What is Quantum Entanglement?

Einstein described it as “Spooky action at a distance”.

Quantum entanglement is a phenomenon observed in photons where particles share information of their state - even if separated by a huge distance. This state sharing phenomenon happens almost instantaneously. Quantum particles can be in any possible state until their state is measured by an observer. These states are called Eigen-Values. In case of quantum entanglement, two particles separated by several miles of distance, when observed, change into the same state.

Quantum entanglement is hugely important for modern day computation tasks. The reason is that the state information between photons travel sometimes at speeds like 10k times the speed of light. This if implemented in physical systems, like quantum computers, can be a huge boost.

Source: picoquant

One important concept for us to understand this idea is ‘Qubit’. What is a Qubit? It’s the unit of information in Quantum computing. Like ‘Bit’ in case of normal computers. A bit can be represented by two states - ‘0’ or ‘1’. Qbits are also like ‘bits’, but they are governed by the weirder rules of Quantum Computing. Qubits don’t just contain pure states like ‘0’ and ‘1’, but they can also exist as superposition of these two states like {|0>,|1>},{ |1>,|0>}, {|0>,|0>}, {|1>,|1>}. This particular style of writing particle states is called the Dirac Notation. Because of these unique superposition of states, the quantum particles get entangled and share their state related information.

A recent research experiment by a Chinese group has claimed to have packed 18 Qubits of information in just 6 entangled photons. This is revolutionary. What this basically means is that if one bit can pack in three times the information that it can carry presently, then our computers would become three times faster and smoother to work with.

The reasons which make this a great start for future implementation of faster and practical quantum computers are:

1. It’s very difficult to entangle so many electrons
2. There are instances of more than 18 qubits getting packed into a larger number of photons, however the degree of entanglement has been much simpler
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3. Entanglement of each new particle takes increasingly more computer simulation time
4. Introducing each new qubit creates a separate simulation taking up more processing time.

The possible reason why this experiment has worked might be credited to the multiple degrees of freedom that photons can have. This particular experiment has been performed using Photons in a networking system. The fact that such a system allows multiple degrees of freedom for the Photon meant that this result is specific to this particular quantum system. It would be difficult to replicate the results in other systems like a Superconducting Network.

Still this result means a great deal for the progress of quantum computing systems and how they can evolve to be a practical solution and not just remain in theory forever.

Quantum Computing is poised to take a quantum leap with industries and governments on.

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