Quantum Computers
Over the last decades, computers have become smaller, and more powerful. This has had countless positive influences on the world over the years. However, humanity is slowly starting to reach the physical boundaries of a classical computer, like the ones most of us have standing on our desks. The problem is that computer parts are starting to become the size of an atom. To understand why and how that is a problem we need to understand how typical computers work first.
Modern-day computers are made up of 3 basic units, the memory unit, the arithmetic unit, and the control unit. These are made up of computer chips that contain basic modules which again are made up of logic gates, containing transistors.
A transistor is the simplest form of a data processor in computers. For example, the iPhone 13 has about 15 billion of them, which is double the human population. It is basically a switch that can block or open the way for data to come through. This allows transistors to be in two distinct states, and so it can store two different numbers, 1 and 0. These 1s and 0s are also called bits. A combination of multiple bits is used to show more complex things, like numbers or even words. Multiple transistors combine to form logic gates, but these still do very simple things, for example, the AND logic gate. It gives out a 1 if all of its inputs, by the transistors, are 1, and otherwise a 0. Multiple logic gates then finally make actually meaningful modules that can carry out proper calculations, like adding two numbers, for example, 5 + 6 = 11. If you have multiple of these meaningful modules, you can multiply, and if you can multiply everything is possible. In other words, try imagining that a computer is a group of children, answering very simple mathematical problems. The bigger the bunch of children the higher the computing or calculation power. Theoretically, a very large group of children could do everything from astrophysics to Zelda. However, if you want to cram more computing power into a smaller space, the individual parts get smaller and smaller, until quantum physics makes things difficult.
Coming back to the idea of transistors. Electricity, which flows through the transistors is simply just electrons. As already mentioned, transistors, can be in an open and in a closed position: The open one allows electrons to pass through, and the closed one blocks the path of the electrons. Most modern-day transistors, are about 14nm in size, which is about 0.000014mm. This means they are about 500 times smaller than a red blood cell, or 700,000 times smaller than the width of a credit card. They are unimaginably small. Now obviously this can cause a lot of problems. As these transistors are shrinking to the size of atoms, electrons may sometimes simply pass through the transistor even if they are not supposed to. A process called quantum tunnelling allows them to pass through the blockade in the transistor. This is because in the quantum realm, physics works a lot different. As you may have heard, scientists are trying to use this “weird” quantum physics to their advantage, by building quantum computers.
As already explained above, in normal computers, bits are the smallest units of information. In quantum computers, instead of bits, there are qubits. Qubits also have 0s and 1s, but they are differentiated by their vertical or horizontal polarized. However, unlike normal bits, qubits can be in something called a super position. In a super position, the qubits exist in both states so 0 and 1 simultaneously, but as soon as you test their value by sending them through a filter, the qubits have to decide to be either vertical or horizontally polarized and collapse into one of the states, that is 0 or 1. The interesting part of this is, that this opens many new doors for calculations. In other words, a group of 4 bits, can be in only one of 16 possible combinations: 1001, 0110, and so forth, so of all combinations, 4 bits can only be in one of the 16 compositions at the same time. A group of 4 qubits, on the other hand, can be in all 16 of those possible combinations at the same time, as the qubits do not have a definite value until they are measured. This number of possible compositions grows with the number of qubits. This means, with only 20 qubits you can already have 1 million different combinations at once.
Another exciting feature of these qubits is entanglement. Entanglement means that the qubits are connected in such a way that; no matter how far these qubits are apart, if you change the value of one of them, the other one will instantly react. This means that if you measure just one qubit, you already know the value of its pair. Another difference from normal computers is that quantum computers have something called qubit manipulation. Remember the normal logic gates from classical computers? They only produced one outcome so either a 0 or 1, based on their inputs. For example all the inputs are 1 then the output is 1 and otherwise a 0. Well for quantum computers that is a bit different. A quantum gate (logic gates for quantum computers) has an input of a superposition, rotates probabilities, and has another superposition as an output. However, this is a super complex process. A supercomputer with only one quantum gate, would have an input of qubits, entangle and process them, and an output of superpositions, and then collapse them using a filter, to have a usable outcome of 0s and 1s. This means all the answers to your questions, would be calculated simultaneously and not one after the other. However, you will only get one of the outcomes as you have to collapse the qubits, but if you cleverly exploit superpositions and entanglement, quantum computers will be a lot more efficient and especially much faster and more powerful than could ever be possible from a normal computer. In a supercomputer with lots and lots of quantum gates, this process of course is even more complex, which is the case. This means quantum computers often are the size of rooms, and are very costly to use, as they only work at degrees way below freezing point. This means that for the moment they are only used by big companies like Google and IBM, for extremely complex tasks that even the most powerful classical computers would take years to complete.
In conclusion, quantum computers are extremely fast and superior to normal computers, but they probably will not replace your home computer in the near future, as they still are too big, expensive, and not optimized for private use. However, they can have a big effect on the future, and open new doors.
Sources:
Staff, ScienceAlert. “How Do Quantum Computers Work?” ScienceAlert, 15 Feb. 2019, https://www.sciencealert.com/quantum-computers
Kurzgesagt, director. YouTube, YouTube, 8 Dec. 2015, https://www.youtube.com/watch?v=JhHMJCUmq28 Accessed 9 Oct. 2022.
Chris Woodford. Last updated: June 6. “How Do Computers Work? A Simple Introduction.” Explain That Stuff, 6 June 2021, https://www.explainthatstuff.com/howcomputerswork.html .
Chris Woodford. Last updated: December 8. “How Do Transistors Work?” Explain That Stuff, 21 Nov. 2021, https://www.explainthatstuff.com/howtransistorswork.html#:~:text=A%20transistor%20is%20a%20miniature,output%20current)%20at%20the%20other
