← Open problems
MUB-10.8
Is the set of MU product bases from Thm. 6.1 unextendible?
In plain terms
Known for d=6 (any three MU product bases are strongly unextendible); open in general.
Our position — ours alone, not the authors'
The d=6 case -- the only one we have instrument for -- is already settled.
Source
Daniel McNulty, Stefan Weigert, Mutually Unbiased Bases in Composite Dimensions -- A Review
Quantum 10, 2051 (2026) · §10.3
https://doi.org/10.22331/q-2026-04-01-2051
Licence:
CC-BY-4.0
— the problem statement is quoted here under that
licence, with attribution, and has not been modified