Experimental quantum randomness generation invulnerable to the detection loophole

Random numbers are essential for multiple applications, including cryptography, financial security, digital rights management and scientific simulations. However, producing random numbers from a finite state machine, such as a classical computer, is impossible. One option is to use conventional quantum random number generators (QRNGs) based on the intrinsic uncertainty of quantum measurement outcomes. The problem in this case is that private randomness relies on assumptions on the internal functioning of the measurement devices. "Device-independent" QRNGs not relying on devices inner workings assumptions can be built but are impractical. They require a detection efficiency that, so far, has only be achieved with trapped ions and with photons detected with transition-edge superconducting sensors. Here we introduce a novel protocol for quantum private randomness generation that makes no assumption on the functioning of the devices and works even with very low detection efficiency. We implement the protocol using weak coherent states and standard single-photon detectors. Our results pave the way towards a second generation of more secure practical QRNGs.