Cited by 118Quantum Computing Algorithms and ArchitectureCold Atom Physics and Bose-Einstein CondensatesQuantum many-body systems

Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions

Open access
Casanova, J., Mezzacapo, A., Lamata, L., Solano, E.·2012·Physical Review Letters

Abstract

We propose a method of simulating efficiently many-body interacting fermion lattice models in trapped ions, including highly nonlinear interactions in arbitrary spatial dimensions and for arbitrarily distant couplings. We map products of fermionic operators onto nonlocal spin operators and decompose the resulting dynamics in efficient steps with Trotter methods, yielding an overall protocol that employs only polynomial resources. The proposed scheme can be relevant in a variety of fields such as condensed-matter or high-energy physics, where quantum simulations may solve problems intractable for classical computers.

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Written from the paper’s full text.

TL;DR

The paper proposes a trapped-ion protocol for quantum simulating many-body interacting fermion lattice models by mapping fermionic operators to nonlocal spin operators via Jordan-Wigner, decomposing the evolution with Trotter methods, and implementing the resulting nonlocal terms with Mølmer-Sørensen gates. It argues the protocol uses polynomial resources and can handle long-range, highly nonlinear interactions in arbitrary dimensions, with numerical Fermi-Hubbard simulations showing convergence of the Trotter approximation.

Key findings

  • The protocol simulates general fermionic lattice Hamiltonians with arbitrary spatial dimension and arbitrarily distant couplings, avoiding auxiliary virtual Majorana fermions and the usual restriction to few neighbors.
  • For a Fermi-Hubbard example with three lattice sites and six modes (two spins per site), the number of Hamiltonian terms scales as \(5N/2 - 4\), giving 11 terms for \(N=6\); the total number of gates per Trotter step is 33, on average 3 gates per Hamiltonian term.
  • Trotter fidelity approaches 1 with increasing Trotter steps \(n_T\); for \(n_T=10\), fidelity is 0.99 in one parameter case and 0.97 in another. Supplementary fits show the error scales as \(1 - C/n_T^2\).
  • The authors state that for more than \(\sim 30\) particles, foreseeable in the near future, one could simulate fermionic systems intractable for classical computers.

Methods

  • Theoretical proposal in three steps: Jordan-Wigner mapping of \(N\) fermionic modes to \(N\) nonlocal spin operators; Trotter decomposition of the total evolution into exponentials of each nonlocal spin term; implementation of each exponential on \(N\) two-level trapped ions using Mølmer-Sørensen gates, local gates, and local rotations.
  • Numerical validation compares exact diagonalization with Trotter-evolved dynamics for the Fermi-Hubbard Hamiltonian on three lattice sites with six modes, simulated by six two-level trapped ions, using initial state \(b^\dagger_{1\uparrow} b^\dagger_{1\downarrow}|0\rangle\).
  • Supplementary analysis argues the number of elementary gates scales polynomially in the Trotter error \(\epsilon\), total evolution time \(t\), and number of fermionic modes \(N\), for bounded Hamiltonians.

Limitations

  • The paper does not include a dedicated limitations section; stated caveats include that the Trotter expansion is approximate and its error decreases with more Trotter steps, and that the error analysis focuses on time-independent Hamiltonians.
  • The numerical demonstration is limited to a small Fermi-Hubbard system of three lattice sites and six modes; no experimental implementation is reported.
  • The text notes that current technology has realized more than 100 gates in a single experiment and that without error correction one would expect more than a thousand gates in the near future, indicating gate counts and scalability depend on future experimental capabilities.

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Integrity signals

Registry

Crossref · 10.1103/physrevlett.108.190502

Cites

42 of 42 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 41 cited sources checked · 0 supported · 0 flagged

  • Findingown data
    § FINAL REMARKS · p. 6

    The error of the Trotter expansion goes to zero polynomially in n_T.

    “Thus, the error goes to zero polynomially in n T , as expected.”
    Quote in the paperNot a substantial claim
  • Findingnone given
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 3

    The number of terms to be implemented scales linearly with the number of modes, 5N/2 - 4.

    “Notice that the number of terms to be implemented scales linearly with the number of modes, 5 N/ 2 -4 (11 in this case, for N = 6).”
    Quote in the paperSubstantial claim
  • Interpretationcitation
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 1

    The method includes calculation of time evolutions and ground state computations, e.g., through adiabatic protocols.

