  Decision making is critical in our daily lives and for society in general and
is finding evermore practical applications in information and communication
technologies. Herein, we demonstrate experimentally that single photons can be
used to make decisions in uncertain, dynamically changing environments. Using a
nitrogen-vacancy in a nanodiamond as a single-photon source, we demonstrate the
decision-making capability by solving the multi-armed bandit problem. This
capability is directly and immediately associated with single-photon detection
in the proposed architecture, leading to adequate and adaptive autonomous
decision making. This study makes it possible to create systems that benefit
from the quantum nature of light to perform practical and vital intelligent
functions.
