  Quantum entanglement lies at the heart of quantum mechanics in both
fundamental and practical aspects. The entanglement of quantum states has been
studied widely, however, the entanglement of operators has not been studied
much in spite of its importance. Here, we propose a scheme to realize arbitrary
entangled operations based on a coherent superposition of local operations.
Then, we experimentally implement several intriguing two-qubit entangled
operations in photonic systems. We also discuss the generalization of our
scheme to extend the number of superposed operations and the number of qubits.
Due to the simplicity of our scheme, we believe that it can reduce the
complexity or required resources of the quantum circuits and provide insights
to investigate properties of entangled operations.
