The first universal quantum control of zero magnetic field NMR and its fidelity evaluation
Release date: 2018-06-26
The Key Laboratory of Micro-Magnetic Resonance of the Chinese Academy of Sciences, led by Du Jiangfeng, a member of the Chinese Academy of Sciences and professor of the University of Science and Technology of China, has made new progress in zero-magnetic magnetic resonance. The laboratory professor Peng Xinhua and the Helmholtz Institute of Germany, Waterloo, Canada University cooperation, for the first time, achieved universal quantum control of the zero-magnetic nuclear spin system and developed methods for evaluating quantum control and quantum states, which is expected to promote zero-magnetic magnetic resonance in the fields of biology, medicine, chemistry, and basic physics. In the application. The research work was titled "Experimental Benchmarking of Quantum Control in Zero-field Nuclear Magnetic Resonance", published in the June 15th issue of Science Progress [Science Advances 4, eaar 6327 (2018)].
Zero-field magnetic resonance is a new field that is rapidly developing. It has many outstanding advantages, such as eliminating the dependence of traditional nuclear magnetic resonance on superconducting magnets, high-resolution spectroscopy, and rich spin dynamics. However, zero magnetic field NMR faces many difficulties: First, under zero magnetic field, the frequency of nuclear magnetic resonance signals is usually less than 1 kHz. The traditional NMR induction detection method is completely ineffective, and it is very difficult to detect zero magnetic field NMR signals. Secondly, Zero-field magnetic resonance NMR Because the ramo precession frequency of different nuclear spins is zero, it is impossible to use selective pulses for manipulation. How to achieve universal quantum control is an urgent problem to be solved.
In the experiment, the extremely weak NMR signal under zero magnetic field was measured using an extremely sensitive atomic magnetometer as a detector with a sensitivity of 10 fT/√Hz. The detector and the sample are placed in a shielding barrel with a magnetic field of less than 0.1 nT (10-10 T). The small magnetic field signal generated by the sample can also be captured by the atomic magnetometer, which can achieve nuclear spin under zero magnetic field. Precision measurement of the system. Based on this powerful detection method, the research team measured the isotope-labeled liquid formic acid molecule, and observed that the formic acid molecule had a relaxation time (T2) of 10.3 seconds and a spectral resolution of 32 mHz in a zero magnetic field environment. The experimental results exceed the spectral resolution of traditional nuclear magnetic resonance, demonstrating the high-resolution spectroscopy achieved by zero-magnetic NMR, and high-resolution spectroscopy has important applications in biology, medicine, and chemistry.
The research team realized the universal quantum control of zero magnetic field NMR by using the well-designed combined pulse to realize the single-bit gate and multi-bit gate of the nuclear spin. At the same time, the method of evaluating the fidelity of quantum control was developed. The quality was evaluated and the fidelity of manipulation was as high as 99%. Based on the quantum control technology developed by this work, the selective measurement of the interaction between different spins can be realized, and the selected anti-symmetric spin interaction can be used to test the parity non-conservation law of the molecule. The possibility of applying zero magnetic field NMR to basic physics research. In addition, the development and implementation of universal quantum control technology is expected to promote the application of zero magnetic field NMR in biology, medicine and chemistry.
Jiang Min, a Ph.D. student at the Micro-Magnetic Resonance Key Laboratory of the Chinese Academy of Sciences, and Wu Teng of the Helmholtz Institute in Germany, are co-first authors. The work was funded by the Ministry of Science and Technology, the National Natural Science Foundation of China, the Chinese Academy of Sciences, the Ministry of Education, and Anhui Province.
The left picture shows the zero magnetic field NMR spectrometer designed for this work; the right picture shows the NMR sample has a longer relaxation time in a zero magnetic field environment.
Source: University of Science and Technology of China
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