Quantum Microwave Parametric Interferometer
Fabian Kronowetter, Florian Fesquet, Michael Renger, Kedar Honasoge, Y. Nojiri, K. Inomata, Yasunobu Nakamura, Achim Marx, R. Gross, Kirill G. Fedorov · Physical Review Applied · 2023
Interferometers are extremely powerful tools for precision measurements in a plethora of research fields and applications, such as the detection of gravitational waves. The authors present experimental realization of a nonlinear microwave interferometer based on superconducting quantum circuits. Useful properties of this device range from a signal-to-noise ratio that exceeds the shot-noise limit, to sub-Poissonian intensity fluctuations between its outputs. These intriguing findings will promote applications ranging from quantum illumination to the search for axionic dark matter.