Living organisms harness a phenomenon called quantum coherence to transfer light energy through their photosynthetic systems with an efficiency that no artificial device has managed to replicate. This process occurs at the molecular level, where particles such as electrons and excitons behave in a dual manner, acting as both particle and wave simultaneously.
What quantum coherence is in photosynthesis
Quantum coherence is a state in which subatomic particles maintain defined phase relationships with one another, allowing them to behave in a coordinated way. In photosynthesis, when sunlight reaches chlorophyll or bacteriochlorophyll molecules, this energy excites electrons. Quantum coherence allows these excitations to propagate along multiple paths at the same time, behaving like waves rather than following a single route.
The FMO complex experiment
In 2007, a team led by Graham Fleming experimentally demonstrated that electronic excitations in the FMO complex of green sulfur bacteria behaved coherently. This complex functions as a network of bacteriochlorophylls that transmits captured energy to the reaction center where photosynthesis begins.
What is remarkable is that these coherence states persisted for hundreds of femtoseconds, an extraordinarily long time considering that biological systems operate at room temperature, where such quantum effects normally disappear very quickly.
How the quantum GPS works
Scientists describe the system as a natural quantum GPS, where the coherent oscillations of the pigments allow the energy to find the optimal route to the reaction center, minimizing losses from heat or dissipation. This arrangement acts as an energy funnel that guides the excitations to the exact point where they are needed.
What this means evolutionarily
The fact that organisms as ancient as sulfur bacteria developed and maintained these mechanisms over millions of years suggests that evolution found an optimal solution for capturing light under conditions where sunlight intensity is limited. It is one of the most efficient energy transfer processes that exist in nature.
Practical applications of this knowledge
Understanding how biology manipulates quantum coherence could revolutionize the design of next-generation solar cells. It also has implications for developing room-temperature quantum computing technologies. In astrobiology, this knowledge broadens the search for extraterrestrial life by raising the possibility that moons such as Titan could host organisms with photosynthetic mechanisms radically different from those on Earth.
