Ultrafast quantum decoherence in semiconductor*

In systems interacting with their environment, applying quantum theory solely to the systems yields different results than when the environment is included. Decoherence, the seemingly inability of a system to maintain its quantumness, is a ubiquitous phenomenon and relies on environmental inclusion for thorough analysis. Although micro spin systems have been extensively investigated, dephasing in real macro systems remains largely unexplored due to its rapid occurrence. Here, we present a near sub-femtosecond decoherence process observed in a crystalline semiconductor using high-order wave-mixing spectroscopy. Our findings indicate that the dephasing time, conventionally considered a fixed preset, can be influenced by our observations, with full quantum theory substantiating this finding. Our research bridges quantum information with strong field physics and contributes to the understanding of system coherence in the real environment.