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arXiv:1503.00451 · Light Science & Applications

Experimental quantum secure direct communication with single photons

Jianyong Hu, Bo Yu, Mingyong Jing, Liantuan Xiao, Suotang Jia, Guo‐Qing Qin, Gui‐Lu Long

Published Apr 7, 2016• 421 citations
arXivHTMLPDF

Abstract

Quantum secure direct communication is an important mode of quantum communication in which secret messages are securely communicated directly over a quantum channel. Quantum secure direct communication is also a basic cryptographic primitive for constructing other quantum communication tasks, such as quantum authentication and quantum dialog. Here, we report the first experimental demonstration of quantum secure direct communication based on the DL04 protocol and equipped with single-photon frequency coding that explicitly demonstrated block transmission. In our experiment, we provided 16 different frequency channels, equivalent to a nibble of four-bit binary numbers for direct information transmission. The experiment firmly demonstrated the feasibility of quantum secure direct communication in the presence of noise and loss.

DOI
10.1038/lsa.2016.144

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Quantum secure direct communication is an important mode of quantum communication in which secret messages are securely communicated directly over a quantum channel. Quantum secure direct communication is also a basic cryptographic primitive for constructing other quantum communication tasks, such as quantum authentication and quantum dialog. Here, we report the first experimental demonstration of quantum secure direct communication based on the DL04 protocol and equipped with single-photon frequency coding that explicitly demonstrated block transmission. In our experiment, we provided 16 different frequency channels, equivalent to a nibble of four-bit binary numbers for direct information transmission. The experiment firmly demonstrated the feasibility of quantum secure direct communication in the presence of noise and loss.
Quantum secure direct communication (QSDC) can guarantee security using the characteristics of quantum mechanics even when a message is directly transmitted through a quantum channel without using a secret key. However, the transmission rate of the QSDC is limited by the dead time of a single photon detector (SPD) as well as channel loss over the distance. To overcome this limited transmission rate, we propose a high-dimensional single photon-based QSDC protocol that applies two optical degrees of freedom: time and phase state. First, an N-dimensional time and phase state generation method that considers the dead time is proposed to minimize the measurement loss of a transmitted message. Second, among the two types of quantum states, the phase state with relatively low measurement efficiency is used only for eavesdropping detection, and the time state is used for sending messages with differential delay time bin-based encoding techniques. Lastly, we propose an efficient method for measuring N-dimensional time and phase-based quantum states and recovering classical bit information. This study performs security analysis against various attacks, and verifies the transmission rate improvement effect through simulation. The result indicates that our proposal can guarantee higher security and transmission rates compared to the conventional DL04 QSDC.
Quantum secure direct communication is the direct communication of secret messages without first producing a shared secret key. It may be used in some urgent circumstances. Here we propose a quantum secure direct communication protocol using single photons. The protocol uses batches of single photons prepared randomly in one of four different states. These single photons serve as a one-time pad which is used directly to encode the secret messages in one communication process. We also show that it is unconditionally secure. The protocol is feasible with present-day technique.
A quantum high secure direct communication with authentication protocol is proposed by using single photons. The high security of the protocol is achieved on levels. The first level involves the verification of the quantum channel security by using fake photons. The authentication process is also ensured by the fake photons. The second level of security is given by the use of multiple polarization bases. The secret message is encoded in groups of photons; each single character of the message is associated with m (m≥7) photons. Thus, at least 27(128) characters will be encoded. In order to defeat the quantum teleportation attack, the string of bits associated to the secret message is encrypted with a secret string of bits by using XOR operator. Encryption of the sender's identity string and the receiver's identity string by the XOR operator with a random string of fake photons defends quantum man-in-the-middle attack efficiently. Quantum memory is required to implement our protocol. Storage of quantum information is a key element in quantum information processing and provides a more flexible, effective and efficient communication. Our protocol is feasible with current technologies.
Quantum secure direct communication (QSDC) is an important branch of quantum communication that is capable of directly transmitting secret messages over a quantum channel. It may be viewed as a concrete realization of Wyner's wiretap channel theory, which ensures the reliable and secure communication of information in the presence of noise and eavesdropping. Hence it is a fully-fledged quantum-communications protocol, which does not require a separate secret key negotiation phase. By contrast, its quantum key distribution (QKD) counterpart represents a secret key-negotiation protocol, which has to be followed up by a separate classical communication session. The essential difference between these two modes of quantum communication lies in the employment of a block-based data transmission technique, proposed by Long and Liu in 2000. However, the original block-based data transmission requires quantum memory, which is not widely available at the time of writing. Recently, this difficulty has been overcome by using classical coding theory, which has been successfully applied to the single-qubit DL04 QSDC. Here we will present a single-photon-memory QSDC protocol based on entangled pairs of photons. We commence by comparing QSDC to QKD, followed by an example of the single-photon QSDC and single-photon QKD protocol. Then we continue by modifying the so-called two-step QSDC protocol designed for deterministic QKD by reducing the number of qubits in a block into a single one, in which Alice prepares Einstein-Podolsky-Rosen (EPR) photon pairs and partitions them into two parts: the so-called pioneer qubit and the follow-up qubit. The pioneer photon is transferred first to Bob, while the follow-up photon is used either for performing encoding or for eavesdropping detection. Bob extracts the candidate key by combining the two particles of the EPR pair to perform Bell-basis measurement. Then the protocol is transformed into a single-photon-memory QSDC using coding theory. Our theoretical analysis shows that the resultant protocol is robust to individual attacks. Additionally, a high communication efficiency is achieved.
Quantum communication provides an absolute security advantage, and it has been widely developed over the past 30 years. As an important branch of quantum communication, quantum secure direct communication (QSDC) promotes high security and instantaneousness in communication through directly transmitting messages over a quantum channel. The full implementation of a quantum protocol always requires the ability to control the transfer of a message effectively in the time domain; thus, it is essential to combine QSDC with quantum memory to accomplish the communication task. In this Letter, we report the experimental demonstration of QSDC with state-of-the-art atomic quantum memory for the first time in principle. We use the polarization degrees of freedom of photons as the information carrier, and the fidelity of entanglement decoding is verified as approximately 90%. Our work completes a fundamental step toward practical QSDC and demonstrates a potential application for long-distance quantum communication in a quantum network.
Quantum secure direct communication (QSDC) is an important branch of quantum cryptography. It can transmit secret information directly without establishing a key first, unlike quantum key distribution which requires this precursive event. One of the most highlighted QSDC protocol is the Two-step protocol. This paper will focus on proposing a frequency coding scheme in the Two-step protocol, while retaining other contents of the QSDC protocol. This new coding scheme will significantly increase the protocol’s ability against channel noise and loss, and provides an efficient protocol for secure direct quantum communication in a noisy environment. Besides, the frequency coding technology is also easy to understand and highly practical. After numerically simulating the performance of the protocol in a noisy channel, the results showed that the scheme was robust against channel noise and loss.