High-fidelity single-shot readout of single electron spin in diamond with spin-to-charge conversion
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-03-09 |
| Journal | Nature Communications |
| Authors | Qi Zhang, Yuhang Guo, Wentao Ji, Mengqi Wang, Jun Yin |
| Institutions | CAS Key Laboratory of Urban Pollutant Conversion, University of Science and Technology of China |
| Citations | 60 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- High-Fidelity Readout Achieved: A single-shot readout fidelity of 95.4 ± 0.2% was achieved for a single electron spin in a Nitrogen-Vacancy (NV) center in diamond, significantly exceeding the 79.6% fidelity of standard resonance fluorescence under the same high-strain conditions.
- Spin-to-Charge Conversion (SCC) Mechanism: The method leverages SCC, where the electron spin state |0> (NV-) is selectively excited and then rapidly photo-ionized to the neutral charge state (NV0) using a Near-Infrared (NIR, 1064 nm) laser.
- Error Suppression: The use of NIR light enhances the ionization rate (Îion) relative to the intrinsic spin-flip relaxation rate (Îflip = 0.75 MHz), thereby suppressing the primary source of readout error.
- Charge State Stability: The subsequent charge state readout (NV- vs. NV0) demonstrated near-unity non-demolition fidelity of 99.96 ± 0.02% due to the stability of the charge states under optical illumination.
- Auxiliary Correction: An auxiliary microwave pulse sequence was implemented to rescue population leaked to the ms = -1 auxiliary state, further boosting the SCC efficiency.
- Fault-Tolerant Potential: The technique is scalable and projected to achieve readout fidelity exceeding the 99.9% fault-tolerant threshold by increasing the NIR power or utilizing NV centers with naturally lower intrinsic strain (and thus lower Îflip).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Average Single-Shot Readout Fidelity (SCC) | 95.4 ± 0.2 | % | Achieved using SCC with Auxiliary Correction. |
| Charge Readout Fidelity (Non-demolition) | 99.96 ± 0.02 | % | Average fidelity for distinguishing NV- vs. NV0. |
| Spin-Flip Rate (Îflip) | 0.75 ± 0.02 | MHz | Observed rate in the high-strain NV center used. |
| Maximum Ionization Rate (Îion) | 2.79 ± 0.08 | MHz | Highest rate achieved with current CW NIR laser power. |
| Ionization Rate Coefficient | 67.0 ± 6.7 | kHz/mW | Dependence of Îion on NIR laser power (1064 nm). |
| Operating Temperature | 8 | K | Cryogenic environment. |
| Non-Axial Strain (ÎŽ) | 5.9 | GHz | Strain introduced by the solid immersion lens fabrication. |
| Optimal SCC Duration | ~10 | ”s | Total time for the spin-to-charge conversion sequence. |
| Resonance Fluorescence Fidelity (Comparison) | 79.6 ± 0.8 | % | Fidelity of standard method under tested conditions. |
| NIR Wavelength | 1064 | nm | Near-Infrared light used for photo-ionization. |
Key Methodologies
Section titled âKey Methodologiesâ- Cryogenic Platform: Experiments were performed on a bulk NV center housed within a solid immersion lens (SIL) at a cryogenic temperature of 8 K to ensure high spin-selectivity of the resonance excitation transitions (Ey and E1,2).
- Spin Initialization: The NV center was initialized to the NV- charge state using a 532 nm laser pulse. The electron spin was initialized to the |0> state using the E1,2 transition.
- Spin-to-Charge Conversion (SCC): The spin state |0> was selectively excited via the Ey cycling transition. Simultaneously, a 1064 nm NIR laser was applied to photo-ionize the excited state (NV-* â NV0). The rapid ionization process ensures the conversion occurs before spin-flip relaxation (Îflip) can interrupt the cycle.
- Auxiliary Correction Sequence: To mitigate leakage errors, an auxiliary correction (AUX Corr.) sequence was implemented. This involved using a microwave pulse (MWAUX Ï pulse) to transfer population that had leaked into the auxiliary state (ms = -1) back into the |0> state, allowing it to be successfully ionized in subsequent SCC rounds.
- Charge Readout: The final charge state (NV- or NV0) was determined by measuring the collected fluorescence photon counts. NV- is âbrightâ under Ey/E1,2 excitation, while NV0 is âdark,â providing a robust, non-demolition readout mechanism.
- Fidelity Evaluation: Readout fidelity was evaluated by measuring the correlation between two consecutive readouts and analyzing the statistical distribution of photon counts for the initialized |0> and |1> states.
Commercial Applications
Section titled âCommercial Applicationsâ- Fault-Tolerant Quantum Computing: The achieved high fidelity (95.4%) and the projected capability to exceed the 99.9% fault-tolerant threshold make this technique essential for building scalable, error-corrected quantum processors based on solid-state spins.
- Quantum Networks and Communication: High-fidelity, fast single-shot readout is a crucial component for deterministic entanglement generation and delivery over long distances in quantum communication architectures.
- Integrated Quantum Devices: The SCC scheme is compatible with integrated optoelectronic devices, enabling the development of compact, diamond-based quantum chips and sensors.
- High-Sensitivity Quantum Sensing: Provides a robust, all-optical readout method for NV-based quantum sensors. The use of NIR light minimizes photo-damage, making it particularly suitable for:
- Bio-Sensing: NIR light is less disruptive to biological samples compared to visible light, enabling high-efficiency quantum sensing in biological environments (e.g., single-protein spin resonance spectroscopy).
- Hybrid Quantum Systems: The method supports projective readout of weakly coupled nuclear spins (which serve as robust quantum memories) even though the electron spin readout is destructive (demolition).