Quantum sensors, which detect most minute differences in magnetic or electric fields, have enabled precise measurements in materials science and fundamental physics. But these sensors were only able to detect a few specific frequencies of these fields, which limits their usefulness. Now, researchers at MIT have developed a way to enable these sensors to detect any random frequency, without losing their ability to measure nanometer-scale features.
The new way the team is already introducing Patent Protectionin the magazine X . physical reviewin a paper written by graduate student Guoqing Wang, Professor of Nuclear Science, Engineering and Physics Paula Capellaro, and four others at MIT and Lincoln Laboratory.
Quantum sensors can take many forms; They are essentially systems in which some particles are in such a finely balanced state that they are affected by even small differences in the fields to which they are exposed. These can take the form of neutral atoms, trapped ions, and solid-state spins, and research using such sensors has grown rapidly. For example, physicists use them to explore exotic states of matter, including so-called time crystals and topological phases, while other researchers use them to characterize practical devices such as experimental quantum memory or computational devices. But many other phenomena of importance span a much wider range repeat Today’s range Quantum Sensors can be detected.
The new system the team devised, which they call a quantum mixer, injects a second frequency into the detector using a beam of microwaves. This converts the frequency of the field being studied to a different frequency – the difference between the original frequency and the frequency of the added signal – which is tuned to the specific frequency to which the detector is most sensitive. This simple process enables the detector to revert to absolutely any desired frequency, with no loss of spatial resolution at the nanoscale of the sensor.
In their experiments, the team used a specific device based on an array of nitrogen vacancy centers in diamond, a widely used quantum sensing system, and successfully demonstrated detection of a 150MHz signal, using a 2.2GHz qubit detector—a detection that would be impossible without a multiplexer. Quantitative. Then they made detailed analyzes of the process by deriving a Theoretical frameworkbased on Flockett’s theory, and testing the numerical predictions of that theory in a series of experiments.
While their tests used this specific system, says Wang, “the same principle can also be applied to any type of sensor or quantum device.” The system will be self-contained, the detector and the second frequency source are assembled into one device.
Wang says that this system can be used, for example, to characterize the performance of a microwave antenna in detail. Can distinguish the field distribution [generated by the antenna] With nanoscale accuracy, so it’s very promising in that direction.”
There are other ways to change the frequency sensitivity of some quantum sensors, but they require the use of large devices and strong magnetic fields Blurs fine detail and makes it impossible to achieve the ultra-high resolution offered by the new system. In such systems today, Wang says, “you need to use a strong magnetic field to tune the sensor, but this magnetic field can break the properties of quantum materials, which can affect the phenomena you want to measure.”
The system may open up new applications in biomedical fields, according to Capellaro, because it can give access to a range of frequencies of electrical or magnetic activity at the level of a single cell. It would be very difficult to obtain useful accuracy for such signals using current quantum sensing systems, she says. It might be possible to use this system to detect output signals from a single neuron in response to some stimulus, for example, which typically include a large amount of noise, making these signals difficult to isolate.
The system can also be used to describe in detail the behavior of exotic materials such as 2D materials that are extensively studied for their electromagnetic, optical and physical properties.
In the work in progress, the team is exploring the possibility of finding ways to extend the system to be able to examine a range of frequencies simultaneously, rather than targeting the single frequency of the existing system. They will also continue to determine the capabilities of the system using more powerful quantum sensors at Lincoln Laboratory, where some members of the research team are.
Guoqing Wang et al, Sensing of arbitrary frequency domains using a quantum mixer, X . physical review (2022). DOI: 10.1103/ PhysRevX.12.021061
Massachusetts Institute of Technology
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