Disentangling a quantum antiferromagnet with resonant inelastic X-ray   scattering
  Low-dimensional copper oxide lattices naturally manifest electronic states with strong short range quantum entanglement, which are known to lead to remarkable emergent material properties. However the nanometer scale many-body wavefunction is challenging to measure or manipulate in a simple way. In this study, X-ray induced $dd$ electronic transitions are used to suppress spin entanglement across a single lattice site in the spin-1/2 antiferromagnetic chain compound SrCuO$_2$, revealing a class of cuprate magnetic excitations that result from breaking the spin chain. These measurements are the first to employ two closely spaced X-ray resonances of copper (M$_2$ and M$_3$) as a form of natural 2-slit interferometer to distinguish between different types of electronic transition and resolve how they influence the dynamics of nearby spin-entangled electrons. 
L. Andrew Wray, Ignace Jarrige, Kazuhiko Ikeuchi, Kenji Ishii, Yuri   Shvyd'ko, Yuqi Xia, M. Zahid Hasan, Charles Mathy, Hir...
cond-mat.str-el