X-ray quantum optics

Abstract

Abstract Quantum optics with X-rays has long been a somewhat exotic activity, but it is now rapidly becoming relevant as precision x-ray optics and novel X-ray light sources, and high-intensity lasers are becoming available. This article gives an overview of the current state of the field and an outlook to future prospects. Keywords: X-ray quantum opticsparametric down conversionsingle-photon superradiancecollective Lamb shiftcoherent controlEITresonance fluorescence Acknowledgements This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357, and by the Alliance Program of the Helmholtz Association (HA216/EMMI). Y.R. gratefully acknowledges the support from the UNT Research Initiation Grant and the summer fellowship UNT program. Notes 1. See author list for address. 2. Type-I ghost imaging uses entangled photons from a down-conversion source. 3. Wave-vector matching requires considerable detuning from the Bragg condition, and the beam that is reflected on the wing of the Bragg reflectivity curve aims between the detectors (see Figure 1). The detectors are exposed to a rather weak background of, mostly, Compton-scattered photons, which amount to a few thousand uncorrelated counts per second, despite the high incident flux of photons. The correlated PDC signal stands out clearly above that background. 4. Because the refractive index of matter to hard x-rays is slightly less than 1, total reflection at close to 100% occurs for x-rays hitting a smooth surface at grazing angles from the vacuum/air side. 5. For the sake of brevity, only nuclear excitations will be discussed here. 6. See 4. 7. It should be noted that this spiky structure can also be exploited in ultrafast spectroscopy Citation[228].