Published online by Cambridge University Press: 20 November 2018
It is known that the normalized standard generators of the free orthogonal quantum group   $O_{N}^{+}$  converge in distribution to a free semicircular system as
 $O_{N}^{+}$  converge in distribution to a free semicircular system as   $N\,\to \,\infty$ . In this note, we substantially improve this convergence result by proving that, in addition to distributional convergence, the operator normof any non-commutative polynomial in the normalized standard generators of
 $N\,\to \,\infty$ . In this note, we substantially improve this convergence result by proving that, in addition to distributional convergence, the operator normof any non-commutative polynomial in the normalized standard generators of   $O_{N}^{+}$  converges as
 $O_{N}^{+}$  converges as   $N\,\to \,\infty$  to the operator norm of the corresponding non-commutative polynomial in a standard free semicircular system. Analogous strong convergence results are obtained for the generators of free unitary quantum groups. As applications of these results, we obtain a matrix-coefficient version of our strong convergence theorem, and we recover a well-known
 $N\,\to \,\infty$  to the operator norm of the corresponding non-commutative polynomial in a standard free semicircular system. Analogous strong convergence results are obtained for the generators of free unitary quantum groups. As applications of these results, we obtain a matrix-coefficient version of our strong convergence theorem, and we recover a well-known   ${{\mathcal{L}}^{2}}\,-\,{{\mathcal{L}}^{\infty }}$  norm equivalence for noncommutative polynomials in free semicircular systems.
 ${{\mathcal{L}}^{2}}\,-\,{{\mathcal{L}}^{\infty }}$  norm equivalence for noncommutative polynomials in free semicircular systems.