Posts tagged ‘delayed choice experiment’

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.

November 6th, 2011

The Delayed Choice Experiment in Quantum Physics

by Max Andrews

Source: SUNY

If photons are fired through the experiment one at a time (firing photons at a wall with two holes and a photon detector on the other side of the holes), they will build up an interference patter on the other side, as if they had gone through both holes at once and interfered with themselves.  If the experiment is set up so that detectors monitor which hole the photo goes through, the photon is indeed observed to be going through only one hole, and there is no interference pattern.  If a detector is set up not at the holes but intermediate between the two holes and the back wall detector screen then it may be possible to see which route a particular photon took after it had passed the two holes before it arrived at the screen.