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A brief Explanation of Quantum Computers: Part II

By eld3niz | A Brief Explanation | 27 Jul 2021

What is the difference between a normal and a Quantum Computer?

If you haven´t read my last article about why we need Quantum Computers, i highly suggest you take a glimpse at it to understand our motives. Understanding difficult Quantum Mechanical principles is hard so i tried my best to explain the basic principles on which Quantum Computers work. But now, let´s get to the article! 

How do computers store data?

In order to understand what makes Quantum Computers so special, we have to take a look at the fundamental principles of our everyday computers. For ordinary working processes so called Bits are used and represent the smallest unit of Information/ Data. They can either be only 0 or 1 depending on the data itself. Imagine an empty box which in the process is filled with a 0 or 1. A combination of the two values in one box is not allowed since we want to ensure that data is stored safe and compact. You can imagine it like a sphere, where the only allowed direction is up or down. Of course we are not bound to these values on their own. By adding 8 Bits (or little boxes in our case) together, we receive a Byte (containing of 8 boxes). This should be familiar and shows the size of an information up to Kilo-, Mega-, Giga-, ....Byte´s. The sequence of Bits can look like 


which in this case would stand for "Bitcoin". So we see that adding up Bits to a specific sequence let´s us save specific data, depending on its size. With every added bit, the amount of possible stored information gets doubled, making it an exponential process. Give it a try yourself on this link.


How do Quantum Computers store data?

Surprisingly, these us Bits too. But here we append a fancy Quantum to it and born is the Quantum-Bit, also known as QuBit. Instead of now showcasing either 0 or 1, the QuBit lives in a Superposition of the two values 0 and 1. Do you remember our sphere with up and down from above? Let us take a look at it again. 


As you can see, where our normal bits are only allowed to direct in one of the two directions up or down, our QuBit vector can point to any arbitrary point on the sphere building up new possible combinations of 0 and 1. This might be too theoretical for now, but just hold on, you nearly got it! When normal Bits are single stored into one box, now we are able to take a new box and put 2 (Qu-)Bits into this box, 0 AND 1. This means our new box can store even more (double the amount) data than our old box. This is the most promising fact about QuBits. Here is an example of what i mean by that.

We combine 2 normal Bits, where each of them can be 0 or 1. Our possible outcomes are (00), (01), (10) and(11). With 3 Bits we would have (000), (001), .... (111) and so on adding up new Bits. Using Qubits we could combine 2 Bits to (00), (01+10), (01-10), (11), adding one more would result in even more since we can combine xxx with yyy in any possible way (x and y as a placeholder for 0 or 1). With this help, Quantum Computers can store exponentially more data than normal computers with every added QuBit. An this is what makes QuBits in Quantum Computers so powerful. Difficult problems can now be solved way faster, since the amount of possible processed data is unimaginably bigger.


In my next post, you will learn which components are used to build a Quantum PC in order to make use of QuBits, since this stuff is highly theoretical and without implementation rather "needless".


TL;DR: Normal computers use Bits, which are the smallest unit of information and is being represented by either 0 or 1. A Quantum Computers uses QuBits which differ in the possible amount of stored data in comparison to Bits. With the help of Superposition you can store exponentially more information by combining 0 and 1, which in the normal case is prohibited.


Thanks for reading the article and make sure to ask questions, correct information or add ideas!


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Dont feel ashamed to ask. Looking forward to learn from everyone. Kinda interested in Blockchain and Physics. My goal is to describe complex things in the easiest way possible.

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