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Quantum Entanglement!

What is Quantum Entanglement?

Quantum entanglement is a core concept in quantum physics that describes the peculiar relationship between two or more particles. When particles become entangled, their properties become correlated in such a way that the state of one particle is immediately connected to the state of the other, regardless of the physical distance between them. This means that measuring or manipulating one entangled particle instantaneously affects the other, even if they are separated by vast distances.

The phenomenon of quantum entanglement challenges our classical intuitions, as it defies the notion of local realism and suggests the existence of non-local connections between entangled particles. It has been experimentally verified through various tests, including the famous Bell's theorem experiments, which provide strong evidence for the non-local nature of entanglement.

Quantum entanglement plays a crucial role in the development of quantum technologies, such as quantum computing, quantum communication, and quantum cryptography. It enables the implementation of quantum algorithms, secure communication protocols, and the creation of entangled states that exhibit unique properties, such as quantum superposition and quantum teleportation.

Entanglement, a fundamental aspect of quantum physics and a key component of future quantum technologies operates at the subatomic level. This phenomenon occurs when two particles, like photons or electrons, become entangled and maintain a connection regardless of the vast distances that separate them. Similar to how a beautiful ballet or tango emerges from the coordination of individual dancers, entanglement arises from the interconnectedness of particles. Scientists classify it as an emergent property, highlighting its unique nature within the quantum realm.

Understanding and harnessing quantum entanglement is of great importance in advancing our knowledge of the quantum world and unlocking the potential of quantum technologies for various applications in fields like computing, communication, and cryptography.

Source: Science Exchange


Does quantum entanglement make faster-than-light communication possible?

Einstein's theory of relativity, particularly the theory of special relativity, posed challenges to our understanding of quantum entanglement. One of the key aspects of special relativity is the principle of locality, which states that information cannot propagate faster than the speed of light. This principle forms the foundation of causality in classical physics, where cause and effect are connected by a local and deterministic relationship.

Image Source: Slideshare

Quantum entanglement, on the other hand, exhibits non-local correlations, meaning that the entangled particles can instantaneously influence each other's states regardless of the distance between them. This non-locality inherent in entanglement seemed to contradict the principle of locality and causality implied by relativity theory.

Einstein, along with his colleagues Boris Podolsky and Nathan Rosen, proposed the famous EPR paradox in 1935 to highlight the apparent conflict between quantum entanglement and relativity. They argued that if the predictions of quantum mechanics were correct, then measuring one entangled particle would instantaneously determine the state of the other, even if it was far away. According to their reasoning, this violated the principle of locality and suggested the existence of "spooky action at a distance."

Image: YouTube
Einstein's scepticism about the non-local nature of entanglement led him to propose alternative explanations or hidden variables theories that would preserve locality. These theories suggested the existence of unknown parameters or properties that determined the outcomes of measurements and restored determinism and locality.

However, in the following years, experimental tests based on Bell's theorem and subsequent experiments, such as the Aspect experiments, provided strong evidence for the non-local correlations predicted by quantum mechanics. These experiments demonstrated that the predictions of quantum entanglement were in conflict with any local hidden variable theories.

While Einstein's theory of relativity was not directly "in danger" due to quantum entanglement, the conflict between the non-locality of entanglement and the principle of locality in relativity posed a significant theoretical and philosophical challenge. It highlighted the need for a deeper understanding of the fundamental nature of reality and the reconciliation of quantum mechanics and relativity in a unified framework, such as the ongoing pursuit of a theory of quantum gravity.


Interesting short facts about quantum entanglement:  Visit here 

  1. We know the entangled particles must have undefined spins before we measure them because if they didn't they would sometimes give the same spin when measured in a direction perpendicular to their well-defined spins (and they never do).


  2. We know the entangled particles can't have hidden information all along about which spin they will give in different directions because if they did we would measure different results at the two detectors >5/9ths of the time and we don't - we only get different results 50% of the time.


  3. We can't use this behaviour to communicate faster than light because we can only pick the direction to measure in, we can't force the spin to be up or down - and it will be random with 50/50 probability. When the two detectors pick the same direction to measure in the results at one detector will be random but the opposite random of those measured at the other detector, which is a bit spooky.

For references:

Entanglement_Caltech_Science_Exchange

Proving that Quantum Entanglement is real

Relativity_Theory

Principle of locality



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