  We implement a protocol to determine the degree of entanglement between a
qubit and the rest of the system on a quantum computer. The protocol is based
on results obtained in paper [Frydryszak et al. (2017)]. This protocol is
tested on a 5-qubit superconducting quantum processor called ibmq-ourense
provided by the IBM company. We determine the values of entanglement of the
Schr\"odinger cat and the Werner states prepared on this device and compare
them with the theoretical ones. In addition, a protocol for determining the
entanglement of rank-2 mixed states is proposed. We apply this protocol to the
mixed state which consists of two Bell states prepared on the ibmq-ourense
quantum device.
