Paper-69: Merlin Implementation of ObliQ - Photonic QUBO solver

[ranjanaditya9061]

Implements the ObliQ and CVaR-VQE algorithm using MerLin 0.4. Utilizes both gradient-based and gradient-free optimization routines with support for hardware evaluation.

Compares against baselines such as QAOA and Annealing using beta values and Q-score (https://ieeexplore.ieee.org/document/9860191). Benchmarks over 100 max-clique problems varying from size 2 to 10. Also includes a direct caller that works on user-defined graph input and optimizes using ObliQ.

[CassNot]

Thank you for this work ! This is the first of its kind in this repo ! I trust you for the implementation because you are the main author of the work in the first place :) I left some comments below and here are general comments:

Major issues:

• no implementation.py main entry point so running python implementation.py --paper ObliQ_photonic_QUBO will fail
• caution with the general layout expected for this folder

Minor issues:

• the ruff version of this repo was changed to use always the latest ones and not 0.4 only (we are 0.16 now) so the ruff fails on this repo now
• you also need to add one line in the table of the main README to describe your work and findings

[CassNot]

This file should go in utils/ or lib/ I believe. The only python file in the root folder is the implementation.py (which does not exist here and this breaks the semantic of the repo)

[ranjanaditya9061]

I moved benchmark to lib/ folder. Do I need another implementation.py in the root folder? Isn't implementation.py being called at the reproduced_papers/ level.

[CassNot]

My mistake, it is not needed

[Copilot]

Pull request overview

Adds a new paper reproduction under papers/ObliQ_photonic_QUBO/ implementing the ObliQ photonic QUBO solver (MerLin/Perceval/torch) plus a Q-score benchmarking harness and baseline solvers (photonic CVaR-VQE, Qiskit QAOA, and D-Wave Ocean solvers). The folder includes runnable CLI tooling, plotting, pinned sweep configs/results, and a comprehensive unit test suite focused on reproducibility and scoring correctness.

Changes:

• Implement photonic solvers (ObliQ static/VQC/hybrid + CVaR-VQE) and baseline solvers (QAOA, SA/Tabu/QPU/hybrid) behind a common solver-dispatch API.
• Add a config-hashed benchmarking harness (benchmark.py) and plotting tooling (plotter.py) aligned to Q-score beta/Q-score computation, plus seeded instance generation.
• Add extensive tests that pin encoding/decoding, config hashing stability, reproducibility, CLI override behavior, and instance regeneration.

