On Mon, Jun 30, 2014 at 5:44 PM, Eugene Salamin via math-fun <math-fun@mailman.xmission.com> wrote:
No, The Copenhagenists assert that the wave function represents a state of knowledge. Wave function collapse is not a physical process obeying an evolution equation. It is an update to our knowledge.
No, you're describing a Bayesian interpretation. From http://en.wikipedia.org/wiki/Quantum_Bayesianism : -------- Quantum Bayesianism applies the Bayesian approach to the fundamentals of quantum mechanics. The Bayesian approach is a mode of statistical inference. It introduces the concept of "degree of belief"... Quantum Bayesianism is an alternative to the (more) popular Copenhagen interpretation of quantum mechanics, which is built upon the idea of wavefunction collapse. The Copenhagen interpretation does not assume a specific interpretation of probability. -----------
From http://en.wikipedia.org/wiki/Copenhagen_interpretation :
The Copenhagen interpretation is one of the earliest and most commonly taught interpretations of quantum mechanics.[1] It holds that quantum mechanics does not yield a description of an objective reality but deals only with probabilities of observing, or measuring, various aspects of energy quanta, entities that fit neither the classical idea of particles nor the classical idea of waves. The act of measurement causes the set of probabilities to immediately and randomly assume only one of the possible values. This feature of mathematics is known as wavefunction collapse. The essential concepts of the interpretation were devised by Niels Bohr, Werner Heisenberg and others in the years 1924-27. -----------
"When the Copenhagen interpretation was first expressed, Niels Bohr postulated wave function collapse to cut the quantum world from the classical.[5] This tactical move allowed quantum theory to develop without distractions from interpretational worries. Nevertheless it was debated, for if collapse were a fundamental physical phenomenon, rather than just the epiphenomenonof some other process, it would mean nature was fundamentally stochastic, i.e. nondeterministic, an undesirable property for a theory.[3][6] This issue remained until quantum decoherence entered mainstream opinion after its reformulation in the 1980s.[3][4][7]" ----------- Decoherence is what happens when you trace out a subsystem that doesn't interest you or over which you have no control. Given a density matrix [A B] [C D], tracing out a qubit gives [A+D]. In particular, an EPR pair (fully entangled pair of particles) has a density matrix 1/2 * [1 0 0 1] [0 0 0 0] [0 0 0 0] [1 0 0 1] but when you trace out one of the particles, the result is the mixed state 1/2 * [1 0] [0 1]. A photon that bounces off a semisilvered mirror so that part of the wavefunction amplitude gets reflected and part goes into a human's eye entangles the human's brain with the photon. Mathematically, there's no reason to choose the basis "human sees photon" (x) /"human doesn't see photon" (y) as opposed to (x + y) / (x - y), but because brains evolved only to perceive information they could use, decoherence pretty much means a human's never going to be aware of being in a superposition. I think, on the other hand, it's likely that viruses could exploit superposition somehow. -- Mike Stay - metaweta@gmail.com http://www.cs.auckland.ac.nz/~mike http://reperiendi.wordpress.com