An international collaboration including researchers from Amsterdam, Paris, Baton Rouge (USA) and Lund University, (Sweden), has made a breakthrough which moves some of the mathematics of quantum mechanics off of the blackboard and into the laboratory - from theory to reality. Using extremely short pulses of light, new knowledge about the wave-like nature of matter can be obtained.
The Lund group presently holds the world record for producing short laser pulses. In the High-power laser facility at the Lund University, trains of pulses where each pulse is 200 attoseconds long and separated from the next pulse by 1.3 femtoseconds, are routinely produced. A femtosecond is 10-15 seconds, i.e. one-millionth-of-a-billionth of a second, while an attosecond is still one thousand times shorter. These incredibly short light pulses allow scientists to make snapshots of the most rapidly moving constituents of atoms and molecules, the electrons. In a paper published in this month’s issue of Nature Physics, the scientists demonstrate that attosecond pulses are an extremely powerful tool for studying the wave-like nature of electrons.
Quantum mechanics describes all the properties of matter in a probabilistic manner with so-called wave functions. Wave functions describe, for example, the probability that an electron is found at a particular position or that an electron moves with a particular velocity. They also describe how – similar to light - matter sometimes behaves more like a particle, and sometimes more like a wave. Importantly, the wave function is – in mathematical terms - a complex quantity, that it is characterized by both an amplitude and a phase. Though theorists can calculate complex valued wave functions and use them to make precise predictions about the behaviour of matter, the complete measurement of a wave function, both its amplitude and phase, is notoriously difficult. This is why most experiments only give information about the amplitudes of wave functions and not their phase.
Göran Frankel | alfa
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