Ensuring the integrity and transferability of digital messages is an important challenge in modern communications. Although purely mathematical approaches exist, they usually rely on the computational complexity of certain functions, in which case there is no guarantee of long-term security. Alternatively, quantum digital signatures offer security guaranteed by the physical laws of quantum mechanics. Prior experimental demonstrations of quantum digital signatures in optical fiber have typically been limited to operation over short distances and/or operated in a laboratory environment. Here we report the experimental transmission of quantum digital signatures over channel losses of up to 42.8 ± 1.2 dB in a link comprised of 90 km of installed fiber with additional optical attenuation introduced to simulate longer distances. The channel loss of 42.8 ± 1.2 dB corresponds to an equivalent distance of 134.2 ± 3.8 km and this represents the longest effective distance and highest channel loss that quantum digital signatures have been shown to operate over to date. Our theoretical model indicates that this represents close to the maximum possible channel attenuation for this quantum digital signature protocol, defined as the loss for which the signal rate is comparable to the dark count rate of the detectors.
Ensuring the integrity and transferability of digital messages is an important challenge in modern communications. Although purely mathematical approaches exist, they usually rely on the computational complexity of certain functions, in which case there is no guarantee of long-term security. Alternatively, quantum digital signatures offer security guaranteed by the physical laws of quantum mechanics. Prior experimental demonstrations of quantum digital signatures in optical fiber have typically been limited to operation over short distances and/or operated in a laboratory environment. Here we report the experimental transmission of quantum digital signatures over channel losses of up to 42.8 ± 1.2 dB in a link comprised of 90 km of installed fiber with additional optical attenuation introduced to simulate longer distances. The channel loss of 42.8 ± 1.2 dB corresponds to an equivalent distance of 134.2 ± 3.8 km and this represents the longest effective distance and highest channel loss that quantum digital signatures have been shown to operate over to date. Our theoretical model indicates that this represents close to the maximum possible channel attenuation for this quantum digital signature protocol, defined as the loss for which the signal rate is comparable to the dark count rate of the detectors.
Quantum digital signatures (QDSs) apply quantum mechanics to the problem of guaranteeing message integrity and non-repudiation with information-theoretical security, which are complementary to the confidentiality realized by quantum key distribution (QKD). Previous experimental demonstrations have been limited to transmission distances of less than 5 km of optical fiber in a laboratory setting. Here we report, to the best of our knowledge, the first demonstration of QDSs over installed optical fiber, as well as the longest transmission link reported to date. This demonstration used a 90 km long differential phase shift QKD to achieve approximately one signed bit per second, an increase in the signature generation rate of several orders of magnitude over previous optical fiber demonstrations.
The security of electronic communications is a topic that has gained noteworthy public interest in recent years. As a result, there is an increasing public recognition of the existence and importance of mathematically based approaches to digital security. Many of these implement digital signatures to ensure that a malicious party has not tampered with the message in transit, that a legitimate receiver can validate the identity of the signer and that messages are transferable. The security of most digital signature schemes relies on the assumed computational difficulty of solving certain mathematical problems. However, reports in the media have shown that certain implementations of such signature schemes are vulnerable to algorithmic breakthroughs and emerging quantum processing technologies. Indeed, even without quantum processors, the possibility remains that classical algorithmic breakthroughs will render these schemes insecure. There is ongoing research into information-theoretically secure signature schemes, where the security is guaranteed against an attacker with arbitrary computational resources. One such approach is quantum digital signatures. Quantum signature schemes can be made information-theoretically secure based on the laws of quantum mechanics while comparable classical protocols require additional resources such as anonymous broadcast and/or a trusted authority. Previously, most early demonstrations of quantum digital signatures required dedicated single-purpose hardware and operated over restricted ranges in a laboratory environment. Here, for the first time, we present a demonstration of quantum digital signatures conducted over several kilometers of installed optical fiber. The system reported here operates at a higher signature generation rate than previous fiber systems.
A quantum digital signature (QDS) guarantees the unforgeability, nonrepudiation, and transferability of signature messages with information-theoretic security, and hence has attracted much attention recently. However, most previous implementations of QDS showed relatively low signature rates and/or short transmission distance. In this Letter, we report a proof-of-principle phase-encoding QDS demonstration using only one decoy state. First, such a method avoids the modulation of the vacuum state, thus reducing experimental complexity and random number consumption. Moreover, incorporated with low-loss asymmetric Mach-Zehnder interferometers and a real-time polarization calibration technique, we have successfully achieved a higher signature rate, e.g., 0.98 bit/s at 103 km, and to date, a record-breaking, to the best of our knowledge, transmission distance of over 280-km installed fibers. Our work represents a significant step towards real-world applications of QDS.
Digital signatures are one of the security cornerstones of the current information age. Compared with classical digital signatures based on computational complexity, quantum digital signatures (QDS) theoretically guarantee data integrity, authenticity, and non-repudiation by quantum mechanics, showing great potential for development in cryptography and thus attracting widespread attention. However, the performance of existing QDS systems are still limited in rate and distance. Here we report the first experimental demonstration of twin-field QDS (TF-QDS) using a GHz system. We achieve a maximum transmission distance of 504 km fiber spools for both single-bit and multi-bit schemes, surpassing all existing state-of-the-art QDS experiments more than 200 km. Furthermore, by combining the one-time universal hash method, we achieve a maximum signature rate of 21.1 times per second for a 1 Mbit file over fiber distances up to 302 km. In this work, the signature rates of both single-bit scheme and multi-bit scheme are more than two orders of magnitude higher than that of previous works at similar distance. Our work provides a new record for long-distance and high-rate QDS, representing a significant step in the development of QDS.
Quantum digital signature (QDS) is an approach to guarantee the nonrepudiation, unforgeability, and transferability of a signature with information-theoretical security. Previous experimental realizations of QDS relied on an unrealistic assumption of secure channels and the longest distance is several kilometers. Here, we have experimentally demonstrated a recently proposed QDS protocol without assuming any secure channel. Exploiting the decoy state modulation, we have successfully signed a one-bit message through an up to 102-km optical fiber. Furthermore, we continuously run the system to sign the longer message ``USTC'' with 32 bits at the distance of 51 km. Our results pave the way towards the practical application of QDS.
Quantum digital signatures (QDS) offer information-theoretic security for message integrity, authenticity, and non-repudiation, and constitute a fundamental cryptographic primitive for future quantum networks. Despite significant progress, the practical deployment of QDS has been severely constrained by limited signature rates and poor tolerance to channel loss, particularly in long-distance and metropolitan-scale networks. Here, we report a high-rate, loss-resilient QDS system that overcomes these two key bottlenecks simultaneously. Our implementation combines intrinsically phase-stable polarization modulation based on a Sagnac interferometer with gigahertz-rate quantum state encoding and low-timing-jitter superconducting nanowire single-photon detectors, enabling robust and continuous operation at high repetition frequencies. By integrating this hardware platform with a one-time universal hashing-based QDS protocol, we achieve a signature rate improvement of more than two orders of magnitude compared with existing QDS implementations under comparable channel-loss conditions. Notably, the system maintains a non-zero effective signature rate of approximately 1.25 times per second at a total channel loss of up to 49.05 dB, representing the highest loss tolerance reported for QDS to date. These results establish a practical and scalable technological pathway for deploying QDS in real-world quantum communication networks.