Experimental implementation of Hardy-like quantum pigeonhole paradoxes

TL;DR

This paper introduces Hardy-like quantum pigeonhole paradoxes for multi-particle states, demonstrating stronger quantum nonlocality and potential applications in secure communication and randomness generation through experimental verification.

Contribution

It develops a general framework linking Hardy-like paradoxes to vertex-coloring problems and experimentally verifies stronger paradoxes using optical setups.

Findings

Hardy-like paradoxes can be associated with un-colorable graph solutions.

Higher success probabilities are achieved in demonstrating quantum conflicts.

Experimental verification confirms the theoretical predictions.

Abstract

We present the general Hardy-like quantum pigeonhole paradoxes for \textit{n}-particle states, and find that each of such paradoxes can be simply associated to an un-colorable solution of a specific vertex-coloring problem induced from the projected-coloring graph (a kind of unconventional graph). Besides, as a special kind of Hardy's paradox, several kinds of Hardy-like quantum pigeonhole paradoxes can even give rise to higher success probability in demonstrating the conflict between quantum mechanics and local or noncontextual realism than the previous Hardy's paradoxes. Moreover, not only multi-qubit states, but high-dimensional states can exhibit the paradoxes. In contrast to only one type of contradiction presented in the original quantum pigeonhole paradox, two kinds of three-qubit projected-coloring graph states as the minimal illustration are discussed in our work, and an optical experiment to verify such stronger paradox is performed. This quantum paradox provides innovative thoughts and methods in exploring new types of stronger multi-party quantum nonlocality and may have potential applications in multi-party untrusted communications and device-independent random number generation.