Breaking symmetry in the quantum world

For the first time, researchers have observed a break in a single quantum system. The observation – and the way they did it – have potential implications for physics that go beyond the standard understanding of how quantum particles interact to produce matter and allow the world to function as we know it.

The researchers published their findings on May 31 in the journal Science.

Called symmetry parity-time (PT), the mathematical term describes the properties of a quantum system – the evolution of time for a quantum particle, as well as the fact that the particle is even or odd. Whether the particle advances or recedes in time, the state of strangeness or regularity remains the same in the balanced system. When the parity changes, the balance of the system – the symmetry of the system – breaks.

In order to better understand quantum interactions and develop next-generation devices, researchers must be able to control the symmetry of the systems. If they can break the symmetry, they can manipulate the spin state of the quantum particles during their interaction, allowing to obtain controlled and predicted results.

"Our work is about quantum control," said Yang Wu, author and PhD journalist. student at Hefei National Laboratory of Physical Sciences at the Microscopic Scale and at the Department of Modern Physics of the University of Science and Technology of China. Wu is also a member of the key laboratory of the Academy of Magnetic Resonance Sciences at the microscopic scale.

Wu, Ph.D. Supervisor Rong and his colleagues used a center of nitrogen vacuum in a diamond. The atom of nitrogen with an extra electron, surrounded by carbon atoms, creates the perfect capsule for deepening the study of PT symmetry of the electron. The electron is a unique spin system, which means that researchers can manipulate the entire system simply by altering the evolution of the spin state of the electron.

Thanks to what Wu and Rong call a dilation method, the researchers applied a magnetic field to the axis of the nitrogen vacuum center, dragging the electron into a state of excitability. They then applied oscillating microwave pulses, modifying the parity and the temporal direction of the system and causing its rupture and decay over time.

"Because of the universality of our dilation method and the high controllability of our platform, these works pave the way for the experimental study of new physical phenomena related to the symmetry of PT," he said. Wu said.

Corresponding authors Jiangfeng Du and Xing Rong, professors at the Hefei National Laboratory of Physical Sciences at Microscale and the Department of Modern Physics at the China University of Science and Technology, agreed.

"The information extracted from this dynamic broadens and deepens the understanding of quantum physics," said Du, also an academician of the Chinese Academy of Sciences. "The work opens the door to the study of exotic physics with unconventional quantum systems."

Provided by
University of Science and Technology of China