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APS Physics: February 8, 2019 • Physics 12, 13
- A quantum effect in which random fluctuations help waves to propagate has been demonstrated in a chain of ten atoms.
Helpful noise. Disorder in the electronic states in a row of ten trapped calcium ions can disrupt the flow of energy among the ions. But adding noise to the system can boost the energy flow.
When electrons move in a conducting material or when energy absorbed from sunlight is shifted between molecules during photosynthesis, the process can be described using the wave equations of quantum mechanics. Wave interference can lead to a suppression of the transport of charge or energy, but, counterintuitively, random fluctuations such as thermal noise can actually improve this transport.
Researchers have now demonstrated both of these effects for energy transport in a chain of ten atoms, where the degree of disorder and noise in the system can be carefully controlled. Studying such effects in a clean, well-controlled experiment could lead to a better understanding of how they operate in larger, more complex situations such as in electronic and optical devices.
An electric current can be described as a wave, but so can other kinds of energy transport. For example, energy can be transferred between atoms or molecules as a series of absorption and emission events of photons, which can be represented as a wave of energy moving from one component to the next. If the waves remain in step, they are said to be coherent, in which case constructive interference (alignment of peaks and troughs) can amplify the flow of charge or energy. But disorder, such as impurities or defects in the lattice of atoms, may cause coherent destructive interference (peaks canceling out troughs) that averages out to suppress the flow entirely. This suppression, which can trap charge or halt the flow of energy in a specific region, is called Anderson localization...