Reviewed changes

Copilot reviewed 61 out of 67 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
papers/ObliQ_photonic_QUBO/utils/readout.py	Shared readout utilities: Fock outcome → bitstring mapping and lazy energy table.
papers/ObliQ_photonic_QUBO/utils/qubo.py	QUBO conversions, problem dispatch, beta computation, normalization, and brute-force helper.
papers/ObliQ_photonic_QUBO/utils/max_cut.py	Max-Cut QUBO formulation, exact solve, and beta normalization.
papers/ObliQ_photonic_QUBO/utils/max_clique.py	Max-Clique QUBO formulation, naive baseline, exact solve, and beta normalization.
papers/ObliQ_photonic_QUBO/utils/graphs.py	Seed-replayable Erdos–Renyi instance generator with retry-on-edgeless behavior.
papers/ObliQ_photonic_QUBO/tests/test_solvers.py	End-to-end solver dispatch, scoring, and reproducibility tests for local solvers.
papers/ObliQ_photonic_QUBO/tests/test_seeding.py	Seed derivation and cross-process stability tests.
papers/ObliQ_photonic_QUBO/tests/test_qubo.py	QUBO matrix/dict correctness tests and small-instance optimality checks.
papers/ObliQ_photonic_QUBO/tests/test_graphs.py	Graph sampling determinism and retry behavior tests.
papers/ObliQ_photonic_QUBO/tests/test_encoding.py	ObliQ augmentation/encoding/decoding and readout behavior-lock tests.
papers/ObliQ_photonic_QUBO/tests/test_config.py	Config hashing, canonicalization, and shipped-config coverage tests.
papers/ObliQ_photonic_QUBO/tests/test_cli.py	CLI-schema-driven parsing and override semantics tests.
papers/ObliQ_photonic_QUBO/tests/conftest.py	Test sys.path setup and common fixtures.
papers/ObliQ_photonic_QUBO/results/d7656dd61c88/config.json	Stored config snapshot for a QAOA max-clique sweep hash.
papers/ObliQ_photonic_QUBO/results/a29bcaa44236/config.json	Stored config snapshot for a tabu max-clique sweep hash.
papers/ObliQ_photonic_QUBO/results/973001a93134/config.json	Stored config snapshot for an ObliQ static max-clique sweep hash.
papers/ObliQ_photonic_QUBO/results/80fbf13e256a/config.json	Stored config snapshot for a photonic CVaR-VQE max-clique sweep hash.
papers/ObliQ_photonic_QUBO/results/6df457c14c8f/config.json	Stored config snapshot for SA max-clique sweep hash.
papers/ObliQ_photonic_QUBO/results/2f9a63e4529a/config.json	Stored config snapshot for ObliQ hybrid max-clique sweep hash.
papers/ObliQ_photonic_QUBO/results/2cdd563cfee8/config.json	Stored config snapshot for ObliQ VQC max-clique sweep hash.
papers/ObliQ_photonic_QUBO/requirements.txt	Paper-local dependency set spanning MerLin/perceval/torch, Qiskit, and D-Wave Ocean.
papers/ObliQ_photonic_QUBO/README.md	Full paper README: method summary, run instructions, config schema, results, and reproducibility notes.
papers/ObliQ_photonic_QUBO/pytest.ini	Paper-local pytest configuration.
papers/ObliQ_photonic_QUBO/plotter.py	Plotting tool for beta/time curves with exact/asymptotic beta modes and Q-score computation.
papers/ObliQ_photonic_QUBO/models/solver.py	Central solver dispatch with capability sets and seeding behavior.
papers/ObliQ_photonic_QUBO/models/qaoa.py	Qiskit-based QAOA baseline with reproducible local sampling and optional hardware backends.
papers/ObliQ_photonic_QUBO/models/obliq.py	ObliQ solver implementation: augmentation, encoding, decoding, and training (Adam/SGD/COBYLA).
papers/ObliQ_photonic_QUBO/models/dwave.py	D-Wave Ocean and Leap solvers: SA/Tabu/QPU/hybrid with timeout/seeding handling.
papers/ObliQ_photonic_QUBO/models/cvar_vqe.py	Photonic CVaR-VQE baseline using MerLin with autograd and COBYLA training options.
papers/ObliQ_photonic_QUBO/models/circuits.py	MerLin/Perceval circuit construction, coefficient management, and local/remote execution.
papers/ObliQ_photonic_QUBO/models/backend.py	Quandela token resolution helper.
papers/ObliQ_photonic_QUBO/LICENSE	Apache 2.0 license file for this paper folder.
papers/ObliQ_photonic_QUBO/lib/timeout.py	Out-of-process timeout enforcement utility.
papers/ObliQ_photonic_QUBO/lib/seeding.py	Deterministic seed derivation and global RNG seeding helper.
papers/ObliQ_photonic_QUBO/lib/config.py	Config loading, CLI overrides, canonicalization, and content hashing for results addressing.
papers/ObliQ_photonic_QUBO/configs/*.json	Sweep/run configuration set covering solver/problem combinations and comparable hyperparameters.
papers/ObliQ_photonic_QUBO/cli.json	CLI schema used to generate the benchmark subcommands and overrides.
papers/ObliQ_photonic_QUBO/benchmark.py	Benchmark runner for single instances and sweeps with config-hashed outputs.
papers/ObliQ_photonic_QUBO/.gitignore	Paper-local ignore rules (incl. token file).

Suppressed comments (1)

papers/ObliQ_photonic_QUBO/models/solver.py:132

• run_obliq_solver is called with backend=backend while solver_options are expanded as **options. If a user supplies backend inside solver_options (the README lists it as an accepted ObliQ option), this will raise TypeError: got multiple values for keyword argument 'backend'. Prefer merging backend into options with setdefault and passing backend only once.

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[CassNot]

Just a fix on the tests and it should be good !