A multi-qubit gate for non-interacting qubits in circuit-QED using the Zeno effect

The quantum Zeno effect is known for freezing dynamics due to observation. The observation can also confine the evolution to an unobserved subspace of the system. This confinement can lead to non-trivial evolution. We show that using a single qubit drive, and a strong continuous observation that blocks part of the evolution, we can create a multi-qubit entangling gate between non-interacting qubits. We use transmon qubits coupled to a 3D cavity. The qubits are far detuned from each other, such that they are effectively non-interacting. We present the experimental results and discuss the fidelity and limitations of this gate.