What is A QUANTUM Computer? Explained in detail. 

quantum computer

In simple language, Quantum computer is the computer that uses quantum theory to solve very complicated calculations. Quantum theory explains the behavior of energy and material on the atomic and subatomic levels. Classical computers (current computer) store data in bits, which is binary number (1 & 0) but on the other hand quantum computer uses Qubits to store data. Where the value of qubits can be a superposition between 1 and 0. Start getting confused? Let’s deep dive into this shocking and mysterious Quantum World. 

History of quantum world.

Let’s go back in time. Around 200 years ago, we thought that the world is very big. We were discussing the planets, moons, stars and galaxy. But what about the small level? After some experiments we found that everything around us is made of atoms and molecules. After 100 years of back, we found that the atoms are made by electrons, protons and neutrons. Then the debate starts about the light, what about the light? Is it a wave or particle?  

To prove this topic, in 1802 A scientist Thomas Younge did an experiment, which was game changer. This experiment is called Double Slit Experiment. This experiment opened a window to the Quantum world. This experiment shocked every scientist because the result showed that subatomic particles showed a strange behavior during the experiment. We will understand this experiment in detail. In short this is the experiment why we are talking about Quantum Computer today.  

3 superpowers of quantum world.

1. Superposition 

As we have talked about double slit experiment, this experiment proves this superpower. So, let’s understand the double slit experiment.

To make it simple, imagine a wall with two slits and after that there is another wall. So, two walls, one with slits and after that normal wall. Now you throw balls to wall with slit then what will happen? Yes, you are correct. Some balls will bounce back and some pass-through slits and hit the second ball. This is the simple explanation.  

Now come to the experiment, here the balls are small particles (electrons, photons etc.). Now when you throw electrons, some will bounce back, and some will pass the slit and hit the observing sheet behind.  

There are two different results, for particles their different patterns and for waves their different pattern. Which is clearer in images above. So, this experiment result provides information about the basic nature of things which are passing through slits. So, this experiment became a tool to know about light, whether it is a particle or wave.  

Till here everything is fine unit scientists used subatomic particles. Because this time the pattern was the same as waves. Now this result made scientists in confusion that how particles can behave as wave. After a lot of experiments the result was the same for subatomic particles. To find out what is happening inside scientists put the observer so they can observe the subatomic particles during the experiment. And now this time the result was shocking because the pattern was for the particles.  

After so many experiments scientists finally found that subatomic particles behave differently.  When there is no observer, they behave like a wave and in the presence of observer they behave like a particle. Now this statement feels like it’s out of this world. But at the quantum level, we cannot predict as per classic physics and that’s why we need to introduce Quantum Physics.  

So, at the end the behavior of subatomic particles called Superposition. Which means subatomic particles have superposition. They can be any state and we can’t predict their state. Until someone observes.  Because without observers they behave like waves and when you observe them, they behave like particles. This is also called wave-particle duality.  

To understand this superposition, imagine you have coin which is spinning. So, when you are not observing there can be heads or tails. But the time you see the spinning coin it will show either heads or tails. This is the simple way you can understand the superposition easily.

2. Quantum entanglement.

This is another superpower of the quantum world. Entanglement means to be connected. There is one more experiment called Bell`s experiment which proves this quantum entanglement. This story is very interesting. Let’s explore more about quantum entanglement.  

After the invention of superposition, Albert Einstein and Erwin Schrödinger were not convinced which theory of wave – particle duality.  These scientists were unconvertable to believe that subatomic particles can be in different position at a same time which superposition. Because they thought nature is not fizzy like this.  

After this, the scientist Erwin Schrödinger introduced the concept of Entanglement. As per his theory two small particles can have a spooky connection between them. And they don’t need any medium to communicate. Doesn’t matter how far they are from each other. Let’s understand this with the example of coins. So, you have two spinning coins which are in their superposition, and they are entangled with each other. Now you send your friend Elone with one coin to mars. Now a coin which you have, you observe it and for example its heads. Now the other entangled coin with Elone automatically collapses its superposition and will show the tails. These entangled coins communicate about their state with almost 0 time. So, in short When two subatomic particles entangled with each other, they can communicate very fast and without any visible connection and medium.  

