Noise: It Turns Out You Need It

Noise: It Turns Out You Need It

We don’t know whether quantum physics proves the universe is truly a strange place or that we are living in a virtual reality simulation, but we know it turns a lot of common sense into garbage. Take noise, for example. Noise — as in random electrical noise — is bad, right? We spend a lot of time designing to minimize noise. Researchers in Austria, Germany, and Australia recently published a paper that shows that noise can actually improve the flow of energy. While the paper is behind a paywall, the Focus article is available and, of course, you can probably find a copy of the paper if you want to read the entire thing.

The paper, titled “Environment-Assisted Quantum Transport in a 10-qubit Network” uses trapped calcium atoms to study an effect suspected of being a key factor in high-efficiency energy transfer such as the transfer observed in optical fibers and photosynthesis.

In a perfect material, you can imagine energy transfer — such as current flow through a conductor — as a wave of energy moving through the material. In the case of electric current, that wave is built from electrons, but it could also for example be photons. In either case, in general the waves say coherent through the material. But imperfections and defects can destroy coherency and cause wave interference where the trough of one wave cancels the peak of another one nearby. This effect is called Anderson (or strong) localization. However, this loss is at a maximum when the waves are totally out of phase with each other. Noise in the system makes it more likely that the waves will change phase relationship and reduce Anderson localization which boosts transfer efficiency.

The ten atoms formed a chain where researchers could use a laser to inject energy into the system and then watch it flow to the end of the chain. Other lasers can introduce disorder into the array, causing the Anderson localization effect. With a stable setup, Anderson localization caused inefficiency in energy transport. However, introducing noise into the disordered system reduced the effect of the Anderson localization — to a point. At some higher level, the noise caused an increased loss due to the Zeno effect.

It turns out that impurities and noise aren’t always bad things. We are always amazed that we live in a time where we are learning about the universe at such a fine level of detail.