Quantum computers are not better computers. They are good for different tasks. They are good to solve tasks that current computers take very long to compute. It's almost impossible to explain how they work in layman terms, because it's quantum technology, which is complete weird shit. Most likely we will never see quantum home computers, maybe we could see some quantum capabilities added to the normal classical computers, but currently the tech is mostly run in lab environment. Because there's lots of interference that will break the function. Also needs to be supercooled to almost absolute zero. An example of a task that is very tedious for a normal computer but easy for a quantum computer is so called "traveling salesman problem". You have a bunch of cities on a map that you want to visit and you need to compute the most optimal route. This problem is easy to solve, but extremely hard to solve to be sure, that your solution is really the most optimal. For normal computers, the more points you have on the map, the longer it will take to compute. And this growth is probably around exponential, so you get to a point where it's simply not practical to even try to compute it, because it would take weeks, months, years. But quantum computers can somehow calculate all the possibilities at the same time and thus making the total time quite short. At least that's how I understand it. Problem with this is, that current computer security and cryptography is based on this, that it is extremely difficult to calculate some things for normal computers. But there will be a point of development in quantum computing where the quantum computer can break through the best current security in minutes. So new security algorythm will have to be developed, and are currently being worked on.

For some kinds of problems, a classical computer considers combinations one at a time:

ABC

ACB

BAC

BCA

CAB

CBA

While a quantum computer does it all on one step:

ABC/ACB/BAC/BCA/CAB/CBA

This is because, in some ways, quantum particles can be in more than one state at the same time!

Now imagine I had used ABCDEFGH for the example. You would be scrolling all day to get to the end of the classic computer example.

Quantum computing is a way of using the properties of quantum mechanics, which is the physics that describes how very small things behave, to perform calculations that are faster than is possible using classical computers.

Classical computers use bits to store information and perform calculations. A bit is a unit of information that can be either a 0 or a 1. Quantum computers use quantum bits, or qubits, to store information. Qubits can represent both a 0 and a 1 at the same time, which allows quantum computers to perform many calculations at once.

Because of this, quantum computers have the potential to solve certain problems much faster than classical computers. For example, they could be used to break encryption codes that would take a classical computer many years to crack. However, quantum computers are still very experimental and there are many challenges to overcome before they can be used for practical applications.

As proven by the other responses, the answer to your question is No. After years of searching, I have never found anyone who can clearly and effectively explain how quantum computing works.

Consider searching for an item in an unsorted list of length N. There's no classical algorithm that lets you find your item in fewer than N/2 queries, on average. This probably makes sense naively.

Grover's algorithm, a quantum computer algorithm, can find your item in sqrt(N) queries.

This seems impossible, but it works because quantum computing Is fucking magic.

Edit: had algorithm name wrong.

First off lex Friedman had a really good podcast on this. Quantum computers use a different processor which is specific to solving one problem, a problem which could take decades to solve on today's supercomputers in days or even hours. A classic computer is great at solving many problems but doesn't specialize in any specific one of them. The use case for me that is interesting is the use of quantum computing in solving complex medicinal, biological, and chemistry problems. IE develop new medicines in an extremely accurate and efficient process

A true quantum computer can perform the calculations a normal computer does in fractions of the time. For instance, you could run a program to solve for the asymmetric cryptography keys for a Bitcoin (hacking ownership of the Bitcoin) that could take years to complete on a modern computer. A quantum computer is so much faster it could do this in fractions of a second. The digital cryptographic cybersecurity solutions used for banking and stock market accounts would also be similarly at risk of being made obsolete in fractions of a second. Luckily, true quantum computers as they exist now are only functional for maybe seconds at a time in isolated development sandboxes as they are only operational at -273 Celsius and below. It's not a technology that could make it to being a household device, probably, ever.

Here is how I think of it (could be wrong, could be too simple).

Traditional computers give information in binary. Example; It is either this or it is not this. It is either on or it is not on.

