  Real-time controls based on quantum measurements are powerful tools for
various quantum protocols. However, their experimental realization have been
limited by mode-mismatch between temporal mode of quadrature measurement and
that heralded by photon detection. Here, we demonstrate real-time quadrature
measurement of a single-photon wavepacket induced by a photon detection, by
utilizing continuous temporal-mode-matching between homodyne detection and an
exponentially rising temporal mode. Single photons in exponentially rising
modes are also expected to be useful resources for interactions with other
quantum systems.
