Quantum phenomena in attosecond science

The ability to manipulate and observe phenomena on attosecond timescales has yielded groundbreaking insights into electron dynamics and the behaviour of matter exposed to intense light fields. The interdisciplinary field of attosecond science connects various research areas, including quantum optics, quantum chemistry and quantum information science. However, the intrinsic quantum effects in attosecond science have been largely ignored. In this Perspective, we discuss the latest theoretical and experimental advances in exploring and understanding quantum phenomena within attosecond science. We focus on distinguishing genuinely quantum observations from classical phenomena in the context of high-harmonic generation and above-threshold ionization. Additionally, we illuminate the often overlooked yet important role of entanglement in attosecond processes, elucidating its influence on experimental outcomes. Attosecond science is a versatile discipline for studying ultrafast dynamics in matter on the microscopic scale. This Perspective explores the theoretical and experimental developments in this field focusing on distinguishing genuinely quantum observations from classical phenomena.