Most computer and information scientists believe that the next big leap forward in computing will be the invention of a quantum computer. Actually, there are people already at work on such a device and very basic prototypes are under scrutiny. However, there’s a problem with quantum computing and it has to with a certain cat.
Erwin Schrödinger, an Austrian physicist, one proposed a thought experiement. Take a cat and put it in a box with a deadly poison. Hook the poison up to a Geiger counter which will detect radiation from a substance that decays at the rate of one atom per hour. If the counter detects a radioactive effect, the poison is released and the cat dies. If not, then the cat lives. Now, seal the box and protect it from outside influence. At that point we don’t know the fate of the cat. The radioactive substance might lose an atom, it might not. Because of this, the cat can be seen as being alive and dead at the same time.
Only when we open the box and observe the cat do we collapse the probablilties into a single reality.
This, in a nutshell, is how a quantum computer works. We take quantum superpositions in atoms or particles and change them to represent data. So instead of a transitor’s power state (on or off) representing a 1 or 0, the spin of an electron indicates a 1 or 0. However, quantum physics indicates that things like spin and superpositions can exist in multiple states at the same time, just like the cat in the box. Only when we observe them do the probabilities fall into reality.
This is called wave function collapse. Quantum mechanics says that some particles exist in multiple states simultaneously, kind of like how light behaves as both a particle and as a wave. As long as nothing observes the particle, it remains in multiple states and perhaps even in multiple places. But, as soon as something or someone observes the particle, it snaps into one state.
In other words, a quantum computer must first protect the atoms manipulating the data from direct observation. A mere glance makes the whole thing fall apart. So while progress is being made on the quantum computer, there’s a long way to go.