By Teodor Teofilov
Scientists have made a major breakthrough in quantum teleportation by successfully transferring the most complex data set yet. The high-dimensional teleportation that was achieved by Austrian and Chinese scientists could play a very important role in the future of quantum computers. The research teams report this international first in the journal Physical Review Letters.
Quantum teleportation is a strange and mysterious phenomenon that has information flung across space. It is very different from the teleportation that we see in science fiction, like Star Trek, where matter is moved through space. Instead the transfer is that of information about the quantum state of a particle. This can have a big impact on the way that we organize and transmit information.
The researchers from the Austrian Academy of Sciences and the University of Vienna have experimentally shown what previously was considered only a theoretical possibility. Together with quantum physicists from the University of Science and Technology of China, they succeeded in teleporting complex high-dimensional quantum states. The researchers teleported the quantum state of one photon — a light particle — to another distant one.
Before this, scientists had only been able to teleport quantum bits (qubits) — the simplest possible piece of quantum information where a particle can only be in two states at once. Meaning that the information has values of “0” and “1”. In quantum physics the “0” and “1” aren’t in an either/or scenario like in computer science, but both are simultaneous or anywhere in between.
However, a qutrit, which was successfully teleported, adds an extra dimension. Where a qubit is polarized in two ways at once, the qutrit has three directions of polarization, or a third possibility that scientists are calling “2”, which makes it vastly more complicated.
A qutrit can be in a superposition of three states at the same time, meaning that it overlaps three different waves at the same time. The transported photon went from one qutrit location to another.
This type of high-dimension quantum teleportation had been theorized since the 1990s, but actually achieving it is something else.
“First, we had to design an experimental method for implementing high-dimensional teleportation, as well as to develop the necessary technology,” said Manuel Erhard from the Vienna Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences in a press statement.
In quantum computing, particles are referred to as entangled when they interact or share spatial proximity in such a way that they cannot be described separately from each other. The simplest version of entanglement is called a Bell state (named after physicist John Bell) and is vital to understanding quantum teleportation.
The scientists had to create a Bell state that wasn’t a qubit but a qutrit. To achieve this, the researchers created a “multiport beam splitter, which directs photons through several inputs and outputs and connects all optical fibers together,” according to the press statement. “In addition, the scientists used auxiliary photons—these are also sent into the multiple beam splitter and can interfere with the other photons.”
This is known as quantum interference. If a photon can be in two places at the same time, because of superposition, then it can interfere with itself or other photons. Sending auxiliary photons as interference allowed the scientists to clear a lane for the qutrits to transport.
The scientists state that working with qutrits will be crucial for handling large amounts of information.
“This result could help to connect quantum computers with information capacities beyond qubits,” says Anton Zeilinger, quantum physicist at the Austrian Academy of Sciences and the University of Vienna, speaking in the press statement.
The achievement of sending a qutrit means that the extra information that can be transferred could power new technologies like a possible unhackable quantum internet because it will allow for instant and extremely secure communication.
“The higher the dimensions of your quantum system, the more secure you can ensure your communication is and the more information you can encode,” Ciarán Lee, from University College London, told New Scientist. “But going from a qubit to a qutrit is especially difficult — the tricks you use for qubits have to do with a nice symmetry that qutrits don’t have.”
The researchers report that the demonstrations of their technique had 75 percent accuracy. This may be low but is currently better than similar techniques that don’t use quantum entanglement and will definitely improve in the future.
We are a long way from an unhackable internet, because quantum teleportation is very difficult, fragile and poorly understood. The bad news is that quantum teleportation probably isn’t useful for transporting people.