Where does this fail? The idea that a benchmark on 250 assets of the S&P 500 validates large-scale portfolio optimization on a quantum computer is a dangerous simplification.
This ignores the plethora of systemic risks and liquidity constraints of the real world that define portfolio management.
Scaling up for European bond markets, for example, requires much more than just technical performance: it must anticipate ECB signals and sovereign credit risks.
A major problem is modeling black swan events like the Swiss franc crisis of 2015, which a 64-qubit system cannot foresee.
The system has a single point of failure in its inability to capture macro-economic nuances and abrupt policy changes.