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Quantum Computing Just Took A (50km) Step Closer To Reality

Wed Feb 19 2020

The dream of a super-fast, super-secure, super responsive quantum internet took a big step closer to reality recently.

A team of Chinese scientists working on quantum computing were able to entangle two quantum memories over 50 kilometres (32 miles) of fibre optic cables.

That distance was nearly forty times the previous record!


For those of you not versed in the theories behind Quantum Communication, it relies on something called quantum entanglement.

That’s when two particles become inextricably linked and reliant on each other, even if they’re no where near each other.

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I cannot seriously believe in it [Quantum Theory] because the theory cannot be reconciled with the idea that physics should represent a reality in time and space, free from spooky actions at a distance.

Albert Einstein

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Fortunately, we’ve come on a bit since Einstein’s day and whilst quantum entanglement might still be spooky, it’s also very, very awesome.

Quantum memory can be thought of as the quantum ‘equivalent’ of traditional computing memory, granting us the ability to store and retrieve quantum information.

For quantum computers to be a viable and economical reality then the issue of quantum memory is one that will need to be solved.

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The main significance of this paper lies in extending the entangling distance in [optical] fibre between quantum memories to the city scale

Jian-Wei Pan – Team Leader, University of Science and Technology of China

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Scientists have in the past managed to entangle photon particles over both empty space ad optic fibres at large distances but adding quantum memory into the mix complicates the entire process, making success a lot harder to achieve.


The Chinese research team suggested in their most recent paper that a different approach to ones previously tried may garner more success.

They tried atom-photon entanglement over successive nodes so the atoms become the nodes and the photons can transmit the messages.  

This new approach, adding atomic matter to the process, produced extra efficiency, reliability and stability.

The team hope that with the right network of nodes a much sturdier foundation for a quantum internet can be established than just relying on the entanglement of photons alone.

For this experiment the Chinese Research Team used two storage units for quantum memory consisting of rubidium atoms chilled down to a low energy state.

When coupled with entangled photons, they each become part of an entangled system.


The problems come in with that most basic of scientific problems, the more complicated a system, the more there is to go wrong.

The greater the lengths a photon needs to go through to move between atoms, the greater the risk of the system becoming disrupted in some way.

That’s why the new 50km record is such an amazing achievement.


The key breakthrough to this quantum leap forward (What? We had to make that joke at least once!) in distance was a technique they’ve called cavity enhancement which works by reducing photon coupling loss during the entanglement process.

It works by placing the atoms being used for quantum memory in special rings that reduce random outside interference that would have previously destroyed the memory.

The process also resulted in the added bonus of improving the retrial of the quantum information stored.

Once accomplished the team of scientists could then convert the photons to a frequency that was suitable to be transmitted over a city sized telecommunications network.

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Despite enormous progress, at present the maximal physical separation achieved between two nodes is 1.3 kilometres [0.8 miles], and challenges for longer distances remain. Our experiment could be extended to nodes physically separated by similar distances, which would thus form a functional segment of the atomic quantum network, paving the way towards establishing atomic entanglement over many nodes and over much longer distances.

Jian-Wei Pan – Team Leader, University of Science and Technology of China

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It’s when that goal becomes a reality that things get really cool…


Although we’ve described quantum memory as the equivalent to computer memory in the traditional sense, the quantum version should be capable of a lot, lot more; capable of processing information exponentially faster and solving problems completely beyond the current generation of computers.

If the technology can be made reliable it’s not just speed that will be improved either; the data will be secured with the very laws of physics themselves!

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Wed Feb 19 2020

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