  Fluorescence lifetime experiments are a standard approach for measuring
excited state dynamics and local environment effects. Here, we show that
entangled photon pairs produced from a continuous-wave (CW) laser diode can
replicate pulsed laser experiments without phase modulation. As a proof of
principle, picosecond fluorescence lifetimes of indocyanine green are measured
in multiple environments. The use of entangled photons has three unique
advantages. First, low power CW laser diodes and entangled photon source design
lead to straightforward on-chip integration for a direct path to distributable
fluorescence lifetime measurements. Second, the entangled pair wavelength is
easily tuned by temperature or electric field, allowing a single source to
cover octave bandwidths. Third, femtosecond temporal resolutions can be reached
without requiring major advances in source technology or external phase
modulation. Entangled photons could therefore provide increased accessibility
to time-resolved fluorescence while also opening new scientific avenues in
photosensitive and inherently quantum systems.
