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Quantum teleportation
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What is quantum teleportation all about?

The biggest brains in physics are working on something with the word ‘teleportation’ in it. Surely, that means the next time you’re hungry, you mother can whip up something delicious back home and ‘beam it up’ to your desk at work? Not quite. Not even close, actually…

There has always been a bit of an issue explaining cutting-edge technology to the layman. It’s always been hard for scientist to dumb things down to the level of us laymen. In fact, the more the expertise of the scientist, the harder it is to think like those of us essentially ignorant on the topic.

Three things can happen when a new technology or science enters the general population’s life.

First, they simply don’t care – think grandparents and smartphones.

Quantum teleportation
This man has no clue what he’s doing

Second, they hate it and oppose it vehemently – when the first steam-powered trains starting running in the UK, doctors all over the country said the human body was not built to go over 10 miles an hour, and that uteruses would fly out of the bodies of women! When telephone lines were being set up all over the US, a devious postmaster arranged for the workmen to be shot and killed in order to stop it. He was convinced that he would lose his job because nobody would send letters any longer. Good call postmaster… not on the murders, obviously, but on the death of letters.

Third would be people who choose to wholeheartedly accept the new technology. Think of A.I. – everyone and their uncles are convinced that it’s the next big thing and should be chased after, even though some very smart people warn against it. Quantum teleportation would be one of those things that would sit squarely in the third category.

It sounds absolutely awesome: it has something to do with quantum physics and has the word “teleportation” in it! How could it not be cool?

Let’s rip the band-aid off real quick here. Quantum teleportation is probably never going to be sending you a home-delivered pizza faster than light. It’s really a misnomer to even use the word “teleportation”, but hey, physicists need to feel cool too. The only thing being teleported is information, and the hope is that (if it works) it might revolutionise the concept of the internet, communication and computation in general. How? Let’s find out…

The How

Quantum physics is not intuitive to us humans because it works at scales pretty much unimaginable to us. It turns out that the quantum scale (about a quadrillionth of a metre, or 15 zeros in the denominator) deals with strange, abstract properties like ‘spin’ for electrons, and ‘polarisation’ for photons of light. While they’re abstract to us in the everyday world, these properties can be, and have been, measured, multiple times, in hundreds of different experiments. This stuff isn’t made up.

Spin and polarisation are interesting to physicists for a whole array of reasons that it would take a few years to cover. What’s key here is that an ‘up’ or ‘down’ spin, or a ‘vertical’ or ‘horizontal’ polarisation – which are measurable states – are kind of analogous to a 0 or 1, a bit. These cool, quantum bits are also called qubits, and can be both 1 and 0 at the same time!

Here’s the final piece in the puzzle – the behaviour of these quantum bits (just electrons or photons) is extremely well-understood mathematically. They follow the well-defined rules of quantum mechanics to a T. And quantum mechanics uses all this math to explain behaviours like ‘entanglement’ (where the states of multiple qubits are fundamentally related to each other in a mathematically inseparable way), ‘interference’ (where a qubit can cross its own trajectory and ‘interfere’ with its own path) and a host of other jargon.

Don’t forget, all this stuff is verified with experiments involving crystals and mirrors. These supposedly simple apparatuses can actually manipulate quantum states in a variety of ways, even if they don’t make intuitive sense. Quantum physicists have learnt to turn off their intuition and follow the evidence instead.

Quantum teleportation
When we say big brains, we’re not kidding around… Pictured: Einstein, the Curies, Schrodinger, Heisenberg, and just a few other Nobel Prize winners

Well, what good is all this math and physics? In 1993, Charles Bennett proposed that entanglement could be used to ‘teleport’ the quantum state of a qubit to another entangled qubit across a large distance without moving either particle. More than 20 years on, this has actually been done. Multiple times. In fact, most recently, a Chinese satellite was successfully communicated an entangled state from a particle on the ground, 1,400 kilometres away. This is more than eight times the previous record. This is mind-blowing, a proof of concept of an idea thought pretty much impossible such a short time ago.

