Many measurements are limited by standard quantum limits (SQL). SQL is defined as the measured noise level set by quantum mechanics. Quantum entanglement can be used to defeat SQL and approach the ultimate limit called the Heisenberg limit (HL). Sub-SQL measurements are implemented on many systems under extreme conditions, and the sensors in these systems are not suitable for realistic measurements under ambient conditions.
The nitrogen vacancy (NV) center of diamond can be used as a sensor for electron and nuclear magnetic resonance.They can work with Environmental condition To protect the solid crystal lattice. The entire sub-SQL measurement process based on a single NV center includes NV spin initialization and entanglement. Ambient conditions, Physical quantity detection, and reading of results. There was a problem with NV initialization and entanglement.
A research team led by Professor Du Jiangfeng of the University of Science and Technology of China (USTC) at the University of Science and Technology of China (USTC) uses the NV Center of Diamonds to achieve sub-SQL measurements under ambient conditions and uses intertwined sensors. It will defeat SQL and provide more accurate measurements.This study was published in Science Advances..
Researchers have applied real-time feedback technology to initialize spins to a high-purity state, faithfully achieving NV-charged states, electron spins, and joint initialization of two nuclear spins.
They replaced the squared pulsed laser with a chopped laser sequence for polarization of electron spins and improved the corresponding laser fidelity from 90% to 97.7%.
In addition, the researchers optimized the experimental setup to better control the experimental conditions. Sophisticated configuration for thermal separation and appropriate proportional integral differential (PID) parameters for feedback provide a very stable magnetic field with relatively low temperature fluctuations of 0.5 mK during the experiment and 1 ppm volatile. Realized.
This research opens new perspectives in the study of solid-state spin systems and lays the foundation for quantum sensing and computing.
Tianyu Xie et al breaks standard quantum limits under ambient conditions with solid-state spins, Science Advances (2021). DOI: 10.1126 / sciadv.abg9204
Chinese Academy of Sciences
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Measurements beyond the standard quantum limit achieved at the center of a diamond’s nitrogen vacancy
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