A full dichotomy for Holantc, inspired by quantum computation

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Colleges, School and Institutes


Holant problems are a family of counting problems parameterised by sets of algebraic-complex valued constraint functions, and defined on graphs. They arise from the theory of holographic algorithms, which was originally inspired by concepts from quantum computation.

Here, we employ quantum information theory to explain existing results about holant problems in a concise way and to derive two new dichotomies: one for a new family of problems, which we call Holant+, and, building on this, a full dichotomy for Holantc. These two families of holant problems assume the availability of certain unary constraint functions – the two pinning functions in the case of Holantc, and four functions in the case of Holant+ – and allow arbitrary sets of algebraic-complex valued constraint functions otherwise. The dichotomy for Holant+ also applies when inputs are restricted to instances defined on planar graphs. In proving these complexity classifications, we derive an original result about entangled quantum states.

Bibliographic note

Not yet published as of 13/10/2021.


Original languageEnglish
JournalSIAM Journal on Computing
Publication statusAccepted/In press - 9 Aug 2021