# Allowed and Forbidden Bipartite Correlations from Thermal States

## TL;DR

This paper investigates the conditions under which bipartite correlations, including entanglement, can be generated from thermal states, and explores the thresholds and resource requirements for such quantum correlations.

## Contribution

It characterizes allowed and forbidden bipartite correlations from thermal states and extends results to separable but not absolutely separable states, proposing strategies for entanglement generation.

## Key findings

- Threshold temperature for entanglement from thermal states is identified.
- Resource states can surpass temperature bounds for entanglement.
- Dimension-dependent upper bounds on temperature for entanglement are derived.

## Abstract

The strong connection between correlations and quantum thermodynamics raises a natural question about the preparation of correlated quantum states from two copies of a thermal qubit. In this work we study the specific forms of allowed and forbidden bipartite correlations. As a consequence, we extend the result to Separable (SEP) but not Absolutely Separable (AbSEP) class of product states. Preparation of a general form of entanglement from arbitrary thermal qubits is studied and as an application we propose a strategy to establish sustained entanglement between two distant parties. The threshold temperature to produce entanglement from two copies of a thermal qubit has also been discussed from the resource theoretic perspective, which ensures that the bound on the temperature can be superseded with the help of a resource state. A dimension dependent upper-bound on the temperature is derived, below which two copies of any d-dimensional thermal state can be entangled in 2xd dimension.