Guo Guangchan and Sun Fangzhian's team at CSU achieve quantum-enhanced microwave ranging

Recently, the team of academician Guangcan Guo at the University of Science and Technology of China has made important progress in practical quantum sensing research. Prof. Sun Fangstean's research group uses micro and nano quantum sensing with local enhancement of electromagnetic fields at deep sub-wavelengths to study the detection and radio ranging of microwave signals to achieve 10-4 wavelength accuracy for localization. The results were published in the internationally recognized journal Nature Communications on March 9.

Radar localization technology based on microwave signal measurement is widely used in activities such as autonomous driving, intelligent production, health inspection, and geological exploration. Especially in the current trend of intelligence and information development, the development of high-performance radar ranging technology is of great significance for both national defense security and economic development.

The development of quantum information technology provides a new solution for the development of radar technology. Quantum sensing and precision measurement use quantum coherence, correlation and other characteristics to enhance the sensitivity of the system to measure physical quantities, which is expected to surpass the accuracy of traditional measurement means.

Facing the practicalization of quantum information technology, Fangsteun Sun's research group has been studying quantum sensing technology for solid-state spin systems for a long time. We have developed a charge-state depletion nano-imaging method to realize super-diffraction limit-resolution electromagnetic field vector sensing and imaging based on diamond nitrogen-vacancy color centers (Phys. Rev. Applied 12, 044039 (2019)), and explored the phenomenon of local enhancement of electromagnetic field in 10-6 wavelength space using super-resolution quantum sensing (Nat. Commun. 12, 6389 (2021)).

In this study, the research group combines quantum sensing in the solid-state regime with micro- and nano-resolution and deep subwavelength localization of electromagnetic fields to develop high-sensitivity microwave detection and high-precision microwave localization techniques.

Results of solid-state spin on object position measurement.

The research group designed a composite microwave antenna composed of diamond spin quantum sensors and metal nanostructures to collect and converge the microwave signals propagating in free space into nanospace, thus measuring the microwave signals by probing the state of solid-state quantum probes in the local domain. The method converts the detection of weak signals in free space into the detection of electromagnetic field interactions with solid-state spins at the nanoscale, improving the sensitivity of microwave signal measurement by solid-state quantum sensors by 3-4 orders of magnitude.

In order to further utilize the high sensitivity microwave detection to achieve high-precision microwave localization, the research group built a microwave interferometry device based on the diamond quantum sensor, and obtained the phase of the reflected microwave signal and the position information of the object through the solid-state spin detection of the interference result between the reflected microwave signal and the reference signal. At the same time, the research group achieved quantum-enhanced position measurement accuracy to the level of 10 microns (about one ten-thousandth of a wavelength) by using solid-state spin quantum probes to interact coherently with microwave photons multiple times.

The reviewers consider this work to be the first application of diamond quantum sensors in quantum ranging (...To my knowledge, this is a first demonstration of quantum ranging platform, based on NV center ...).

Compared with conventional radar systems, this quantum measurement method eliminates the need for active devices such as amplifiers at the detection end, reducing the influence of factors such as electronic noise on the measurement limits. The subsequent research will allow further improvement of the radio localization accuracy, sampling rate and other indexes based on solid-state spin quantum sensing, and the development of practical solid-state quantum radar localization technology that exceeds the performance level of existing radars.