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  • For most of our history, human technology consisted of our brains, fire, and sharp sticks

  • While fire and sharp sticks became power plants and nuclear weapons

  • The biggest upgrade has happened to our brains

  • Since the 1960's, the power of our brain machines has kept growing exponentially

  • allowing computers to get smaller and more powerful at the same time

  • But this process is about to meet its physical limits

  • Computer parts are approaching the size of an atom

  • To understand why this is a problem, we have to clear up some basics

  • In a Nutshell -By Kurzgesagt

  • A computer is made up of very simple components

  • doing very simple things

  • Representing data, the means of processing it, and control mechanisms

  • Computer chips contains modules which contains logic gates, which contains transistors

  • A transistor is the simplest form of a data processor in computers

  • basically a switch that can either block, or open the way for information coming through

  • This information is made up of bits

  • Which can be set to either 0 or 1

  • Combinations of several bits are used to represent more complex information

  • Transistors are combined to create logic gates which still do very simple stuff

  • For example, an AND Gate sends an output of 1 if all of its inputs are 1 and a output of 0 otherwise

  • Combinations of logic gates finally form meaningful modules say for adding two numbers

  • Once you can add, you can also multiple

  • and once you can multiple, you can basically do anything

  • Since all basic operations are literally simpler than first grade math

  • You can imagine a computer as a group of 7 year old answering really basic math questions

  • A large enough bunch of them could compute anything

  • from astrophysics to zelda

  • However, with parts getting tinier and tinier

  • Quantum physics are making things tricky

  • In a nutshell, a transistor is just a electric switch

  • Electricity is electrons moving from one place to another

  • So, a switch is a passage that can block electrons from moving in one direction

  • Today, a typical scale for Transistors is 14 nanometers

  • Which is about 8 time less than a HIV virus' diameter

  • and 500 times smaller than a red blood cells

  • As transistors are shrinking to the size of only a few atoms

  • Electrons may just transfer them to the other side of a blocked passage

  • viral process called Quantum Tunneling

  • In the quantum realm, physic works quite differently from the predictable way were used to

  • and traditional computers just stop making sense

  • We are approaching a real physical barrier for our technological progress

  • To solve this problem

  • scientist are trying to use these unusual quantum properties to their advantage

  • by building quantum computers

  • In normal computers, bits are the smallest unit of information

  • Quantum computers use Qubits which can also be set to one of two values

  • A qubit can be any two level quantum system

  • such as a spin and a magnetic field or a single photon

  • 0 and 1 are the system's possible states

  • like the photons horizontal or vertical polarization

  • In the quantum world, the qubit doesn't have to be just one of those

  • It can be any proportions of both states at once

  • This is called Superposition

  • But as soon as you test its value say by sending the photon through a filter

  • It has to decide to be either vertically or horizontally polarized

  • So as long as it's unobserved

  • The qubit is in a superposition of probabilities for 0 and 1 and you can't predit which it'll be

  • But the instant you measure it

  • It collapses into on of the definit states

  • superposition is a game changer

  • Four classical bits can be in one of two to the power of four different configurations at a time

  • that's 16 possible combinations at which you can use just one

  • Four qubits in superposition however, can be in all of those 16 combinations at once

  • This number grows exponentially with each extra qubit

  • 20 of them can already store a million values in parallel

  • A really wired and uninsured property qubits can have is Entanglement

  • A close connection that makes each of the qubits react to a change in the other state instantaneously

  • no matter how far they are apart

  • This means when measuring just one entangled qubit, you can directly to use property of it's partner's

  • without having to look

  • Qubit Manipulation is a mind bender as well

  • A normal logic gate gets a simple set of inputs and produce one definite output

  • A quantum gate manipulates an input of superposition rotates probabilities

  • and produces another superposition as its output

  • So a quantum computer sets up some qubits, apply quantum gates to entangle them and manipulate probabilities

  • then finally measures the outcome collapsing superposition to an actual seqence of 0s and 1s

  • What this means is you get entire lot of calculations that are possible with your setup all done at the same time

  • Ultimately you can only measure one of the results and it'll only probably be the one you want

  • So you might have to double check and try again

  • But by cleverly exploiting superposition and entanglement

  • this can be exponentially more efficient than would ever be possible on a normal computer

  • So, while quantum computers will not probably not replace our home computers

  • in some areas, they are vastly superior

  • One of them is database searching

  • to find something in a database, a normal computer may have to test every single one of its entries

  • Quantum algorithms need only the square root of that time

  • which for large databases, is a huge difference

  • The most famous use of quantum computers is ruining IT sercity

  • right now you are browsing email and banking data is being kept secure by an encryption safety system

  • in which you give everyone a public key to encode messages only you can decode

  • The problem is that this public key can actually be used to calculate your secret private key

  • Luckily, doing the necessary math on any normal computer would literally take years of try and error

  • But a quantum computer with exponential speed-up could do it in a breath

  • Another really exciting new use is simulations

  • Simulations of the quantum world are very intense on resources

  • and even for bigger structures such as molecules they often lack accuracy

  • So why not simulate quantum physics with actual quantum physics

  • Quantum simulations could provide new insights on proteins that might revolutionize medicine

  • Right now we don't know if quantum computers will be just a specallized tool

  • or a big revolution for humanity

  • We have no idea where the limits of technology are

  • and there's only one way to find out

  • This video is supported by the Australian Academy of Science

  • which promotes and supports excellence in science

  • Learn more about this topic and others like it at nova.org.au

  • It was a blast to work with them, so go check out their site!

  • Our video are also made possible by your support on patreon.com

  • If you want to support us and become part of the Kurzgesagt bird army, check out our Patreon page!

  • Subtitles by James Zhang [revisioned by Pietro Pasquero]

For most of our history, human technology consisted of our brains, fire, and sharp sticks

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Quantum Computers Explained – Limits of Human Technology

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    mommy posted on 2015/12/20
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