A photoelectron, emitted due to the absorption of light quanta as described by the photoelectric effect, is often characterized experimentally by a classical quantity, its momentum. However, since the photoelectron is a quantum object, its rigorous characterization requires the reconstruction of the complete quantum state, the photoelectron’s density matrix.
Here, the researchers use quantum-state tomography to fully characterize photoelectrons emitted from helium and argon atoms upon absorption of ultrashort, extreme ultraviolet light pulses. While in helium we measure a pure photoelectronic state, in argon, spin–orbit interaction induces entanglement between the ion and the photoelectron, leading to a reduced purity of the photoelectron state. This work shows how state tomography gives new insights into the fundamental quantum aspects of light-induced electronic processes in matter, bridging the fields of photoelectron spectroscopy and quantum information and offering new spectroscopic possibilities for quantum technology.
Authors:
Hugo Laurell, Sizuo Luo, Robin Weissenbilder, Mattias Ammitzböll, Shahnawaz Ahmed, Hugo Söderberg, C. Leon. M. Petersson, Vénus Poulain, Chen Guo, Christoph Dittel, Daniel Finkelstein-Shapiro, Richard J. Squibb, Raimund Feifel, Mathieu Gisselbrecht, Cord L. Arnold, Andreas Buchleitner, Eva Lindroth, Anton Frisk Kockum, Anne L’Huillier, and David Busto.
The publication: “Measuring the quantum state of electrons” (Nature Photonics)
