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Quantum algorithm for simulating the wave equation

Simulate the wave equation under Dirichlet and Neumann boundary conditions on a quantum computer, using Hamiltonian simulation and quantum linear system algorithms as subroutines.

Attested & literatureUpdated

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  • Record typeLiterature reference
  • Reference implementationmaxwell_equation
  • Reported costImproved scaling in truncation error and improved scaling for the cost of state preparation, relative to general-purpose linear differential-equation algorithms, for the wave-equation algorithm this abstract presents. The abstract states this comparison only in those qualitative terms — no complexity expression, exponent, or constant is given for the wave-equation algorithm or for the general-purpose algorithms it is compared against, and no bound at all is given for the separately mentioned, merely considered use of the same approach for Klein-Gordon or Maxwell's equations.
  • Papers1

A part this method uses, worked through

This page says using Hamiltonian simulation and quantum linear system algorithms as subroutines — here is a concrete, runnable instance of it.

2 Trotter steps of a transverse-field Ising chain

4 qubits starting at |0000⟩, J=1, h=0.5, dt=0.3, 2 first-order Trotter steps.

q0q1q2q3Ising Trotter step(4)Ising Trotter step(4)

Where it ends up

  • 000075%
  • 00016%
  • 10006%
  • 00105%
  • 12 more outcomes8%

The state spreads from |0000⟩ across several nearby basis states. The exact split is a regression value from this file's own simulator, not a claim about a real material.

Open this part in Studio

Simulate the wave equation under Dirichlet and Neumann boundary conditions on a quantum computer, using Hamiltonian simulation and quantum linear system algorithms as subroutines. Costa, Jordan and Ostrander present a quantum algorithm for simulating the wave equation under Dirichlet and Neumann boundary conditions. The algorithm uses Hamiltonian simulation and quantum linear system algorithms as subroutines, and relies on factorizations of discretized Laplacian operators. The authors state that this factorization allows for improved scaling in truncation errors and improved scaling for state preparation, relative to general-purpose linear differential-equation algorithms; the abstract gives this comparison in qualitative terms only, without a complexity expression for either side. The authors also state that they consider using the same Hamiltonian-simulation approach for Klein-Gordon equations and Maxwell's equations — the abstract goes no further than naming this as something considered, with no algorithm described and no result reported for either equation.

References

  • Quantum Algorithm for Simulating the Wave Equation

    Pedro C.S. Costa, Stephen Jordan, Aaron Ostrander · 2017

    Primary source: it presents the wave-equation algorithm built from Hamiltonian simulation and quantum linear system subroutines, states that factoring the discretized Laplacian improves the scaling of truncation error and of state preparation relative to general-purpose linear differential-equation algorithms, and states that Klein-Gordon equations and Maxwell's equations are considered as further uses of the same Hamiltonian-simulation approach. Consult it for the complexity expressions themselves, for the wave-equation algorithm's qubit and gate counts, and for whatever it says about Klein-Gordon and Maxwell's equations beyond the sentence the abstract gives.

Attested & literature
  • Peer-reviewed paper
Method
Curation only. This record documents the algorithm a published reference implementation demonstrates, not the demonstration itself: nothing in Leona runs Qmod. The primary reference's title, authors and submission year were read from its arXiv abs page, and the complexity claim taken from a clause of that paper's abstract (The abstract of arXiv:1711.05394 states no big-O expression, qubit count, or gate count. Its complexity claim is comparative and qualitative: "It relies on factorizations of discretized Laplacian operators to allow for improved scaling in truncation errors and improved scaling for state preparation relative to general purpose linear differential equation algorithms." The abstract also names the subroutines the algorithm is built from — "The algorithm uses Hamiltonian simulation and quantum linear system algorithms as subroutines" — without quoting a cost for either. On the further, separately mentioned use of the same approach, the abstract states only "We also consider using Hamiltonian simulation for Klein-Gordon equations" and, in the same sentence, Maxwell's equations — naming both as something considered, with no algorithm described and no result or bound given for either. The demonstration this record covers states no bound. Those are the only sources read for this field.). No circuit was constructed, simulated or run.
Result
Pass · the record's problem statement and primary reference agree with the sources named above.
Caveat
This is a literature record. No circuit was built, compiled, simulated or run for it, no wave-equation instance was solved, and no timing or resource figure was produced here; the record documents the algorithm the abstract states and does not reproduce or verify any published demonstration of it. The index entry read for this record is at applications/physical_systems/maxwell_equation and gives that directory path and a file list, maxwell_2d_simulation.ipynb, nothing about what the file contains. This record's reference implementation pairs with a paper whose subject, on its own abstract, is the wave equation, not Maxwell's equations: the abstract's only sentence naming Maxwell's equations is that the authors also consider using Hamiltonian simulation for Klein-Gordon equations and Maxwell's equations, with no algorithm described, no complexity stated, and no result reported for either equation. This record accordingly documents the wave-equation algorithm and treats the Maxwell connection as exactly that tentative — a stated intention to consider the approach, not a demonstrated algorithm for Maxwell's equations — and it should not be read as a record of a quantum algorithm for Maxwell's equations. The improved-scaling claim that is stated concretely applies to the wave-equation algorithm only, is qualitative rather than quantified — no exponent, no constant, no explicit dependence on the error tolerance or the discretization is given — and is a comparison against general-purpose linear differential-equation algorithms as a class, which is a comparison against a stated point of reference rather than a proven lower bound on that class. The abstract states no experiment, simulation run, or hardware result for the wave-equation algorithm, so none is carried here, and nothing here supports a claim about state preparation cost, readout, or hardware feasibility beyond the qualitative improved scaling for state preparation the abstract itself gives.
Quantum Algorithm for Simulating the Wave Equation ↗
Kind
curated reference
Reviewed by
Leona Quantum curation pass
License
Citation metadata only; source publication terms apply
wave equationhamiltonian simulationlinear systemsboundary conditionslaplacian discretization

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