Quantum sensors for electromagnetic signals of any frequency

A team of researchers led by ISN-affiliated MIT faculty member Paola Cappelaro and an MIT Lincoln Laboratory scientist Dr. Danielle Braje, working on research funded through the ISN by DARPA, has developed a new process that allows quantum sensors to detect electromagnetic signals of any frequency. Unlike previous methods, which detect tiny variations in the highly specific EM fields to which they are exposed, this new technique retains these sensors’ extraordinary sensitivity but vastly expands the range of frequencies they can perceive. Future work may address the system’s inability to detect more than one frequency at a time, imparting the ability to sense multiple frequencies simultaneously.
An experimental setup on a laser table

MIT researchers have developed a method to enable quantum sensors to detect any arbitrary frequency, with no loss of their ability to measure nanometer-scale features. Quantum sensors detect the most minute variations in magnetic or electrical fields, but until now they have only been capable of detecting a few specific frequencies, limiting their usefulness. Image: Guoqing Wang

Scientific charts labeled "Quantum frequency mixing," and "Electron spin resonance (Rabi sensing)"

(a) Quantum frequency mixing schematic. The effective Hamiltonian (red) emerges from the frequency mixing of the signal (purple) and bias (green) Hamiltonians. The effective Hamiltonian frequency πœ”π‘‡ can be probed experimentally. (b) Electron spin resonance (ESR) experiment to probe πœ”π‘‡ using an ensemble of NV centers. We sweep the bias field frequency πœ”π‘ to detect the presence of a signal field at πœ”π‘ =(2β’πœ‹)⁒150  MHz, which is not in the accessible range of typical sensing methods. We observe a resonance when the down-converted frequency πœ”π‘‡ =Β±(πœ”π‘  βˆ’πœ”π‘) matches the probing drive amplitude at Ξ©=(2β’πœ‹)⁒3  MHz.