Detuned) |
| Applied Rabi Frequency (ΩR/2Ï) | 50 | MHz | Single-qubit rotation speed |
| NV Center Coherence Time (T2) | ~ 10-3 | s | Crucial material advantage for robustness |
| SPQ Coherence Time (T2) | ~ 10-5 | s | Compared to NV stability |
| Required Resonator Quality Factor (Q) | > 106 | (Unitless) | For high-Q Transmission Line Resonators (TLRs) |
| Computational Qubit States | ms = -1> and | ms = +1> |
Key Methodologies
Section titled âKey MethodologiesâThe successful implementation relies on controlling rapid, sequential operations involving resonant and large-detuning interactions between the hybrid components.
- Hybrid System Setup: Two spatially separated NVEs are coupled magnetically to the vacuum field of their respective high-Q Transmission Line Resonators (TLRs). The TLRs, acting as quantum data buses, are capacitively coupled and linked via a current-biased Josephson-junction Superconducting Phase Qubit (SPQ).
- NV Qubit Encoding: The computational space uses the |ms = -1> and |ms = +1> states of the NV-center, leveraging the auxiliary state |ms = 0> to facilitate complex single-qubit rotations and gate mechanisms.
- Local Resonant Interaction: Energy transfer between the NVE and the TLR (e.g., |0>NVE <â> |1>TLR) is achieved by tuning the NV transition frequency (via external magnetic field B) to local resonance with the fixed TLR frequency.
- Tunable SPQ Coupling: The SPQ serves as a switch and mediator. Its coupling strength (g) to the TLRs is dynamically adjusted (tuned via external flux bias) to facilitate rapid state transfer between TLRa and TLRb (high g) or to decouple the SPQ entirely (low g, 0.5 MHz) during NVE-TLR operations.
- Fast Single-Qubit Rotation: External drive fields (Rabi pulses, ΩR/2Ï = 50 MHz) are applied directly to the NVEs to induce required transitions (e.g., |1> <â> |U>) on time scales (Ï/ΩR) much shorter than the decoherence time.
- Gate Construction: The C-Phase gate and CNOT gate protocols require five and nine steps, respectively, sequentially combining single-qubit rotations on the NVEs and tuned resonant energy transfers across the TLR-SPQ-TLR link.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research validates the use of NV ensembles in diamond as robust quantum memories for hybrid architectures, demanding the highest quality diamond material and precision fabrication. 6CCVD is uniquely positioned to supply the foundational materials necessary to replicate and advance this critical technology.
| Paper Requirement | 6CCVD Material & Service | Engineering Solution & Value Proposition |
|---|---|---|
| Ultra-Long NV Coherence Time (T2) | Optical Grade Single Crystal Diamond (SCD) | Our MPCVD SCD offers residual nitrogen concentrations potentially < 1 part per billion (ppb), which is crucial for minimizing decoherence and achieving the long T2 (~ 10-3 s) required for stable, robust quantum gates. |
| Integration of Hybrid Circuits | Custom Substrate Dimensions & Thickness Control | We supply SCD wafers from 0.1 ”m up to 500 ”m thickness, enabling precise control over NV implantation depth and optimal coupling to the circuit QED elements. We support plates/wafers up to 125mm (PCD) for scalable circuit layouts. |
| High-Q Resonator Deposition | Ultra-Smooth Polishing (Ra < 1 nm for SCD) | The performance of high-Q TLRs and SPQs is highly sensitive to substrate surface quality. Our sub-nanometer SCD polishing reduces microwave loss, supporting the required quality factors (> 106). |
| Fabrication of Superconducting Circuits | Custom Metalization Services | We offer in-house deposition and patterning of crucial metals (Ti/Au, Pt/Ti, W, Cu) required for ohmic contacts, gate structures, and the subsequent fabrication of aluminum or niobium-based superconducting circuits (TLRs/SPQs) onto the diamond substrate. |
| Scalable Array Development | Custom Laser Cutting and Shaping | To construct the proposed 2D $n \times n$ cluster state grids (Fig. 4b), precise dimensions and edge finishes are necessary. 6CCVD offers laser cutting to customize wafer geometry to fit specific quantum device footprints. |
Engineering Support
Section titled âEngineering SupportâThe successful engineering of the interface between the NV centers, the diamond lattice, and the superconducting circuits is paramount. 6CCVDâs in-house PhD material science team specializes in optimizing MPCVD diamond crystal quality specifically for hybrid quantum systems and circuit QED applications. We provide consultative support to researchers determining optimal crystal orientation, target impurity levels, and surface preparation for demanding quantum fabrication workflows.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
With the local resonant interaction between a nitrogen-vacancy-center ensemble (NVE) and a superconducting coplanar resonator, and the single-qubit operation, we propose two protocols for the state transfer between two remote NVEs and for fast controlled-phase (c-phase) on these NVEs, respectively. This hybrid quantum system is composed of two distant NVEs coupled to separated high-Q transmission line resonators (TLRs), which are interconnected by a current-biased Josephsonjunction superconducting phase qubit. The fidelity of our state-transfer protocol is about 99.65% within the operation time of 70.60 ns. The fidelity of our c-phase gate is about 98.23% within the operation time of 93.87 ns. Furthermore, using the c-phase gate, we construct a two-dimensional cluster state on NVEs in n*n square grid based on the hybrid quantum system for the one-way quantum computation. Our protocol may be more robust, compared with the one based on the superconducting resonators, due to the long coherence time of NVEs at room temperature.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2000 - Quantum Computing and Quantum Information