Quantum technology is flourishing, revolutionizing humanity's ability to acquire, transmit, and process information, and heralding a new era in information technology. The newly released national 15th Five-Year Plan proposal also specifically calls for the strategic development of future industries, including quantum technology, to foster new economic growth drivers. Amid the ongoing global quantum race, Hong Kong's scientific research is tangibly contributing to the nation's related development efforts.
The newly established Chinese University of Hong Kong (CUHK) State Key Laboratory of Quantum Information Technology and Materials focuses on the development of diamond quantum sensing technology. Professor Liu Renbao, Director of the laboratory, told Wen Wei Po in an exclusive interview that the research team leverages the study of nanodiamonds. Utilizing the stability of their atomic structure and specific "color centre" defects within them, they maintain the extremely sensitive quantum spin properties responsive to magnetic fields. This has successfully enabled the quantum probes to achieve a sensitivity ten thousand times that of traditional probes, potentially significantly advancing precision measurement capabilities in areas like life sciences and energy materials.
Approved by the Ministry of Science and Technology, the former state key laboratories located in Hong Kong were reorganized into 15 national key laboratories in July this year. The CUHK State Key Laboratory of Quantum Information Technology and Materials is one of three newly established laboratories, aimed at addressing the nation's latest major strategic needs and targeting the frontiers of world science and technology.
This laboratory focuses on multiple quantum technology fields, including diamond quantum sensing technology and its applications in condensed matter physics, biology, and the development of energy materials and devices. It will also utilize novel quantum interferometers for high-precision quantum metrology; combine research on new superconducting materials to explore quantum material systems for quantum information processing; and develop integrated photonic devices for applications in optical quantum computing, quantum communication, quantum sensing, and neuromorphic computing.
Professor Liu particularly highlighted a very significant breakthrough in quantum sensing applications achieved by the laboratory in recent years: the proposal of "quantum nonlinear spectroscopy." Furthermore, it employs nanodiamonds as quantum probes, replacing traditional probes to extract information from the environment more efficiently and sensitively.
Quantum probes primarily utilize the property of quantum superposition, which allows a quantum system to exist in multiple possible states simultaneously until it is observed. However, quantum systems generally require ultra-low temperature environments and are highly susceptible to interference and collapse. The "colour centre" structure, considered an impurity in diamonds, can be particularly useful here.
Professor Liu explained that the carbon atomic structure of nanodiamond crystals provides stability, making them almost immune to external environmental influences and allowing them to maintain good quantum properties even at room temperature. By replacing two adjacent carbon atoms in the centre with one nitrogen atom and one vacancy, creating a "nitrogen-vacancy (NV) colour centre," a special quantum system is formed, known in physics as a quantum spin. "Essentially, it's a very tiny magnetic needle, the smallest unit of magnetism," he said. When the surrounding magnetic field changes even slightly, this magnetic needle can rotate many, many times, demonstrating extreme sensitivity. By simply observing the angle of rotation, the magnitude of the magnetic field can be rapidly detected.
Laser can read magnetic field changes at quantum level
He mentioned that the widely used Magnetic Resonance Imaging (MRI) technology also applies the principle of quantum spin magnetic fields. However, reading the signals requires trillions of such magnetic needles to generate a detectable signal via coils. In contrast, the new quantum diamond probe technology uses lasers to read magnetic field changes at the quantum level, vastly surpassing previous frameworks in precision measurement.
Using medical imaging as an example, Professor Liu stated that with the new high-sensitivity quantum probe technology, existing centimetre or millimetre-scale measurements could potentially advance to the single-molecule or single-cell level. It might even be possible to measure the weak magnetic signals generated by the brain during thought. By analyzing these signals and combining them with computational techniques, internal brain electrical activity could be visualized, obtaining finer brain maps to understand the active patterns and functions of different brain regions, thereby enabling deeper research into the brain's operational mechanisms. He described this as something unimaginable in the past, which is now gradually becoming a reality.
In temperature measurement, the team has also achieved a ten-thousand-fold increase in sensitivity. Professor Liu said that compared to typical scientific environments capable of detecting a one-degree change per second, "the sensitivity of our quantum probe can roughly detect a change of one ten-thousandth of a degree within one second, and the probe's volume is only a few hundred nanometres, making it one of the best measurements globally."
Furthermore, the laboratory team has also managed to perform quantum measurement and control in environments up to 1,100°C. Its unique advantage in high-temperature quantum research is also leading globally among similar detection methods.
(Source: Wen Wei Po; Journalist: Luk Nga-nam; English Editor: Darius)
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