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U.S. Researchers Discover Quantum Sensor That Can Detect Any Electromagnetic Pulse

Image credits: web.mit.edu

Researchers at the Massachusetts Institute of Technology (MIT) have developed a method that allows them to measure nanometer-scale features at any arbitrary frequency. Precision measurements in materials science and fundamental physics have been made possible by quantum sensors, which detect the most minute variations in magnetic or electrical fields. However, these sensors can only detect a few specific frequencies of these fields, limiting their utility.

Quantum sensors can take a variety of shapes; fundamentally, they are systems in which some particles are in such a delicately balanced condition that they are impacted by even minute alterations in the fields to which they are exposed.

It can characterise the distribution of the field [generated by the antenna] with nanoscale resolution, so it’s very promising in that direction.

– Guoqing Wang, Professor of Nuclear Science and Engineering, Massachusetts Institute of Technology

Professor Wang added that this system could be used, for example, to characterise in detail the performance of a microwave antenna. These can take the form of neutral atoms, trapped ions, and solid-state spins, and research utilising these types of sensors has expanded significantly.

The new system that the team made, which they call a “quantum mixer,” uses a beam of microwaves to add a second frequency to the detector. This changes the frequency of the field being studied into a different frequency.

This simple process lets the detector home in on any frequency it wants, and it doesn’t change the sensor’s ability to see things on a nanoscale. This simple procedure allows the detector to zero in on any desired frequency while maintaining the sensor’s nanoscale spatial resolution. Because it can make a variety of frequencies of electrical or magnetic activity accessible at the level of a single cell, the technology may enable new biomedical applications.

Using present quantum sensing technologies, it would be exceedingly difficult to get a usable resolution for such signals. Using this method, it may be able to identify output signals from a single neuron in response to a stimulus. The new system could potentially be used to characterise the behaviour of exotic materials, such as 2D materials, whose electromagnetic, optical, and physical properties are being intensively researched.

In ongoing research, the team investigates the idea of expanding the system to simultaneously explore many frequencies, as opposed to the current system’s single frequency targeting. Using more potent quantum sensing devices at Lincoln Laboratory, where several members of the research team are located, the researchers will also continue to define the system’s capabilities.

Furthermore, during the experiments, the team used a specific device based on an array of nitrogen-vacancy centres in diamond, which is a widely used quantum sensing system. Using a qubit detector with a frequency of 2.2 gigahertz, they were able to detect a signal with a frequency of 150 megahertz, which would not have been possible without the quantum multiplexer. Then, they did detailed analyses of the process by building a theoretical framework based on Floquet theory and doing a series of experiments to test the theory’s numerical predictions.

There are other ways to change how sensitive some quantum sensors are to frequency, but they require using large devices and strong magnetic fields that blur the fine details and make it impossible to get the very high resolution that the new system offers.

Wang says that in modern systems like these, “you need to use a strong magnetic field to tune the sensor, but that magnetic field can break the quantum material properties, which can change the phenomenon you want to measure.”

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