Quantum computers provide a spectrum answer; it is on, it is not on, it is somewhat on, it is off.

Some computational problems (the things computers solve at their root level) are fine with binary math and don’t benefit from what quantum offers. Counting problems for example. Some computational problems, particularly ones that require advanced math will benefit from computational capabilities of a quantum computer.

Hope this helps.

This answer by the way is right, kind of right and wrong all at the same time. QUANTUM!

The quantum world deals with the very small. It's really hard to grasp it because we're not able to imagine that kind of scale. The atom is like a miniature solar system with lots of empty space. In the beginning of the previous century Rutherford bombarded gold atoms with alpha particles, helium, and some of the particles were scattered back. There were other strange experiments showing the interaction of light and slits which made people think that light was made of waves but also behaved as waves. The photo electric effect showed that light can interact with matter, producing electricity.

Theoreticians came up with mathematical functions. These correspond to probability. Quantum wave functions. In this theory some things are unknowable. Einstein scoffed that 'God does not play with dice!' But the theory has been tested. We can compute probabilities. This is done with special integrals, mathematical functions. But the gist of it is, that particles are not localized. They can go though potential barriers. Quantum tunneling. It's equivalent in our world to walking through a wall. And there is the Heisenberg uncertainty principle which states that you can't know everything about a particle. You can measure certain properties accurately but that will prevent you from knowing more about other properties.

The wave functions when turned into numbers through the appropriate operations that we can use give a probability between one and zero. However, in the quantum world everything is much quicker than in our world and very little energy makes quite a difference. Quantum states want to be in their ground state. You can think of them as pendulums in rest most of the time. If you give them a quantum of energy, they want to go back. This happens in such a short time that none of us can really imagine it.

Unfortunately, we need to bring qubits out of their ground state to do meaningful computation. This means shielding them from outside influences. Which currently requires a special mix of helium isotopes, tubing, and other stuff. This part is hard to shrink.

Also because the quantum world is a busy chaos and decoherence, going back to ground state, exists, quantum computers make many errors. Algorithms to fix them are still in development.

Qubits work fast and due to their nature can explore possibilities that classic computers simply can't. They could be useful for AI systems which will have impact for consumers. For the foreseeable future the resources required are unaffordable for almost everyone.

But never say never. If we have better algorithms and someone figures out how to keep the qubits coherent longer at somewhat higher temperature, perhaps just by having many qubits we could get closer to your wish

A traditional CPU is measured in actions per second. So 4GHz is 4 billion calculations per second.

It works be performing these actions on each cycle of an internal clock. And these actions are based in binary (0 or 1).

A qubit has more than two states. So by encoding a qubit’s states you can ‘use’ more bits per clock. It’s a multiplicative performance increase. And additional tricks/encoding can make it roughly exponential.

When I was in college, one of my friends was a math major. I asked him what math he was studying for, and he said, "Quantum Mathematics." When I asked him what that even meant, he looked up at me with eye bags that wouldn't pass a TSA check in and a dead stare, then said "weird, space math."

I'm going to assume it's like that but with computers.

https://www.youtube.com/watch?v=Eak_ogYMprk

A lot of encryption revolves around super primes 3 * 5 = 15 (put way bigger numbers). A classic computer just has to try every formula in sequence and brute force what primes make up 15 if any. A quantum computer can be asked 15??? and the super position is somehow trying all the answers at once and gives you 3 * 5 in a single hz.

General purpose CPU have bits, mostly 64 bit now, that's how complex a task they can do per cycle. A single qbit quantum computer that can even solve that basic problem above needs to be super cooled with lasers and such though. So at least today it can't instantly crack any harddrive or mine all the bitcoins left because those tasks are too large to fit in the instructions per clock the processor can do.

Let’s say there is a football game between the Rams and the Vikings. A classic computer will pick a winner based on which team has the better record.

A quantum computer will analyze every possible statistic available about both teams to mankind and come up with a prediction.

