<p>The quantum approximate optimization algorithm (QAOA) is a promising algorithm for solving combinatorial optimization problems (COPs), with performance governed by variational parameters <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41534_2025_1082_Article_IEq1.gif" Format="GIF" Height="23" Rendition="HTML" Resolution="72" Type="Linedraw" Width="76" /> </InlineMediaObject> <EquationSource Format="TEX">\({\{{\gamma }_{i},{\beta }_{i}\}}_{i = 0}^{p-1}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mrow> <mrow> <mo>{</mo> <mrow> <msub> <mrow> <mi>γ</mi> </mrow> <mrow> <mi>i</mi> </mrow> </msub> <mo>,</mo> <msub> <mrow> <mi>β</mi> </mrow> <mrow> <mi>i</mi> </mrow> </msub> </mrow> <mo>}</mo> </mrow> </mrow> <mrow> <mi>i</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>p</mi> <mo>−</mo> <mn>1</mn> </mrow> </msubsup> </math></EquationSource> </InlineEquation>. While most prior work has focused on classically optimizing these parameters, we demonstrate that fixed linear ramp schedules, linear ramp QAOA (LR-QAOA), can efficiently approximate optimal solutions across diverse COPs. Simulations with up to <i>N</i><sub><i>q</i></sub> = 42 qubits and <i>p</i> = 400 layers suggest that the success probability scales as <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41534_2025_1082_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="139" /> </InlineMediaObject> <EquationSource Format="TEX">\(P({x}^{* })\approx {2}^{-\eta (p){N}_{q}+C}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>P</mi> <mrow> <mo>(</mo> <mrow> <msup> <mrow> <mi>x</mi> </mrow> <mrow> <mo>*</mo> </mrow> </msup> </mrow> <mo>)</mo> </mrow> <mo>≈</mo> <msup> <mrow> <mn>2</mn> </mrow> <mrow> <mo>−</mo> <mi>η</mi> <mrow> <mo>(</mo> <mrow> <mi>p</mi> </mrow> <mo>)</mo> </mrow> <msub> <mrow> <mi>N</mi> </mrow> <mrow> <mi>q</mi> </mrow> </msub> <mo>+</mo> <mi>C</mi> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation>, where <i>η</i>(<i>p</i>) decreases with increasing <i>p</i>. For example, in Weighted Maxcut instances, <i>η</i>(10) = 0.22 improves to <i>η</i>(100) = 0.05. Comparisons with classical algorithms, including simulated annealing, Tabu Search, and branch-and-bound, show a scaling advantage for LR-QAOA. We show results of LR-QAOA on multiple QPUs (IonQ, Quantinuum, IBM) with up to <i>N</i><sub><i>q</i></sub> = 109 qubits, <i>p</i> = 100, and circuits requiring 21,200 CNOT gates. Finally, we present a noise model based on two-qubit gate counts that accurately reproduces the experimental behavior of LR-QAOA.</p>

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Toward a linear-ramp QAOA protocol: evidence of a scaling advantage in solving some combinatorial optimization problems

  • J. A. Montañez-Barrera,
  • Kristel Michielsen

摘要

The quantum approximate optimization algorithm (QAOA) is a promising algorithm for solving combinatorial optimization problems (COPs), with performance governed by variational parameters \({\{{\gamma }_{i},{\beta }_{i}\}}_{i = 0}^{p-1}\) { γ i , β i } i = 0 p 1 . While most prior work has focused on classically optimizing these parameters, we demonstrate that fixed linear ramp schedules, linear ramp QAOA (LR-QAOA), can efficiently approximate optimal solutions across diverse COPs. Simulations with up to Nq = 42 qubits and p = 400 layers suggest that the success probability scales as \(P({x}^{* })\approx {2}^{-\eta (p){N}_{q}+C}\) P ( x * ) 2 η ( p ) N q + C , where η(p) decreases with increasing p. For example, in Weighted Maxcut instances, η(10) = 0.22 improves to η(100) = 0.05. Comparisons with classical algorithms, including simulated annealing, Tabu Search, and branch-and-bound, show a scaling advantage for LR-QAOA. We show results of LR-QAOA on multiple QPUs (IonQ, Quantinuum, IBM) with up to Nq = 109 qubits, p = 100, and circuits requiring 21,200 CNOT gates. Finally, we present a noise model based on two-qubit gate counts that accurately reproduces the experimental behavior of LR-QAOA.