On the Pure Quantum Polynomial Hierarchy and Quantified Hamiltonian Complexity

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Hauptverfasser: Grewal, Sabee, Rudolph, Dorian
Format: Preprint
Veröffentlicht: 2025
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author Grewal, Sabee
Rudolph, Dorian
author_facet Grewal, Sabee
Rudolph, Dorian
contents We prove several new results concerning the pure quantum polynomial hierarchy (pureQPH). First, we show that QMA(2) is contained in pureQSigma2, that is, two unentangled existential provers can be simulated by competing existential and universal provers. We further prove that pureQSigma2 is contained in QSigma3, which in turn is contained in NEXP. Second, we give an error reduction result for pureQPH, and, as a consequence, prove that pureQPH = QPH. A key ingredient in this result is an improved dimension-independent disentangler. Finally, we initiate the study of quantified Hamiltonian complexity, the quantum analogue of quantified Boolean formulae. We prove that the quantified pure sparse Hamiltonian problem is pureQSigma-complete. By contrast, other natural variants (pure/local, mixed/local, and mixed/sparse) admit nontrivial containments but fail to be complete under known techniques. For example, we show that the exists-forall mixed local Hamiltonian problem lies in NP^QMA \cap coNP^QMA.
format Preprint
id arxiv_https___arxiv_org_abs_2510_06522
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the Pure Quantum Polynomial Hierarchy and Quantified Hamiltonian Complexity
Grewal, Sabee
Rudolph, Dorian
Quantum Physics
Computational Complexity
We prove several new results concerning the pure quantum polynomial hierarchy (pureQPH). First, we show that QMA(2) is contained in pureQSigma2, that is, two unentangled existential provers can be simulated by competing existential and universal provers. We further prove that pureQSigma2 is contained in QSigma3, which in turn is contained in NEXP. Second, we give an error reduction result for pureQPH, and, as a consequence, prove that pureQPH = QPH. A key ingredient in this result is an improved dimension-independent disentangler. Finally, we initiate the study of quantified Hamiltonian complexity, the quantum analogue of quantified Boolean formulae. We prove that the quantified pure sparse Hamiltonian problem is pureQSigma-complete. By contrast, other natural variants (pure/local, mixed/local, and mixed/sparse) admit nontrivial containments but fail to be complete under known techniques. For example, we show that the exists-forall mixed local Hamiltonian problem lies in NP^QMA \cap coNP^QMA.
title On the Pure Quantum Polynomial Hierarchy and Quantified Hamiltonian Complexity
topic Quantum Physics
Computational Complexity
url https://arxiv.org/abs/2510.06522