# Science

Particle & wave

SNS | March 4, 2015 9:33 am

Since the days of Einstein, scientists have been trying to directly observe how light can be both a particle and a wave at the same time. Never before has an experiment able to capture both natures of light at the same time — the closest we have come is seeing either wave or particle, but always at different times — but taking a radically different experimental approach, scientists at the École Polytechnique Fédérale de Lausanne have now been able to take the first ever snapshot of light behaving both as a wave and as a particle. The breakthrough work is published in Nature Communications.

The team team led by Fabrizio Carbone carried out an experiment with a clever twist: using electrons to image light. They captured, for the first time ever, a single snapshot of light behaving simultaneously as both a wave and a stream of particles. They fired a pulse of laser light at a tiny metallic nanowire. The laser added energy to the charged particles in the nanowire, causing them to vibrate. Light traveled along this tiny wire in two possible directions, like cars on a highway. When waves travelling in opposite directions met each other they formed a new wave that looked like it was standing in place. Here, this standing wave became the source of light for the experiment, radiating around the nanowire. “This experiment demonstrates that, for the first time ever, we can film quantum mechanics — and its paradoxical nature — directly,” said Carbone. In addition, the importance of this pioneering work can extend beyond fundamental science and to future technologies.

As Carbone explained, “Being able to image and control quantum phenomena at the nanometre scale like this opens up a new route towards quantum computing.”