Abstract Quantum communication has been leading the way of many remarkable theoretical results and experimental tests in physics. In this context, quantum communication complexity (QCC) has recently drawn earnest research attention as a tool to optimize the amounts of transmitted qubits and energy that are required to implement distributed computational tasks. On this matter, we introduce a novel multi-user quantum fingerprinting (QF) protocol that is ready to be implemented with existing technology. Particularly, we extend to the multi-user framework a well-known two-user coherent-state fingerprinting scheme. This generalization is highly non-trivial for a twofold reason, as it requires not only to extend the set of protocol rules but also to specify a procedure for designing the optical devices intended for the generalized protocol. Much of the importance of our work arises from the fact that the obtained QCC figures of merit allow direct comparison with the best-known classical multi-user fingerprinting protocol, of significance in the field of computer technologies and networking. Furthermore, as one of the main contributions of the manuscript, we deduce innovative analytical upper bounds on the amount of transmitted quantum information that are even valid in the two-user protocol as a particular case. These original analytical bounds are of interest for estimating the realistic protocol performance prior to experimental realizations. Ultimately, comparative results are provided to contrast different protocol implementation strategies and, importantly, to show that, under realistic circumstances, the multi-user protocol can achieve tasks that are impossible by using classical communication alone. Our work provides relevant contributions towards understanding the nature and the limitations of QF and, on a broader scope, also the limitations and possibilities of quantum-communication networks embracing a node that is accessed by multiple users at the same time.
One of the standard communication complexity problems is deciding whether bit strings held by two separate parties Alice (A) and Bob (B) are equal or different. In the simultaneous message passing model, A and B send certain information to a Referee, who makes the decision. The overall goal is to minimize the amount of communication involved while not exceeding desired error probability. This is achieved by sending only fingerprints of the original n-bit strings. In the best classical protocols, these scale as O(√n) if A and B have no access to shared randomness [1]. The recently proposed [2] and demonstrated quantum fingerprinting [3], exploiting phase-modulated weak coherent pulses, provides O(log2n) scaling in the number of used qubits, but needs phase stability between A and B. Here we introduce and analyse a quantum fingerprinting protocol based on two-photon interference which does require a shared phase reference and works in scenarios when the global phase of transmitted signals becomes completely random. Interestingly, the performance of this protocol, quantified in terms of the Chernoff information [4], is enhanced through the use of non-classical single-photon states, even in the regime of high transmission loss.
Quantum fingerprinting allows two remote parties to determine whether their datasets are identical or different by sending exponentially less information compared to the classical protocol with equivalent performance. Optical implementations of the quantum protocol based on weak coherent states have been proposed and realized. However, in these realizations phase stability between the sending parties is required. Here we analyze the practical feasibility of the recently introduced quantum fingerprinting protocol based on higher-order interference, which does not require a phase lock between transmitters. We show that an experimental demonstration of a quantum fingerprinting protocol beating the known bound on the performance of classical schemes should be possible using currently available technology.
Quantum digital signatures (QDSs) promise information-theoretic security against repudiation and forgery of messages. Compared with currently existing three-party QDS protocols, multiparty protocols have unique advantages in the practical case of more than two receivers when sending a mass message. However, complex security analysis, numerous quantum channels and low data utilization efficiency make it intractable to expand three-party to multiparty scenario. Here, based on six-state non-orthogonal encoding protocol, we propose an effective multiparty QDS framework to overcome these difficulties. The number of quantum channels in our protocol only linearly depends on the number of users. The post-matching method is introduced to enhance data utilization efficiency and make it linearly scale with the probability of detection events even for five-party scenario. Our work compensates for the absence of practical multiparty protocols, which paves the way for future QDS networks.
We introduce several families of quantum fingerprinting protocols to evaluate the equality function on two
n-bit strings in the simultaneous message passing model. The original quantum fingerprinting protocol uses a tensor product of a small number of
O(logn)-qubit high-dimensional signals [H. Buhrman et al., Phys. Rev. Lett. 87, 167902 (2001)], whereas a recently proposed optical protocol uses a tensor product of
O(n) single-qubit signals, while maintaining the
O(logn) information leakage of the original protocol [J. M. Arazola and N. L\"utkenhaus, Phys. Rev. A 89, 062305 (2014)]. We find a family of protocols which interpolate between the original and optical protocols while maintaining the
O(logn) information leakage, thus demonstrating a tradeoff between the number of signals sent and the dimension of each signal. There has been interest in experimental realization of the recently proposed optical protocol using coherent states [F. Xu et al., Nat. Commun. 6, 8735 (2015); J.-Y. Guan et al., Phys. Rev. Lett. 116, 240502 (2016)], but as the required number of laser pulses grows linearly with the input size
n, eventual challenges for the long-time stability of experimental setups arise. We find a coherent state protocol which reduces the number of signals by a factor
21 while also reducing the information leakage. Our reduction makes use of a simple modulation scheme in optical phase space, and we find that more complex modulation schemes are not advantageous. Using a similar technique, we improve a recently proposed coherent state protocol for evaluating the Euclidean distance between two real unit vectors [N. Kumar et al., Phys. Rev. A 95, 032337 (2017)] by reducing the number of signals by a factor
21 and also reducing the information leakage.
Authentication is one of the security services that assures the system’s adequate security through identification and verification. Additionally, it guarantees that the communication party is who they claim to be. In politics, the economy, banking, daily life, and other areas, quantum identity authentication is essential to guarantee the security of information in communication. The multiphoton strategy is an improved version of the single-photon approach, with higher transmission rates and longer photon travel distances via the Quantum Communication network. Despite the advantages of multiphoton, enforcing authentication on behalf of numerous participants in the quantum channel remains a problem, since existing multiphoton only considers two parties involved in secret message sharing. The issue of scalability arises here when the number of parties involved in the quantum network increases. Furthermore, an eavesdropper might hide her position among other parties and take advantage of the situation to obtain a certain information. Therefore, we require a protocol, that creates a more secure environment in term of authentication in which multiple parties may freely and openly communicate. This paper further identifies research gaps covering critical aspect on how Quantum Identity Authentication (QIA) can be realized and effectively utilized for multiphoton without entanglement based. These include suggestion of future direction to implement multiphoton in multiparty from current protocol.