Quantum Computers Explained – Limits of Human Technology

For most of our history,

human

technology

has consisted of our brains, fire, and sharp sticks. While fire and sharp sticks have been turned into power plants and nuclear weapons, the biggest improvement has been in our brains. Since the 1960s, the power of our brain machines has continued to grow exponentially, allowing

computers

to become smaller and more powerful at the same time. But this process is about to reach its physical

limits

. Computer parts are approaching the size of the atom. To understand why this is a problem, we need to explain some basic concepts. In a nutshell - By Kurzgesagt A computer is made up of very simple components that do very simple things.

Data presentation, data processing tools and control mechanisms. Computer chips contain modules, which contain logic gates, which contain transistors. A transistor is the simplest form of data processor in

computers

, basically a switch, which can stop or open the way for information to arrive. This information is made up of bits, which can take the values ​​0 or 1. Combinations of different bits are used to represent more complex information. Transistors combine to create logic gates, which again do very simple things. For example, an AND gate sends output 1 if all its inputs are 1 and output 0 otherwise. Combinations of logic gates eventually form meaningful modules, for example to add two numbers.

When you know how to add, you can also multiply, and when you know how to multiply, you can do, in principle, anything. Since all basic operations are practically simpler than first grade math, you can imagine the computer as a group of 7-year-olds answering simple math questions. A large enough set of them can explain anything from astrophysics to Zelda. However, as the pieces get smaller and finer,

quantum

physics complicates things. In short, the transistor is simply an electrical switch. Electricity is the movement of electrons from one place to another. So a switch is a passageway that can prevent electrons from moving in one direction.

Today, the typical size of transistors is 14 nanometers, about 8 times smaller than the diameter of the HIV virus and 500 times smaller than a red blood cell. As transistors shrink to the size of a few atoms, electrons can be transferred to the other side of the blocked passage through a process called

quantum

tunneling. In the quantum world, physics works differently than the predictable way we are used to, and traditional computers no longer make sense. We are approaching a true physical barrier to the progress of our

technology

. To solve this problem, scientists are trying to take advantage of these quantum properties by building quantum computers.

In normal computers, bits are the smallest unit of information. Quantum computers use qubits, which can also have one of two values. A qubit can be any two-level quantum system, such as a spin in a magnetic field or a single photon. 0 and 1 are the possible states of this system such as the horizontal or vertical polarization of the photon. In the quantum world, the qubit does not have to be just one of them. It can be a proportion of both states simultaneously. This is called Overlay. But once its value is tested, for example by sending the photon through a filter, it should decide whether it is vertically or horizontally polarized.

So, as long as it is not observed, the qubit is a superposition of probabilities for 0 and 1, and you cannot predict which one it will be. But, the moment you measure it, it appears in one of the defined states. Overlay changes everything. Classic bits can be in one of two to four different configurations at a time. There are 16 possible combinations of which you can only use one. Overlapping qubits, on the other hand, can be in those 16 combinations simultaneously. This number grows exponentially with each additional qubit. 20 of these can hold a million values ​​in parallel. One strange and contradictory property that qubits can have is interconnectedness, a tight connection that causes each of these qubits to react instantly to the changing state of the other, no matter how far away they are.

This means that when just one of the entangled qubits is measured, the properties of its partner can be directly deduced without having to see it. Manipulating qubits also affects the brain. A normal logic gate takes a simple number of inputs and produces a defined output. A quantum gate manipulates an input of superpositions, rotates the probabilities, and produces another superposition as an output. So a quantum computer creates several qubits, applies quantum gates to connect them and manipulate probabilities, and finally measures the result, collapsing the superpositions into a string of 0s and 1s. This means that it simultaneously solves a large number of possible calculations based in your scheme.

After all, you can only measure one of those results and it will probably be the one you want, so you might want to double-check and try again. But by making clever use of overlay and interconnection, this can be exponentially more efficient than would be possible on a normal computer. So while quantum computers probably won't replace our home computers, in some areas they are far superior. One of those areas is database research. To find something in a database, a normal computer may need to try each of the records. Quantum algorithms only need the square root of that time, which for large databases makes a huge difference.

The most famous use of quantum computers is the destruction of computer security. Right now, your web browsing, email, and banking details are kept secure using an encryption system where you give everyone a public key to encrypt messages that only you can decrypt. The problem is that the public key can be used to calculate your private secret key. Fortunately, doing the necessary calculations on a normal computer would take years of trial and error. But an exponentially accelerated quantum computer could do it instantly. Another interesting new use is simulations. Simulations of the quantum world require a lot of reserve and even for larger structures, such as molecules, they often lack precision.

So why not simulate quantum physics with quantum physics? Quantum simulations could give us new insights into proteins, revolutionizing medicine. Right now we don't know if quantum computers will be just a specialized tool or a great revolution for

human

ity. We have no idea where the

limits

of technology are and there is only one way to find out. This video is supported by the Australian Academy of Sciences, which promotes and supports excellence in science. Find out more about this topic and others like it at nova.org.au. It was a pleasure working with them, so check out their site!

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