top of page
Search

Quantum Hardware vs Simulator

  • Nov 11, 2025
  • 2 min read

 

Hidden Quantum Hardware Realities:

  • Calibration windows: recalibration is done daily - your circuit behaves differently Tuesday vs Wednesday

  • Qubit retirement: Sometimes qubits go "bad" and get disabled

  • Temperature sensitivity: Cosmic rays can flip qubits 

  • Cross-talk patterns: Specific qubit pairs have worse errors

  • Time-of-day effects: Queue congestion, shared dilution refrigerator cooling


Cases where Simulator ≠ Hardware:

  1. Crosstalk: Simulators often model qubits independently, hardware has interference

  2. Pulse-level effects: Gate timing overlaps, frequency collisions

  3. Measurement-induced errors: Real measurements can disturb neighboring qubits

  4. Leakage: Qubits can leak to non-computational states (|2⟩, |3⟩) - simulators usually ignore

  5. Contextual errors: Error rate depends on previous operations, not just current gate

  6. 1/f noise: Low-frequency noise has temporal correlations simulators miss


Example: Same circuit, simulator predicts 85% success, hardware gives 62% success. 


Which Simulator to use? Simulator Selection Decision Tree


→ Learning quantum computing?

  → Use: Qiskit Aer statevector (simple, visual)


→ Developing algorithm (< 25 qubits)?

  → Use: Statevector simulator (exact results)


→ Testing on large circuits (> 30 qubits)?

  → Is circuit highly entangled?

     YES → Use: Tensor network MPS

     NO → Use: Clifford simulator if possible


→ Preparing for hardware run?

  → Use: Noisy simulator matching target hardware

  → Run both with/without noise to estimate error impact


→ Testing error mitigation?

  → Use: Density matrix simulator with custom noise model


→ Need speed over accuracy?

  → Use: GPU-accelerated simulator


→ Research / comparing backends?

  → Use: Multiple simulators + real hardware for ground truth


References and further reading:


Comments

Rated 0 out of 5 stars.
No ratings yet
Add a rating
bottom of page