First Ever Picture of Light as Both a Particle and a Wave

“We have two contradictory pictures of reality; separately neither of them fully explains the phenomena of light, but together they do.” -Albert Einstein.

ADual nature of light has been a topic of debate and research for past many years. Quantum mechanics explains that light has two forms- particle or wave nature. Different properties of light are explained by either of the two forms. Scientists at EPFL, research institution in Switzerland, have been able to take the first ever picture of light behaving as particle and wave simultaneously.

Fabrizio Carbone and his team at EPFL performed an experiment involving targeting a beam of electrons close to a preset nanowire. The nanowire was prepared by firing a laser beam on a thin strand of nanowire. This excites and adds to the energy of charged particles and hence making them vibrate. Vibrating particles travel around the nanowire strand. The particles travelling opposite directions give rise to standing waves. The standing waves produced act as the source of light in the experiment. Then the light travelling around nanowire was allowed to interact with a stream of electrons fed in the nearby region of the nanowire.

light-wave-particle-duality — Picture of light both as a wave and a particle

The result of the interaction was either speeding up or slowing down of electrons. This was captured using ultrafast electron microscope- more specifically EPFL’s ultrafast energy-filtered transmission electron microscope – one of the two in the world. The standing wave imaged by the microscope acts as a fingerprint of wave nature of light. In addition, the particle nature was demonstrated by speed difference of electrons. The electrons hit the light particles i.e. photons and hence the change speeds occurred due to energy exchange between electrons and photons via quanta.

“Being able to image and control quantum phenomena at the nanometer scale like this opens up a new route towards quantum computing.” says Fabrizio Carbone

The whole experiment and imaging was performed in collaboration of Laboratory for Ultrafast Microscopy and Electron Scattering of EPFL, the Department of Physics of Trinity College (US) and the Physical and Life Sciences Directorate of the Lawrence Livermore National Laboratory.

The detailed work paper was published in Nature Communications.

Watch out the following video uploaded by EPFL: