It can be argued that the modern aim of ultrafast science is to enable dynamic control of condensed matter with light. The multi-THz frequency band is particularly attractive as it spans over many fundamental collective excitations in solid state. I will demonstrate synthesis of multi-THz coherent state wavepackets with polar asymmetry on a sub-cycle timescale . By focusing such transients within a gap between gold contacts deposited on a narrow-gap semiconductor InSb, we controlled the induced current by polar asymmetry of light . Next, I will present analysis of mult-THz quantum fields with sub-cycle resolution. At the ultimate sensitivity limit, electro-optic detection can access local fluctuations of quantum fields . Furthermore, we can modify the multi-THz vacuum state by acting on it with a strong control pulse, co-propagating in a second nonlinear crystal. In this case, we imprint strong deviations of the statistics of the local quantum field above and below the vacuum level . While the demonstrated ability to detect bare and squeezed vacuum states lays the foundation for a new approach to subcycle physics, current work is underway to improve the methodology toward the ultimate goal of time-domain quantum spectroscopy.
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