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Maybe you've heard this phrase before, maybe you haven't. But all the same "quantum computers" is a pretty evocative name to be tossing around. Most of the time when you hear the word "quantum" put together with anything else it's typically to explain away some facet of a science fiction show. However in this case, while still being some years away, quantum computers are achievable. And the interesting field of science and engineering surrounding them is what we will be exploring over the next few articles as I hopefully explain the complicated world of quantum computers. This week we will be covering the basics of quantum mechanics.
The word "quantum" is so commonly used in science fiction that it has become a trope for writers to explain away some facet of their world and has lost much of it's meaning
First of all you should know what scientist mean when they say quantum. Quantum itself is just the smallest amount of mass possible, and often this isn't what people are talking about. Instead, they are usually talking about something in relation to the mechanics surrounding particles of this size. Because when things get as small as when they are described as quantum physics just starts saying "nope" and strange things start happening. Bellow is a list and description of some of the most important effects.
Superposition:
This is probably the most well known part of quantum mechanics, Essentially what it means is that any quantum particle can be in 2 states at once at any given time even when the two states would otherwise be mutually exclusive or contradictory. Then when the quantum particle is observed it settles into one of the states, but doesn't have to remain there. To explain this further, imagine a particle has a 50% chance of being 2 colors. And if you were to observe the particle you would see that it is blue instead of red. Normally you could expect to look at it again and see that it was still blue, but a quantum particle in a superposition can change, making it so that every time you look at it again there is a 50% chance it is either color. This can work for a number of properties including hardness, and position in space.
This is a classic thought experiment on superposition called Schrodinger's box, in which, while the cat is not observed, it is both alive and dead until someone opens the box and sees if the cat is alright.
Entanglement:
Entanglement occurs when two quantum particles interact with one another (this interaction occurs when particles are close enough together). When this happens the particles become connected and their superpositions link together. In this state when one particle is observed the other takes the opposite state and vice versa, seemingly instantaneously. No one knows exactly how this effect happens as it is one of the big mysteries of quantum physics.
Some people believe that worm holes are connected to quantum entanglement, and hope that someday our mastery of the quantum realm will lead to instantaneous travel through space.
Interference:
This is fairly complicated but electrons, the quantum particle most commonly used are both a wave and a particle. When observed out of it's super state the electron is a single particle, but mathematically it only makes sense to see it as a wave. When these quantum waves interact they can do a couple of things. Waves of a similar frequency (waves shaped the same) increase the frequency of each other creating a higher likely hood that the superposition will resolve one way when observed, this is called positive interference. Adversely the frequency of the two waves can be very different, this creates negative interference that decreases the likely hood that a particle will resolve one way.
The diagram above shows interference. The one wave at the bottom splits into two once it hits the two holes in the wall. These two waves interact causing interference. Positive interference shown in white increases the chance of light going to that position and negative interference shown in black decreases the chance of light going there.
These three essential components are the basics of quantum mechanics. However that was a lot of info I just dumped on you so let me review.
Quantum particles have a superstate, this is when there is a chance that they could be many different things. In this superstate they are a wave. When quantum particles are observed the come out of the super state and settle into one thing. In this regular state they are a particle.
When these quantum particles interact with one another they become linked, when a linked particle is observed and pulled out of its superstate, the same happens for the other linked particle, no matter the distance.
When quantum particles are in a wave form and interact with one another, they cause interference which either increases or decreases the chance that they will be observed a certain way when pulled out of their superstate by observation.
That's all for now, hopefully next week we can move on to what these rules mean for computers, and what exactly quantum computers are. However quantum mechanics is a complicated field and if anything serious about our understand in the field comes up, I will make a separate blog post on that.