Hello Steemians! 

You may skip to the introduction part. 

As I am writing this article, I'm fully aware that there had been a lot of posts on quantum computing. But still I am eager to write one myself because I want to share what I have learned.

If you have read my previous posts you might have gotten an idea that I try to write at layman's level of understanding. 

So this post won't include quantum jargon as I'm sure you are aware it has heavy to digest equations and formulae which are not understandable for layman. But still it covers everything important.

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Definition

Quantum computing revolves around certain principles of quantum mechanics like super-position and entanglement.

Introduction

Quantum computing is simultaneous computation of tasks. It involves  fundamental principles of quantum mechanics and can be performed on quantum devices or computers.

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Quantum mechanics include super-position and entanglement. 

Super-position in simple terms is an addition of two states or the occurrence of two states at the same time.

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Entanglement happens when two states effect the presence of each other and no matter from how far they are connected.

How Quantum Computers differ from Classical Computers?

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Classical computers store information in binary bits i.e 0,1. 

Whereas quantum computers store information in qubits i.e 0,1 or super-position of state 1 or 0.

Classical computers, when given tasks, perform one by one. Whereas quantum computers perform operations simultaneously. In other words, they do parallel computing which makes them quite faster than classical computers.

Quantum Algorithms 

These Algorithms are specifically designed for quantum devices. It's not that they can't run on classical computers. It's just that those computers take too much time when problems become complex. 

There is a quite famous example of prime factorization algorithms. 

The best and most powerful algorithm that run on classical computers is General Number Field Sieve. It's said to be the most efficient algorithm for factoring numbers larger than  10^100. It's is very complicated as it consists of mathematical jargon of high level. But still it does great job. 

However, there is an algorithm designed by Peter Shor which is commomly known as Shor's Algorithm.

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As you can see, we are trying to compute prime factors of number 15.

 An arbitrary number 2 is chosen. Then 2^1 is divided by 15 and it's remainder is 2.

Then 2^2 is divided by 15 and it's remainder is 4.

Then 2^3 is divided by 15 and it's remainder is 8.

2^4 divided by 15 and remainder is 1.

We keep on computing until the remainder is 1.

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2^4 when divided by 15 gave remainder 1. So 2^4/2 +- 1 gives us 3 and 5 which are prime factors of 15.

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You must be thinking what's so special about this algorithm. We could have done it easily on our personal general purpose computers. Yes, We could have. 

But I missed out one thing. The four computations while finding remainder 1, were done simultaneously. Means we get the all four answers at once. Not like classical computers who would've computed each remainder one by one.

See, we get same answer by both methods. But can you imagine how fast the results would be if we get all computations computed and resulted at once.

Cloud Computing and Quantum Computers

In simplest words, using services of remote servers on our computers without caring what goes on behind those services is cloud computing. Like we use Google search engine at our computers or handheld devices. Yet there is huge organisation for that which is working on the implementation, maintenance and services of that search engine. We don't have to bear that load and just care about the output or services it provide. There are lot more examples of cloud computing but I don't want to go off the topic.

Coming back to Quantum Computers, you may have a very good idea by now after reading so many detailed posts here that these Computers require a certain type of environment. Temperature below zero degrees and those qubits are so sensitive that any disturbance or noise can tamper them and increase the error rate. 

So it is being provided as a cloud service so that common users can easily understand how it works and learn quantum algorithms and moreover test and experiment new computations at the comfort of their own place.

IBM has given 20 qubits quantum computer on cloud service and recently in Asia, 11-qubit quantum computer is also being launched on cloud by Alibaba.

Recent Breakthrough

The most powerful quantum computer was IBM's with 50-qubits. 

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Recently Google has launched its 72-qubits quantum processor, Bristlecone. While number of qubits doesn't decide the power of quantum computers, it is actually what these can do. This new processor is said to be having lesser error rate than their previous 9-qubit quantum computer whose error rate was 0.6 percent. 

Bristlecone has not yet surpassed the fastest classical type super-computer. But it is very close. It is said that 100-qubits would successfully beat the super-computer.

And I'm not sure about the credibility of the source but it's likely that if we reach 4000 qubits then RSA coding mechanism will collapse. 

Limitations and Shortcomings 

So far I have been admiring this quantum giant. But if you have read closely you might have found little uncertainties and impracticality.

I would like to share mine assessment:

• The super-perfect environment for quantum computers. As mentioned before, extreme cooling conditions are required for these giants. Qubits are so sensitive that any accidental external shocks or even noise can make them error-prone. What's the use of all the hard work if some noise can tamper our computations? Scientists are still figuring ways to avoid this.
• Shor's algorithm can factorize only small prime numbers. The largest number factorized by another quantum algorithm is 56153 which used 4 qubits. It may be fast but still no existing quantum computer can compute numbers as large as Genreal Number Sieve Field can.
• Quantum computers are still experimenting and testing their own capabilities. There is much less practical use because of its limitations. 
• To deal with more complexity, larger number of qubits are required, thus making the computer more error prone as discussed in point 1.
• Even some people are saying quantum computing is a scam, there is no thing like being in two states at the same time. It refers to parallel worlds which are pure fiction. But my point is, if it is solving problems then who cares it's practically possible or not.

Quantum Artificial Intelligence

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When the above discussed limitation will be overcome by the quantum computers, the whole tone of technology will change. Artificial Intelligence is the one field that will have a major push. Classical Computers analyze large set of data and learn through them to act and think like humans. When quantum principles will be applied to Machine Learning, computers will be able to analyze much more faster and make better decisions. Maybe better than human. Surpass us mankind? Wow! And I'm again thinking about Winston, I think he was programmed with Quantum AI. 

References

1- Cloud Computing

2- RSA coding

3- Quantum Computing is scam

4- Google quantum supermacy