If any of the inventions brought to life in Star Trek can claim to be the most iconic, it must surely be the transporter. But could we ever build such a thing in real life?
The image of James Kirk and crew disintegrating in a shimmering beam of light is instantly recognisable. “Beam me up, Scotty” has been in the popular vernacular for decades.
And yet, this famous device almost never made it to our screens. The show’s creators introduced it as a last-minute, cost-cutting measure when the use of model ships landing on planets was deemed too expensive.
Like much high technology from Star Trek, the transporter had an element of magic about it. Later incarnations of the show demystified it to some extent, allowing us to describe its workings.
How does it work?
The transporter is a chamber into which an object can be placed and instantaneously moved from one location to another. The subject is disintegrated into its component atoms, which are then transmitted (beamed) to the destination. There, the atoms are reassembled and the object rematerialises in its original form as though nothing had happened. Seemingly anything can be transported, even life forms. In fact, Starfleet crewmembers regularly use the transporter as a convenient way to travel from an orbiting ship to a planet’s surface.
It appears the future has no need for Uber.
The writers on Star Trek have given us clues over the years to the transporter’s workings, allowing us to piece together a description. Here goes…
The process begins when the transporter locks onto the subject to be transported. Apparently it recognises the subject by its bio-signal (if it’s a living thing) or energy signature. Next, the subject is scanned at the quantum level by a molecular imaging scanner. The exact states of all its molecules are recorded, assisted by Heisenberg compensators that take the Uncertainty Principle into account (see below). After this, the subject is broken down into a stream of matter which is then transmitted to another location. At the destination, the process is put into reverse and the subject is reassembled.
All sounds quite simple, doesn’t it?
The fax machine analogy
One thing the articles in this series will do is look at the current state of the art in the real world and find the closest equivalent to the fictional science. However, the transporter presents us with a difficulty. There’s an important question that must be answered, but finding the answer is frustrated by the lack of an exact or consistent description of the transporter’s workings.
The question is: what exactly is being transmitted? Is it just information about the subject, or is the transporter sending the actual matter that makes up the subject? If it’s somehow sending the actual atoms that make up the subject, then that’s something we are nowhere near to producing today. If it’s only information, then there are things we can examine in the here and now. Let’s therefore put the matter-based model to one side.
We can consider a purely information-based teleporter to be like a fax machine. A fax machine scans a document to build up a picture of the document’s physical appearance. That picture is stored as a digital information, nothing more than a string of one and zeroes. When the scan is complete, that information is sent via the phone line to another fax machine. The receiving machine decodes it back into an image and prints it out.
If we use this analogy, a teleporter would be like a fax machine for 3D objects. The principle would be the same. At one end, the teleporter scans an object and builds up a description of its physical structure. That information is sent to a 3D printer, which uses the description to assemble a duplicate of the original object.
However, this analogy contains some flaws.
Most striking is that such a teleporter doesn’t actually move an object, rather it creates a copy of an object at the destination. At the end of the process there are two objects. It’s a copy and paste rather than a cut and paste, but science fiction has led to us to think of teleportation as the latter.
Another flaw in the analogy regards the ‘fidelity’, which simply means the quality of the transmitted data. When you scan a document you don’t get an exact copy. Look at the last fax you received or, if you live in the 21st century, the last scan of a document you made. You’ll notice the copy has subtle differences compared to the original: the shape of the letters is slightly wobbly, pixels are missing here and there, and a few extra pixels have even sneaked into the image. That’s OK. As long as the document is readable we can accept a less-than-perfect fidelity.
But imagine teleporting yourself using a less-than-perfect fidelity. A process 99% accurate would introduce errors into 1% of your body. That means millions of cells missing, flaws appearing in your tissues, thousands of neurons in your brain misaligned. You’d be lucky to survive it once without serious damage. Imagine if you beamed around on a regular basis. You’d be the human equivalent of that dogeared old joke article that’s been photocopied and faxed around every office in the country.
You probably need to be over 40 to appreciate that last line. Here’s something for the rest of you.
The curse of uncertainty
“Fine,” you might say, “then we have to crank up the accuracy of the scan. Forget 99%. Make it 100%!”
That’s all very well, but there is a problem here. When we scan a document, we use a resolution of something like 100 dots per inch. That’s why there are inaccuracies. If we want to teleport an object, we must accurately represent its molecular structure, and that means scanning at the resolution of atoms. That’s on the order of 10,000,000,000,000,000,000,000 dots per inch1. Yes, that’s a colossal amount of data to record, but there’s also a more fundamental problem. When scanning an object for teleportation, the properties of its atoms must be recorded. An atom has many properties, but let’s focus on its position and momentum2. Observation at the atomic level is much like observation for you and me. Light (i.e. a load of photons) bounces off the subject and into our eyes, which relay the light as electrical signals to our brain. The brain thens interprets these signals, allowing us to see the world around us.