But there were some guys who did not agree with this entanglement theory. Einstein, with his collaborators Boris Podolsky and Nathan Rosen (known together as EPR), took the argument a step further by analyzing two entangled electrons that are far apart. The EPR paper published in 1935, says that the communication between two particles is illogical. Because the fastest thing in the world is the speed of light. Nothing can travel faster than the speed of light. After a few more explanations this EPR paper successfully concluded that this quantum theory is incomplete. They said that there might be a more detailed explanation which goes beyond quantum mechanics. Einstein said there will be some hidden variables which will solve this spooky connection and Mistry of communication between entangled particles.  

Einstein did not question the predictions of quantum mechanics itself; rather he believed there was a deeper truth in the form of hidden variables that govern reality. After the release of EPR paper, the debate for quantum entanglement was stopped. But Bell came up with a game changing experiment in 1965. This experiment proved Einstein wrong. Bell proved with his experiment that the two entangled particles can transfer information and communicate with each other faster than the speed of light. 

3. Interference.


This is another most important topic in quantum mechanics. Why do we need to use interference? We need to use it to take advantage of superposition and entanglement. To understand this, we need to take help with classical physics. So, there are two types of interference constructive and destructive interference. When two waves collapse and create another more energetic wave will be called constrictive. And on the other hand, when two waves collapse and destroy each other’s energy, it is called destructive interference. At the quantum level, the calculation and mathematics are quite different but for the understanding we can take this interference fundamental as reference.

beam split experinment

The Beam splitter experiment gives a better explanation for this. By the result of this experiment, it proved that we could manipulate the quantum system and get the desired outcome. With the help of interference, we can take advantage of superposition and entanglement. We can manipulate the quantum system with the help of interference and get the desired results. In a quantum system, out of many possible outcomes, we can influence the probability of the desired outcome through quantum interference.  

Why do we need Quantum Computers? 

After looking at so many experiments, explanations and theory about quantum computers, the question why do we need them? Which is obvious. So, how quantum computers can make changes in our life? The most effective answer is Simulation. 

Simulation is creating a copy of a particular process or situation which is way closer than an actual reality. At the current time we can simulate a car, airplane, submarine, ship, helicopter etc. For example, Airplane simulation. In this simulation we simulate everything which we experience during the actual airplane. We simulate everything like vibrations, incline, declines, visuals, controls everything. Which helps our student pilots to experience the airplane. So, they can learn without any risk of crash which is safe and less expensive way to learn flight. So, simulation helps to understand things easy, cheap and faster.  

Now in the research of material science and drugs in healthcare, simulating a molecules and atoms could be a very important and effective. We think that if we can simulate a big airplane simulating a small atom is not a big deal. But it is not like that. Let’s understand with the example of cup of coffee. In the cup of coffee let’s assume that there is 36gms caffeine. Now if we want to simulate 36gms of caffeine, just imagine how many molecules of caffeine are there? Then don’t forget to count electrons. Each caffeine molecule has 50 electrons, and they are spinning and connected with each other. Now just imagine how many combinations are possible for just 36gms of caffeine. At this stage our classical computers are useless, not even classical, super computers are also unable to simulate a single molecule of caffeine.

To simulate atoms and molecules, there are a huge number of combinations possible. To calculate and simulate these combinations we need a computer, which can do a massive calculation in a small amount of time and that’s why we need quantum computers. Because using a superposition and entanglement we can simulate very easily. There is famous saying that “we can’t use sword to kill fly.” So, to understand the behavior and reaction of atoms, molecules and subatomic particles, simulation is the best and fastest way to understand. And to understand these kinds of quantum fundamentals we need to take help from quantum superpowers such as superposition and entanglement. And that’s why we need quantum computers.

How does quantum computer work? 

