Title
Quantum generalizations of the polynomial hierarchy with applications to QMA(2).
Abstract
The polynomial-time hierarchy ($\mathrm{PH}$) has proven to be a powerful tool for providing separations in computational complexity theory (modulo standard conjectures such as $\mathrm{PH}$ does not collapse). Here, we study whether two quantum generalizations of $\mathrm{PH}$ can similarly prove separations in the quantum setting. The first generalization, $\mathrm{QCPH}$, uses classical proofs, and the second, $\mathrm{QPH}$, uses quantum proofs. For the former, we show quantum variants of the Karp-Lipton theorem and Toda's theorem. For the latter, we place its third level, $\mathrm{Q} \Sigma_3$, into $\mathrm{NEXP}$ {using the Ellipsoid Method for efficiently solving semidefinite programs}. These results yield two implications for $\mathrm{QMA}(2)$, the variant of Quantum Merlin-Arthur ($\mathrm{QMA}$) with two unentangled proofs, a complexity class whose characterization has proven difficult. First, if $\mathrm{QCPH} = \mathrm{QPH}$ (i.e., alternating quantifiers are sufficiently powerful so as to make classical and quantum proofs "equivalent"), then $\mathrm{QMA}(2)$ is in the Counting Hierarchy (specifically, in $\mathrm{P}^{\mathrm{PP}^{\mathrm{PP}}}$). Second, unless $\mathrm{QMA}(2)={\mathrm{Q} \Sigma_3}$ (i.e., alternating quantifiers do not help in the presence of "unentanglement"), $\mathrm{QMA}(2)$ is strictly contained in $\mathrm{NEXP}$.
Year
DOI
Venue
2018
10.4230/LIPIcs.MFCS.2018.58
mathematical foundations of computer science
DocType
Volume
ISSN
Conference
abs/1805.11139
Proceedings of 43rd International Symposium on Mathematical Foundations of Computer Science (MFCS 2018)
Citations 
PageRank 
References 
0
0.34
0
Authors
5
Name
Order
Citations
PageRank
sevag gharibian1447.72
Miklos Santha272892.42
Jamie Sikora394.29
Aarthi Sundaram443.18
Justin Yirka501.01