  Maximally entangled two-qubit states (Bell states) are of central importance
in quantum technologies. We show that heralded generation of a maximally
entangled state of two intrinsically open qubits can be realized in a
one-dimensional (1d) system through strong coherent driving and continuous
monitoring. In contrast to the natural idea that dissipation leads to
decoherence and so destroys quantum effects, continuous measurement and strong
interference in our 1d system generate a pure state with perfect quantum
correlation between the two open qubits. Though the steady state is a trivial
product state which has zero coherence or concurrence, we show that, with
carefully tuned parameters, a Bell state can be generated in the system's
quantum jump trajectories, heralded by a reflected photon. Surprisingly, this
maximally entangled state survives the strong coherent state input---a
classical state that overwhelms the system. This simple method to generate
maximally entangled states using classical coherent light and photon detection
may, since our qubits are in a 1d continuum, find application as a building
block of quantum networks.
