Nuclei in the Mirror
In everyday life, mirrors are at first sight confusing: walking towards the mirror causes the image to step closer. We have shown that an x-ray mirror can significantly "confuse" an array of atomic nuclei used as x-ray storage device leading to single-photon entanglement of the incident and reflected directions. The retrieval of the stored single photons then occurs in a forwards-backwards quantum superposition with promising applications. X-rays are one of the most penetrating types of radiation, routinely used to medically image bones and internal tissue of the human body. Despite this, a solid-state sample of iron nuclei has been previously shown to potentially act as a nuclear memory for single x-ray photons. Under the short action of a mirror which is held behind such a memory and then quickly removed, the nuclear array looses track of which photon direction was involved in the storage process and is forced to memorize both. This leads to the release of the stored single photon in two counter-propagating entangled branches. The stored photon then forms a standing-wave pattern in the memory which is sensitive to nuclear positions and can be used to probe matter on the atomic scale. This novel protocol allows not only probing atomic vibrations but also controlling x-ray quanta for future quantum information on an extremely compact scale. Please see Phys. Rev. Lett. 112, 057401 (2014) for details.
