Consider the Hamiltonian H=Z⊗3 acting on 3 qubits.

What is the ground energy of the system? (I.e. the lowest eigenvalue of H?)
What is the dimension of the ground energy subspace? (I.e. multiplicity of that eigenvalue?)
Which of the following correctly describes the ground energy states of this system?

|000⟩ is the only ground energy state.
|111⟩ is the only ground energy state.
|000⟩,|111⟩ and their linear combinations
|001⟩,|010⟩,|100⟩ and their linear combinations
|000⟩,|001⟩,|010⟩,|100⟩ and their linear combinations
|000⟩,|011⟩,|110⟩,|101⟩ and their linear combinations
|001⟩,|010⟩,|100⟩,|111⟩ and their linear combinations

4 answers

000> is the only ground energy state, I think... don't know others
last option
sure last option?justify
last option worked for me