Dressed-state control of effective dipolar interaction between strongly-coupled solid-state spins
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-08-01 |
| Journal | npj Quantum Information |
| Authors | Mamiko Tatsuta, Andrew Xu, Erik Bauch, Mark Ku |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Demonstrated deterministic control of the effective magnetic dipolar coupling (Veff) between two strongly-coupled solid-state Nitrogen Vacancy (NV) centers in diamond.
- Methodology: Utilized a doubly-dressed state scheme by applying two resonant Rabi driving fields (microwaves) to the control spin (NVB).
- Tunability Range: The effective coupling strength (Veff) was continuously tuned from approximately -Vdip/2 to +Vdip/2, where Vdip is the bare dipolar coupling strength (0.250 MHz).
- Validation: Tuning was verified spectroscopically using Ramsey interferometry on the sensor spin (NVA) and dynamically using spin-lock-based polarization transfer measurements (Hartmann-Hahn conditions).
- Engineering Benefit: This technique provides a robust method to tune effective coupling dynamics in a spin-1 qutrit system, relying primarily on the ratio of driving field amplitudes (Ω+/Ω-), which suppresses systematic errors from inhomogeneous Rabi driving.
- Impact: Enables the homogenization of interaction strengths within NV ensemble systems, crucial for generating high-fidelity multi-spin correlated states and improving quantum-enhanced sensing applications.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Zero-Field Splitting (D) | 2.87 | GHz | NV electronic spin (S=1) |
| Bare Dipolar Coupling (Vdip) | 0.250 ± 0.015 | MHz | Measured NVA-NVB coupling |
| NV Separation (Inferred) | ~6 | nm | Corresponds to Vdip |
| NV Creation Method | Molecular Ion Implantation (28N) | N/A | 6 keV energy, 1 x 109 cm-2 dosage |
| Diamond Material | CVD Grown, 12C Isotopically Purified | 99.99% | Host lattice purity |
| Annealing Temperature 1 | 800 | °C | 8 hours duration |
| Annealing Temperature 2 | 1000 | °C | 10 hours duration |
| Bias Magnetic Field (Bext) | ~45 | G | Aligned with NVA axis |
| NVA T2 Coherence Time | 49.7 ± 4.5 | ”s | Measured spin lifetime |
| NVA T2* Dephasing Time | 7.2 ± 0.5 | ”s | Measured spin lifetime |
| NVB T2* Dephasing Time | 2.1 ± 0.2 | ”s | Measured spin lifetime |
| Single HH Rabi Frequency (ΩA) | 7.66 ± 0.1 | MHz | SHH matching condition |
| Double HH Rabi Frequency (ΩA) | 10.51 ± 0.1 | MHz | DHH matching condition |
| Polarization Transfer Rate (SHH) | 119 ± 10 | kHz | Measured via Spin-Lock coherence loss |
| Polarization Transfer Rate (DHH) | 73 ± 10 | kHz | Measured via Spin-Lock coherence loss |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a home-built NV-diamond confocal microscope setup combined with precise microwave control to manipulate the NV spin qutrits.
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Sample Fabrication:
- A CVD-grown, 12C isotopically purified diamond substrate was used.
- Strongly-coupled NV pairs were created via 6 keV 28N molecular ion implantation at a dosage of 1 x 109 cm-2.
- The sample underwent two high-temperature annealing steps (800 °C for 8 h, followed by 1000 °C for 10 h) to enhance N-to-NV conversion.
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Microwave Control System:
- Microwave signals were generated using an arbitrary waveform generator (AWG) and an IQ mixer for phase and amplitude modulation.
- Signals were amplified and delivered to the NV spins via a gold coplanar waveguide fabricated on a glass cover-slip mounted directly on the diamond.
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Bare Coupling Measurement (DEER):
- The intrinsic dipolar coupling (Vdip) was measured using a Double Electron-Electron Resonance (DEER) pulse sequence.
- Measurements were performed in both the Single Quantum (SQ: |0> â |±1>) and Double Quantum (DQ: |+1> â |-1>) bases of the sensor spin (NVA) to confirm Vdip = 0.250 MHz.
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Dressed State Generation:
- The control spin (NVB) was driven simultaneously by two resonant Rabi fields (Ω+ and Ω-) corresponding to the |0> â |+1> and |0> â |-1> transitions, creating a doubly-dressed state.
- The effective coupling Veff was tuned by adjusting the ratio of the Rabi frequencies (α = (Ω+2 - Ω-2) / (Ω+2 + Ω-2)).
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Veff Spectroscopy (Ramsey):
- The change in Veff was detected by performing Ramsey spectroscopy on the sensor spin (NVA) in the DQ basis while NVB was prepared in various dressed states (varying α).
- Fast Fourier Transformation (FFT) of the Ramsey signal revealed the modulation frequency, which corresponds to the effective coupling strength.
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Interaction Dynamics (Spin-Lock Transfer):
- Spin polarization transfer was measured using a spin-lock (SL) pulse sequence under Hartmann-Hahn (HH) matching conditions.
- The transfer rate was measured for both Singly-Dressed HH (SHH) and Doubly-Dressed HH (DHH) conditions by matching the NVA Rabi frequency to the effective energy splitting of the dressed NVB state.
Commercial Applications
Section titled âCommercial ApplicationsâThe deterministic control of spin-spin interactions is foundational for advanced quantum technologies, particularly those relying on solid-state spin ensembles.
| Industry/Application | Relevance of Dressed-State Control |
|---|---|
| Quantum Sensing (Metrology) | Enables the generation of multi-spin correlated states (e.g., GHZ states) with high fidelity, leading to enhanced sensitivity beyond the standard quantum limit. |
| Quantum Simulation | Allows deterministic engineering of the NV-NV coupling dynamics and local disorder amplitude, crucial for studying non-equilibrium phases (e.g., Discrete Time Crystals) and complex many-body physics. |
| Quantum Computing (Qudit Systems) | Provides a robust method for controlling interaction gates between fixed-location spin qutrits (S=1 systems), overcoming challenges related to stochastic defect placement. |
| Solid-State Qubit Engineering | Reduces the variation in spin-spin coupling strengths across an ensemble, leading to more uniform system behavior and extended spin entanglement lifetimes. |
| Spin Bath Noise Mitigation | The scheme can be used to suppress interactions between the central NV spin and off-axis NV bath spins, improving the overall coherence time (T2) of the sensor. |
View Original Abstract
Abstract Strong interactions between defect spins in many-body solid-state quantum systems are a crucial resource for exploring non-classical states. However, they face the key challenge of controlling interactions between the defect spins, since they are spatially fixed inside the host lattice. In this work, we present a dressed state approach to control the effective dipolar coupling between solid-state spins and demonstrate this scheme experimentally using two strongly-coupled nitrogen vacancy (NV) centers in diamond. Through Ramsey spectroscopy on the sensor spin, we detect the change of the effective dipolar field generated by the control spin prepared in different dressed states. To observe the change of interaction dynamics, we deploy spin-lock-based polarization transfer measurements between the two NV spins in different dressed states. This scheme allows us to control the distribution of interaction strengths in strongly interacting spin systems, which can be a valuable tool for generating multi-spin correlated states for quantum-enhanced sensing.