An ion channel in a cell membrane is a gate just a few atoms wide. Every second, millions of charged particles, sodium and potassium ions, pass through it. Classical physics said that to get through, an ion must jump over an energy barrier, like a traveler crossing a high mountain pass. But calculations showed that channels let far more ions through than such a jump would allow.
It turns out ions don't jump over the barrier: they pass right through it. This is quantum tunneling, an effect where a particle seeps through an obstacle as if a person walked through a wall without breaking it. The authors built a model where the ion tunnels through the channel's narrow filter and obtained exact conductance values for sodium and potassium channels — the very ones measured in experiments.
The quantum approach changes how we see the living cell. Ion channels emerge not just as pores but as quantum conductors. The authors predict that such channels should exhibit resonances at terahertz frequencies — something that can be tested experimentally. If the prediction holds, quantum biology gains a solid foundation, and we gain a new understanding of how life harnesses the laws of the microworld.
An ion channel is about 0.3 nanometers wide—300,000 times thinner than a human hair, yet it can pass up to 100 million ions per second.
In Greg Egan's novel 'Permutation City,' people scan brains down to quantum states — perhaps tunneling in ion channels will become part of such technologies.