English

Conjecture C Still Stands

Quantum Physics 2022-09-07 v1 Computational Complexity

Abstract

More than ten years ago the author described a parameter K(ρ)K(\rho ) for the complexity of nn-qubit quantum state ρ\rho and raised the conjecture (referred to as "Conjecture C") that when this parameter is superpolynomial in nn, the state ρ\rho is not experimentally feasible (and will not be experimentally achieved without quantum fault-tolerance). Shortly afterward [6] (arXiv:1204.3404), Steve Flammia and Aram Harrow claimed that the simple easy-to-construct WW states are counterexamples to "Conjecture C." We point out that Flammia and Harrow's argument regarding WW-states is incomplete. Moreover, the emergent picture from experimental progress of the past decade on noisy intermediate scale quantum (NISQ) computers suggests that WW-states, as simple as they appear, cannot be achieved experimentally by NISQ computers, and can not be constructed without quantum fault-tolerance.

Keywords

Cite

@article{arxiv.2209.01648,
  title  = {Conjecture C Still Stands},
  author = {Gil Kalai},
  journal= {arXiv preprint arXiv:2209.01648},
  year   = {2022}
}

Comments

12 pages, one figure

R2 v1 2026-06-28T00:42:10.622Z