theatlantic | The mere mention of “quantum consciousness” makes most physicists
cringe, as the phrase seems to evoke the vague, insipid musings of a New
Age guru. But if a new hypothesis proves to be correct, quantum effects
might indeed play some role in human cognition. Matthew Fisher, a physicist at the University of California, Santa Barbara, raised eyebrows late last year when he published a paper in Annals of Physics
proposing that the nuclear spins of phosphorus atoms could serve as
rudimentary “qubits” in the brain—which would essentially enable the
brain to function like a quantum computer.
As recently as 10 years ago, Fisher’s
hypothesis would have been dismissed by many as nonsense. Physicists
have been burned by this sort of thing before, most notably in 1989,
when Roger Penrose proposed that mysterious protein structures called
“microtubules” played a role in human consciousness by exploiting
quantum effects. Few researchers believe such a hypothesis plausible.
Patricia Churchland, a neurophilosopher at the University of California,
San Diego, memorably opined that one might as well invoke “pixie dust in the synapses” to explain human cognition.
Fisher’s
hypothesis faces the same daunting obstacle that has plagued
microtubules: a phenomenon called quantum decoherence. To build an
operating quantum computer, you need to connect qubits—quantum bits of
information—in a process called entanglement. But entangled qubits exist
in a fragile state. They must be carefully shielded from any noise in
the surrounding environment. Just one photon bumping into your qubit
would be enough to make the entire system “decohere,” destroying the
entanglement and wiping out the quantum properties of the system. It’s
challenging enough to do quantum processing in a carefully controlled
laboratory environment, never mind the warm, wet, complicated mess that
is human biology, where maintaining coherence for sufficiently long
periods of time is well nigh impossible.
Over
the past decade, however, growing evidence suggests that certain
biological systems might employ quantum mechanics. In photosynthesis,
for example, quantum effects help plants turn sunlight into fuel. Scientists have also proposed
that migratory birds have a “quantum compass” enabling them to exploit
Earth’s magnetic fields for navigation, or that the human sense of smell
could be rooted in quantum mechanics.
Fisher’s notion of quantum
processing in the brain broadly fits into this emerging field of quantum
biology. Call it quantum neuroscience. He has developed a complicated
hypothesis, incorporating nuclear and quantum physics, organic
chemistry, neuroscience and biology. While his ideas have met with
plenty of justifiable skepticism, some researchers are starting to pay
attention. “Those who read his paper (as I hope many will) are bound to
conclude: This old guy’s not so crazy,” wrote John Preskill,
a physicist at the California Institute of Technology, after Fisher
gave a talk there. “He may be on to something. At least he’s raising
some very interesting questions.”