    “This includes the calculation of time evolutions and ground state computations, e.g. through adiabatic protocols [34].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [34] source

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  • Interpretationcitation
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 2

    Each exponential can be implemented, for arbitrary k and up to local rotations, with a Mølmer-Sørensen gate upon k ions, one local gate upon one of the ions, and the inverse Mølmer-Sørensen gate.

    “Each of these exponentials can be implemented, for arbitrary k and up to local rotations, with a Mølmer-Sørensen gate upon k ions, one local gate upon one of the ions, and the inverse Mølmer-Sørensen gate [31].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [31] source

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  • Interpretationreasoning
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 3

    The method can simulate Fröhlich Hamiltonians to recover polaron physics.

    “We can simulate this kind of Hamiltonians in order to recover the polaron physics, a critical open issue for the deep understanding of correlated electrons in solids [38].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [38]

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  • May combine two claims. 11
  • Classified as probably not a substantial claim. 3
  • May combine two claims.

    Findingreasoning
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 3

    The number of gates in each term of the Hamiltonian is, in the worst case, linear in the number of modes, and in many cases just constant.

    “At the same time, the nonlocal gates upon several ions are efficiently implementable with few lasers, such that the number of gates in each term of the Hamiltonian is, in the worst case, linear in the number of modes, and in many cases just constant.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingcitation
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 3

    The number of gates for the highly nonlocal coupling b†_1 b_10 + b†_10 b_1 can be as small as 10 per Trotter step with the proposed method, whereas in the general case it would require about 10^6 elementary gates.

    “In the general case, it would require a number of elementary gates of 2 20 ≃ 10 6 [2]. With our method, the number of gates can be as small as 10 per Trotter step, consisting of Mølmer-Sørensen gates (dark blue and green), local exp( iφ ′ σ y 2 ) gates (red), exp[ ± i ( π/ 4) ∑ i σ y i ] (yellow) and exp[ ± i ( π/ 4) ∑ i σ x i ] (cyan) gates (see Fig. 1b) [35].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [2] M. M¨ uller, K. Hammerer, Y. L. Zhou, C. F. Roos, and P. Zoller, New J. Phys. 13 , 085007 (2011). source

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    • cites [35] source

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  • May combine two claims.

    Findingown data
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 3

    The fidelity of the Trotter expansion goes to 1 with the number of Trotter steps n_T, and for n_T=10 it is 0.99 (b) or 0.97 (d).

    “Notice that the fidelity of the Trotter expansion goes to 1 with the number of Trotter steps n T , and for n T = 10 it is 0.99 (b) or 0.97 (d).”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingreasoning
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 3

    In the particular example of three lattice sites with six modes, the total number of gates per Trotter step is 33, i.e., on average 3 gates per Hamiltonian term.

    “In this particular example the total number of gates per Trotter step is of 33, i.e., on average 3 gates per Hamiltonian term, which is very efficient.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationnone given
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 2

    The method is general and extends the hopping terms to arbitrarily distant pairs of electrons.

    “Notice that our method is general and extends the hopping terms to arbitrarily distant pairs of electrons.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationreasoning
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 1

    The method can simulate highly nonlinear and long-range interactions in arbitrary spatial dimensions, applying the Jordan-Wigner transformation without the usual restriction of a reduced number of neighbors, and without the need of auxiliary virtual Majorana fermions.

    “Our method can simulate highly nonlinear and long-range interactions in arbitrary spatial dimensions, applying the Jordan-Wigner transformation without the usual restriction of a reduced number of neighbors, and without the need of auxiliary virtual Majorana fermions [33].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [33] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 3

    The mapped spin Hamiltonians are highly nonlocal but their evolution is efficiently realizable.

    “Thus, the mapped spin Hamiltonians are highly nonlocal but their evolution is efficiently realizable.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationreasoning
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 1

    The resulting dynamics are decomposed in efficient steps with Trotter methods, yielding an overall protocol that employs only polynomial resources.

    “We map products of fermionic operators onto nonlocal spin operators and decompose the resulting dynamics in efficient steps with Trotter methods, yielding an overall protocol that employs only polynomial resources.”
    • Also stated in: § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 1 · plain
      “These three steps yield an efficient protocol that employs only polynomial resources.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [2] M. M¨ uller, K. Hammerer, Y. L. Zhou, C. F. Roos, and P. Zoller, New J. Phys. 13 , 085007 (2011). source

      Not checked in the free run.

