November 8th, 2012
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.
read more »
October 24th, 2012
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. 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 . 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. An orthogonal state is one that is mutually exclusive. A system cannot be in two orthogonal states at the same time. As a result of the measurement interaction, the states of the observer have evolved into exclusive states precisely linked to the results of the measurement. At the end of the measurement process the state of the observer is the sum of eigenstate—or a combination of the sums of eigenstates, one sum for each possible value of the eigenvalue. Each sum is the relative state of the observer given the value of the eigenvalue . What this means is that all-possible states are true and exist simultaneously.
read more »
October 23rd, 2012
In a brief section of Karl Popper’s Quantum Theory and the Schism in Physics 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:
- The MWI is completely objective in its discussion of quantum mechanics.
- 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).
- 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.
read more »
September 7th, 2012
Pioneering experiments have cast doubt on a founding idea of the branch of physics called quantum mechanics.
The Heisenberg uncertainty principle is in part an embodiment of the idea that in the quantum world, the mere act of observing an event changes it.
But the idea had never been put to the test, and a team writing in Physical Review Letters says “weak measurements” prove the rule was never quite right.
That could play havoc with “uncrackable codes” of quantum cryptography.
Quantum mechanics has since its very inception raised a great many philosophical and metaphysical debates about the nature of nature itself.
The experiment requires preparing pairs of “entangled” photons, the particles from which light is made (BBC)
read more »
August 29th, 2012
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. 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.
In 1957 Everett coined his theory as the Many Worlds Interpretation 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. What this means is that all possible states are true and exist simultaneously.
We have a problem of using secondary sources. I’ve provided a link below that takes you back to Everett’s original dissertation to read for ourselves.
July 26th, 2012
The level three multiverse is particular to a certain interpretation of quantum mechanics being Hugh Everett’s Many Worlds Interpretation. It is a mathematically simple model in support of unitary physics. Everything that can happen in the particle realm actually does happen. Each of the many worlds following a split represents one of the possible worlds remaining after the event which led to the split. There are no interactions between these worlds. No observer or inhabitant of them will notice anything about the other worlds.
Everett’s interpretation is not impossible due to the fact that we do not experience the continual splitting of our world. Observers would only view their level one multiverse, but the process of decoherence—which mimics wave function collapse while preserving unitary physics—prevents them from seeing the level three parallel copies of themselves. It is no more contradicted by our failure to experience the splitting than the theory that the earth rotates is contradicted by our failure to experience its movement. 
 Max Tegmark, “The Multiverse Hierarchy,” arXiv:0905.1283v1 (accessed March 15, 2011), 10.
 Some of the commentary is summarized by Karl Popper in Quantum Theory and the Schism in Physics, ed. W.W. Bartley, III (Totowa, NJ: Rowman and Littlefield, 1982): 91-2.
July 18th, 2012
Word of the Week: String Theory
Definition: The leading theory of everything, which describes the earliest moments of the universe in which the four fundamental forces of nature (gravity, electromagnetic, strong nuclear, and weak nuclear) were one force. The most fundamental element of reality are cosmic strings, and their vibration determines what particles or forms it takes.
More about the term: The spontaneous breakdown of symmetries in the early universe can produce linear discontinuities in fields, known as cosmic strings. Cosmic strings are also common in modern string theories in which the most fundamental reality are astronomically tiny vibrating strings (either closed or open depending on the interpretation of the mathematics). The combination of the string/scalar landscape with eternal inflation has in turn led to a markedly increased interest in anthropic reasoning. In this multiverse scenario life will evolve only in very rare regions where the local laws of physics just happen to have the properties needed for life, giving a simple explanation for why the observed universe appears to permit the evolutionary conditions for life. It is argued that such anthropic reasoning can give the illusion of intelligent design without the need for any intelligent intervention. There are at least four ways we can understand the different universes described by string landscape.
read more »
July 11th, 2012
With the recent discovery of a new boson, which is likely to be the elusive Higgs boson, the standard model for particle physics would not be complete. Keep in mind that this only confirms the model that has been used for a long time now. This explains the early moments after the big bang where there was the electroweak force which separated and became the electromagnetic and weak nuclear forces (there’s also the strong nuclear force). This doesn’t unify the theory of gravity. Physicists must still develop a theory of quantum gravity.
read more »
July 11th, 2012
Word of the Week: Decoherence
Definition: A loss of coherence between the angles of components in a superposition and a loss of information due to environment, which gives the appearance of a wave function collapse.
More about the term: A wave function collapse occurs when the outcome of a quantum state is determined by an observer. An observer can be a concious observer or even the interaction of particles. Instead of a determinate state, decoherence is akin to pulling one string out from an entire knot of strings. Decoherence is a major talking point and factor in multiverse scenarios.
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. 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.
read more »