A photon is an elementary excitation of a single mode of quantized electromagnetic
radiation at a fixed point in space and time. The term photon was
named by Gilbert Lewis in 1926 for the first time, and it has been used ever since. This complicated tale begins with Einstein's vision of light as
an unbreakable collection of indivisible particles whose energy and momentum are
conserved throughout their interaction with matter and continues through the rest of
twentieth-century physics to the present day . In the intervening years, there has been a
lot of debate over the need and appropriateness of such a notion. British physicists Robert
Hanbury Brown and Richard Quentin Twiss presented an experiment in 1956, and this
experiment is one of the most recognized physics experiments today, known as the
Hanbury Brown and Twiss (HBT) experiment . The findings of HBT then questioned
and cast doubt on the idea of the photon hypothesis and asked for more research. Scientists
at that time were surprised by the conclusions of the HBT experiment, which initiated a
debate among the community of physicists that included Eric Brannen, Emil Wolf, Harry
Ferguson, Peter Fellgett, Lajos Janossy, Richard Sillitto, Leonard Mandel, and Edward
Purcell, as well as Hanbury Brown and Twiss themselves. In the 1950s, physicists
continued to think of photons as indivisible particles and wave packets, but the HBT
experiment prompted physicists to reconsider and reinterpret, or comprehend, the photon
concept for the first time .
