# Quantum Entanglement

Persistent quantum entanglement in Heisenberg spin-glass

A collection of spins or qubits will have a definite z-component of the total angular momentum. This conserved angular momentum component is also referred to as a particle-number. Definite-particle states are quantum states of the entire system with a definite particle-number. Earlier works have showed that that in the case of random one-particle states, the average entanglement between any two qubits decreases with the number of spins and that in the case of random two-particle states, the average entanglement between any two qubits decreases with the square of the number of spins. While this is true when averaged over all two-particle states, we find a special class of two-particle states, which can be obtained fron one-particle states, for which the average entanglement still scales inversely to the first power of the number of qubits. We also show that such states occur very naturally in systems such as the Heisenberg spin-glass. We provide both analytical and results from numerical simulations and distinguish these states from typical two-particle states.

Paper that has come out of this project:

- Persistent entanglement in a class of eigenstates of quantum Heisenberg spin glasses

**A. Kannawadi**, A. Sharma, A. Lakshminarayan (2016) EPL 115, 57005