Direct characterization of coherence of quantum detectors by sequential measurements

The quantum properties of measurements are indispensable resources in information processing and have drawn extensive research interest. conventional approach to reveal the relies on reconstruction entire measurement operators by detector tomography. However, many specific can be determined a part matrix entries operators, which provides us possibility simplify process property characterization. Here, we propose general framework directly obtain individual sequentially measuring two non-compatible observables. This method allows circumvent complete tomography extract useful for our purpose. We experimentally implement this scheme monitor coherent evolution determining off-diagonal entries. investigation precision indicates good feasibility protocol arbitrary measurements. Our results pave way revealing selectively operators.