Complexity and hardness of random peaked circuits

• URL: http://arxiv.org/abs/2510.00132v1
• Date: Tue, 30 Sep 2025 18:10:43 GMT
• Title: Complexity and hardness of random peaked circuits
• Authors: Yuxuan Zhang,
• Abstract summary: We study an explicit construction for random peaked circuits.<n>We demonstrate that the circuits generated by this method are non-trivial.<n>We also study using peaked circuits as a practical attempt for a verifiable quantum advantage protocol.
• Score: 6.472219867780061
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Near-term feasibility, classical hardness, and verifiability are the three requirements for demonstrating quantum advantage; most existing quantum advantage proposals achieve at most two. A promising candidate recently proposed is through randomly generated peaked circuits. In this work, we study an explicit construction for random peaked circuits: first selecting a random circuit $C$ of polynomial size, which forms a $k$-design. Subsequently, a second random circuit $C'$ is chosen from the same architecture, subject to a postselection criterion: $C'$ must exhibit a high overlap with $C$ in one of their rows. Utilizing unitary design properties, we demonstrate that the circuits generated by this method are non-trivial; specifically, $C'$ is provably far from $C^\dagger$. Indeed, with overwhelmingly high probability, a random peaked circuit generated this way is non-compressible and is of circuit complexity $\tilde \Omega(nk)$. This resolves an open problem posed by Aaronson in 2022. Secondly, we analytically establish that estimating the peakedness of a random peaked circuit to within a $2^{-\text{poly}(n)}$ additive error, is average-case \#P-hard. When the additive error is relaxed to $1/\text{poly}(n)$, we note that the worst-case scenario for this problem is BQP-complete. Under widely accepted assumptions on random quantum circuits, we identify a regime where no classical polynomial-time sequential simulator attains inverse-polynomial additive accuracy on the peak on a non-negligible fraction of instances. Thirdly, we study using peaked circuits as a practical attempt for a verifiable quantum advantage protocol. While the postselection method for generating peaked circuits could be costly, we demonstrate that numerical search for $C'$ with randomized initialization successfully returns a random peaked circuit, achieving the properties as theoretically predicted.

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