Siu-Hin Ng

The Single-Copy Quantum Bandit Is Classical: An Exact Spectral Collapse

We study multi-armed bandits whose arms supply unknown quantum states and whose mean rewards are defined by a known effect $F$. Each fresh copy may be measured by an arbitrary, adaptively chosen POVM. We prove an exact collapse: the measured relative entropy from an arm state to its confusing reward half-space equals t...