However, when scanning at the resolution of individual atoms, the very act of observation alters the atom’s properties. For example, let’s say a scientist wants to scan a particle’s position with 100% accuracy. To do this, the wavelength of the light needs to be comparable in size to a particle (i.e. trillionths of a metre), and light with a wavelength this short has a high frequency. This makes it very energetic. But when an energetic photon bounces off a particle, some of the photon’s energy is passed onto the particle and alters its velocity in an unpredictable way. The more accurately you attempt to scan a particle’s position, the more you disturb its velocity. But if you attempt to minimise this problem by using a lower frequency photon, you give up some of the positional accuracy.
Click the buttons to try measuring particles for yourself.
The physicist Werner Heisenberg formulated this as the Uncertainty Principle and it’s a fundamental limitation when trying to measure particles with high accuracy. That makes it a real problem if your ambition is to build a teleporter.
But in 1993, a group of scientist managed to find a way around this limitation.
Quantum teleportation is born
The quantum world is a strange place, confounding those scientists who would prefer a classical, deterministic explanation. Quantum mechanics throws up unintuitive and seemingly impossible phenomena that are nevertheless accurate and verifiable by experiments.
One of these is quantum entanglement, a phenomenon that connects particles in an extraordinary way. When particles become entangled they have been connected in such a way that they have essentially become a single system. Describing the properties of one particle in the system necessarily describes the properties of all other particles in it.
For example, it’s possible under certain conditions to convert a certain amount of energy into a pair of entangled particles, A and B. After being created, the particles will fly apart with an equal but opposite amount of momentum. Measuring the momentum of particle A will tell us the momentum that particle B has, and vice versa.
The same is true of each particle’s spin3 which, put simply, can have the value of ‘up’ or ‘down’. Because they’re entangled, it is certain that one electron will have up-spin and the other will have down-spin. But we don’t know which electron has which spin until we observe them. If some property of a particle is as yet unobserved, it is considered to have all possible values of that property until an observation is made4. But because of entanglement, as soon as we discover the spin of one electron, we instantly deduce the spin of the other. If A has up-spin then B must have down-spin, and vice versa.
Still with me? OK, back to teleportation.
In 1993, a group of scientists at the IBM Thomas J. Watson Research Center used this phenomenon to come up with a theoretical way to achieve teleportation5. Their proposal contained a kind of communications channel with two entangled photons, A and B, acting as the endpoints. At each endpoint is a person (Alice at A, and Bob and B). Alice also has her own photon, P, that she wishes to teleport to Bob. To do this, she collides P with A, which yields information about both particles. This information is then sent using a ‘classical’ link, such as an optical fibre, to Bob. Once in possession of this information, he knows what he has to do to manipulate B in order to make its properties precisely mimic P.
This research didn’t stay theoretical for long. It was confirmed by experiment in 1998 when a team at Caltech teleported the quantum state of a beam of light across 1 metre6.
The good news is that all this work yielded a way to analyse particles in one location and then arrange other particles in a second location to exactly match them. More good news is that quantum entanglement can theoretically work over any distance. It doesn’t matter how far apart you separate entangled particles, their freaky quantum relationship persists.
But there’s also bad news. Because some information has to be transmitted via classical means for this whole process to work means there’s a speed limit to it. Classical communications cannot exceed the speed of light. More bad news: the process of analysing the state of a teleported particle necessarily destroys the particle’s original state.
Is this really teleportation?
For those of us brought up on a diet of science fiction, these experiments might inspire both wonder and disappointment. We can wonder at the weird world of quantum physics, but at the same time this ‘copy and paste’ model of teleportation isn’t quite what we’d hoped for. It’s not the case that actual matter gets moved from one place to another. What we have is a way to accurately describe matter at the quantum level so that it can be reproduced precisely in another location.
So if it’s not a mode of instantaneous travel, what is it good for? This is still a young area of science, so many unexplored possibilities exist.
One proposed application of quantum teleportation is ultra-secure communications. In such a setup, two communicating parties (let’s call on Alice and Bob again) can each receive a steady stream of entangled photons; Alice gets one half of all the pairs, Bob the other half. When Alice wants to send a message to Bob, she encodes her own photons with information and makes them interact with the stream of entangled photons. She then sends information about these interactions to Bob via a classical channel. Bob then uses that information to manipulate his stream of entangled photons and turns them into Alice’s original photons. This turns them into copies of Alice’s original photons that carry Alice’s message. Because some of the information being transported between two endpoints doesn’t actually move through intervening space, an eavesdropper can’t intercept it. What’s more, trying to read photons necessarily disturbs them, so the very act of eavesdropping on the entangled photon stream will raise the alarm.
