A brief About Quantum Entanglement

Quantum world is more interesting and complex than the real world. If we want to reveal the secret of the universe, we should look into the quantum world. Quantum theory is more expensive than other theories. Quantum mechanics is able to answer almost every questions to every problems.Until the world of Quantum world was not discovered, many scientists faced problems for it. Albert Einstein, greatest among the greats, also faced enormous problem for not having the idea of Quantum theory.

He never liked the view of Quantum world. To disprove Quantum Mechanics ,he started a thought experiment with his two scientist-friends B. Podolsky and N. Rosen. But they failed, Quantum won. For this thought experiment a new paradox was created. It is called EPR paradox or Einstein, Podolsky, Rosen PARADOX. Why is it a paradox? Cause in this experiment they found that the information travels between two particles in a higher speed, more than the speed of light. But we know that speed of light is the highest speed in the universe, so naturally it breaks the rules of relativity. Now we will discuss about that. EPR paradox has also another name called Quantum. Entanglement To know about Quantum Entanglement, we should know at first about the Superposition and Entangled Particle.

Now what is Superposition? Our whole relativity and classical physics say that everything is in fixed position. But 

Quantum mechanics says that No,nothing is in fixed position. It says that until we are not observing anything, we are unable to say about itspossible state . Now take an example. Imagine that you put a cat in a box with some poison and you close the box.

After half an hour you enter the room 

and start thinking about the cat’s state. But I am sure that you cannot answer clearly about the cat’s condition: dead or alive. So you need to open the box to know its actual position. So within this time the cat may be in may probable conditions . But when you observe the cat opening the box you come to know that the cat is alive (somehow) . So the cat was in many possible state in the box 

namely “Superposition state”. Do you know who did this experiment with the cat? Schrödinger put the famous experiment and called it Schrödinger cat experiment. Same was happened with electron. We know that electron has two possible spins :up and down. So when we are not observing the spin of electron, we cannot say about the spin. It is in superposition state. Whenever we observe it, the wave function collapse and we can see one of the possibilities.

Now what is Entangled particle? Entangled particles are connected to each other. It is a simple and easy way to answer. But in detail it is very complex. We know that photon has no mass, no charge, no spin. So if particles are created from the fusion of photon, the sum of the charge, spin might be zero. So if any particle with positive charge is created, a negative charged particle is also created. And if one has up spin, the other has down spin. We know that from fusion of photon an electron is created, so a 

positron with positive charge must be created at the same time.

And if the spin of electron is up, the spin of positron will be down and vise versa. As they are in a bondless connection with each other, it is called entangled particles.EPR paradox is also known as Quantum Entanglement based on two concepts:Superposition and Quantum Entanglement. To describe it, take an another example. Consider 

Ram has a positron and he is in one part of the universe. And in the other hand, Sam has an electron and he is another part of the universe. So the distance between them is 93 billion light years. Ram and Sam both don’t know about the spin of those entangled particles. Now if Ram however calculate the spin of his positron, he can surely say about the spin of the electron placed on Sam’s hand. How? This way... At first If Ram finds that the spin of positron is up, he can say that the spin of electron in Sam’s hand is definitely down cause they are entangled and they try to maintain the rule of conservation of angular momentum. Now if anyway Ram is able to change the spin of the positron in his hand, the spin of the electron in Sam’s hand will automatically change. Cause they are entangled. But you can see that the distance between the two boys don’t affect the transmission of the information. So we can see that the information is travelling in much higher speed than the speed of light. It is in brief about Quantum Entanglement. In 

this way we can use many high technologies like Quantum Teleportation. Recent studies are able to do the Quantum Teleportation successfully. And we also can use it to make Quantum Computer. Google and IBM both companies successfully make 

Quantum computer. But it is in now under 

construction. So we can see that the Quantum World helps us very much.

Interesting facts: This article which   was written by me , was published in the renowned magazine in India: Cosmos Now