“Beam me up, Scotty.”
Nobody on Star Trek ever actually said those words. But the phrase has become part of our culture anyway. The concept of instantaneous (or near-instantaneous, at least) transportation is tantalizing: who wouldn’t like to be able to cross a continent, or travel from the Earth’s surface to a ship in orbit, simply by stepping onto a platform and saying, “Energize.”
We are a long way from being able to skip the commute and simply beam to work in the morning. But the concept is no longer pure science fiction like it was in the 1960s.
The Star Trek approach to matter transmission relied on Einstein’s famous mass-energy equivalence. Basically, the idea was that physical objects could be converted to energy, and that energy could be “beamed” from one location to another, where the energy would then be converted back into its original, material form. The problem with this approach is that mass-energy conversion is unfortunately not practical for real-world applications involving ordinary objects, because the amount of energy involved is staggering. If all of the matter contained in a human body were converted to energy, the results would literally be explosive.
The atomic bombs that devastated Hiroshima and Nagasaki converted only a very small percentage of their total mass into energy. Those explosions were the energy released by a mere 700 mg of matter. A human adult weighing 135 lb (62 kg, or 62,000,000 mg) has about 88,571 times that much mass.
Try to imagine 88,571 atomic bombs, all identical to the ones that destroyed Hiroshima and Nagasaki, exploding simultaneously in the same laboratory. Now, try to imagine controlling that much energy.
It is possible that, at some point in the far distant future, we may find a way to control that much energy without destroying the laboratory — and everything else within a hundred kilometres — in the process. But there are other problems with this approach. The Star Trek vision of matter transmission was essentially like saying, “We can ‘beam’ an ice cube by melting it, directing the steam to another location, and then cooling that steam to turn it back into an ice cube.”
The problem is that converting matter to energy isn’t like converting steam to ice. 100% conversion only takes place if the particles are completely annihilated, as in a matter-antimatter reaction (which is a topic for another post).
But there are easier ways to approach the problem of matter transmission, and two of them are currently in their early development stages.
A group at the Hasso Plattner Institute in Brandenberg, Germany, has created a device called “Scotty” (named in honour of the Enterprise chief engineer) that uses a 3D scanner to “read” an object. The object is then destroyed by the scanner, and the data is transmitted to a 3D printer in another location, which then recreates the object. (Want to read their paper?) This device makes it possible to, in effect, “fax” a physical object to somebody else.
The object received on the other end is a re-creation, not the original object, and the device can only transmit items that can be constructed by a 3D printer. (So it is not possible to, for example, use Scotty to send a package of medical supplies to the International Space Station, because the 3D printer would be unable to “print” the actual medicines.) Still, this has the potential to revolutionize the shipping industry as 3D printing technology becomes more sophisticated: sending an encrypted data packet is much faster, and much cheaper, than sending a physical item.
The other approach to matter transmission is “quantum teleportation” which is based on a principle of quantum mechanics known as “quantum entanglement.” Entire books can be — and in fact have been — written on the subject of entanglement. But basically, what quantum entanglement means is that under certain conditions, subatomic particles can become linked together so that their individual quantum states can only be described in terms of the combined whole, rather than describing each particle as a separate entity. Essentially, once particles are entangled, they no longer behave independently. Measuring the state of one entangled particle will tell you the states of both particles.
And the critical point here is that the distance between the particles is irrelevant. Two entangled particles can be on different continents, and they will still continue to behave as a single quantum system. Measuring one of these particles will still tell you about the other one, and the second particle does not need to be in the same room (or even the same galaxy, for that matter).
Einstein described this as “spooky action at a distance” and he never did accept this consequence of quantum theory. Nonetheless, it has been validated in experiment after experiment. Like so much of quantum theory, it might be counterintuitive, but it works.
But how does this make teleportation possible? Well, to start, it’s important to remember that what is being transmitted is the information that makes up the quantum state of the particles, not the particles themselves. First, scientists entangle, then physically separate, two photons. Once linked in this way, any change made to one of the photons will have an effect on the other.
Then, at the starting location, the qubits (quantum bits, or the data that makes up the quantum state) of the particle to be teleported is measured. This measurement is then transmitted to the final location, where the other entangled photon is already determined by the measurement at the starting point (thanks to quantum entanglement). This allows the quantum state to be transferred to a second particle, which is now identical to the first.
This is a long way from “Beam me up, Scotty.” While we have succeeded in teleporting elementary particles, there are significant technological challenges involved in mapping the complete quantum states of every particle that makes up a human body. But the key point is that these are technological challenges — not theoretical issues.
In other words, teleportation falls into the category of “It could become possible, if we can ever build a powerful enough computer.”