An unholy trinity: TFNP, polynomial systems, and the quantum satisfiability problem

TL;DR

This paper introduces new subclasses of TFNP based on algebraic geometry and establishes a connection between quantum complexity and TFNP through the Quantum SAT problem with SDR, revealing novel computational hardness results.

Contribution

It defines two new TFNP subclasses, MHS and SFTA, and proves QSAT with SDR is MHS-complete, linking quantum complexity to algebraic geometric principles.

Findings

QSAT with SDR is MHS-complete

SFTA is contained in a zero-error version of MHS

Classical SAT with SDR is easy, quantum QSAT with SDR is hard

Abstract

The theory of Total Function NP (TFNP) and its subclasses says that, even if one is promised an efficiently verifiable proof exists for a problem, finding this proof can be intractable. Despite the success of the theory at showing intractability of problems such as computing Brouwer fixed points and Nash equilibria, subclasses of TFNP remain arguably few and far between. In this work, we define two new subclasses of TFNP borne of the study of complex polynomial systems: Multi-homogeneous Systems (MHS) and Sparse Fundamental Theorem of Algebra (SFTA). The first of these is based on B\'ezout's theorem from algebraic geometry, marking the first TFNP subclass based on an algebraic geometric principle. At the heart of our study is the computational problem known as Quantum SAT (QSAT) with a System of Distinct Representatives (SDR), first studied by [Laumann, L\"auchli, Moessner, Scardicchio, and Sondhi 2010]. Among other results, we show that QSAT with SDR is MHS-complete, thus giving not only the first link between quantum complexity theory and TFNP, but also the first TFNP problem whose classical variant (SAT with SDR) is easy but whose quantum variant is hard. We also show how to embed the roots of a sparse, high-degree, univariate polynomial into QSAT with SDR, obtaining that SFTA is contained in a zero-error version of MHS. We conjecture this construction also works in the low-error setting, which would imply SFTA is contained in MHS.