A team of Chinese quantum physicists has demonstrated the world’s first 18-qubit entanglement. This is the largest entangled state ever in all physical systems, and represents a big step towards large-scale highly efficient quantum computing. Lead researcher Pan Jianwei and colleagues at University of Science and Technology of China and CAS-Alibaba Quantum Computing Laboratory published the paper last week in Physics Review Letter.

Qubit entanglement is a distinctive feature of qubits that distinguishes quantum computers from classical computers. A set of entangled qubits can express high-level correlation regardless of their locations, allowing quantum computers to perform specific tasks not possible in classical computers. Generating an increasing number of entangled particles is an important benchmark for quantum information processing.

18-Qubit Entanglement with Six Photons’ Three Degrees of Freedom demonstrates an experimental result of an 18-qubit Greenberger-Horne-Zeilinger (GHZ) entanglement by simultaneous exploiting three different Degree of Freedoms (DoFs) of six photons, including their paths, polarization, and orbital angular momentum (OAM). Previously, multi-qubit entanglements have been reported up to 14 trapped ions, 10 photons, and 10 superconducting qubits.

The paper presents a method of developing quantum logic operations on photons’ DoFs, which successfully enables concurrent readout of 262,144 outcome combinations of the 18-qubit state. A state fidelity of 0.708 ± 0.016 is measured, confirming the genuine entanglement of all 18 qubits.

Lead researcher Pan is widely recognized for his achievements in quantum entanglement with photons and superconducting circuits.