Quantum candies (qandies) represent a type of pedagogical simple model that describes many concepts from quantum information processing (QIP) intuitively without the need to understand or make use of superpositions and without the need of using complex algebra. One of the topics in quantum cryptography that has gained research attention in recent years is quantum digital signatures (QDS), which involve protocols to securely sign classical bits using quantum methods. In this paper, we show how the "qandy model" can be used to describe three QDS protocols in order to provide an important and potentially practical example of the power of "superpositionless" quantum information processing for individuals without background knowledge in the field.
Quantum candies (qandies) represent a type of pedagogical simple model that describes many concepts from quantum information processing (QIP) intuitively without the need to understand or make use of superpositions and without the need of using complex algebra. One of the topics in quantum cryptography that has gained research attention in recent years is quantum digital signatures (QDS), which involve protocols to securely sign classical bits using quantum methods. In this paper, we show how the "qandy model" can be used to describe three QDS protocols in order to provide an important and potentially practical example of the power of "superpositionless" quantum information processing for individuals without background knowledge in the field.
The field of quantum information is becoming more known to the general public. However, effectively demonstrating the concepts underneath quantum science and technology to the general public can be a challenging job. We investigate, extend, and greatly expand here "quantum candies" (invented by Jacobs), a pedagogical model for intuitively describing some basic concepts in quantum information, including quantum bits, complementarity, the no-cloning principle, and entanglement. Following Jacob's quantum candies description of the well-known quantum key distribution protocol BB84, we explicitly demonstrate additional quantum cryptography protocols and quantum communication protocols, using generalized quantum candies (including correlated pairs of qandies). These demonstrations are done in an approachable manner, that can be explained to high-school students, without using the hard-to-grasp concept of superpositions and its mathematics. The intuitive model we investigate has a fascinating overlap with some of the most basic features of quantum theory. Hence, it can be a valuable tool for science and engineering educators who would like to help the general public to gain more insights into quantum science and technology. For the experts, the model we present, due to not employing quantum superpositions, enables - in some sense - extending far beyond quantum theory. Most remarkably, "quantum" candies of some unique type can be defined, such that non-local boxes (of the Popescu-Rohrlich type) as well as regular (correlated) quantum candies can be generated by a single `"quantum" candies machine.
Quantum Candies or Qandies provide us with a lucid way of understanding the concepts of quantum information and quantum science in the language of candies. The critical idea of qandies is intuitively depicting quantum science to the general public, making sense as most of the research in this domain is funded by the taxpayers. The qandies model is already used to explain the essential concepts of quantum science and quantum cryptography. However, teleportation and related concepts are yet to be explained. Motivated by this fact, we investigate and extend the idea of Jacobs and Lin-Mor-Shapira to explain teleportation using qandies. Here, we explicitly design the teleportation protocol and perform a circuit model using qandy gates. The protocol is successful when the correlated qandies are appropriately pre-shared and use of some local operations at both ends. The model we develop can be a valuable tool for science and engineering educators who want to help the general public to gain more insights into quantum science and technology.
The field of information is becoming more known to the general public. However, effectively demonstrating the concepts underneath science and technology to the general public can be a challenging job. We investigate, extend, and much expand here quantum (invented by Jacobs), a pedagogical model for intuitively describing some basic concepts in information, including bits, complementarity, the no-cloning principle, and entanglement. Following Jacob's candies description of the well-known key distribution protocol BB84, we explicitly demonstrate various additional cryptography protocols using candies in an approachable manner. The model we investigate can be a valuable tool for science and engineering educators who would like to help the general public to gain more insights into science and technology: most parts of this paper, including many protocols for cryptography, are expected to be easily understandable by a layperson without any previous knowledge of mathematics, physics, or cryptography.
Ensuring the security of digital communication and data transfer has become essential in the modern era. Classical cryptographic techniques are increasingly vulnerable due to advances in quantum technologies and algorithms. Consequently, quantum computers and quantum communication offer promising solutions for secure data transfer and encryption. This study explores the generation of Quantum Digital Signatures (QDS) using Quantum Continuous Variables (QCV), providing a novel approach to secure digital signature technologies. The paper outlines the core principles of QDS generation with QCV, detailing the signature creation and verification processes. It highlights the advantages of this technology in secure communication and data transfer and discusses potential security vulnerabilities and future development prospects. Quantum Continuous Variables (QCVs), typically used in quantum optical systems, represent physical quantities with continuous spectra, such as the wavelength or phase of light. These variables enable efficient and secure quantum information processing and communication. Despite significant progress in quantum cryptography protocols using QCVs, practical application and optimization of these technologies face numerous challenges. These include complexities in preparing and measuring quantum states, managing quantum errors, and achieving higher efficiency and security standards. Moreover, the practical applications of QCV in industrial contexts remain limited, highlighting the need for further experimental and applied research. The methodology for generating QDS using QCVs involves employing specific quantum states, such as coherent and squeezed states. The process includes key distribution, signature creation and verification, and addressing potential quantum attacks. The system model comprises a sender (Alice), a receiver (Bob), and an arbiter (Charlie), facilitating secure and authenticated message transmission.
The quantum digital signature (QDS) has attracted much attention as it ensures the nonrepudiation, unforgeability, and transferability of signature messages based on information-theoretic security. Amiri et al. ( Phys. Rev. A 93 032325 ) proposed the first practical QDS protocol based on orthogonal coding, which has realized information-theoretic security and become the mainstream paradigm in QDS research. The procedure of QDS involves two essential stages, the one is the distribution stage, in which Alice-Bob and Alice-Charlie individually utilize the three-intensity decoy-state quantum key distribution protocol but without error correction or privacy amplification, namely, key-generation protocol, to generate correlated bit strings, the other is the messaging stage, in which Alice transmits signature messages to the two recipients. However, previous theoretical and experimental studies both overlooked the modulation errors that may be introduced in the state preparation process due to the imperfections in modulator devices. Under the traditional framework of GLLP analysis method, these errors will significantly reduce the actual signature rates. Therefore, we propose a state-preparation-error tolerant QDS and use parameter analysis to characterize the state preparation error to make the simulation analysis more realistic. In addition, we analyze the signature rates of the present scheme by using the three-intensity decoy-state method. Compared with previous QDS protocols, our protocol almost shows no performance degradation under practical state preparation errors and exhibits a maximum transmission distance around 180 km. Furthermore, state preparation errors do not have a significant influence on the bit error rate induced by normal communication between the legitimate users or the one produced by an eavesdropper. These results prove that the method proposed in this paper has excellent robustness against state preparation errors and it can achieve much higher signature rates and signature distances than other standard methods. Besides, signature rates are basically unchanged under different total pulse numbers, which shows that our protocol also has good robustness against the finite-size effect. Additionally, in the key generation process, our method is only required to prepare three quantum states, which will reduce the difficulty of experiment realizations. Furthermore, the proposed method can also be combined with the measurement-device-independent QDS protocol and the twin-field QDS protocol to further increase the security level of QDS protocol. Therefore, our work will provide an important reference value for realizing the practical application of QDS in the future.
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.