The term 'quantum teleportation' might conjure thoughts of space crew members being beamed across space in Star Trek. While the reality is not quite as impressive, the mysterious nature of quantum mechanics still makes it an undeniably compelling subject.
This week, new findings have been released: for the first time ever, researchers have teleported a qutrit, a unit of quantum information that exists as three orthogonal quantum states.
Qutrit teleportation experiments
As Scientific American reports, the independent results from two teams have detailed important progress in the field of quantum teleportation.
Quantum teleportation has long been limited to qubits. These are the unit of quantum information equivalent to a 'bit' in classical computing.
Through proof-of-concept experiments, it was shown that qutrits, which can carry more information than qubits, can be entangled and could possibly be used in quantum networks of the future.
Led by physicist Guang-Can Guo, a team of researchers at the University of Science and Technology of China (USTC) carried out their research and reported the findings in a preprint paper on April 28. Their work is yet to be published in a peer-reviewed journal.
Soon after, on June 24, another team, headed by Anton Zeilinger of the Austrian Academy of Sciences and Jian-Wei Pan of USTC, reported its results in a preprint paper that will be published in Physical Review Letters.
“Each of these [experiments] is an important advance in the technology of teleportation,” William Wootters, a physicist at Williams College who was not involved in the studies, told Scientific American.
Quantum entanglement: creating an unhackable password
Quantum entanglement is so strange that Albert Einstein once described it as "spooky action at a distance."
It describes a relationship between the fundamental properties — such as momentum, position, or polarisation — of separate particles that can't have happened by chance.
The fact that actions performed on one particle affects its 'twin' entangled particle - even at a distance - allows these particles to be used in quantum computing.
Scientists have captured the first ever image of a phenomenon Albert Einstein described as "spooky action at a distance". Photo shows a strong form of quantum entanglement, where two particles interact and share physical states for an instant. @BBCNews https://t.co/qP3aeo0Q5g pic.twitter.com/UtxGCzG8jG— The SETI Institute (@SETIInstitute) July 13, 2019
A lot of research, for example, is going into the utility of entanglement in cybersecurity.
In 2017, Pan, Zeilinger, and their team used China's Micius satellite to perform an experiment. Two photons — each one acting as a qubit — were zapped to Vienna and China. Researchers in each location were effectively able to compile an unhackable password, which they used to make a secure video call. As tampering with one photon affects the other, any eavesdropping is immediately detectable thanks to entanglement. This is the primary foundational principle of quantum cryptography.
Research has also been carried out on quantum mechanics for other purposes, such as battery technology. In theory, the properties of entanglement should make it possible for a battery to charge instantaneously.
Proving Qutrit entanglement
The two Qutrit experiment teams had to confirm entanglement in order to validate their research. Determining entanglement is essential in quantum mechanics - it allows the extraction of information from the particles and proves the fidelity at which the information is conveyed.
The teams used carefully assembled optical systems of lasers, beam splitters, and barium borate crystals in order to carry out their experiments.
In order to prove entanglement, Guo and his colleagues took over ten measurements of the Bell State — another term for entanglement — of their particles. This is more than Zeilinger's team carried out.
The rivalry between both teams seems to be cordial, as per Scientific American. Though both sets of researchers claim they got there first, both groups agree that they each teleported a qutrit.
Where next? In the near future, both teams aim to start experimenting on teleporting ququarts, four-level units, or even higher.