Quantum computing takes a different approach than normal computing does. As far as my understanding goes, they are more likely to specialize in a certain area than a classical computer is. Take for example a problem that can have a lot of variables and possibly trillions of combination answers. A classical supercomputer might fail at this task because the brute force computing it does would require memory that it simply cannot possess. A quantum computer might instead create a model where patterns may emerge, with the best combination of patterns being the answer. This is however a very rudimentary way of explaining the differences.

As regards to the possibility of there being Quantum PCs, the chances seem very slim. For one, Quantum computers require their processors to be super-cooled, we are talking at the very least a few degrees above absolute zero. They may become more common, but Quantum PCs don't seem achievable, at least for now.

For the ELI5 answer:

A normal computer will compute things as True or False. So a binary 1 or a 0. This forces the computer into only accepting two possible answers for any given problem (True or False). The issue is that no matter how big or small the problem is it has to be solved using that exact same method. It just scales accordingly. Whether it's 2+2 or some calculus equation. This is very time consuming and CPUs today get around that from shear horsepower.

A quantum computer understands that not everything is solved with a True or False statement. It has the capability of engaging with more possible options right from the start. It instead says "How are all of these bits going to relate to my problem" rather than "Is this true, no, is this true, yes, is this true, no"

This might not be entirely accurate but I think it illustrates the point well enough.

ChatGPT got you homie:

Prompt: explain it to me like I'm a drunk five year old: what is the difference between classic computing and quantum computing

Sure! Classic computing is like using a regular old calculator to do math. It can only do one thing at a time, and it can only do things that you tell it to do using a special language called code. Quantum computing is like using a super fancy calculator that can do lots of math problems at the same time, and it can do things that you might not have even thought to ask it to do. It's really fast and powerful, but it's also really hard to understand and use.

Classic computing represents information in 0 and 1 binary digits (bits). Quantum computing bits (qubits) can represent any proportion between 0 and 1, which allows quantum computers to process information in exponential fractions of time when compared to classic computers.

From my understanding and keeping it short and sweet. No. You will never run a QC as your home computer. They do have some very cool uses, but you will only see them pop up in a few places. Things like better computer security and more accurate weather forecasts. Most of the other stuff will be in ways that a consumer wouldn't really see.

This is a gross oversimplification, but a classical computer will think about A and then B and then C. A quantum computer can think about ABC all at the same time.

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Eli10: some problems get much harder when they get bigger. Rather than difficulty scaling linearl (eg, y=a*X), they can scale like a polynomial or exponential (eg y =a**X)

This rule isn't necessarily true for all problems on a quantum computer. You can have problems that take an exponential amount of time to solve on a classical computer, actually take a linear amount of time on a quantum one.

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This is a good read.

Quantum Computing: The World-Changing Race to Develop the Quantum Computer

https://www.newyorker.com/magazine/2022/12/19/the-world-changing-race-to-develop-the-quantum-computer

Classical computer - calculates slowly, with an output answer of "yes" or "no"

Quantum computer - calculates very quickly, with an output answer of "maybe"

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Suppose you had a dice and wanted to know how it rolls. Well, you could build a physics simulator, 3D model, run it on a classical computer and find out, or you could just roll the die and have reality sort it out.

Quantum computing is more like the second option, except with particles and systems that exhibit quantum behavior. The important bit, is that it's not just rolling the die. It's possible to map computation tasks to behavior of these quantum systems. That is an incredibly powerful concept, it can compute some things that are just plain not computable on classical computers because it would take longer than age of the universe to run the computation.

Hard part about it is to map useful computational tasks to quantum computing, it's very much not like programming we are used to on classical computers, it's very demanding on actually understanding the physics involved which is very complicated. The other hard part is building a good enough quantum computer, that's not easy and all the presently working quantum computers have significant limitations.

In summary, don't expect to directly use a quantum computer any time soon, but if things go well, you may be able to use something created using computations done on a quantum computer that couldn't have otherwise been computed.