    • cites [29] source

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    • cites [30] source

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  • May combine two claims.

    Interpretationreasoning
    § ANALYSIS OF THE TROTTER ERROR · p. 6

    The total norm of H is bounded by ||H|| ≤ sum ||H_j|| = sum h_j ≤ m h_max_j, and thus ||H|| is polynomial in m and in N.

    “iii) the total norm of H is bounded by || H || ≤ ∑ m j =1 || H j || = ∑ m j =1 h j ≤ mh max j , where h max j is the maximum among all h ′ j s . Thus, || H || is polynomial in m , and in consecuence, also in N .”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationreasoning
    § ANALYSIS OF THE TROTTER ERROR · p. 6

    The scaling of the number of elementary gates needed in the expansion is polynomial (a power law) in ε, t, and N, such that the method for implementing arbitrary fermionic Hamiltonians that occur in nature is efficient.

    “Accordingly, we have shown that the scaling of the number of elementary gates needed in our expansion, is polynomial (more specifically, a power law) in ϵ , t , and N , such that our method for implementing arbitrary fermionic Hamiltonians that occur in nature is efficient.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 2

    The Fermi-Hubbard Hamiltonian takes into account a range of effects in condensed-matter physics, as the Mott transition, and is also believed to be relevant in high-Tc superconductivity.

    “The Fermi-Hubbard Hamiltonian [25] takes into account a range of effects in condensed-matter physics, as the Mott transition, and is also believed to be relevant in highT c superconductivity.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 2

    The Kondo Hamiltonian provides a variety of interesting features in different systems, as the minimum in the resistivity at low temperatures.

    “The long debated Kondo Hamiltonian provides a variety of interesting features in different systems, as the minimum in the resistivity at low temperatures [36].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [36]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Quantum Simulation of Interacting Fermion Lattice Models in Trapped Ions · p. 2

    The Fröhlich Hamiltonian models the interaction of electrons with phonons.

    “The Fr¨ ohlich Hamiltonian [26] models the interaction of electrons with phonons,”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [26] source

      Not checked in the free run.

13 of 13

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Second quantized fermionic Hamiltonians are efficiently simulatable in trapped ions.

    “This kind of second quantized fermionic Hamiltonians are efficiently simulatable in trapped ions23.”
  • The phonon degrees of freedom in trapped-ion systems provide a natural platform for addressing spin-boson or fermion-boson-type problems through quantum simulation.

    “The phonon degrees of freedom in trapped-ion systems provide a natural platform for addressing spin-boson or fermion-boson-type problems through quantum simulation233637383940.”

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Expansion of the nonlinear Hamiltonian omits an identity term

    Minor

    Expanding the stated product produces an additional g Ij ⊗ Ij+1 / 4 term. The subsequent expression calls itself equal to the product but omits that term, which changes the Hamiltonian by a constant.

  • Figure 2 panel for the second fidelity is mislabeled

    Minor

    The prose says panels (b) and (c) show fidelity, while the Figure 2 caption assigns the second fidelity to panel (d) and says panel (c) shows excitation numbers.

2 of 2

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Authors
Casanova, J., Mezzacapo, A., Lamata, L., & Solano, E.
Affiliations
  • University of the Basque Country (ES)
  • Ikerbasque (ES)
Venue
Physical Review Letters
Published
2012-05-10
Volume
108
Issue
19
Pages
190502-190502
ISSN
  • 0031-9007 (ISSN-L)
  • 1079-7114
OpenAlex
W2088422359
Cited by
118
References
42
Citations by year
2026: 1 · 2025: 2 · 2024: 7 · 2023: 2 · 2022: 11 · 2021: 6 · 2020: 6 · 2019: 8 · 2018: 14 · 2017: 8 · 2016: 5 · 2015: 16 · 2014: 19 · 2013: 7 · 2012: 6
FWCI
15.11
Type
journal article
Language
en
Open access
Locations
  • Physical Review Letters (publishedVersion)
  • PubMed (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Computing Algorithms and Architecture
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Cold Atom Physics and Bose-Einstein Condensates
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum many-body systems
Keywords
quantum simulation, trapped ions, Trotter decomposition, long-range coupling, quantum many-body systems

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