Semi-quantum cryptography involves at least one user who is semi-quantum or “classical” in nature. Such a user can only interact with the quantum channel in a very restricted way. Many semi-quantum key distribution protocols have been developed, some with rigorous proofs of security. Here we show for the first time that quantum random number generation is possible in the semi-quantum setting. We also develop a rigorous proof of security, deriving a bound on the random bit generation rate of the protocol as a function of noise in the channel. Our protocol and proof may be broadly applicable to other quantum and semi-quantum cryptographic scenarios where users are limited in their capabilities.
Semi-quantum cryptography involves at least one user who is semi-quantum or “classical” in nature. Such a user can only interact with the quantum channel in a very restricted way. Many semi-quantum key distribution protocols have been developed, some with rigorous proofs of security. Here we show for the first time that quantum random number generation is possible in the semi-quantum setting. We also develop a rigorous proof of security, deriving a bound on the random bit generation rate of the protocol as a function of noise in the channel. Our protocol and proof may be broadly applicable to other quantum and semi-quantum cryptographic scenarios where users are limited in their capabilities.
Semi-quantum key distribution protocols are designed to allow two users to establish a secure secret key when one of the two users is limited to performing certain "classical" operations. There have been several such protocols developed recently, however, due to their reliance on a two-way quantum communication channel (and thus, the attacker's opportunity to interact with the qubit twice), their security analysis is difficult and little is known concerning how secure they are compared to their fully quantum counterparts. In this paper we prove the unconditional security of a particular semi-quantum protocol. We derive an expression for the key rate of this protocol, in the asymptotic scenario, as a function of the quantum channel's noise. Finally, we will show that this semi-quantum protocol can tolerate a maximal noise level comparable to certain fully quantum protocols.
Semi-quantum key distribution protocols are designed to allow two users to establish a secure secret key when one of the two users is limited to performing certain “classical” operations. There have been several such protocols developed recently, however, due to their reliance on a two-way quantum communication channel (and thus, the attacker's opportunity to interact with the qubit twice), their security analysis is difficult and little is known concerning how secure they are compared to their fully quantum counterparts. In this paper we prove the unconditional security of a particular semi-quantum protocol and derive an expression for its key rate, in the asymptotic scenario.
The idea of semi-quantum communication protocols provides a theoretical solution for the high costs of quantum resources. In this study, we propose an efficient semi-quantum key distribution protocol that allows Alice and quantum-capable restricted Bob to establish a secure key. Then, we demonstrate that the protocol is information-theoretic secure in the asymptotic scenario. As long as the channel noise is less than the noise tolerance of the protocol, Alice and Bob can withdraw a secure key. The proposed protocol has advantages over previous protocols regarding qubit efficiency and communication cost. Besides, our efficiency analysis is more fair and practical because noise factors are taken into account. Based on these features, it may have potential applications in future quantum communications.
Quantum key distribution, which allows two distant parties to share an unconditionally secure cryptographic key, promises to play an important role in the future of communication. For this reason such technique has attracted many theoretical and experimental efforts, thus becoming one of the most prominent quantum technologies of the last decades. The security of the key relies on quantum mechanics and therefore requires the users to be capable of performing quantum operations, such as state preparation or measurements in multiple bases. A natural question is whether and to what extent these requirements can be relaxed and the quantum capabilities of the users reduced. Here we demonstrate a novel quantum key distribution scheme, where users are fully classical. In our protocol, the quantum operations are performed by an untrusted third party acting as a server, which gives the users access to a superimposed single photon, and the key exchange is achieved via interaction-free measurements on the shared state. We also provide a full security proof of the protocol by computing the secret key rate in the realistic scenario of finite-resources, as well as practical experimental conditions of imperfect photon source and detectors. Our approach deepens the understanding of the fundamental principles underlying quantum key distribution and, at the same time, opens up new interesting possibilities for quantum cryptography networks
Quantum random number generators (QRNGs) produce true random numbers based on the inherent randomness of quantum theory, rendering them a foundational segment of quantum cryptography. Distinguished from trusted-device QRNGs whose security depends on characterized devices, semi-device-independent (semi-DI) QRNGs permit partial devices to be defective or even maliciously manipulated, which achieves a good trade-off between generation rate and security. In this paper, we propose a semi-DI QRNG that resists general attacks while accounting for finite-size effects. The protocol requires no rigorous characterization of the source and measurement devices other than limiting the energy of the emitted states, significantly reducing the demands on practical QRNG systems. Leveraging the tight Kato inequality for correlated variables, we show that our protocol generates more randomness than it consumes. Furthermore, we demonstrate the scheme on a continuous-variable system with ternary inputs of states. Heterodyne detection is employed to enable phase compensation through data postprocessing, alleviating the stringent requirement on system stability. The system operates at 100 MHz, achieving a net random number generation rate of 1.165 Mbps at 5.3x10^9 rounds. Our work offers a promising approach to achieve both the robust security and high generation rate with a simple experimental setup.
Since the introduction of quantum computation by Richard Feynman in 1982, Quantum computation has shown exemplary results in various applications of computer science including unstructured database search, factorization, molecular simulations to name a few. Some of the recent developments include quantum machine learning, quantum neural networks, quantum walks on graphs, fault tolerant scalable quantum computers using error correction codes etc. One of the crucial modern applications of quantum information is quantum cryptography and secure key distribution over quantum channels which have several advantages over classical channels, especially detection of eavesdropping. Based on such properties of quantum systems and quantum channels, In this paper we propose three secure key distribution protocols based on a blend of classical and quantum channels. Also the proposed protocols exploits the property of quantum computers to generate natural random numbers that can be easily transmitted using a single qubit over a quantum channel and can be used for distributing keys to the involved parties in a communication network.