Interferometric measurement of nuclear resonant phase shift with a nanoscale Young double waveguide

TL;DR

This paper introduces a nanoscale x-ray interferometer inspired by Young's experiment to measure nuclear resonant phase shifts, enabling precise photon energy-resolved phase analysis near nuclear resonances.

Contribution

It demonstrates a novel nanoscale interferometric method for measuring nuclear resonant phase shifts using single-photon interference patterns and Bayesian inference.

Findings

Successfully measured phase shifts near 14.4 keV nuclear resonance.

Revealed microscopic coupling parameters inaccessible from intensity data alone.

Established a basis for integrated x-ray interferometric sensors.

Abstract

The phase shift of an electromagnetic wave, imprinted by its interaction with atomic scatterers, is a central quantity in optics and photonics. In particular, it encodes information about optical resonances and photon-matter interaction. While being a routine task in the optical regime, interferometric measurements of phase shifts in the x-ray frequency regime are notoriously challenging due to the short wavelengths and associated stability requirements. As a result, the methods demonstrated to date are unsuitable for nanoscopic systems. Here, we demonstrate a nanoscale interferometer, inspired by Young's double-slit experiment, to measure the dispersive phase shift due to the 14.4 keV nuclear resonance of the M\"ossbauer isotope $^{57}$Fe coupled to an x-ray waveguide. From the single-photon interference patterns, we precisely extract the phase shifts in the vicinity of the nuclear resonance resolved in photon energy by using Bayesian inference. We find that the combined information from phase shift and absorbance reveals microscopic coupling parameters, which are not accessible from the intensity data alone. The demonstrated principle lays a basis for integrated x-ray interferometric sensors.