Observing interferences between past and future quantum states in resonance fluorescence

Understand

In quantum physics, measurement results are random but their statistics can be predicted assuming some knowledge about the system in the past.

• Additional knowledge from a future measurement deeply changes the statistics in the present and leads to purely quantum features.
• In particular conditioned average outcomes of a weak measurement, so-called weak values, were shown to go beyond the conventional range, give a way to directly measure complex quantities, and can be used to enhance the sensitivity of quantum meters.
• Recently, these concepts have been considered in the general case of open quantum systems where decoherence occurs.