For example, battery manufacturers have tried to find better materials for making batteries using quantum computers. The particular experiment didn't yield useful results, but it's a good example of how one day results of quantum computing might reach a consumer.

normal computer have to try every combination one at a time (or per number of cores).
Quantum computer can try all of them at once.
It’s very useful if you have a lot of combinations to try, like trying what molecule works best as a treatment for X.
It isnt very useful in task, like if X then Y. Or keep track of Z.
So basically, it wouldn’t enhance your smartphone in any other way, but in use cases where you have lot of combinations, it’s light years ahead of any other computer

Classic is like a light switch on off. Quantum is like a switch with more settings. Yellow green blue etc. these are called states. More states helps with certain types of tasks.

Simple answer don’t worry about it, it’s going to be another 100 years before an individual is going to be able to afford one let alone have a portable version within your life time

Biggest difference imo is Quantum is analog(continuous) while classic computing is digital(discrete).

This mean quantum computing can potentially model the real world but classic computing can only ever be an abstraction at best.

Classical computing will still be better in terms of energy tradeoff to calculate discrete problems like simple decision making, but quantum will be better for real world modelling like pathfinding where all paths can be considered at once.

How I would explain it is if you turn on a smoke machine in a maze, the smoke will spread and try all paths at once and the edge of the smoke and hence the whole smoke will always know whether it found an exit. This is like quantum. Whereas classical computing is like have multiple people trying all routes but they still have to come back to each other before they all know where the exit is.

It's all about speed and having multiple tasks to undertake, using Less power to do it, from old slow chips of the past, Pentium , to a single bio chip computer , to quantum going from binary, numeric, to automatically create even smaller and higher advanced bio micro technology. Technologically, we are still not, where we're supposed to be, based on historical evidence of other civilisations that have risen and fallen.

I'm sure it'll have all sorts of real world uses but it'll just end up trying to serve more ads to people.

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Here's my take on an ELI5 answer

Imagine you're travelling to some destination. A straight line is the shortest path. However, traditional computing requires tracing the path with Right/Left directions. Quantum computing provided a way to estimate a turn much like degrees on a compass. This is because of the superposition of states (not relevant to this explanation).

When measured, these will "collapse" (as-is the term for describing wave-form probabilities resolving to concrete values) into the Left/Right directions we're familiar with, but it will have arrived at the destination/solution with fewer total turns.

Sometimes this isn't a better solution. If you have a straight line path already, then you don't need to use Quantum Computing for it (they are generally slower at resolving simple problems). If you have a path that is all Left/Right turns, then Quantum Computing will likely save you no time (number crunching is often better performed on Traditional Computers).

Hope this helps

In classic computers, their is a small unit called “bit”. It can be either “on” or “off”.

In quantum computers, the small unit is called “Qbit” (Q for quantum). It can be “on”, “off” or “I don’t know “ state.

In layman terms, Quantum mechanics has a state called “I don’t know” which basically means you don’t know until you know. It’s like when you were in school, your parents wants to know if you are studying or not. They have to peep into your room to really see if you are studying or not. You may be studying, you may be dancing, you may be watching p@rn etc. At minute scale lot of things behave like you in the room. We don’t know until we peep to see what they are doing.

Coming back to quantum computers, having that third state will help in calculations taking lesser time than classic computers.

Hope it helps.

Maybe I'm too late, but there's one other applications that might one day reach the average consumer and that's quantum encryption. So the basic idea is that if you send out signals that have specific spin states, so it could be either up or down, then nobody could intercept that signal without you knowing it. Because if they intercept that signal they will mess with it causing some of these spin states to flip.

Now you could argue that they could piece together the original information, but with real signals that is extremely unlikely. You have to consider that most real data is extremely large, literally millions or billions of individual bits. Plus they already have an encryption, because the information will probably be in a format that is readable to a certain programm. You can think about it like this: if you opened an image in an editor you could still read the information in the image, but it will look like gibberish. If you know change random values here, it's impossible to decode this information again. Plus you will also get random information, because the would be hacker will have messed with your signal too.

