Concurrent remote entanglement is an essential primitive in quantum information science. It consists of entangling on demand two arbitrary, distant quantum systems which never directly interact.
In quantum optics, concurrent remote entanglement experiments have recently provided loophole-free tests of quantum non-locality and form the basis for the modular architecture of quantum computing. In these experiments, the Alice and Bob qubits are each first entangled with their respective traveling photons. Subsequently, the two photon paths interfere on a beam-splitter, which acts as a which-path eraser, and are then directed to single-photon detectors. A key feature of this remote entanglement protocol is its robustness to photon losses, unlike schemes that rely on continuous variable states. This robustness arises from heralding the entanglement on the detection of events which can be selected for their unambiguity and are uniquely linked to the production of a pure entangled state. Here we demonstrate this protocol in the domain of superconducting quantum circuits where the natural carriers of information between modules are traveling microwave photons. Our demonstration exploits, in a single experiment, a set of tools that had been previously the exclusive privilege of quantum optics experiments, namely microwave single-photon sources and detectors together with the spatial and temporal control of these photons to make them indistinguishable. With these tools, we have realized the which-path erasure of microwave photons and thus the generation of loss-tolerant entanglement between distant superconducting qubits by concurrent measurements. The protocol speed and prospects for improving fidelity make this a very promising implementation for the distribution of quantum information with microwave flying photons. Our experiment opens for superconducting qubits the new prospect of modular quantum information.