A qubit is a quantum bit and represents some value in a quantum computation.

The concept is similar to that of the basic unit of information in computing called a bit. However, the bit is a binary unit in which only two values are recognized, while the qubit can represent a wide range of values.

For Example: for a binary unit, there are two values, “0” and “1” where 0=Off and 1=On. In this case, a bit can either be 1 or 0, while a qubit can be 1, 0, or a combination of both.

At this point, we must remember that quantum mechanics attempts to define probabilities of something happening (an electron going through the left slit or the right slit), so in this sense, a qubit must be a combination of values that = 1

If we want to describe what happens in an atomic event, we have to realize that the word “happens” can only apply to the observation, not to the state of affairs between two observations.

• Heisenberg

Do not keep saying to yourself, if you can possibly avoid it, ‘But how can it possibly be like that?’ because you will go down the drain into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.

• Feynman

http://youtu.be/DfPeprQ7oGc?t=2m

When comparing this with the expected P12(x), we can clearly see the difference and where about the conflict arises.

What occured

What we thought would occur

Keep in mind that when shooting a single particle, such as an electron, we would not expect to see the tendencies of a wave.

For another visual aid, we would assume something like this would occur:

If a single particle was shot at this screen, we know there is a 50% chance it will go through the left slit and an equal probability of it going through the right. A single photon, shot only once, cannot demonstrate interference. But, over time a pattern of interference will begin to emerge.

In this example, remember that P1(x) would occur when slit 2 is covered and P2(x) would occur when slit 1 is covered.

[Don’t worry about P12(x) yet!!]

At this point in our experiment, we expect these things to happen because the wave theory was still the most firmly held explanation for the nature of light at the time.

According to wave theory, light will be refracted by the slit and scatter along the detector in a way that the center line through that slit will show the most intense portion of light. For example:

Although it can not tell you what will happen, quantum mechanics sets out to determine what the probability that something could happen is.

Spoiler Alert!!

According to the wave-particle duality school of thought, the movement of particles can be described mathematically by what is called a probability amplitude in a similar manner to waves. The amplitudes of multiple particles then, can create a sort of interference due to the interaction of 2 waves' frequencies.

Click here to see interference in thermal vision!!