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Quantum

The NISQ Trap: Eight Years of Demonstrations the Hardware Was Built to Lose

Amit Hagar

Featured July 24, 2026

Original Paper

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Simply

Quantum computers built recently often get stuck in a "NISQ trap": they can only run simple problems that regular computers can also solve easily, meaning they haven't shown a real quantum advantage yet.

In depth
The paper argues that nearly all NISQ-era quantum advantage demonstrations have been classically reproduced or shown to rely on classically tractable structures. This occurs because the hardware constraints (noise, shallow depth, strong algebraic structure) force experiments into regions of circuit-space that are inherently classically simulable, creating a "closed loop" where quantum hardware's capabilities align with classical algorithms' efficiency.

Key Takeaways

  • 1
    The NISQ era (2018-2026) has been characterized by a "closed loop" where quantum hardware limitations (noise, shallow circuits, strong algebraic structure) force demonstrations into regions that are classically simulable.
  • 2
    Six theoretical simulability theorems from 2024-2026 formally explain why NISQ demonstrations are classically tractable, identifying features like logarithmic effective depth and algebraic structure as common enablers for both hardware execution and classical compression.
  • 3
    True, unassailable quantum advantage is conjectured to exist outside this closed loop, requiring fault-tolerant quantum computation to overcome noise and access deeper, unstructured circuit regimes.

Conceptual Flow

HIGH LEVEL
1
Methodology: The NISQ Closed Loop

Quantum computers can only run simple problems, and those simple problems are exactly what regular computers can also solve easily.

Quantum Hardware Limits
Forces
Simple Quantum Problems
2
Results: Path to True Quantum Advantage

To beat regular computers, quantum machines need to be much better at fixing their own mistakes, which is called 'fault tolerance'.

Current Noisy Quantum
Needs
Error-Corrected Quantum