Quantar Lab
(Quantum algorithms and technologies for advanced research)
Home Resources Quantum algorithms & compilation
Last updated: 2026 Jan

Quantum Algorithms & Compilation

Efficient, device-aware methods for near-term quantum optimization and simulation — from algorithm ideas to hardware-executable circuits.

quantum compilation QAOA VQE FALQON gradients benchmarks

What we mean by “practical” quantum algorithms

Near-term quantum devices have limited qubit counts and are affected by noise. For that reason, our goal is not only to propose algorithms, but also to make them implementable and measurable under realistic constraints: gate sets, connectivity, depth budgets, and measurement cost.

Key idea: “Algorithm” and “compiler” must be designed together. A good theoretical circuit is not enough if it becomes too deep after routing or too expensive to measure.
Algorithm → circuit → compiled circuit → execution/feedback loop
Workflow: algorithm design → circuit representation → device-aware compilation → execution and feedback.

Compilation & circuit synthesis

Quantum compilation translates an abstract circuit into a form that can actually run on a specific device. This includes gate decomposition, qubit routing under limited connectivity, and circuit simplification.

Device-aware routing

Map logical qubits onto physical qubits, insert SWAPs efficiently, and keep two-qubit gates minimal.

Depth & error budgeting

Reduce depth and entangling gates, because they dominate error on many platforms.

Unitary / gate synthesis

For targets like Toffoli or multi-qubit primitives, we study synthesis strategies that minimize resources while keeping gradients reliable for optimization-based compilation.

QAOA for combinatorial optimization

QAOA (Quantum Approximate Optimization Algorithm) is a leading approach for near-term optimization. We study how to make QAOA work reliably in practice: choosing cost/mixer design, improving trainability, and understanding performance under finite depth and noise.

Problem-aware design

Encode structure (constraints, symmetry, hardware limits) into mixers and cost Hamiltonians.

Trainability

Diagnose optimization difficulty (cost function landscape), use schedules/initializations that converge faster.

VQE & ground-state preparation

VQE (Variational Quantum Eigensolver) targets ground states of Hamiltonians important in simulation and chemistry. Our focus is on ansatz design, gradient stability, and measurement efficiency — so that performance is reproducible.

What we optimize

  • Ansatz expressibility vs depth (avoid over-parameterized circuits that become noisy)
  • Gradient reliability (cross-check PSR/estimators when needed)
  • Measurement cost (grouping, shot allocation, and variance control)

FALQON & feedback-based control

FALQON is a feedback-based quantum algorithm where parameter updates are guided by measurable quantities, reducing reliance on heavy classical outer-loop training. We explore how feedback can improve robustness, and how to hybridize feedback with adaptive schedules.

Why feedback matters: it can provide a more “physics-guided” update rule, which may help in settings where naive variational training becomes unstable or slow.

How we evaluate performance

We emphasize metrics that matter on real devices, not only ideal simulations.

Resource metrics

Depth, two-qubit gate count, routing overhead, and measurement cost.

Robustness metrics

Sensitivity to noise, calibration errors, and reproducibility across runs.

Where it can be used

Our algorithm + compilation pipelines support research and prototyping across multiple directions: optimization, simulation, and hardware benchmarking.

FAQ

Do you focus more on theory or implementation?

Both. We start from clear algorithmic goals, then design compilation and evaluation so the ideas can be tested on realistic devices and simulator baselines.

What problems are a good fit for QAOA / VQE?

QAOA is often used for combinatorial objectives (graph and constraint-based problems). VQE targets Hamiltonian ground states and simulation tasks. In practice, problem structure and measurement cost strongly influence feasibility.

Can I join as a student or visiting researcher?

Yes. If you have interest in quantum software, optimization, or experimental constraints, we welcome collaborations.

Selected reading

If you want, we can list your lab’s key papers here (with DOI/arXiv) in a clean bullet format. For now, these are placeholders.

  • Algorithm–compiler co-design for near-term devices (placeholder)
  • Verified gradient methods for circuit synthesis (placeholder)
  • Feedback-based quantum control and FALQON-style updates (placeholder)