New preprint: molecular quantum eraser!

Our new preprint reports a quantum eraser experiment with a molecule: by selecting the final state of the ion, we erase “which-way” information and bring back the interference pattern of the photoelectron.

In quantum mechanics, what you can measure depends on what information about the system is available. The quantum eraser experiment shows this very clearly. If “which-way” information about the path of an otherwise coherent particle is available, the particle no longer interferes with itself. However, erasing the which-way information brings the interference pattern back, and this can even be done afterwards, by postselection once the measurement is complete.

In our recent work, we demonstrate such a quantum eraser in the strong-field photoionization of $D_2$ molecules. When the molecule interacts with an intense femtosecond laser pulse, the outgoing photoelectron becomes entangled with the residual molecular ion. Through this entanglement, which-way information can be stored in the ion, and as a result the holographic interference fringes in the photoelectron momentum distribution disappear. By measuring the electron and the ion in coincidence and selecting a specific ionic state, we erase the which-way information and the interference fringes return. Theoretical models fully support our observations.

The preprint is available on the arXiv.