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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]


Quantum Computers Explained – Limits of Human Technology

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mommy 2015 年 12 月 20 日 に公開
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