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We prove that estimating the ground state energy of a translationally-invariant, nearest-neighbour Hamiltonian on a 1D spin chain is QMAEXP-complete, even for systems of low local dimension (roughly 40). This is an improvement over the best…

Quantum Physics · Physics 2017-11-15 Johannes Bausch , Toby Cubitt , Maris Ozols

In this work, we study a variant of the local Hamiltonian problem where we restrict to Hamiltonians that live on a lattice and are invariant under translations and rotations of the lattice. In the one-dimensional case this problem is known…

Quantum Physics · Physics 2025-09-03 Jon Nelson , Daniel Gottesman

We prove an entanglement area law for a class of 1D quantum systems involving infinite-dimensional local Hilbert spaces. This class of quantum systems include bosonic models such as the Hubbard-Holstein model, and both U(1) and SU(2)…

Quantum Physics · Physics 2022-11-04 Nilin Abrahamsen , Yu Tong , Ning Bao , Yuan Su , Nathan Wiebe

The study of ground state energies of local Hamiltonians has played a fundamental role in quantum complexity theory. In this paper, we take a new direction by introducing the physically motivated notion of "ground state connectivity" of…

Quantum Physics · Physics 2019-01-08 Sevag Gharibian , Jamie Sikora

Recent results on the stability of the spectral gap under general perturbations for frustration-free Hamiltonians, have motivated the following question: Does the entanglement entropy of quantum states that are connected to states…

Quantum Physics · Physics 2012-07-12 Spyridon Michalakis

We prove that the entanglement entropy of the ground state of a locally gapped frustration-free 2D lattice spin system satisfies an area law with respect to a vertical bipartition of the lattice into left and right regions. We first…

Quantum Physics · Physics 2023-02-21 Anurag Anshu , Itai Arad , David Gosset

Computing ground states of local Hamiltonians is a fundamental problem in condensed matter physics. We give the first randomized polynomial-time algorithm for finding ground states of gapped one-dimensional Hamiltonians: it outputs an…

Quantum Physics · Physics 2013-07-22 Zeph Landau , Umesh Vazirani , Thomas Vidick

The area law for entanglement entropy fundamentally reflects the complexity of quantum many-body systems, demonstrating ground states of local Hamiltonians to be represented with low computational complexity. While this principle is…

Quantum Physics · Physics 2025-02-21 Donghoon Kim , Tomotaka Kuwahara

Understanding the entanglement structure of local Hamiltonian ground spaces is a physically motivated problem, with applications ranging from tensor network design to quantum error-correcting codes. To this end, we study the complexity of…

Quantum Physics · Physics 2026-05-29 Sevag Gharibian , Jonas Kamminga

Recently it was shown that the so-called guided local Hamiltonian problem -- estimating the smallest eigenvalue of a $k$-local Hamiltonian when provided with a description of a quantum state ('guiding state') that is guaranteed to have…

Quantum Physics · Physics 2024-02-08 Chris Cade , Marten Folkertsma , Jordi Weggemans

A family of quantum Hamiltonians is said to be universal if any other finite-dimensional Hamiltonian can be approximately encoded within the low-energy space of a Hamiltonian from that family. If the encoding is efficient, universal…

Quantum Physics · Physics 2018-02-21 Stephen Piddock , Ashley Montanaro

All Hamiltonian complexity results to date have been proven by constructing a local Hamiltonian whose ground state -- or at least some low-energy state -- is a "computational history state", encoding a quantum computation as a superposition…

Quantum Physics · Physics 2018-10-16 Carlos E. González-Guillén , Toby S. Cubitt

In this note we present two natural restrictions of the local Hamiltonian problem which are BQP-complete under Karp reduction. Restrictions complete for QCMA, QMA_1, and MA were demonstrated previously.

Quantum Physics · Physics 2007-12-28 Peter C. Richter

We show that ground states of unfrustrated quantum spin-1/2 systems on general lattices satisfy an entanglement area law, provided that the Hamiltonian can be decomposed into nearest-neighbor interaction terms which have entangled excited…

Quantum Physics · Physics 2015-05-20 Niel de Beaudrap , Tobias J. Osborne , Jens Eisert

A central result in the study of Quantum Hamiltonian Complexity is that the k-Local hamiltonian problem is QMA-complete. In that problem, we must decide if the lowest eigenvalue of a Hamiltonian is bounded below some value, or above…

Quantum Physics · Physics 2017-09-20 Naïri Usher , Matty J. Hoban , Dan E. Browne

Entanglement entropy obeys area law scaling for typical physical quantum systems. This may naively be argued to follow from locality of interactions. We show that this is not the case by constructing an explicit simple spin chain…

Quantum Physics · Physics 2015-05-18 G. Vitagliano , A. Riera , J. I. Latorre

In this paper, we consider spin systems in three spatial dimensions, and prove that the local Hamiltonian problem for 3D lattices with face-centered cubic unit cells, 4-local translationally-invariant interactions between spin-3/2 particles…

Quantum Physics · Physics 2017-11-27 Johannes Bausch , Stephen Piddock

We prove that generic quantum local Hamiltonians are gapless. In fact, we prove that there is a continuous density of states above the ground state. The Hamiltonian can be on a lattice in any spatial dimension or on a graph with a bounded…

Quantum Physics · Physics 2017-12-06 Ramis Movassagh

The presence of symmetries, be they discrete or continuous, in a physical system typically leads to a reduction in the problem to be solved. Here we report that neither translational invariance nor rotational invariance reduce the…

Quantum Physics · Physics 2008-07-24 Alastair Kay

We introduce a family of Hamiltonian systems for measurement-based quantum computation with continuous variables. The Hamiltonians (i) are quadratic, and therefore two body, (ii) are of short range, (iii) are frustration-free, and (iv)…

Quantum Physics · Physics 2011-03-01 Leandro Aolita , Augusto J. Roncaglia , Alessandro Ferraro , Antonio Acín