We hit a wall with quantum computers where feeding them more data stops making them smarter—it's like the hardware just gives up.
arXiv · March 13, 2026 · 2603.12235
Why it matters
In most scientific experiments, more data leads to more precision, but this study found that on photonic quantum chips, error abruptly hits a floor where more measurements are useless. This reveals a fundamental limit to how much we can ever know about a quantum state using current hardware, regardless of how much data we gather.
From the abstract
The theoretical efficiency of classical shadow tomography is predicated on a perfect Haar-random unitary ensemble, yet this mathematical ideal remains physically unattainable in near-term hardware. Here, we report the experimental discovery of a fundamental accuracy bound on integrated photonic processors: a ``Hardware Horizon'' where the reconstruction error undergoes a sharp phase transition. While the error initially obeys the predicted statistical scaling $\mathcal{O}(M^{-1/2})$, it abruptly