科学家第一次直接拍摄到光的两种形态

#研究分享#【科学家第一次直接拍摄到光的两种形态】光既是一种高频的电磁波,又是一种由称为光粒子的基本粒子组成的粒子流。从爱因斯坦时代开始,科学家就尝试同时观测到光的两种形态。洛桑理工学院的科学家日前第一次成功拍摄一组照片,展示光的两种形态。这是人类第一次直接拍摄量子力学现象及其矛盾的形态,这意味着人类能够在纳米量级控制量子现象,从而为量子计算提供了新的可能性。

 

First ever photograph of light as a particle and a wave

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Light behaves both as a particle and as a wave. Since the days of Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at EPFL have succeeded in capturing the first-ever snapshot of this dual behavior.

Quantum mechanics tells us that light can behave simultaneously as a particle or a wave. However, there has never been 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. Taking a radically different experimental approach, EPFL scientists 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.

When UV light hits a metal surface, it causes an emission of electrons. Albert Einstein explained this "photoelectric" effect by proposing that light -- thought to only be a wave -- is also a stream of particles. Even though a variety of experiments have successfully observed both the particle- and wave-like behaviors of light, they have never been able to observe both at the same time.

A new approach on a classic effect

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A research team led by Fabrizio Carbone at EPFL has now carried out an experiment with a clever twist: using electrons to image light. The researchers have captured, for the first time ever, a single snapshot of light behaving simultaneously as both a wave and a stream of particles particle.

The experiment is set up like this: A pulse of laser light is fired at a tiny metallic nanowire. The laser adds energy to the charged particles in the nanowire, causing them to vibrate. Light travels along this tiny wire in two possible directions, like cars on a highway. When waves traveling in opposite directions meet each other they form a new wave that looks like it is standing in place. Here, this standing wave becomes the source of light for the experiment, radiating around the nanowire.

This is where the experiment's trick comes in: The scientists shot a stream of electrons close to the nanowire, using them to image the standing wave of light. As the electrons interacted with the confined light on the nanowire, they either sped up or slowed down. Using the ultrafast microscope to image the position where this change in speed occurred, Carbone's team could now visualize the standing wave, which acts as a fingerprint of the wave-nature of light.

While this phenomenon shows the wave-like nature of light, it simultaneously demonstrated its particle aspect as well. As the electrons pass close to the standing wave of light, they "hit" the light's particles, the photons. As mentioned above, this affects their speed, making them move faster or slower. This change in speed appears as an exchange of energy "packets" (quanta) between electrons and photons. The very occurrence of these energy packets shows that the light on the nanowire behaves as a particle.

"This experiment demonstrates that, for the first time ever, we can film quantum mechanics -- and its paradoxical nature -- directly," says Fabrizio Carbone. In addition, the importance of this pioneering work can extend beyond fundamental science and to future technologies. As Carbone explains: "Being able to image and control quantum phenomena at the nanometer scale like this opens up a new route towards quantum computing."

Cartoon video: https://www.youtube.com/watch?v=mlaVHxUSiNk


Story Source:

The above story is based on materials provided by Ecole Polytechnique Fédérale de Lausanne. Note: Materials may be edited for content and length.


Journal Reference:

  1. L Piazza, T.T.A. Lummen, E Quiñonez, Y Murooka, B.W. Reed, B Barwick, F Carbone. Simultaneous observation of the quantization and the interference pattern of a plasmonic near-field. Nature Communications, 2015; 6: 6407 DOI: 10.1038/ncomms7407

文章来源:sciencedaily

文章链接:http://www.sciencedaily.com/releases/2015/03/150302104731.htm


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