H. W. Shawn Liew | Searcharxiv

arXiv2026

Informed Trading model with quantum walks

The seminal Kyle model offers a framework to understand the price impact of an informed trader in a market model for a single asset. We study variants in which the asset's future value is modeled by a classical random walk and by a continuous-time quantum walk, respectively. With these assumptions, we analytically approximate and numerically identify the market equilibrium between risk-neutral market maker and informed trader. In the classical equilibrium, the informed trader possesses a linear strategy, whereas the market maker's pricing rule resembles a logistic curve. The informed trader's profit is also identified to grow sub-linearly with time t. In the quantum equilibrium, the informed trader's strategy forms multiple clusters and the pricing rule exhibits multiple jumps correspondingly. Despite the increasing non-linearity of the equilibrium, the informed trader's profit grows linearly with time t.

quant-ph↗

arXiv2026

Scalable tests of quantum contextuality from stabilizer-testing nonlocal games

Soon after the dawn of quantum error correction, DiVincenzo and Peres observed that stabilizer codewords could give rise to simple proofs of quantumness via contextuality. This discovery can be recast in the language of nonlocal games: every $n$-qubit stabilizer state defines a specific "stabilizer-testing" $n$-player nonlocal game, which quantum players can win with probability one. If quantum players can moreover outperform all possible classical players, then the state is contextual. However, the classical values of stabilizer-testing games are largely unknown for scalable examples beyond the $n$-qubit GHZ state. We introduce several new methods for upper-bounding the classical values of these games. We first prove a general coding-theory bound for all stabilizer-testing games: if the classical value $p_{\mathrm{cl}}^* < 1$, then $p_{\mathrm{cl}}^* \leq 7/8$, i.e., there is no classical strategy that can perform as well as the optimal quantum strategy even in an asymptotic sense. We then show how to tighten this bound for the most common scalable examples, namely GHZ, toric-code and cyclic cluster states. In particular, we establish an asymptotically tight upper bound for cyclic cluster states using transfer-matrix methods. This leads to the striking conclusion that measuring an exponentially small fidelity to the cyclic cluster state will suffice to witness its contextuality.

quant-ph↗