Microwave Single Photon Detection using Superconducting Circuits

Abstract

The field of quantum optics at microwave frequencies using superconducting circuits has progressed tremendously in the last 10 years. The availability of a non-dissipative, nonlinear element like the Josephson junction combined with the ability to lithographically define structures for microwave propagation has pushed this field into new regimes previously impossible with optical light. The detection at optical frequencies is typically done using photon detectors whereas the natural detector at microwave frequencies is linear amplifiers. Since the type of detection has a direct impact on the quantum state is observed, it is important to choose the right kind of detection technique for the particular application. Due to the low energy of the microwave photon, it makes it challenging to detect it. In this project, we reviewed the available technologies for single-photon detection and studied different types of microwave photon detection protocols based on their pros and cons. We then tried to design a single qubit and four qubit architecture after simulating the respective systems on COMSOL and Microwave Office. We also performed two-tone spectroscopy to measure qubit’s resonant frequency and anharmonicity. We further measured relaxation times and dephasing times and found them to be very low than expected.