But, yeah if this will ever hit average consumers, who knows.

Biggest benefit is security, there is no way to predict or measure a qbit without changing it, so it creates theoretically impossible to crack passwords

Another is instantaneous communication, theoretically a quantum linked quark and it’s partner will always change at the exact same moment no matter how far away they are.

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In simplest terms, a quantum computer will never be better for your purposes as an average consumer. They'll be for science and crypto nerds.

Benefit us? Depends on who you are. For example, if you like the total collapse of encryption, then yes.

It was explained to me that normal computers work on a yes/no type system. It has to do each yes/no one at a time, that's where processing time comes into play. With a quantum computer it is able to do all yes/no questions at once, so basically instant computers.

Useful comments here but if still not understood look at the recent post in r/OurGreenFuture - it might help.

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To simplify, classical computers use 0 or 1 known as "bits", quantum computers use "qubits" which is 0 and 1 which exist in a superposition state that can be false and true at the same time. This allows them to perform complex calculations exponentially faster than classical computers. Classical computers will likely still be a thing which offloads complex computations to quantum computers through the quantum internet.

Not a Computer Scientist. I don’t have a Computer Science degree. The way I understood it is this.

Computer works on 1 and 0. So if you apply that over a light bulb. 1 is on. 0 is off. So 8 bit is 8 light bulbs in a row. 16 bit is 16 light bulbs in a row. 32 is … so on and so on.

Each combo of 1 and 0 are used to represent something. Thus 10111001 = something. (I just made that up. No clue what it might represent)

For the majority of computers today. We managed to arrange millions of light bulbs in a grid and layers upon layers on top of each other on a single surface, and that is a single computer chip. That’s the computing today.

Now imagine we managed to do that on a cube which has 6 surfaces vs 1 on today’s computer chips. Thus one computer chip in Quantum Computing is essentially 6 computer chips of today. How much more data can be processed in a single Quantum Computing chip vs a single Computer chip today?

That’s how I know understood it. However I’ve not idea how accurate this is, if at all.

I am a layman when it comes to quantum computing, but I have heard it described similarly to the jump in register size in traditional computers. Every bit you add doubles the computing power and addressable memory.

So a 16 bit computer is orders of magnitude more capable than an 8 bit computer and our current generation of 64 bit computers are orders of magnitude over that.

With quantum computers instead of each additional bit increasing capacity by the power of 2, it is increased by the power of 6 (as it was explained to me at the time). So a 16 Qbit quantum computer would theoretically outperform an equivalent clock speed 64 bit digital computer.

This could be incorrect, but it was how it was presented to me by someone who works in the field.

I read an article that was probably not great that said quantum computers can barrow from parallel universes via superposition. Then it went to explain that what it means is just being able to use energy via superposition??? Idk man, but I was just curious if anyone who knows more about quantum computing thinks about that because from what I'm reading here quantum computing is just a step up from Binary right ?

And just because I can see the replies coming : No I do not believe it, yes it's probably a shit article , I have nothing to do with this article besides taking interest in the subject of quantum computing. Please don't insult insult me , insult the article.

Classic: 1 or 0

Quantum: 1 or 0 or (1 and 0 at the same time)

Rule 2 - Submissions must be futurology related or future focused.

Quantum computing uses things found in quantum physics right? Light reflection and reading is simple optics learned in early physics.

Think of this instead of working with the lights, they work with the atoms that create that light.

Doesn’t the term quantum refer to microscopic size?

Quantum computing is based on quantum principles, so it is really fucking hard to put it in layman terms. I took quantum mechanics 1 and 2. I also took many classes on electrical/computer engineering logic. I won’t even both to try to explain it. You need to understand so many different things. You need to know things beyond what most undergrad physics students know. Plus you’d ideally need a good understanding of computer engineering.