Posts tagged ‘Schrödinger’

October 3rd, 2013

Quantum Entanglement and the Many Worlds Interpretation

by Max Andrews

Erwin Schrödinger introduced quantum entanglement in a 1935 paper[1] delivered to the Cambridge Philosophical Society in which he argued that the state of a system of two particles that have interacted generally cannot be written as a product of individual states of each particle.

|Particle A interacting with B〉 ≠ |A〉|B〉

Such a state would be an entanglement of individual states in which one cannot say with any certainty which particle is in which state. Disentanglement occurs when a measurement is made.[2] This is what gave rise to Schrödinger’s famous (or infamous) cat illustration, which will be useful in understanding the role of measurement and the following consequent for a quantum version of many worlds.

The non-interactive state of two particles cannot be expressed as a certain conjunction of the two states. An example of an entangled state is

Screen Shot 2013-10-03 at 1.38.29 PM

November 26th, 2012

New Paper: The History and Macro-Ontology of the Many Worlds Interpretation of Quantum Physics

by Max Andrews

In 1956 Hugh Everett III published his Ph.D. dissertation titled “The Theory of the Universal Wave Function.”  In this paper Everett argued for the relative state formulation of quantum theory and a quantum philosophy, which denied wave collapse. (DOWNLOAD HERE)

Initially, this interpretation was highly criticized by the physics community and when Everett visited Niels Bohr in Copenhagen in 1959 Bohr was unimpressed with Everett’s most recent development.[1] In 1957 Everett coined his theory as the Many Worlds Interpretation (MWI) of quantum mechanics.  In an attempt to circumvent the problem of defining the mechanism for the state of collapse Everett suggested that all orthogonal relative states are equally valid ontologically.[2]  What this means is that all-possible states are true and exist simultaneously.

November 8th, 2012

Entangle Schrödinger’s Cat

by Max Andrews

Nothing is more adorable than a kitten playing with string, but when Schrödinger’s cat becomes entangled, things get really weird.

Two research teams have independently added an extra layer of quantum oddity – the property of entanglement - to a test of wave-particle duality, a real-life demonstration of the ideas captured by physicist Erwin Schrödinger’s famous thought experiment involving a box and a precarious puss.

This extra layer of entanglement lets the researchers delay measuring the results of the test for an indefinite amount of time, even though the measurement itself is supposed to have determined earlier on whether a photon is behaving as a particle or a wave at a particular point in the experiment. It’s the equivalent of putting off the decision to check whether Schrödinger’s cat is alive, dead or something in between, for as long as you like.

Understanding this doubly quantum effect could be useful when building quantum computers and communication networks, which depend on entanglement to function.

October 23rd, 2012

Karl Popper on the Many Worlds Interpretation

by Max Andrews

In a brief section of Karl Popper’s Quantum Theory and the Schism in Physics[1] he discusses his attraction to the Many Worlds Interpretation of quantum physics as well as the reason for his rejection of it. Popper is actually quite pleased with Everett’s three-fold contribution to the field of quantum physics. Despite his attraction to the interpretation he rejects it based on the falsifiability of the symmetry behind the Schrödinger equation.

Popper’s model allows for a theory to be scientific prior to supported evidence.  There is no positive case for purporting a theory under his model. There can only be a negative case to falsify it and as long as it may be potentially falsified it is scientific.  Thus, a scientific theory could have no evidence or substantiated facts to provide good reasons for why it may be true. What makes this discussion of MWI interesting is that despite Popper’s attraction to MWI it’s not the attraction that makes it scientific, it’s his criterion of falsification.

In favor of MWI:

  1. The MWI is completely objective in its discussion of quantum mechanics.
  2. Everett removes the need and occasion to distinguish between ‘classical’ physical systems, like the measurement apparatus, and quantum mechanical systems, like elementary particles.  All systems are quantum (including the universe as a whole).
  3. Everett shows that the collapse of the state vector, something originally thought to be outside of Schrödinger’s theory, can be shown to arise within the universal [Schrödinger] wave function.
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