There are other possible applications to do with quantum computing and communications, but it’s still very early days. Nevertheless, scientists are overcoming practical barriers all the time. For one thing, transporting entangled photons is very tricky because they are so fragile. If the quantum state of a photon gets disturbed in transit, the link to the other member of the pair is lost. A photon traversing an optical fibre is prone to hitting the glass and becoming disturbed that way. The further it travels, the more likely a disturbance happens. That’s why early experiments placed particles only short distances apart, like a few metres.
That hardly makes for a useful form of communication when you partner is in the same room, but those distances have since been greatly surpassed. Scientists at The University of Science and Technology of China have made huge leaps forward in the last few years. Instead of using optical fibre, they’ve instead settled on using laser beams to transport entangled photons7. Although the method is still vulnerable to losses, in 2012 they managed to teleport photons over a distance of 97 kilometres (about 60 miles). This is not only significant distance but it opens up the way to quantum communications via satellite. The current long-distance record (as of 2015) was set by physicists at the University of Vienna and the Austrian Academy of Sciences and stands at 143 kilometres (about 89 miles).
But ordinary optical fibre remains in the running. In 2014, physicists at the University of Geneva successfully transported the quantum state of a photon over 25 kilometres8 via cable. This indicates that the emerging field of quantum computing could reuse our existing communications infrastructure instead of us having to build a new one.
What does the future hold?
And so we come to the final part of the story. How could we get from today to the future depicted in Star Trek? Could we ever achieve teleportation of objects or even people?
Quite obviously, we would need to scale up our current approach to handle macroscopic objects. At the moment, scientists are dealing with a tiny number of atoms. The experiments that took place in China in 2012 were able to teleport only five particles per minute9. Objects like you and me have a lot of atoms in them - about 1028 to be exact10. That need not discourage us. Technology has a habit of making unimaginable leaps in ability. Imagine talking to a computer engineer in the 1960s, for whom a megabyte was a colossal amount of storage. How would they react if told about computers that could store a petabyte (that’s one billion times bigger than a megabyte)? Nevertheless here we are just fifty years later, and petabyte-level storage is quite normal.
Scientists and engineers will also need to find better ways to handle the fragile entangled particles. Today, a significant portion of particles are lost in the process of teleportation, either through material imperfections or atmospheric disturbance. Better methods and materials should reduce these losses.
Quite apart from the scientific and technical issues to be overcome, we would also need to develop a whole new area of philosophy dealing with the ethics and implications of teleportation. What it would need to come to terms with depends on how teleportation develops. If, as seems likely, teleportation of things requires destroying the original object and assembling a copy at the destination, how does that impact our sense of what a thing essentially is. Would you teleport an object of sentimental value knowing that what came out of the other end was merely a copy? Would you teleport yourself knowing that your body would be, for all intents and purposes, destroyed, and that none of the stuff making up the reassembled version of you was original material? Would teleportation mean the end of ‘your’ consciousness? Doesn’t that mean to teleport someone involves killing someone? Who knows? Consciousness is far from resolved, but this old puzzle would need resolving, whether it be down to physics, philosophers, or members of some as-yet-unknown discipline.
About ‘Achieving Star Trek’
This series explores inventions from the world of Star Trek, devices that its characters take for granted but to us are miraculous.
Each article explains how close we are today to achieving such an invention, what the scientific state of the art is, and what steps would we need to take to get ourselves from now to the future.
References and Notes
Roughly speaking, 100 picometres as the average width of an atom. Every centimetre that’s 10-2 / 100-12 atoms, or about 2.5 x 1021 dots per inch. ↩
An object’s momentum is its mass multiplied by its velocity. ↩
Spin is a particles angular momentum. ↩
This is where Schrödinger’s famous cat comes in. The poor cat of his thought experiment is put into a soundproof box with a sealed flask of deadly poison. A mechanism also lies inside the box primed to open the flask automatically at some unknown point in the future. Once the box is closed and locked, the cat may occupy one of two states: dead or alive. Until we actually open the box and observe the cat, it could be either. This is an analogy for the properties of particles. The value of the property (e.g. up-spin or down-spin) could be one of many possibilities so, until we observe it, it is thought of in terms of probability. This has odd consequences. For example, the position of a particle is a property so, until we observe its position, the particle is considered to be in multiple places at once! ↩
That’s 10,000,000,000,000,000,000,000,000,000. ↩