Self‐Referenced Subcycle Metrology of Quantum Fields.

A new time‐domain method for subcycle metrology of quantum electric fields using a combination of a third order nonlinear optical process and homodyne detection with a local oscillator (LO) field is proposed and analyzed. The new method enables isolation of intrinsically weak quantum noise contribution by subtraction of the shot noise of the LO on a pulse‐by‐pulse basis. Together with the centro‐symmetric character of the nonlinearity, this method unlocks novel opportunities toward terahertz and mid‐infrared quantum field metrologies. [ABSTRACT FROM AUTHOR]