  We propose a theoretical scheme to witness quantum entanglement via the
geometric phase in an impurity-doped Bose-Einstein condensate (BEC), which is a
micro-macro quantum system consisting of two Rydberg impurity qubits and the
BEC. We calculate the geometric phase of the impurity qubits in the presence of
the initial micro-micro and micro-macro entanglement, respectively. It is
demonstrated that the geometric phase of the impurity qubits can witness not
only inter-qubit micro-micro entanglement, but also qubit-BEC micro-macro
entanglement. Our work provide a new insight to witness micro-micro and
micro-macro entanglement in a impurity-doped BEC.
