  The reviewed paper describes an analog device that empirically solves small
instances of the NP-complete Subset Sum Problem (SSP). The authors claim that
this device can solve the SSP in polynomial time using polynomial space, in
principle, and observe no exponential scaling in resource requirements. We
point out that (a) the properties ascribed by the authors to their device are
insufficient to solve NP-complete problems in poly-time, (b) runtime analysis
offered does not cover the spectral measurement step, (c) the overall technique
requires exponentially increasing resources when scaled up because of the
spectral measurement step.
