This paper presents the use of a single photon entangled state to secure the transmission data via a wireless communication link and a biological tissue study where the encrypted data/qubit is prepared and formed by using a simple optical system. The encrypted data can transmit securely i.e. without cloning to theintended recipient via a public wireless link. We have shown that the result of the entangled states has good visibility for the use of data quantum encryption. The generated entangled photon for up-link via wireless communication is proposed and the problem of quantum cloning described. The biological tissue characterizations using such a short pulse can be realize by using a simple optical arrangement and components. Such an implemented system has the advantage of that the ultra-short pulse of a single photon with its quantum state identification can be used to provide the required measured data.
This paper presents the use of a single photon entangled state to secure the transmission data via a wireless communication link and a biological tissue study where the encrypted data/qubit is prepared and formed by using a simple optical system. The encrypted data can transmit securely i.e. without cloning to theintended recipient via a public wireless link. We have shown that the result of the entangled states has good visibility for the use of data quantum encryption. The generated entangled photon for up-link via wireless communication is proposed and the problem of quantum cloning described. The biological tissue characterizations using such a short pulse can be realize by using a simple optical arrangement and components. Such an implemented system has the advantage of that the ultra-short pulse of a single photon with its quantum state identification can be used to provide the required measured data.
Data encryption/decryption is a very important issue in communication and networks. In the absolute security technique of quantum security, the data are encrypted/decrypted by quantum transported channel. The transported signals are randomly coded/decoded by using the quantum entanglement pairs. The quantum entangle is created by using a single pulse i.e. single photon that occupies the random polarization states, where the required polarization states can be formed by sender and receiver at any time via a quantum channel. In this paper, the single pulse is created by a CW laser diode in the classical Mach-Zehnder interferometer. The single pulse is generated and detected when a light beam is modulated by signal from signal generator with suitable driven frequency on a LiNbO/sub 3/ crystal. Then the entanglement signals can be realized and transmitted via classical optical system. The quantum dense coding can also be performed by the technique of dense wavelength division multiplexing technique, where each transmitted wavelength can be randomly formed entanglement pairs and the dense code/decode schemes use via cable or wireless transmission.
The secure distribution of the secret random bit sequences known as `key' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is an emerging technology for secure key distribution with single-photon transmissions: Heisenburg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal single-photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single- photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. In our optical fiber experiment we have performed quantum key distribution over 24-km of underground optical fiber using single-photon interference states, demonstrating that secure, real-time key generation over `open' multi-km node-to-node optical fiber communications links is possible.
Quantum Key Distribution (QKD) is used in Quantum Cryptographic Systems to exchange secret key between parties who need to communicate secretly. Such a key can be used with a symmetric encryption schemes to establish a secure communication. Until recently, QKD is possible using optical fiber over few tens of kilometers but not more due to single photons getting absorbed by the fiber. There are no commercial wireless quantum crypto products yet, but QKD will soon be used in wireless medium from satellite to the earth so we could get 10,000 miles. But wireless medium brings its own problems. The energy transmitted via a wireless link spreads out, leading to higher and varying transmission losses, ambient daylight, or even light from the moon at night couple into the receiver, leading to a higher error rate. Interference from other photon sources air with clouds, dust and unsettled conditions creates intervention. In this paper, different techniques for communication in Quantum Cryptography using wireless networking infrastructure are discussed.
The secure distribution of the secret random bit sequences known as {open_quotes}key{close_quotes} material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is an emerging technology for secure key distribution with single-photon transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal single-photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. In our optical fiber experiment we have performed quantum key distribution over 24-km of underground optical fiber using single-photon interference states, demonstrating that secure, real-time key generation over {open_quotes}open{close_quotes} multi-km node-to-node optical fiber communications links is possible. We have also constructed a quantum key distribution system for free-space, line-of-sight transmission using single-photon polarization states, which is currently undergoing laboratory testing. 7 figs.
Two deterministic secure quantum communication schemes are proposed, one based on pure entangled states and the other on d-dimensional single-photon states. In these two schemes, only single-photon measurements are required for the two authorized users, which makes the schemes more convenient than others in practical applications. Although each qubit can be read out after a transmission of additional classical bit, it is unnecessary for the users to transmit qubits double the distance between the sender and the receiver, which will increase their bit rate and their security. The parties use decoy photons to check eavesdropping efficiently. The obvious advantage in the first scheme is that the pure entangled source is feasible with present techniques.
At the heart of quantum physics lies the principle of superposition, and at the heart of information theory lies the bit. Perhaps the most useful property of quantum systems is that they can be loaded with information bits, so-called qubits, that are indefinitely both 0 and 1 until a measurement is made. Another consequence is that several qubits can become entangled, which is manifested by the non-classical correlations between such quantum systems when measured in all possible bases. Within the rapidly progressing fields of quantum information and quantum communication these quantum effects are utilized to perform tasks such as quantum computing and quantum cryptography. In this thesis we present experimental and theoretical work using single photon sources to prepare ``flying'' photonic qubits. We describe work using mainly quasi-phase-matched nonlinear crystals to generate beams of entangled photon pairs, that are either encoded in polarization at near-visible wavelengths, or in time at optical fiber telecommunication wavelengths (1550 nm). The optical fiber is the medium used for transporting the qubits over a long distance, and it is therefore essential to couple the photons well into the fibers. By focusing the beams optimally, we have investigated how this problem can meet the requirement of creating photons of a narrow frequency bandwidth and a high photon flux. Furthermore, we have generated truly single photons that are heralded by an electrical signal. As a result of modifying the statistics of such sources we have been able to show the effect of photon antibunching. In two separate works, we have implemented a quantum key distribution system based on faint laser pulses at the telecom wavelength of 1550 nm, as well as protocols based on entanglement for performing authentication of key distribution in quantum cryptography.