Abstract In this work, we propose a quantum key distribution protocol using the polarization and transverse spatial degrees of freedom of single photons. We show that the protocol is secure and easy to implement experimentally, thus being able to be used in investigations on optical communication. In addition, we show that the information transmitted between two separate parties is always greater than the information retained by a eavesdropper. In this way, it is always possible to employ classical error correction and privacy amplification to minimize eavesdropper information.
Abstract In this work, we propose a quantum key distribution protocol using the polarization and transverse spatial degrees of freedom of single photons. We show that the protocol is secure and easy to implement experimentally, thus being able to be used in investigations on optical communication. In addition, we show that the information transmitted between two separate parties is always greater than the information retained by a eavesdropper. In this way, it is always possible to employ classical error correction and privacy amplification to minimize eavesdropper information.
Abstract Most existing semi-quantum dialogue (SQD) protocols have low communication efficiency and often require classical party to configure different delay lines, resulting in high costs and complex systems. This paper ingeniously combines the concepts of semi-quantum key distribution and semi-quantum secure direct communication, utilizing single photons with both polarization and spatial mode degrees of freedom as information carriers to design a high-capacity SQD protocol. Theoretical analysis confirms that the protocol has good security and can resist common quantum attacks. Compared with most current schemes, its advantages are not only its novel design style and higher communication efficiency, but also the elimination of the need for a delay line at classical party, which effectively reduces communication costs and system complexity. Furthermore, given the maturity of single-photon manipulation techniques, the scheme is easy to implement in experiments and thus shows promising application prospects.
This paper puts forward a novel quantum dialogue (QD) protocol without information leakage based on single photons in both polarization and spatial-mode degrees of freedom. In this protocol, the receiver sends his private message to the sender in the way of quantum secure direct communication; and the receiver decodes out the private message of the sender with the help of auxiliary single photons in two degrees of freedom, double controlled-not (CNOT) operations and an auxiliary classical bit sequence sent from the sender. As a result, no information leakage takes place. Moreover, this protocol is proven to defeat the intercept-resend attack, the measure-resend attack, the entangle-measure attack and the Trojan horse attack from an outside eavesdropper. This protocol only employs single photons in two degrees of freedom as quantum resource and needs single-photon measurements. The qubit efficiency of this protocol is as high as 66.7%.
Quantum communication is an important branch of quantum technology. It can safely transmit private information between legitimate parties and its unconditional security is guaranteed by quantum physics. So far, deterministic secure quantum communication without entanglement usually transmits single photons in two-way quantum channels. We propose a deterministic secure quantum communication proposal, and it requires a one-way quantum channel and a classical channel. In our protocol, a sender encodes logical bits by using two conjugate bases consisting of the polarization and time-bin degrees of freedom of a photon and transmits it to a receiver over a quantum channel. Upon receiving this photon, the receiver measures it randomly in two bases and can decode the bit deterministically with the help of the sender. Any attack from eavesdroppers will be detected by the legitimate parties. Furthermore, this protocol can be implemented with linear-optic elements and single-photon detectors.
In this paper, we propose a new controlled quantum secure direct communication (CQSDC) protocol with single photons in both polarization and spatial-mode degrees of freedom. Based on the defined local collective unitary operations, the sender’s secret messages can be transmitted directly to the receiver through encoding secret messages on the particles. Only with the help of the third side, the receiver can reconstruct the secret messages. Each single photon in two degrees of freedom can carry two bits of information, so the cost of our protocol is less than others using entangled qubits. Moreover, the security of our QSDC network protocol is discussed comprehensively. It is shown that our new CQSDC protocol cannot only defend the outsider eavesdroppers’ several sorts of attacks but also the inside attacks. Besides, our protocol is feasible since the preparation and the measurement of single photon quantum states in both the polarization and the spatial-mode degrees of freedom are available with current quantum techniques.
With the increasing complexity of cyber threats and the emergence of quantum computing, enhancing secure communication is essential. This study explores an effective hybrid quantum key distribution (QKD) protocol that integrates photonic and atomic systems to leverage their respective strengths. The concept of symmetry plays a crucial role in this context, as it underpins the principles of entanglement and the balance between key generation and error correction. The photonic system is used for the initial key generation, while the atomic system facilitates entanglement swapping, error correction, and privacy amplification. The comprehensive theoretical framework encompasses key components, detailed security proofs, performance metrics, and an analysis of system vulnerabilities, illustrating the resilience of the hybrid protocol against potential threats. Extensive experimental studies demonstrate that the hybrid QKD protocol seamlessly integrates photonic and atomic systems, enabling secure key distribution with minimal errors and loss rates over long distances. This combination of the two systems reveals exceptional resilience against eavesdropping, significantly improving both security and robustness compared with traditional QKD protocols. Consequently, this makes it a compelling solution for secure communication in the increasingly digital world.
In this dissertation, it is realized a study of light polarization and its applications in quantum communications. Initially, the mathematical tools needed for single-photon and coherent states polarization analyses are presented: coherence matrix, Stokes parameters and polarization degree. Following, using numerical simulations, it is presented the variation of the degree of polarization of a single-photon pulse during depolarizing channel propagation. At last, the result of an experiment using coherent states, aiming to measure the degree of polarization after propagation in 200 m optical fiber is presented. The experiment is useful for determination of the parameter of the qubit depolarizing channel model. Since light polarization is easily changed when environment fluctuations are present during fiber propagation, optical schemes able to correct unpredictable polarization changes are studied. Such schemes are employed for error correction in quantum communication systems. Based on already proposed error correction schemes, two new schemes are proposed, one for systems that employs polarization of singlephoton light, and other for systems that employs polarization of two-mode coherent states, being the first active, that is, requiring a control and synchronism protocol, while the second is passive. At last, it is realized a security analysis of a quantum key distribution system, employing the proposed error correction scheme, when the same is under Fuch-Peres-Brandt attack. It is shown that using the proposed error correction scheme the presence of an eavesdropper monitoring the quantum channel is more visible.