## ON THE WEIGHT OF ENTANGLEMENT

*Does entanglement have a weight?*This question stems from the observation that the effects of the quantum character of a system on its gravitation are unknown. Entanglement, a genuine quantum property of quantum systems, can be viewed as correlations between physical degrees of freedom. Therefore, at first it might appear as confusing to ask how do correlations contribute to the weight of a system. In fact, a quantum state of a physical system can be prepared, detected, employed, and the correlations present within can be measured. Both theory and overwhelming experimental evidence seem to indicate that the concepts of weight and entanglement live within different domains of physics.

In the past few years, advances in quantum thermodynamics have shown that work can be stored in the quantum correlations of a state. A thermal state is the most entropic state one can prepare given a fixed amount of energy. However, with the same amount of energy, one can prepare a state that contains some amount of entanglement which, in turn, can be used within specifically designed protocols to "store energy". If this is true, then it seems only the natural conclusion that entanglement must have a weight, since relativity has introduced the fundamental notion that energy has a weight.

I have worked on this topic by employing semiclassical gravity, a theory that assumes that gravity is classical but its source can manifest quantum features. The formalism has its domain of validity and its own pitfalls, but I have been careful to apply it only to those regimes where it can be safely used.

More about this topic can be found in my publications "On the weight of entanglement" and "Self gravity affects quantum states".

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