Xiao-Gang Wen is a theoretical condensed matter physicist, recognized for his work on introducing the notion topological order (1989) and developing the theories of this new class of quantum states of matter. Since 2000, the study of topological states of matter slowly became a very active new field in condensed matter physics.
Wen was born in Beijing and grew up in Xi'an, China. He went to University of Science and Technology of China after the reopening of universities in China in 1977. Through T.D. Lee's CUSPEA program, he obtained a chance to enter the graduate school of Princeton University in 1982, and earned a PhD degree in the field of superstring theory under Prof. Witten. During his postdoctoral period (1987-1989) in ITP, Santa Barbara, he started to pursue research in condensed matter physics. After a two-years stay in IAS, Princeton, he joined the faculty of department of Physics, MIT in 1991. He was awarded Oliver E. Buckley Condensed Matter Prize by APS in 2017 and ICTP Dirac medal in 2018.
Xiao-Gang Wen is interested in new quantum states of matter beyond the conventional band theory and symmetry breaking theory. People used to think that symmetry breaking can describe all phases of mater. However, Wen’s study on chiral spin states and fractional quantum Hall states in 1989 revealed the existence of a new class of quantum states of matter, which he named topological order. He found many topologically ordered states to have perfect conducting edge, which may lead to device application of topological order. Soon after, Wen and others discovered Z2 spin liquid, which has emergent fermions despite the spin liquid is formed by purely bosonic qubits. In 1991, a more complicated topological order—non-abelian topological order—was discovered by Wen and by Moore-Read. It turns out that non-abelian topological order is the “Silicon” for making fault tolerant topological quantum computer. The connection between topological order and quantum computer is natural, since topological order is nothing but patterns of long range quantum entanglement. Since 2005, Wen became interested in the mathematical foundations of topological order, which turns out to be higher category and group cohomology theories, and discovered a new class of topological states of matter – symmetry protected topological order in 2011. Wen is also applying the theory of topological order to obtain an unification of elementary particles and interactions in term of qubits (i.e. it from qubit).