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Abstract

In 1935, Einstein, Podolsky and Rosen (EPR) considered two particles in an
entangled state of motion to illustrate why they questioned the completeness of
quantum theory. In the past decades, microscopic systems with entanglement in
various degrees of freedom have successfully been generated, representing
compelling evidence to support the completeness of quantum theory. Today, the
generation of an EPR-entangled state of motion of two massive objects of up to
the kilogram-scale seems feasible with state-of-the-art technology. Recently,
the generation and verification of EPR-entangled mirror motion in
interferometric gravitational wave detectors was proposed, with the aim of
testing quantum theory in the regime of macroscopic objects, and to make
available nonclassical probe systems for future tests of modified quantum
theories that include (non-relativistic) gravity. The work presented here
builds on these earlier results and proposes a specific Michelson
interferometer that includes two high-quality laser mirrors of about 0.1 kg
mass each. The mirrors are individually suspended as pendula and located close
to each other, and cooled to about 4 K. The physical concepts for the
generation of the EPR-entangled centre of mass motion of these two mirrors are
described. Apart from a test of quantum mechanics in the macroscopic world, the
setup is envisioned to test predictions of yet-to-be-elaborated modified
quantum theories that include gravitational effects.