Researcher Helen Chrzanowski operates an experiment at the Australian National University that unlocks quantum discord in pairs of laser beams. (Photo : The Australian National University)
Quantum computing is hailed as the next great leap in processing that will theoretically open up an exponential amount of computing power to us. Until now, a phenomenon known as quantum entanglement was thought to be a necessary attribute of any quantum computer. An international team of researchers are now proposing that a new, easier to access method instead: quantum discord.
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Quantum entanglement is a funky characteristic in the sub-atomic world of quantum physics. Essentially, it states that two particles can become so intertwined with each other, that observing and changing one particle, changes the other accordingly, regardless of where the other particle is located. The problem with quantum entanglement is that it is easy to recreate in ideal, lab settings. Making it work in the real world, where it can prove useful in quantum computers, is much harder.
Instead, the team of researchers from the University of Vienna, the Austrian Academy of Sciences, the National University of Singapore (NUS), and the University of Oxford chose to focus on a phenomenon known as quantum discord.
"We've shown that quantum discord is a resource that we can tap with the right quantum tools," said Mile Gu, a Research Fellow of the Centre for Quantum Technologies at NUS.
Quantum discord has been described by two of its founding theorists as the measure of the "quantumness" of correlations. Basically, it means that rather than retrieve information based on observing quantum entanglement, quantum discord observations take note of other physical effects at the quantum level in a quantum system.
Ping Koy Lam, Professor at ANU, said "the experiment is analogous to decoding music from a AM/FM radio simulcast that is badly affected by static."
By paying attention to the unwanted "static," the researchers were actually able to extract more information than if they had ignored the quantum discord as simply background noise.
"By measuring the polarization state of a certain photon we prepare the state of the respective partner photon remotely", explains Philip Walther. "In the experiment we observe how the quality of our remotely prepared quantum state is affected by changes in the quantum discord."
Watch one of the authors of the study, Vlatko Vedral, give a lecture on quantum discord and its efficiencies: