https://www.selleckchem.com/products/VX-770.html We address the relation between quantum metrological resolution and quantum coherence. We develop a quantum version of the Wiener-Khintchine theorem for a suitable model of a quantum ruler, putting the contributions of the probe and measurement on equal footing. We illustrate this approach with several examples of linear metrology.A hydrogen sensor with high sensitivity was demonstrated by coating the metal organic frameworks of $\rmUiO\! -\! \rm66 \!-\! N\rmH_2$ on an optical fiber Mach-Zehnder interferometer (MZI). The MZI was made of a fiber mismatch structure by using a core-offset fusion splicing method. The effective refractive index of the $\rmUiO\! -\! \rm66\! -\! N\rmH_2$ film varied with the absorption and release of hydrogen, and the interference resonant dip wavelength and the intensity of the MZI changed with the variations of the concentration of hydrogen. The experimental results showed that the proposed sensor had a high hydrogen sensitivity of 8.78 dB/% in the range from 0% to 0.8%, which is almost seven times higher than the existing similar hydrogen sensor.We demonstrate a spectrum-continuous narrowband filter based on multi-section Mach-Zehnder interferometer (MZI) structures on a silicon nitride platform. Enhanced in-band flatness and sharp out-of-band roll-off features are achieved by cascading MZIs of specific functionalities in a series. This filter is fabricated in a single chip with a total waveguide length exceeding 237 cm. We experimentally demonstrate for the first time, to the best of our knowledge, a four-channel spectrum-continuous filter with a 3 dB bandwidth of 580 MHz, a 1 dB fluctuation bandwidth as high as 356 MHz, and an excellent 20 dB roll-off factor of 1.26 that are obtained simultaneously. Both the optical and electrical experimental results show that the proposed filter can play a key role in integrated microwave photonic front-end systems.Microresonator-based platforms with