Physical Paradox - Quantum Mechanical Paradoxes

Quantum Mechanical Paradoxes

A significant set of physical paradoxes are associated with the privileged position of the observer in quantum mechanics.
Three of the most famous of these are:

1. the Double-slit experiment;
2. the EPR paradox and
3. the Schrödinger's cat paradox,
   

all of them proposed as thought experiments relevant to the discussions of the correct interpretation of quantum mechanics.
These thought experiments try to use principles derived from the Copenhagen interpretation of quantum mechanics to derive conclusions that are seemingly contradictory. In the case of Schrödinger's cat this takes the form of a seeming absurdity.

A cat is placed in a box sealed off from observation with a quantum mechanical switch designed to kill the cat when appropriately deployed. While in the box, the cat is described as being in a quantum superposition of "dead" and "alive" states, though opening the box effectively collapses the cat's wave function to one of the two conditions. In the case of the EPR paradox, quantum entanglement appears to allow for the physical impossibility of information transmitted faster than the speed of light, violating special relativity. Related to the EPR paradox is the phenomenon of quantum pseudo-telepathy in which parties who are prevented from communicating do manage to accomplish tasks that seem to require direct contact.

The "resolutions" to these paradoxes are considered by many to be philosophically unsatisfying because they hinge on what is specifically meant by the measurement of an observation or what serves as an observer in the thought experiments. In a real physical sense, no matter what way either of those terms are defined, the results are the same. Any given observation of a cat will yield either one that is dead or alive; the superposition is a necessary condition for calculating what is to be expected, but will never itself be observed. Likewise, the EPR paradox yields no way of transmitting information faster than the speed of light; though there is a seemingly instantaneous conservation of the quantum-entangled observable being measured, it turns out that it is physically impossible to use this effect to transmit information. Why there is an instantaneous conservation is the subject of which is the correct interpretation of quantum mechanics.

Speculative theories of quantum gravity that combine general relativity with quantum mechanics have their own associated paradoxes that are generally accepted to be artifacts of the lack of a consistent physical model that unites the two formulations. One such paradox is the black hole information paradox which points out that information associated with a particle that falls into a black hole is not conserved when the theoretical Hawking radiation causes the black hole to evaporate. In 2004, Stephen Hawking claimed to have a working resolution to this problem, but the details have yet to be published and the speculative nature of Hawking radiation means that it isn't clear whether this paradox is relevant to physical reality.