# Stabilizer extent is not multiplicative

Arne Heimendahl1, Felipe Montealegre-Mora2, Frank Vallentin1, and David Gross2

1Department Mathematik/Informatik, Universität zu Köln, Weyertal 86–90, 50931 Cologne, Germany
2Institute for Theoretical Physics, Universität zu Köln, Zülpicher Str. 77, 50937 Cologne, Germany

### Abstract

The Gottesman-Knill theorem states that a Clifford circuit acting on stabilizer states can be simulated efficiently on a classical computer. Recently, this result has been generalized to cover inputs that are close to a coherent superposition of logarithmically many stabilizer states. The runtime of the classical simulation is governed by the $\textit{stabilizer extent}$, which roughly measures how many stabilizer states are needed to approximate the state. An important open problem is to decide whether the extent is multiplicative under tensor products. An affirmative answer would yield an efficient algorithm for computing the extent of product inputs, while a negative result implies the existence of more efficient classical algorithms for simulating largescale quantum circuits. Here, we answer this question in the negative. Our result follows from very general properties of the set of stabilizer states, such as having a size that scales subexponentially in the dimension, and can thus be readily adapted to similar constructions for other resource theories.

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### Cited by

[1] James R. Seddon, Bartosz Regula, Hakop Pashayan, Yingkai Ouyang, and Earl T. Campbell, "Quantifying quantum speedups: improved classical simulation from tighter magic monotones", arXiv:2002.06181.

[2] Arne Heimendahl, Markus Heinrich, and David Gross, "The axiomatic and the operational approaches to resource theories of magic do not coincide", arXiv:2011.11651.

The above citations are from SAO/NASA ADS (last updated successfully 2021-08-01 14:08:42). The list may be incomplete as not all publishers provide suitable and complete citation data.

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