Quantum Brain Mechanics

The relation between quantum mechanics

and higher brain functions, including consciousness, is often discussed, but is far from

being understood. Physicists, ignorant of

modern neurobiology, are tempted to

assume a formal or even dualistic view of

the mind–brain problem. Meanwhile, cognitive neuroscientists and neurobiologists

consider the quantum world to be irrelevant

to their concerns and therefore do not

attempt to understand its concepts. What

can we confidently state about the current

relationship between these two fields of

scientific inquiry?

All biological organisms must obey the

laws of physics, both classical and quantum.

In contrast to classical physics, quantum

mechanics is fundamentally indeterministic. It explains a range of phenomena that

cannot be understood within a classical

context: the fact that light or any small particle can behave like a wave or particle

depending on the experimental setup

(wave–particle duality); the inability to

simultaneously determine, with perfect

accuracy, both the position and momentum

of an object (Heisenberg’s uncertainty principle); and the fact that the quantum states

of multiple objects, such as two coupled

electrons, may be highly correlated even

though the objects are spatially separated,

thus violating our intuitions about locality

(entanglement).

Major philosophical and conceptual

problems surround the process of making

measurements in quantum mechanics. To

illuminate the paradoxical nature of superposition — that is, the fact that particles or

quantum bits (qubits) are allowed to exist

in a superposition of states — Schrödinger

proposed a celebrated thought experiment: a sealed box containing the quantum superposition of both a dead and a

live cat. When an observer peers inside the

box, measuring its content, the wave function, which describes the probability that

the system will be found in any one particular state, is said to collapse, and the system will be found in...