After these much discussion there might be a question coming in your mind that how does the computer work? To understand this let’s have a quick look into classical computers. In the classical computer there is one processor with bits. Bit is a basic unit of information. Bits store data. The value of bit can be only 0 & 1. In all classical computers all information is stored in the form of 0 & 1 which is called binary number. To increase the performance of classical computers, we can simply increase the number of bits. So, this is the basic understanding of classical computers. Doesn’t matter how advanced laptop and computer you have they are working on this fundamental.  

quantum computer

Now let’s talk about quantum computers. Where classical computers have bits, quantum computers have Qubits. But here the value of qubits is not like classical computer (0 & 1), in the quantum computers the value of qubits is not accurate, it will be on the superposition between 0 & 1. The small subatomic particles are in superposition and entangled with each other in qubits. To make sure that they don’t get disturbed and perform them without collapsing their superposition, they must be kept in very cool temp in the core of quantum computer.

With the help of qubit signal amplifier, the electromagnetic pulses are sent to the qubits. These electromagnetic pulses help to create manipulation and help to get desired outcomes. Subatomic particles are in their superposition and entangled with each other in the qubits, to interference we use electromagnetic pulses. That’s how quantum computers work.  

recent updates on quantum computers.

In the development of quantum computers, so many scientists gave their contribution. But there is one guy who pushed quantum theory from papers to lab. In 1981, IBM and MIT (Massachusetts institute of technology) organized a conference to discuss computer science and quantum mechanics. In this conference Pro. Richard P. Feynman gave a speech to introduced quantum theory in computer science. He said that “Nature isn’t classical, dammit, and if you want to make a simulation of nature, you’d better make it quantum mechanical.” This speech was game changing in this field. After that in the year 1998, the first basic quantum computer came to say, “hello World”.  

In the last 25 years, research and development in quantum computers has been very impressive. In November 2022, Maria Spiropulu at the California Institute of Technology and her colleagues announced that they had used Google’s Sycamore quantum computer to simulate a holographic wormhole. The world’s first universal quantum computer with more than 1000 qubits is IBM`s Condor. In 2022 China claimed that they have developed quantum computer which can calculate 100 trillion times faster than the supercomputer. They can handle multiple tasks at once and can quickly solve complex problems that would take supercomputers months to solve. 

Till now (2023), There are around 81 companies that have adopted quantum computers and are trying to develop them faster and more advanced. Of the four major US-founded players in the quantum computing (QC) market consisting of Google, IBM, Microsoft, and AWS Braket (Amazon), only IBM has a legacy in technological innovation that stretches back more than a century. The other three, Google, Microsoft and AWS, have a shorter history in computing. 

Future of quantum computers. 

After discussing this much, I think you have got an idea about quantum computers and how powerful they are. Still, we are in the developing state of quantum computers. I personally compare a quantum world with the ocean, and we are still exploring the surface. Still, it remains to explore deep. In future when we are successful in inventing a perfect quantum computer that will make a huge impact on us.  

Quantum computers will help to create a simulation of molecules and atoms which will help us to do research on material science. Where we can simulate atoms and invent new material for more convenience. We can simulate atoms and molecules to create some new drugs which help us to invent some new drugs and will change the whole healthcare industries. We can predict weather with accuracy by using quantum computers. Some scientists believe that we can also simulate the whole universe by quantum computers.  

Till now still we are not able to predict the actual usage of quantum computers. When we developed classical computers, no one thought that we would run Facebook, twitter, Instagram, Facebook, etc. on these computers. So, the wide usage of quantum computers will only improve in time. May be quantum computers will remain only in research and development industries or there is also chance to use quantum computers commercially.  


After a long discussion of quantum world, I hope this article will be helpful to understand quantum world. Still, we need to work on this much more. But I believe that quantum computers will make a big impact on the world and will help us to improve our life faster and better.  

Still there are so many topics which I couldn’t cover in this article. This field is very huge. It is impossible to cover everything in one article. But if you guys want me to create more articles on quantum mechanics, comment on this article and I will defiantly cover possible topics. And if you like my research and this article please comment on this article. In case if you find any mistake or anything where I am wrong you can contact me by visiting this link ( https://aralop.dev/contact-us/). I will defiantly improve and clear up the issue.  

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Thanks a lot for reading till here and best of luck.  


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