Stabilizer codes are among the most successful quantum error-correcting codes, yet they have important limitations on their ability to fault tolerantly compute. In a recent paper by Sherman Fairchild Postdoctoral Scholar Tomas Jochym-O’Connor, IQIM alum Alex Kubica and Theodore Yoder introduce a new quantity, the disjointness of the stabilizer code, which, roughly speaking, is the number of mostly nonoverlapping representations of any given nontrivial logical Pauli operator.
The notion of disjointness proves useful in limiting transversal gates on any error-detecting stabilizer code to a finite level of the Clifford hierarchy. For code families, they can similarly restrict logical operators implemented by constant-depth circuits. For instance, they show that it is impossible, with a constant-depth but possibly geometrically nonlocal circuit, to implement a logical non-Clifford gate on the standard two-dimensional surface code.
Read the full paper: Tomas Jochym-O’Connor, Aleksander Kubica, and Theodore J. Yoder, Disjointness of Stabilizer Codes and Limitations on Fault-Tolerant Logical Gates, Phys. Rev. X 8, 021047 – Published 21 May 2018