Selective nuclear-spin interaction based on a dissipatively stabilized nitrogen-vacancy center
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-04-15 |
| Journal | Physical review. A/Physical review, A |
| Authors | Jiawen Jiang, Q. Chen |
| Institutions | Hunan Normal University |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research presents a novel protocol for achieving selective, high-fidelity quantum gates between heteronuclear nuclear spins mediated by a Nitrogen-Vacancy (NV) center in diamond, operating robustly under ambient conditions.
- Core Innovation: Achieves the nuclear-nuclear ZZ quantum gate (UZZ) between different spin species (e.g., Carbon-13 and Silicon-29) at room temperature, overcoming the primary limitation of short NV electron spin lifetime (T1ρ).
- Dissipative Stabilization: The NV electron spin acts as a quantum bus but is decoupled from the long-term dynamics by periodic reinitialization (resetting) to the |-)e state (e.g., every 20 µs), effectively stabilizing the system dissipatively.
- High Selectivity: Individual control over different nuclear spin species is achieved using suitably tuned Radio-Frequency (RF) fields, enabling selective interaction even in complex spin environments.
- Performance Metrics: The protocol demonstrates exceptional process fidelity (greater than 0.99) for the one-step nuclear ZZ gate, a significant improvement over previous methods (typically less than 0.66).
- Robustness: The second-order coupling mechanism makes the quantum gate operation insensitive to detunings and errors in the Microwave (MW) driving frequency of the NV center.
- Application Scope: Extends the use of NV centers for quantum computation, simulation, and high-sensitivity quantum sensing applications under practical, ambient conditions.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Operating Condition | Ambient | N/A | Room temperature operation. |
| NV Zero-Field Splitting (D) | 2.87 | GHz | Electronic ground state splitting. |
| NV Electron Spin Lifetime (T1ρ) | 200 | µs | Practical lifetime limitation. |
| NV Reset Period (tre) | 20 | µs | Cycle time for dissipative stabilization. |
| MW Rabi Frequency (Ω) | 400 | (2π)kHz | Standard electron spin driving field. |
| RF Rabi Frequency (Ωrf) | 1 | (2π)kHz | Nuclear spin control field strength. |
| Target Nuclear Species | Carbon-13, Silicon-29 | N/A | Example heteronuclear register. |
| C-13 Resonance (γn1B) | 4 | (2π)MHz | Used for selective RF tuning. |
| Si-29 Resonance (γn2B) | 5.06 | (2π)MHz | Used for selective RF tuning. |
| C-13 Parallel Coupling (a||1) | 9 | (2π)kHz | Hyperfine coupling component. |
| Si-29 Parallel Coupling (a||2) | 11 | (2π)kHz | Hyperfine coupling component. |
| Nuclear ZZ Gate Fidelity | > 0.99 | N/A | Achieved fidelity in one-step operation. |
| Frequency Resolution Limit | 0.5 | (2π)kHz | Limited by target spin decoherence (T2 = 200 ms). |
Key Methodologies
Section titled “Key Methodologies”The protocol relies on a combination of continuous MW driving, selective RF control, and periodic dissipative stabilization of the NV electron spin to mediate the nuclear-nuclear interaction.
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System Initialization:
- A large magnetic field (B) is applied along the NV axis (z-axis).
- The NV electron spin is optically initialized to the |-)e state.
- Target nuclear spins (n1, n2) are polarized and initialized (e.g., to |+1-2⟩).
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MW Driving and Effective Hamiltonian:
- A continuous Microwave (MW) field is applied, resonant with the |−1⟩ ↔ |0⟩ transition, to dress the NV electron spin states.
- The system Hamiltonian is simplified using the Schrieffer-Wolff (SW) transformation, adiabatically eliminating the fast electronic degrees of freedom and deriving a second-order effective coupling (Heff) between the nuclear spins.
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Dissipative Stabilization (Periodic Reset):
- To overcome the NV electron spin relaxation (T1ρ), the electron spin is periodically reset to the |-)e state (e.g., every tre = 20 µs).
- This process stabilizes the NV spin in a quasi-steady state, allowing the nuclear spins to evolve coherently well beyond the NV lifetime.
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Selective RF Control:
- Two weak Radio-Frequency (RF) fields are applied, individually tuned to the Larmor frequencies (ωrfi) of the two different nuclear spin species (n1 and n2).
- This selective tuning ensures that the effective nuclear-nuclear interaction (ZZ gate) is only activated between the desired heteronuclear pair.
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Gate Implementation:
- The nuclear spins evolve under the effective master equation, governed by the Hamiltonian HN, which includes the desired p*ge*Iz1Iz2 coupling term (where p is the steady-state polarization).
- The gate operation time T is chosen to achieve the desired state transfer (e.g., |+1-2⟩ → |-1+2⟩).
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Readout:
- The final nuclear spin states are read out by transferring their quantum information back to the NV electron spin, followed by standard electron state-dependent fluorescence detection.
Commercial Applications
Section titled “Commercial Applications”The ability to perform high-fidelity, selective quantum control over heteronuclear nuclear registers at room temperature opens several avenues for commercialization in quantum technology and advanced sensing.
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Quantum Computing Hardware:
- Enables the development of robust, multi-qubit quantum registers based on nuclear spins in diamond, leveraging their extremely long coherence times (T2).
- Crucial for building scalable quantum processors where different nuclear species (e.g., C-13, Si-29, N-14) can serve as distinct, individually addressable qubits.
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Quantum Simulation:
- Provides a platform for simulating complex quantum many-body systems and spin dynamics by precisely controlling interactions between different types of localized spins.
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High-Resolution Quantum Sensing (NMR/EPR):
- The scheme can be used to detect external nuclear spins (e.g., Hydrogen-1 in surrounding materials or molecules) with high frequency resolution, unconstrained by the NV T1ρ limit.
- Applicable in nanoscale Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) spectroscopy for material characterization and chemical analysis.
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Room-Temperature Quantum Devices:
- By eliminating the need for cryogenic cooling, this technology significantly reduces the complexity, size, and operational cost of diamond-based quantum devices, accelerating their deployment outside specialized laboratories.
View Original Abstract
Current typical methods to realize nuclear-nuclear quantum gates require a sequence of electronnuclear quantum gates by using dynamical decoupling techniques, which are implemented at low temperature because of short decoherence and relaxation time of the NV spin at room temperature. This limitation could be overcome by using periodical resets of an NV spin as a mediator of interaction between two nuclear spins [Chen, Schwarz, and Plenio, 119, 010801 (2017)]. However, this method works under stringent coupling strengths condition, which makes it not applicable to heteronuclear quantum gate operations. Here we develop this scheme by using radio-frequency (RF) fields to control different nuclear spin species. Periodical resets of the NV center protect the nuclear spins from decoherence and relaxation of the NV spin. RF control provides probability to have highly selective and high fidelity quantum gates between heteronuclear spins as well as detecting nuclear spins by using a nuclear spin sensor under ambient conditions.