Dutch researchers have brought us all one step closer to super-fast, ultra-secure internet connections using quantum technologies.
A team from QuTech, a collaboration between Delft University of Technology in the Netherlands and the Netherlands Organization for Applied Scientific Research, achieved the first transmission of information of its kind over a very small quantum network of three nodes.
The nodes of the network were built using tiny quantum processors, and sending quantum information between these processors has been a major hurdle, but it is also essential to harnessing the quirks of quantum mechanics to transmit information.
What the researchers did was create a quantum “teleporter” using two entangled quantum “processors,” which they named Alice and Charlie. Quantum information transfer between two entangled processors is not entirely new, but previous efforts have been limited to adjacent quantum processors. This was an important step, but if quantum information transfer between two points it’s going to be functionally useful, so we’re going to have to have points that are a certain distance from each other.
Is quantum teleportation possible?
Ultimately, why do all this and what does it really mean? The QuTech team believes they have created one of the building blocks of a quantum Internet, and while replicability of this work will be a big key, these are still very encouraging results.
“We are now building small quantum networks in the lab,” said Ronald Hanson, a Delft physicist who oversees the QuTech team, at the New York Times. “But the idea is eventually to build a quantum Internet.”
What makes the idea of that quantum internet so attractive is that it would allow the seemingly instantaneous transfer of data from one place to another through a phenomenon called quantum teleportation.
“The idea of quantum teleportation is that one can teleport the information carried by a qubit, but not the physical qubit itself,” said Dr. Sophie Hermans, lead author of the study published May 25 in the journal. Naturesaying interesting engineering. “To do so, you would need an entangled state between two qubits in the hands of the sender and receiver. An entangled state is a property known only in quantum mechanics and represents a very strong connection, even between very distant qubits.”
The QuTech researchers appear to have done just that by using a third processor, designated Bob, that was capable of taking quantum information from Charlie and passing it to Alice, effectively entangling Charlie and Alice, allowing them to transfer information between them.
“Once the entangled state is established, the connection, can be used to teleport the information stored in a third qubit that is held by the sender. By doing a special type of measurement (a Bell measurement), the information disappears from the qubit in the sender and appears in the qubit of the receiver”.
There’s a lot more involved, especially around how the data is ultimately received, so “in order for the information to be useful,” Hermans told us, “one has to perform an operation, like a bit inversion, for example, depending on the results of the Bell measurement”.
Quantum teleportation is not the same as the physical teleportation seen in science fiction, although it is very close. The difference with quantum teleportation is that no physical matter is transmitted, only information, thanks to a quirk of quantum mechanics that allows two quantum particles to “share” a quantum state.
The best way to describe this quantum state is like describing a pair of gloves. When you see which hand one of those gloves is put on, you also know which hand the other is put on, even if you never see it. Note that this is a very basic description of the phenomenon, as even a century after the founding of quantum mechanics, there is still a lot we don’t actually know about the quantum world, but we seem to know enough to be to be able to start extending our knowledge to practical applications like a quantum internet.
Is quantum teleportation faster than light?
No, unfortunately, and it probably never can be. This is due to something known as the no communication theorem which posits that when an observer takes a quantum measurement, the information cannot be transmitted to another more distant observer faster than the speed of light.
“The fact that the receiver needs to know the results of the Bell measurement [for the information to be interpreted]creates the need to communicate these results,” Hermans told us. “This can be done using classical or normal communication, but this prevents faster-than-light communication.”
Still, the transmission of information is significantly faster than it currently is, namely fiber optics and light-encoded digital bits. And while it might seem like light would be the faster of the two, light also has a major problem, namely the eventual loss of signal that currently hampers classic digital communication.
Quantum teleportation preserves this information intact through the process of “teleportation”, and has the added benefit of being more secure. Because this is quantum information, any attempt to intercept the data will cause it to lose coherence, and without the proper information to interpret the resulting information, the intercepted data would look like random bits. Furthermore, the intended receiver could also detect this decoherence, which would indicate that the connection was being intercepted.
But work is still required to get to that point, and we’re still a decade or more away from a truly functional quantum internet, but we’re one step closer to making it a reality, and that’s something.