High-precision tests of bound-state quantum electrodynamics (BS-QED) in strong fields can be performed using highly charged ions (HCI). In such systems, only the innermost electrons remain, experiencing the strong fields emanating from the nucleus. The Alphatrap experiment is a cryogenic Penning-trap setup which performs strong-field QED tests via the measurement of the bound electron g-factor. This is done non-destructively, using the continuous Stern-Gerlach effect. Recently, we measured the g factor of hydrogen-like tin to sub parts-per-billion precision, which was ionized within the Heidelberg electron beam ion trap (EBIT). Our ultimate aim is to perform such tests in the heaviest HCI, 208Pb81+ and beyond. Since the ionization energy of 208Pb81+ is around 100 keV, a new EBIT, called the “Hyper-EBIT” is being constructed at Max-Planck-Institut für Kernphysik, which will operate at beam energies of up to 300 keV and 500 mA of beam current. The recent developments of Hyper-EBIT will be outlined in the talk.
The second part will focus on the generation of entangled photons and subsequent verification of CHSH inequality. Entangled biphotons are one of the building blocks for quantum-assisted technologies. Realizing a reliable and practical single-photon source is a prerequisite from the application perspective. The project aims at generating entangled photon pairs in the polarization degree of freedom. This is made possible with spontaneous parametric down-conversion, which is a second-order, non-linear optical process that is achievable in bulk systems. A beta barium borate (BBO) crystal is pumped with 405 nm photons, which get down-converted into two 810 nm signal and idler photons. Since type II down conversion is employed, the entangled photons are formed at the intersection points of two overlapping cones which are then imaged using an electron multiplying charge coupled device (EMCCD) camera and analysed using a high-resolution spectrometer. The violation of Bell’s theorem is also verified using CHSH inequality.
