Positronium, as a simple leptonic system, allows to make precise bound-state QED predictions on its properties such as its lifetime. Second order loop corrections to the ortho-Positronium decay rate have been calculated, fixing the lifetime up to the 1ppm level [1]. In comparison to the state-of-the-art measurements [2][3], the theory is two orders of magnitude more precise. As the main...
Using known methods now significantly improvable because of recent advances in the input data, we obtain the currently most accurate calculation of the hyperfine splitting (HFS) in muonic hydrogen. The crucial part of the calculation is the hadronic or proton structure dependent two photon exchange correction, which is calculated in a data driven approach that uses the proton electromagnetic...
Precision measurements on calculable systems are widely used for tests of e.g. quantum electrodynamics (QED) calculations, determinations of some of the fundamental constants, and as sensitive probes to search for new physics beyond the standard model. In this context we perform high-precision spectroscopy on the doubly forbidden 2$^3$S$_1$ – 2$^1$S$_0$ transition at 1557nm in both $^3$He and...
Several experiments have been performed where cold atoms are being guided through hollow optical fibers. The potential acting on the atom comprises the repulsive potential from the light propagating within the fiber, and the Casimir-Polder potential induced by the vacuum fluctuations. Typically, the Casimir forces acting on atoms are approximated as ones with a flat surfaces — the so called...
The Bethe–Salpeter (BS) QED wave equation and its equal-time variant $[1, 2, 3]$ are considered for numerical precision computations. If only single-photon instantaneous Coulomb(–Breit) interactions are considered in the interaction kernel, then the equal-time BS equation simplifies to the with-pair Dirac–Coulomb(–Breit) wave equation. Mathematical properties and numerical results are...
Position dependent microwave transitions in Rydberg helium were driven to investigate anomalous systematic effects in the waveguide apparatus used to measure the n = 2 fine structure of positronium [1]. The Stark broadening of the resulting line shapes was used to map out stray electric fields [2] along the beam axis and characterize frequency shifts dependent on the microwave propagation...
The accurate computation of QED corrections to the energy levels of heavy atoms and molecules poses a significant challenge. At the one-loop level the corrections to the electron-nucleus interaction are the vacuum polarization and the electron self-energy. The leading-order (in $Z\alpha$) vacuum polarization correction can be included in molecular computations as an effective local potential...
The positronium (Ps) $n=2$ fine structure intervals can be used to test bound-state quantum electrodynamics (QED) [1], with current measurements using microwave waveguides at a precision of 100 parts-per-million (ppm) [2]. However, the 10 mm scale of waveguides in the GHz regime results in short transit times and low phase acceptance of the fast and divergent Ps beam. We therefore use...
Precise measurements of absolute nuclear charge radii are crucial ingredients for QED tests and are valuable benchmarks for modern nuclear structure theory [1]. Muonic atom spectroscopy is well known as an ideal method to accurately determine the root-mean-square (RMS) radii of the nuclear charge density distribution. By measurements of the 2p-1s transitions of muonic atoms, this technique has...
We demonstrate low-excitation transport and separation of two-ion crystals consisting of one $^9 \mathrm{Be} ^+$ and one $^{40} \mathrm{Ca} ^+$ ion, with a high mass ratio of 4.4. The full separation involves transport of the mixed-species chain, splitting each ion into separate potential wells, and then transport of each ion prior to detection. We find the high mass ratio makes the protocol...
Bound states of positrons with small neutral atoms have not yet been detected experimentally. However, they are expected to have very small positron affinities. Not only does this pose a challenge for modeling such states reliably, but it also raises a question of how important the relativistic effects are and whether they can alter the dynamical stability of the weakly bound positron-atom...
Positronium being a purely leptonic atom provides an ideal test-bench of bound-state QED. Because of its simplicity, any deviation from calculations could hint to new physics beyond the standard model. This poster presents the ongoing experimental progresses made in the laser 1S—2S spectroscopy with the help of a pulsed slow positron beam at ETH.
We present an innovative approach for in-vacuum cavity-enhanced UV spectroscopy that enables almost continuous measurements over multiple days, reducing mirror degradation due to high-power UV radiation. Our technique utilizes pulsing of the cavity's internal power, which elevates the UV intensity to its peak only briefly when the atom under study is within the cavity mode volume, while...
The ASACUSA Cusp collaboration aims to measure the ground-state hyperfine splitting of antihydrogen to a relative precision of parts per million, using a spin polarised antihydrogen beam in a low magnetic field region [1].
The first antihydrogen was successfully synthesised in the ASACUSA-Cusp experiment in 2010 [2] by mixing antiprotons and positrons in the so-called Cusp trap, which is a...
Precision spectroscopy of atomic hydrogen is a powerful tool to test QED theory as energy transitions can be measured, calculated and subsequently compared on a high level of precision. As free parameters in the theory, the Rydberg constant $R_\infty$ and the proton charge radius $r_p$ remain to be determined by spectroscopy [3], since other parameters entering the calculation, such as the...
The Lagrange-mesh method in perimetric coordinates is an efficient and rather simple method to study three-body Coulomb systems such as He, H$^−$, Ps$^−$, or H$^+_2$ [1], as well as quasibound states of exotic Coulomb atoms such as He$^+\bar{p}$, $\bar{p}$H, and He$^+\pi^-$ [2-4]. Recently, two extensions of the method have been developed to properly describe resonant states [3-7]: one based...
Bound-state quantum electrodynamics (QED) accurately describes the energy levels of hydrogen-like atoms and ions. High-precision laser spectroscopy experiments provide one of the best tests of the theory. The frequency of the narrow 1s-2s transition of atomic hydrogen has been measured with a relative uncertainty of less than $10^{-14}$. By combining two spectroscopic measurements of a...
As the lightest known atom, Positronium (Ps) presents a significant challenge for high-precision spectroscopy. Time-of-flight broadening and second-order Doppler shifts are the main factors affecting the accuracy in the measurement of the 1S-2S transition. We propose using two photon optical Ramsey spectroscopy. Our detailed simulation shows that with this method, the line width of the 1S-2S...
A common problem for experimental scientists is computing averages of scattered data, i.e., with uncertainties much smaller than the distance between the different values. In such a case, a weighted average generally gives a very small uncertainty that does not reflect the bad agreement of the data. Different strategies are implemented in the literature, such as the application of a scale...
