  In this note, we show that $O(\log (1/\epsilon))$ rounds of parallel
repetition with a threshold suffice to reduce completeness and soundness error
to $\epsilon$ for single-prover quantum interactive proof systems. This
improves on a previous $O(\log (1/\epsilon) \log \log (1/\epsilon))$ bound from
Hornby (2018), while also simplifying its proof. A key element in our proof is
a concentration bound from Impagliazzo and Kabanets (2010).
