The Insane Mechanism of a Quantum Computer?

this video is sponsored by brilliant stay tuned to the end for a very special offer for arvanash viewers computers have become essential for our modern lifestyle we use them for studying banking shopping and much much more they're now a core component of our everyday lives but in the past couple of decades a new type of computer has been under development the quantum computer it promises to change our lives by potentially revolutionizing medicine communication encryption and artificial intelligence companies like google ibm and microsoft are investing billions to become the dominant player in this technology what's all the fuss about how is a quantum computer fundamentally different than the everyday computers we use and how does it really work that's coming up right now in order to learn how a quantum computer works we need a basic understanding of how an ordinary classical computer works both the classical and quantum computer share many general components so let's look at some of these basic components shared by both types of computers for any computer to work it needs a power supply because energy is needed to run the system in order to work with data they both also need some place to store the data for this purpose both computers generally use hard drive and solid state drives also known as ssds for storing bulk data there is however one big problem with this type of storage it's simply too slow the data transfer between the bulk data storage devices and the processor needs to be faster to help this issue most computers have something called ram or random access memory quantum computers in principle could use a kind of quantum ram memory so the quantum equivalent of ram could look different but its functionality would be the same this memory is much faster than any hard disk or ssd and it's also physically closer to the processor this means the data bandwidth can be much higher and the data can flow much faster the downside is that ram is much more expensive per gigabyte and it's volatile this means that the power goes the data and the ram can get lost also necessary is some kind of central processing unit or cpu this is the brain of the computer that does the actual computation the ram storage is used to keep the cpu fed with data that it needs to work with we also need some device that connects all the different components together this is the motherboard it connects the cpu with the ram storage and any other component necessary to make a functioning computer both the quantum and classical computer need these components that we just mentioned but the main difference between these two types of computers is in how the cpu works a classical cpu is made from transistors a transistor is basically like an on off switch if it's on then it's like the number one and if it's off it's like the number zero one and zero can also represent true or false respectively in this way the transistor has two possible values this is what binary means a transistor represents a binary bit one or zero or on and off or true or false and sets of binary numbers can represent numbers and letters as shown here the most fundamental difference between the quantum and classical computer is that quantum computers do not use binary bits they use quantum bits or qubits now what is a cube it's a bit in a superposition of one and zero what does superposition mean quantum theory shows that quantum objects such as electrons prior to measurement are in multiple states at the same time so something like the spin of an electron which is a measurement of its intrinsic angular momentum when measured is either up or down for simplicity this means that it's either spinning clockwise or counterclockwise however prior to measurement it is said to be spinning both clockwise and counterclockwise at the same time this is what superposition means the electron is in a superposition of both up and down spin only upon measurement does the universe decide that the spin is one or the other it is never measured to be anything in between only up or down but before measurement it's in some combination of both we can visualize a qubit by using a sphere a classical bit can be one or zero this would be the equivalent of the up and down spin or two different distinct positions on the sphere the qubit on the other hand can be in any place on the surface of the sphere depending on the superposition a single qubit can have any value on the sphere this represents the fact that the qubit can be any mixture of one and zero so the possible values are infinite this is the crux of the power of quantum computing so whereas the classical binary bit can only take one of two values the superposition allows a qubit to take on a potentially infinite number of values practically a qubit can be created by various quantum objects like photons electrons or even atoms it doesn't really matter it just needs to be a quantum object in superposition mathematically we write the superposition as this where psi represents the wave function representing the superposition of a cubit alpha squared is the probability of being in the zero state and beta squared is the probability of being in the one state and for the math to be consistent we must have that alpha squared plus beta squared equals one this makes sense because the total probability must be one or a hundred percent thus if we choose alpha to be 1 then beta must be 0 and vice versa but this is the same as the classical case with binary numbers however in a quantum computer these alpha and beta values can be any value between 0 and 1 as long as the equation is satisfied for example we could have a mixture where alpha and beta are each 1 over the square root of 2. this would satisfy the equation because when you square and add these numbers you get 1. the fact that we can use qubits and superpositions is very powerful because it means we can ask several questions at once what is the result if the qubit is one what is the result if the qubit is zero what is the result if it is anything in between so we can calculate the process where the bit is both zero and one and anything in between the downside is of course that the result will also be some superposition so the quantum computer needs to maintain superposition throughout the process the inputs are in superposition and the output will also be in superposition during a computation the quantum computer operates without any measurement of any kind because there are no measurements the computer state evolves according to quantum mechanics the computer follows multiple computational paths at the same time analogous to the way a