[ZeroZero (OP)]

So I am trying to understand qubits. I used Utube, but although there are many descriptive videos and a few that go over my head, I still dont understand the Qubit, though I can describe it.
First i explain what I can understand. In a Classical computer bits are binary. in a 4 bit computer you can store up to the number 15 (16 including zero) in  one address. With each binary bit the number you can store doubles 1bit can store two numbers (0 or 1) 2 bits 4 numbers, 3 bits 8 numbers.
In a Cubit I am told (but I don't understand how) that each extra cubit multiplies the potential number stored exponentially.  As such adding further qbits increases the storage potential by a exponant.
When I try to understand this people say that a qubit can be in more than one spin state - i.e. up and down at the same time (until read). This  apparently gives the power to store more numbers

But how??

I am not necessarily looking for a physical explanation of the hardware, though I know its some kind of deeply frozen qubit wired with probes. Hopefully I can skip over that stuff, but how, abstractly can one quibit be considered?
Let me phrase the question this way. Suppose you have a three qbit quantum machine
You want to store a series of numbers in it starting at zero and increasing until you run out of power. The first Qubit could be zero and it could be one (just like a classical  binary machine)  but  allegedly it can also be in both states simultaneously. What happens then? Is it still a 1 and still a zero? Is it both added together - in this case 1? How are the numbers managed?

Hopefully people will understand my question?

[evan_au]

The first Qubit could be zero and it could be one (just like a classical  binary machine)  but  allegedly it can also be in both states simultaneously. What happens then?

When measured, a qubit can be either 0 or 1.
- If it is set to emulate a "classical" computer, a qubit can be set to represent exactly 1 or 0, so that when it is read, it will be 1 or 0 (respectively).
- However, a qubit can be set to anywhere in a 2-dimensional space, of which 1 and 0 are just two particular values.
- This 2-dimensional coordinate space can represent a point on the surface of the Earth (specified by the latitude and longitude), of which the North Pole and South Pole are just two particular locations
- If the qubit is any value except 1 and 0, there is a finite probability that they could be either 1 or 0 when read.
- This becomes really powerful when multiple qubits become entangled, and are processed together (without reading them)

To make it more complicated, qubits are very delicate, and easily disturbed, so there is a finite probability that a qubit will be read as a 0, even if you initially set it to exactly 1. Practical and effective correction of these errors is an unsolved problem in quantum computers.
 
See: https://en.wikipedia.org/wiki/Qubit

[yor_on]

That question is really difficult to answer. First of all you need to look at what a superposition is thought to mean, It's a representation of several possibilities that give you one specific answer at your measurement. Before a measurement all those possibilities are viable, and although you might be able to define different probabilities to them, they all 'co exist' in a same physical and mathematical space. If we take an atom you can excite it, give it more 'energy' which then will put it in another energy state (transitions). The states you create there could be seen as you programming it into superpositions, as well as defined 'zeros' and 'ones''. So some of them you define as 'ones', others as 'zeros', then some as 'super positioned' into a undefined mix of both.

Another thing with superpositions is that they can be at 'several locations' at a same time, or if you like, the possibility of them actually being 'somewhere' will only materialize in your measurement, before that they can be seen as 'everywhere', although once again with different probabilities depending on 'location' . https://www.scientificamerican.com/article/quantum-physics-may-be-even-spookier-than-you-think/

Then again, maybe it's just a physical interaction in this? Saw it referred to as the 'Rydberg state'. https://www.sciencedirect.com/topics/chemistry/rydberg-state

" A Rydberg state is a state of an atom or molecule in which one of the electrons has been excited to a high principal quantum number orbital. Classically, such a state corresponds to putting one electron into an orbit whose dimensions are very large compared to the size of the leftover ion core. Among the novel properties of these states are extreme sensitivity to external influences such as fields and collisions, extreme reactivity, and huge probabilities for interacting with microwave radiation. A wide variety of types of experiments of current interest in atomic, molecular, and optical physics involve the use of Rydberg states." http://www.phys.ttu.edu/~gglab/rydberg_state.html

But they have still not 'fell out' into one definite outcome. The idea of programming qubits is pretty weird in that you can put in several 'programs' at a same time, by how you define (set) those superpositions. That as they can contain both a 'one' and a 'zero' at a same time. Here's one such program https://medium.com/qiskit/making-a-quantum-computer-smile-cee86a6fc1de

okay, the link describes them as being entangled instead. Don't really know if that is the better way to look at it? Normally a entanglement presumes something 'bumping' into something else correlating for example a spin. maybe I'm missing something here. Ahh, okay it's a question of terminology. A superposition is a 'entangled state' as you have both the 'one' and the 'zero' undefined but present.

Heh :)

Here's the last bit of the puzzle. I realized that I didn't mention how one then would be able to 'superposition' a atom. Setting them to 'ones' and 'zeros' is easy. You just have to define two energy states arbitrarily, but how the heck do you then set those other atoms into a intermediate state, aka this 'superposition'? https://www.forbes.com/sites/chadorzel/2017/02/28/how-do-you-create-quantum-entanglement/

what strikes me here is that it seems you need a entanglement between two atoms to create this 'undefined state'? So maybe I'm bicycling in the blue yonder thinking about it as a singular atoms superposition? That is, you need two to create a entanglement? That doesn't strike me as correct, after all, as long as you haven't interacted with the atom it should be in a super position. Now this is a wild guess, but I would assume that you only interact with those you want to set to defined values, and leave the rest be.

" One of the main principles of quantum physics is the superposition of states. Systems exist simultaneously in different states until they are measured and the system opts for one of the possibilities. As long as the superposition lasts, the system is said to be in a coherent state. In real systems, sets of diverse elemental particles or atoms exist in a state of superposition, for example, in different positions simultaneously, with different levels of energy, or with two opposite spin orientations. These have weak coherence—the superposition is broken easily by the vibrations associated with temperature and the interactions with the environment.  " https://phys.org/news/2016-03-quantum-distillation-method-coherence-states.html

Then again, there's also a method referred to as 'setting the atom in a excited state where it oscillates between the ground and excited state over time'  'by shining coherent electromagnetic radiation'

Now I don't know what method you might like, I'll just leave that up to you :) https://physics.stackexchange.com/questions/190944/how-to-experimentally-create-an-atom-in-a-superposition-of-ground-and-excited-st

And it is tricky.

It gives you even more questions thinking of it. As you order those atoms into a 'system' you should destroy all superpositions as it seems to me. And presuming they interact through Rydberg states should, as far as I see, indeed create a entanglement, they 'bump' into each other sort of. So the method using coherent 'electromagnetic radiation' seem like a necessity if you want to 'set' new superpositions. But I don't see how one creating this system still can guarantee them to stay that way?