October 29, 2018

IF YOU BELIEVE IN sCIENCE YOU HAVEN'T UNDERSTOOD SCIENCE:

"Schrödinger's Bacterium" Could Be a Quantum Biology Milestone: A recent experiment may have placed living organisms in a state of quantum entanglement (Jonathan O'Callaghan, October 29, 2018, Scientific American)

Scaled up to our seemingly simpler and certainly more intuitive macroscopic world, however, things change. No one has ever witnessed a star, a planet or a cat in superposition or a state of quantum entanglement. But ever since quantum theory's initial formulation in the early 20th century, scientists have wondered where exactly the microscopic and macroscopic worlds cross over. Just how big can the quantum realm be, and could it ever be big enough for its weirdest aspects to intimately, clearly influence living things? Across the past two decades the emergent field of quantum biology has sought answers for such questions, proposing and performing experiments on living organisms that could probe the limits of quantum theory.

Those experiments have already yielded tantalizing but inconclusive results. Earlier this year, for example, researchers showed the process of photosynthesis--whereby organisms make food using light--may involve some quantum effects. How birds navigate or how we smell also suggest quantum effects may take place in unusual ways within living things. But these only dip a toe into the quantum world. So far, no one has ever managed to coax an entire living organism--not even a single-celled bacterium--into displaying quantum effects such as entanglement or superposition.

So a new paper from a group at the University of Oxford is now raising some eyebrows for its claims of the successful entanglement of bacteria with photons--particles of light. Led by the quantum physicist Chiara Marletto and published in October in the Journal of Physics Communications, the study is an analysis of an experiment conducted in 2016 by David Coles from the University of Sheffield and his colleagues. In that experiment Coles and company sequestered several hundred photosynthetic green sulfur bacteria between two mirrors, progressively shrinking the gap between the mirrors down to a few hundred nanometers--less than the width of a human hair. By bouncing white light between the mirrors, the researchers hoped to cause the photosynthetic molecules within the bacteria to couple--or interact--with the cavity, essentially meaning the bacteria would continuously absorb, emit and reabsorb the bouncing photons. The experiment was successful; up to six bacteria did appear to couple in this manner.

Marletto and her colleagues argue the bacteria did more than just couple with the cavity, though. In their analysis they demonstrate the energy signature produced in the experiment could be consistent with the bacteria's photosynthetic systems becoming entangled with the light inside the cavity. In essence, it appears certain photons were simultaneously hitting and missing photosynthetic molecules within the bacteria--a hallmark of entanglement. "Our models show that this phenomenon being recorded is a signature of entanglement between light and certain degrees of freedom inside the bacteria," she says.

Posted by at October 29, 2018 12:57 PM

  

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