photon could follow multiple paths through a double slit experiment it only has a certain probability of ending up on certain locations at the end there is a measurement needed to read the result or output this occurs only when the computation is finished as the computer operates no physical record is made of which computation is done it does them all now it's very important to understand that although the calculations are done while qubits are in superposition the final measured answer has to be classical so the result is always a classical result a one or zero you might ask how do we go from superpositions to the final classical answer to do this we have to measure the superpositions to get a one or zero the problem is how do we know what we should get should we get a zero or should we get a one which one is correct this is where quantum algorithms come into the picture these are clever programs created by programming scientists that use mathematical tricks to make sure that the probability of getting the correct answer is as high as it can be how does this work because superpositions are like waves to get the correct answer you want to apply destructive interference to the wrong results and constructive interference on the correct results at the end it combines the results of all these computational paths and does a kind of interference experiment this process of what the correct result is most likely to be is controlled by the algorithm so these algorithms are the key to turning superpositions into the correct classical result so how is this so much more powerful than classical computers for solving certain types of problems the quantum computer doesn't do the usual stuff in a faster way it doesn't calculate all the possible results very quickly it calculates multiple functions at once for multiple possible inputs so for example if you wanted to find a person's phone number in a phone book containing a million entries it's not a problem you would just look up their name in alphabetical order but what if you had the inverse problem you had a phone number and you were trying to find the name that it belongs to a classical computer would have to look up one number at a time on average 500 000 numbers or 500 000 operations before it found the correct name the worst case would be examining 999 99999 numbers before finding the name that it belongs to however the phonebook data was on a quantum computer it could find the name in a thousand operations a thousand is the square root of a million where does this number come from love grover in 1996 developed a quantum algorithm that could quadratically reduce the number of operations needed to find a unique entry other scientists proved that any quantum solution for unstructured searches like the phone book data problem would only need to evaluate the square root of the total number of data points the problem it can solve is searching for a target and a large set of possibilities if you were looking for a needle in a million haystacks you would want to solve it on a quantum computer similarly if you had a large maze and you were trying to figure a way out a classical computer would try each path one at a time make an adjustment then try again many iterations would be needed a quantum computer can try all paths at once and give you an answer almost instantly so what's the holdup in building large quantum computers it's hard to build because first it has to be isolated from the outside world in order to preserve the superposition it cannot interact with any molecules or photons or other particles which could collapse the superposition this superposition throughout the computation process also requires extreme cooling the problem with heat is that thermal fluctuations can either modify or destroy the superposition because the heat energy can interact with the qubits so this is why quantum computers are cooled to near absolute zero that's negative 273 degrees celsius to effectively eliminate all external thermal energy so that the superposition is not modified or broken in addition the different parts of a computer must interact very rapidly with each other qubits can't talk to the outside world but they have to be able to talk to each other very fast so these connections that the qubits must have is not trivial the only thing i haven't covered is how the computer actually works at the central processing unit or cpu level in other words what is actually taking place inside the logic of the central processor how would a computer do something simple like add two numbers together i'll cover this in an upcoming video the interesting thing is that if you think about it the universe itself can be thought of as a kind of computer it processes the present which is the input and computes the result which is the future it computes this based on a set of instructions it is given and what are these instructions they are the laws of physics these laws determine the algorithm of the universe and that's what this channel is all about the study of the instructions the universe uses to determine our destiny if you want to learn more about quantum computing one of the best courses available is on brilliant today's sponsor called quantum computing it's a hands-on interactive course consisting of 33 short lessons that walk you all the way from some of the basic fundamentals such as the nature of computation and quantum bits to building entangled quantum circuits to actually creating quantum algorithms along your journey you'll take quizzes and solve problems which will help you master and retain these concepts long term it's a great way to learn brilliant has a special offer for arvind ash viewers right now if you're among the first 200 people to click the link in the description you get 20 off the subscription if you haven't tried brilliant already this is a great opportunity to start so be sure to click the link in the description and if you have a question please leave it in the comments and i will do my very best to answer it i'll see you in the next video my friend [Music] you

Channel: Arvin Ash

Views: 162,138

Keywords: quantum computing, quantum computers explained, what is a qubit, what is quantum computing, classical vs quantum computing, how does a quantum computer work, what is superposition, quantum mechanics, quantum computing explained, quantum algorithm, quantum algorithms explained, why are quantum computers, why are quantum computers faster, why are quantum computers hard to make, grovers algorithm, binary vs quantum computing, quantum computer, what are quantum computers

Id: RCj_BJ6BddM

Length: 13min 36sec (816 seconds)

Published: Sun Aug 29 2021