Preparing the bound instance of quantum entanglement

TL;DR

This paper reports the first experimental unconditional preparation and detection of a bound entangled state of light, demonstrating its irreversibility and potential applications in quantum information and metrology.

Contribution

It introduces a novel experimental method for preparing and certifying bound entangled states of light using convex optimization and continuous-variable entanglement.

Findings

Successfully prepared a bound entangled state with high statistical significance.

Demonstrated the irreversibility of entanglement in a practical setting.

Showcased potential applications in quantum information and high-precision measurements.

Abstract

Among the possibly most intriguing aspects of quantum entanglement is that it comes in "free" and "bound" instances. Bound entangled states require entangled states in preparation but, once realized, no free entanglement and therefore no pure maximally entangled pairs can be regained. Their existence hence certifies an intrinsic irreversibility of entanglement in nature and suggests a connection with thermodynamics. In this work, we present a first experimental unconditional preparation and detection of a bound entangled state of light. We consider continuous-variable entanglement, use convex optimization to identify regimes rendering its bound character well certifiable, and realize an experiment that continuously produced a distributed bound entangled state with an extraordinary and unprecedented significance of more than ten standard deviations away from both separability and distillability. Our results show that the approach chosen allows for the efficient and precise preparation of multimode entangled states of light with various applications in quantum information, quantum state engineering and high precision metrology.