Austrian
and Chinese scientists have for the first time succeeded in transferring
three-dimensional quantum states (symbolic image). Credit: ÖAW/Harald Ritsch |
For the first time, Austrian and Chinese scientists have teleported three-dimensional quantum states. Future quantum computers may rely heavily on high-dimensional teleportation.
Researchers
from the Austrian Academy of Sciences and the University of Vienna have shown
experimentally what had previously only been a theoretical possibility. They
were able to transmit sophisticated high-dimensional quantum states with the
help of quantum physicists from China's University of Science and Technology.
The research teams published their findings in the journal Physical Review
Letters, which is a worldwide first.
The
researchers used quantum teleportation to send the quantum state of one photon
(light particle) to another. Only two-level states ("qubits") were
previously communicated, i.e. data with values of "0" or
"1." The scientists did, however, manage to transport a three-level
condition known as a "qutrit." In quantum physics, unlike in
classical computer science, "0" and "1" do not have to be
"either/or" - they can be both at the same time, or anything in
between. With a third option "2," the Austrian-Chinese team has now
shown this in practice.
Novel experimental method
Since the
1990s, it has been known that multidimensional quantum teleportation is
theoretically feasible. However, according to Manuel Erhard of the Austrian
Academy of Sciences' Vienna Institute for Quantum Optics and Quantum
Information, "first we had to establish an experimental method for
implementing high-dimensional teleportation, as well as develop the requisite
equipment."
The
quantum state to be transmitted is encoded in the various photon routes. These
pathways can be visualized as three optical fibres. Surprisingly, in quantum
physics, a single photon can exist simultaneously in all three optical cables.
The researchers employed a novel experimental method to transport this
three-dimensional quantum state. The so-called Bell measurement lies at the
heart of quantum teleportation. It uses a multiport beam splitter to route
photons through many inputs and outputs while still connecting all optical
fibres. Auxiliary photons were also used by the researchers, which are put into
the multiple beam splitter and can interfere with the other photons.
Quantum
information can be conveyed to another photon far away from the input photon
via smart interference patterns, without the two ever physically interacting.
As Erhard points out, the experimental notion is not restricted to three
dimensions, but can theoretically be expanded to any number of dimensions.
Higher information capacities for quantum computers
Because
high-dimensional quantum systems can transfer bigger amounts of information
than qubits, the worldwide research team has taken a significant step toward
practical applications such as a future quantum internet. "This work could
help connect quantum computers with information capacity beyond qubits,"
says Anton Zeilinger, a quantum physicist from the Austrian Academy of Sciences
and the University of Vienna.
Multidimensional
quantum teleportation also appeals to the Chinese experts who took part in the
study. "Our foundational research now is building the basics for
next-generation quantum network systems," says Jian-Wei Pan of China's
University of Science and Technology. Pan recently gave a speech in Vienna at
the University of Vienna and the Academy's invitation.
Quantum
physicists will focus their efforts in the future on how to apply their newly
acquired knowledge to enable teleportation of a single photon or atom's whole
quantum state.
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