Gravitationally sensitive structured x-ray optics using nuclear resonances

Einstein's general theory of relativity not only revolutionized our understanding of the universe but also led to numerous gravitational applications on large spatial scales, such as gravitational-wave astronomy and the operation of the global positioning system. On Earth, the gravitational redshift has been experimentally observed over spatial scales ranging from a few millimeters to thousands of kilometers. However, finding an application of gravitational effects in a quantum system at small spatial extensions on Earth remains a challenge. Along this line, we introduce a structured x-ray waveguide that serves as an x-ray mode converter, and its performance is influenced by an altitude change in the order of millimeters or even microns. Our results suggest that the gravitational redshift can be another way to fine adjust the x-ray detuning for any devices using a nuclear clock transition.