Learning low-degree quantum objects
- URL: http://arxiv.org/abs/2405.10933v1
- Date: Fri, 17 May 2024 17:36:44 GMT
- Title: Learning low-degree quantum objects
- Authors: Srinivasan Arunachalam, Arkopal Dutt, Francisco Escudero GutiƩrrez, Carlos Palazuelos,
- Abstract summary: We show how to learn low-degree quantum objects up to $varepsilon$-error in $ell$-distance.
Our main technical contributions are new Bohnenblust-Hille inequalities for quantum channels and completely boundedpolynomials.
- Score: 5.2373060530454625
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: We consider the problem of learning low-degree quantum objects up to $\varepsilon$-error in $\ell_2$-distance. We show the following results: $(i)$ unknown $n$-qubit degree-$d$ (in the Pauli basis) quantum channels and unitaries can be learned using $O(1/\varepsilon^d)$ queries (independent of $n$), $(ii)$ polynomials $p:\{-1,1\}^n\rightarrow [-1,1]$ arising from $d$-query quantum algorithms can be classically learned from $O((1/\varepsilon)^d\cdot \log n)$ many random examples $(x,p(x))$ (which implies learnability even for $d=O(\log n)$), and $(iii)$ degree-$d$ polynomials $p:\{-1,1\}^n\to [-1,1]$ can be learned through $O(1/\varepsilon^d)$ queries to a quantum unitary $U_p$ that block-encodes $p$. Our main technical contributions are new Bohnenblust-Hille inequalities for quantum channels and completely bounded~polynomials.
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