Generation of a hybrid W entangled state of three photonic qubits with different encodings

The W-type entangled states are very useful in quantum computing and quantum communication. Many works have been devoted to preparing non-hybrid W states (i.e., all qubits with the same encoding) in various physical systems. On the other hand, hybrid W entangled states are key ingredients for hybrid quantum computing and quantum communication. In this work, we propose to create a hybrid W entangled state of three photonic qubits each with a different encoding. The hybrid W state is prepared by employing three microwave cavities coupled to a superconducting flux qutrit (i.e., a three-level quantum system). This proposal requires only a single qutrit to couple the three cavities, thus the system architecture is greatly simplified. Since there is no need of making any measurement, the W state is created deterministically. As an example, our numerical simulation demonstrates that within current experimental technology, the proposed hybrid W state can be created with a high fidelity. This proposal is universal and can be applied to create the proposed hybrid W state, by using three microwave or optical cavities coupled to a three-level natural or artificial atom.