A light approach to quantum advantage Quantum computational advantage or supremacy is a long-anticipated milestone toward practical quantum computers. Recent work claimed to have reached this point, but subsequent work managed to speed up the classical simulation and pointed toward a sample size–dependent loophole. Quantum computational advantage, rather than being a one-shot experimental proof, will be the result of a long-term competition between quantum devices and classical simulation. Zhong et al. sent 50 indistinguishable single-mode squeezed states into a 100-mode ultralow-loss interferometer and sampled the output using 100 high-efficiency single-photon detectors. By obtaining up to 76-photon coincidence, yielding a state space dimension of about 10 30 , they measured a sampling rate that is about 10 14 -fold faster than using state-of-the-art classical simulation strategies and supercomputers. Science , this issue p. 1460

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Quantum communication has historically been at the forefront of advancements, from fundamental tests of quantum physics to utilizing the quantum-mechanical properties of physical systems for practical applications. In the field of communication complexity, quantum communication allows the advantage of an exponential reduction in the transmitted information over classical communication to accomplish distributed computational tasks. However, to date, demonstrating this advantage in a practical setting continues to be a central challenge. Here, we report a proof-of-principle experimental demonstration of a quantum fingerprinting protocol that for the first time surpasses the ultimate classical limit to transmitted information. Ultralow noise superconducting single-photon detectors and a stable fiber-based Sagnac interferometer are used to implement a quantum fingerprinting system that is capable of transmitting less information than the classical proven lower bound over 20 km standard telecom fiber for input sizes of up to 2 Gbits. The results pave the way for experimentally exploring the advanced features of quantum communication and open a new window of opportunity for research in communication complexity and testing the foundations of physics. DOI: 10.1103/PhysRevLett.116.240502 The quantum-communication network [1] is believed to be the next-generation platform for remote information processing tasks. So far, however, only one protocolquantum key distribution (QKD) [2,3]-has been widely investigated and deployed in commercial applications. The extension of the practically available quantum communication protocols beyond QKD in order to fully understand the potential of large-scale quantum communication networks is therefore highly important. Significant progress has been made in this direction [4][5][6][7][8][9], but the rich class of quantum communication complexity (QCC) protocols [10-12] remains largely undemonstrated, except for a few proof-of-principle implementations [13][14][15][16]. The field of QCC explores quantum-mechanical properties in order to determine the minimum amount of information that must be transmitted to solve distributed computational tasks [11]. It not only has many connections to the foundational issues of quantum mechanics [12,17], but also has important applications for the design of communication systems, green communication techniques, computer circuits, and data structures [18]. For instance, QCC essentially connects the foundational physics questions regarding nonlocality with those of communication complexity studied in theoretical computer science [12]. Quantum fingerprinting, proposed by Buhrman, Cleve, Watrous, and Wolf, is the most appealing protocol in QCC [19]. Specifically, the simultaneous message-passing model [10] corresponds to the scenario where two parties, Alice and Bob, respectively, receive inputs x a ; x b ∈ f0; 1g n and send messages to a third party, Referee, who must determine whether x a equals x b or not, with a small error probability ϵ. This model has...