Recently, MIT researchers have developed a method to enable quantum sensors to detect any frequency and still have the ability to measure at the nano scale< Img alt= "image from Massachusetts Institute of Technology (MIT)" style= "width:600px;" src=" https://imagecloud.thepaper.cn/thepaper/image/202/25/591.jpeg ">
the picture is from the Massachusetts Institute of Technology (MIT)
at present, the team has applied for patent protection for the new method. Through this method, the ability of ultra sensitive nano quantum detectors can be expanded, and can be potentially applied to the field of quantum computing and biosensor. The relevant results are published in Physical Review X. 
pictures from physical review x
it is reported that the quantum sensor is essentially a system in which some particles are in a delicate equilibrium state. Even if the field changes slightly, the state of the particles in the system will be affected. Quantum sensors can take many forms, such as neutral atoms, trapped ions and solid-state spins. The research using these sensors has also developed rapidly. For example, physicists use quantum sensors to study strange states of matter, including time crystals and topological phases. However, many physical phenomena of interest to scientists will still involve a large frequency range, which is beyond the detection range of existing quantum sensors< Br>
this time, a new system was designed by the team of Paola cappellaro, Professor of nuclear science and engineering and physics of Massachusetts Institute of technology, and the personnel of Lincoln Laboratory affiliated to the U.S. Department of defense. They call it a quantum mixer, which can also be called a quantum mixer. The mixer injects the second frequency into the detector through a beam of microwave. Through frequency conversion, the detector can locate any required frequency without losing the nano spatial resolution of the sensor< Br>
in the experiment, the research team used a special device based on the nitrogen vacancy color center array in diamond. Nitrogen vacancy color center (NV color center) is a common point defect in diamond crystal structure. It is formed by nitrogen atoms replacing carbon atoms and adjacent holes. Using its quantum paramagnetic resonance effect and fluorescence radiation characteristics in the magnetic field, it can be used for precise magnetic measurement and can be widely used in quantum sensing< Img alt= "(a) schematic diagram of quantum mixing, (b) electron spin resonance spectrometer is based on the detection results of nitrogen vacancy color center array in diamond. The picture is from the paper" style= "width:500px;" src=" https://imagecloud.thepaper.cn/thepaper/image/202/25/757.png ">
(a) schematic diagram of quantum mixing, (b) electron spin resonance spectrometer is based on the detection results of nitrogen vacancy color center array in diamond. The picture is from the paper
based on the above device, the team successfully demonstrated how to use a 2.2 GHz quantum bit detector to detect a signal with a frequency of 150 MHz. In the past, this could not be achieved without the help of quantum multiplexers. Then, by deriving a (Floquet) theory, the team made a detailed analysis of this process and tested the numerical prediction of this theory in a series of experiments. Flockey theory is a kind of ordinary differential equation theory< Br>
“the same principle can also be applied to any type of sensor or quantum device.” Wangguoqing, the first author of the paper and a graduate student of Massachusetts Institute of technology, said, “this system is independent. The detector and the second frequency source are encapsulated in one device.”< Br>
he said that the aforementioned system can be used to describe the performance of microwave antennas in detail. The transmitting or receiving antennas that work in meter wave, centimeter wave, millimeter wave and other wavebands are collectively referred to as microwave antennas. “The system can describe the distribution of fields (generated by microwave antennas) with nanometer resolution, so it is very promising in this field.”< Br>
although other methods can also change the frequency sensitivity of some quantum sensors, they are inseparable from large equipment and strong magnetic field. And these will just reduce the accuracy, unable to achieve the ultra-high resolution achieved by the new system. For example, the strong magnetic field used to adjust the sensor may destroy the properties of quantum materials, thus affecting the physical phenomena to be measured< Br>
cappellaro, a professor at MIT, said that the aforementioned system may have new applications in the biomedical field because it can obtain a series of frequency electrical and magnetic activities at the single cell level. “It is difficult to obtain useful resolution of such signals using existing quantum sensing systems.” However, the new system may be able to detect the output signals of a single neuron in response to certain stimuli, which usually contain a lot of noise, making it difficult to separate the output signals. The new system may also be used to describe the behavior of exotic materials in detail, such as the electromagnetic, optical and physical properties of two-dimensional materials< Br>
at present, the research team is exploring how to expand the new system so that it can detect a series of frequencies at the same time, rather than a single frequency. They will also continue to use the quantum sensing equipment of Lincoln Laboratory to further determine the capabilities of the new system.