Description
Entanglement Control and Transfer: From Strong Coupling to Spontaneous Decay
We theoretically investigate how phase-locked laser pulses can generate, control, and transfer quantum entanglement in photoionization. Recent XUV free-electron laser experiments have enabled access to strong-field dynamics in this regime [1]. Ionization followed by laser-driven coupling between ionic states induces Rabi oscillations and a characteristic splitting of the photoelectron spectrum [2], which reflects ion–electron entanglement arising from phase correlations in the ionic superposition.
By controlling the phase of the pulse sequence with attosecond precision, we demonstrate control over both the generation and manifestation of this entanglement [3]. In-phase pulses yield overlapping spectra with phase-dependent correlations while out-of-phase pulses produce non-overlapping spectra. In the latter case, the entanglement is encoded in the amplitudes of the wave function and can be detected via coincidence measurements [4]. We quantify this amplitude entanglement. Furthermore, we show that the phase relation determines the entanglement generated by the second pulse.
We show that spontaneous emission transfers the entanglement from the ion–electron system to the electron–photon system, with transient multipartite entanglement [5]. These results establish a route to coherently shape entanglement in photoionization and open new possibilities for accessing and controlling quantum correlations in systems where measurements are intrinsically basis constrained.
References
[1] Nandi S. et al., Nature 608, 488–493 (2022).
[2] Nandi S.; Stenquist A. et al., Sci. Adv. 10, eado0668 (2024 ).
[3] Stenquist A.; Dahlström J. M., Phys. Rev. Research 7, 013270 (2025).
[4] Stenquist A.; Dahlström J. M., Manuscript in review.
[5] Stenquist A. et al., Rep. Prog. Phys. 88, 080502 (2025).
