A group of Chinese physicists has broken a record in the field of quantum computing, successfully attaining quantum entanglement of 18 qubits. This nearly doubles the previous record – an entanglement of 10 qubits that was also achieved by Chinese physicists. The physicists’ research represents a substantial breakthrough for quantum computing and has potential applications in any field that utilizes quantum information processing.
The power of qubits
The number of manipulable qubits controls the power of a quantum computer – each additional qubit exponentially increases the power of the system. The new record of 18 entangled qubits, for instance, allows for 262,144 (218) potential combinations.
The research was conducted by scientists from the University of Science and Technology of China and published in late June in the journal Physical Review Letters. “This represents the largest entanglement so far,” explained co-author Chao-Lang Lu. “Entangling an increasingly large number of qubits not only is of fundamental interest (i.e., pushing the physical limit, if there is one, in order to explore the boundary between quantum and classical, for example). But also, probably more importantly, entangling large numbers of qubits is the central task in quantum computation.”
Leveraging degrees of freedom
Effective qubits can be increased either by adding more particles or through “hyper-entanglement” – utilizing the particles’ degrees of freedom (DoFs). While moving beyond two DoFs has proved difficult in the past, the physicists who conducted this research managed to produce scalable hyper-entanglement, resulting in an entanglement comprised of six photos with three DoFs. Utilizing three DoFs doubled the information capacity of the photons and increased efficiency by 13 orders of magnitude relative to a single-DoF entanglement.
“Controlling multiple DoFs is tricky, as it is necessary to touch one without disturbing any other,” Lu elaborated. “To solve this, we develop methods for reversible quantum logic operations between the photon’s different DoFs with precision and efficiencies both close to unity. We believe that our work creates a new and versatile platform for multi-photon quantum information processing with multiple DoFs.”
About the paper
The paper referenced in this article, “18-Qubit Entanglement with Six Photos’ Three Degrees of Freedom,” was written by Xi-Lin Wang, Yi-Han Luo, He-Liang Huang, Ming-Cheng Chen, Zu-En Su, Chang Liu, Chao Chen, Wei Li, Yu-Qiang Fang, Xiao Jiang, Jun Zhang, Li Li, Nai-Le Liu, Chao-Yang Lu, and Jian-Wei Pan. It can be found in the June 2018 issue of Physical Review Letters.