Posts tagged ‘quantum entanglement’

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 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.