However, another reality check is in order: over 32 nights of experimentation, only about 900 pairs of qubits showed verifiable teleportation. This is because working with light is tricky, and there are just too many variables. From the slightest change in atmospheric density to the smallest vibration, pretty much anything can disturb the experiment – they are, after all, dealing with reading spins on individual electrons!

Quantum teleportation
The not-so-simple experimental setup of a quantum ‘eraser’

So why is quantum teleportation even considered useful? Let’s break it down:

Speed

Without quantum physics, the fastest we can beam information from one place to another is at the speed of light. On the ground, most information is transmitted by cables at about two thirds of that speed. The best fibre optic cables operate at 99% of the speed of light, and cost a bomb. Quantum teleportation of information would be able to bypass all such restrictions. and information is transferred instantly, and thus the speed is, well, infinite!

So crazy is this thought, that Einstein himself refused to believe it was possible because it went against the laws of classical electrodynamics. He called it “spooky action at a distance” – “spooky” because it made no sense and there was obviously something wrong with it. However, over the years, we’ve come to realise that it was Einstein who was wrong.

However, there are those that disagree and maintain that Einstein was essentially right. Although the quantum coupled photons, atoms, electrons, etc., seem to allow faster than light communication, we aren’t sure how that would work. Let’s say you are trying to communicate with someone 1 light hour away, using a bunch of quantum entangled stuff exchanged between you and them earlier. Now what? Let’s say you read or write to 10 of those qubits. How would those people 1 light hour away know to read their qubits to understand that you’re communicating with them? They cannot monitor qubits, because the very act of reading a quibit changes it. They’d still have to wait for a regular bit from you (travelling at the speed of light) to tell them, “Hey, sent you a message, read qubits 1 to 10.” In that sense, Einstein was also perfectly correct in stating that even communication cannot travel faster than light, but how do the atoms “know” when the other changes, instantly? We have no clue, really…

Security

Classical cryptography is an expensive process in terms of time, skill, and even computing power. Imagine the perfect security system, in which even the act of reading the data would destroy it. Because the laws of quantum mechanics state that it is impossible to observe a quantum object without affecting it, it’s akin to someone not being able to read data without changing it. Imagine writing your password down on a piece of magic paper, which, if read, will magically change the written password to gibberish. If someone else read it, you’d know, immediately.

What this means is that information stored in a qubit is tamper-proof using the rules of physics.

Work on quantum cryptography has only just begun, and accuracy leaves much to be desired, though the fascinating field of Quantum Error Correction has been showing some promise recently. Similarly, algorithms for quantum computation have been found to be exponentially more efficient, which started another field called Quantum Complexity Theory.

An example of this is Shor’s algorithm, which is a quantum algorithm written for qubits, which could find prime factors of a given integer N. Normal computers can also do this, but when N is very large, regular computers would take way too long to crack this. A proper quantum computer with enough qubit crunching capabilities would do this orders of magnitude faster than a regular computer. The popular RSA public-key cryptosystem uses this type of encryption, a quantum computer running Shor’s algorithm would make short work of the RSA encryption. It’s widely believed that quantum computers will spell the death of public-key encryption.

Quantum teleportation
DWave, a quantum computing company, has rolled out models with up to 2000 qubit computing capacities

Challenges

While the math exists, the proofs exist, and the ideas exist, the technology doesn’t; not yet. However, ideas for the ‘teleportation’ of energy, and even of matter have been proposed as well, and given our history of innovation, you wouldn’t want to bet against us finding a way. Another more minor problem is that a completely quantum internet will require a complete replacement of all hardware to quantum-information compatible devices. From storage to interfacing equipment, and simple switches to processors, everything will have to go in one massive upgrade cycle! It will probably be crystal-based, so say goodbye to the PCB as well. Don’t worry though, all your existing hardware is safe for decades to come still, but your grandkids might not be able to plug in and use any of your ‘antique’ devices, about 50 years from now.

This article was first published in the August 2017 issue of Digit magazine. To read Digit’s articles first, subscribe here or download the Digit app for Android and iOS. You could also buy Digit’s previous issues here.

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Aabir Abubaker