uOttawa and the NRC capture the first-ever holographic images of the quantum wave function of an electron

Posted on Thursday, June 15, 2017

David Villeneuve, adjunct professor at the University of Ottawa and Research Officer at the National Research Council of Canada

Dr. David Villeneuve, adjunct professor at the University of Ottawa and Research Officer at the NRC. Photo credit: Dave Weatherall, University of Ottawa

The “perfect” experiment using attosecond technology

For the first time ever, physicists from three continents have been able to completely measure and describe the quantum-mechanical wave function of an ionized electron by using attosecond science techniques.

This breakthrough was made by physicists from the University of Ottawa and the National Research Council of Canada (NRC) in Canada, the Max-Born Institute for Nonlinear Optics and Short Pulse Spectroscopy in Germany, and Waseda University in Japan.

“Attosecond research is still in its infancy,” says Canadian research lead Dr. David Villeneuve, adjunct professor at the University of Ottawa and Research Officer at the NRC. “It is only because of very recent developments in quantum photonics that experiments of this kind have become possible. Attosecond experiments allow us to view at the quantum level the electrons within atoms and molecules.”

The experiment demonstrates a fundamental property of quantum mechanics. By capturing the first-ever holographic images of the quantum wave function of an electron, the physicists have highlighted the exquisite control of the quantum state of an atom that can be achieved with state-of-the-art attosecond science, and show how attosecond science techniques are currently revolutionizing ultrafast laser physics research.

An attosecond is one quintillionth of a second (1x10-18 of a second), roughly equivalent to the relationship between one second and the age of the universe. Attosecond light pulses can profoundly change the states of matter. Results of this research are published in tomorrow’s edition of the journal Science.

Importance of attosecond research

An attosecond is one quintillionth of a second (1x10-18 of a second), roughly equivalent to the relationship between one second and the age of the universe. Because attosecond pulses are faster than the motion of electrons within atoms and molecules, they provide a new tool to control and measure quantum states of matter.

Electrons are negatively-charged elementary particles that make everyday things like electricity possible. The interaction of light with electrons is the basis for photosynthesis and the operation of solar cells. In this experiment, scientists irradiated neon atoms with attosecond pulses to create an excited state of neon. At the same time, a precisely synchronized infrared laser pulse provided the extra energy needed to ionize the neon atom, resulting in the ejection of an electron. Because of the precise combination of laser pulses, the quantum state of the ejected electron could be controlled. Each electron was ejected in six different directions at the same time, due to the magic of quantum mechanics.

Because the electron’s wave function has an imaginary part, it is impossible to record an image.   The quantum wave function “collapses” when it is measured, so only the absolute value of the wave function can be seen. To access the imaginary part of the wave function, another coherent pathway to freeing the electron is added, creating a holographic reference. This enables both the amplitude and sign of the wave function to be imaged.

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Amélie Ferron-Craig
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University of Ottawa
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