Multiple Quantum Hypothesis Testing: One-Shot Pairwise Bounds and Sharp Asymptotics
Provides fundamental theoretical advances in quantum hypothesis testing, resolving open problems and improving prior bounds for both finite and infinite-dimensional settings.
The paper resolves a conjecture on one-shot multiple quantum hypothesis testing, providing dimension-free bounds and sharp asymptotics for infinite-dimensional Hilbert spaces, and shows binary quantum error probability is within a factor of two of the optimal classical error probability.
We consider Bayesian discrimination among multiple quantum states and establish a dimension-free one-shot upper bound on the minimum probability of error in terms of the sum of pairwise errors. This resolves a conjecture of Audenaert and Mosonyi [J. Math. Phys. 55 (2014)] and improves the multiple quantum Chernoff bound of Li [Ann. Statist. 44 (2016)] by removing its dimension-dependent prefactor. In the asymptotic many-copy regime, our bound proves the achievability of the multiple quantum Chernoff distance for arbitrary separable Hilbert spaces, thereby settling the previously open infinite-dimensional case, and further yields constant-factor sharp asymptotics for the optimal error probability. In binary quantum hypothesis testing, we prove that the minimum error probability is characterized, up to universal constants, by a trace harmonic-mean quantity. Consequently, the optimal binary quantum error probability is within a factor of two of the optimal classical error probability for the associated Nussbaum-Szkoła distributions, complementing the lower bound of Nussbaum and Szkoła [Ann. Statist. 37 (2009)].