Implementations Of Quantum Cryptography Research Articles

Quantum cryptography for secured communication networks

Quantum cryptography is a method for accessing data with the cryptosystem more efficiently. The network security and the cryptography are the two major properties in securing the data in the communication network. The quantum cryptography uses the single photon passing through the polarization of a photon. In Quantum Cryptography, it's impossible for the eavesdropper to copy or modify the encrypted messages in the quantum states in which we are sending through the optical fiber channels. Cryptography performed by using the protocols BB84 and B92 protocols. The two basic algorithms of quantum cryptography are Shor’s algorithm and the Grover’s’s algorithm. For finding the number of integer factorization of each photon, Shor’s algorithm is used. Grover’s’s algorithm used for searching the unsorted data. Shor’s algorithm overcomes RSA algorithm by high security. By the implementation of quantum cryptography, we are securing the information from the eavesdropper and thereby preventing data in the communication channel.

Efficient semiquantum key distribution without entanglement

Semiquantum cryptography was proposed to deal with the issue that some players require only partial quantum power, such as preparing or measuring quantum states in the classical basis, which simplifies the implementations of quantum cryptography. However, the efficiency of the existing semiquantum cryptographic protocols was relatively low from a practical point of view. In this paper, we devise improved semiquantum key distribution (SQKD) protocols to improve the efficiency of SQKD protocols. Our improved SQKD protocols utilize the discarded X-SIFT bits in the previous SQKD protocols for improving the efficiency of previous SQKD protocols (Boyer et al. in Phys Rev Lett 99:140501, 2007; Zou et al. in Phys Rev A 79:052312, 2009). Besides, the efficiency of our new protocols can be made asymptotically close to 100% by letting players select their actions asymmetrically. We prove the information theoretical secure of the proposed SQKD protocols against the most general attacks. Our security proof is suitable for the single-state SQKD protocol (Zou et al. in Phys Rev A 79:052312, 2009).

Necessary detection efficiencies for secure quantum key distribution and bound randomness

In recent years, several hacking attacks have broken the security of quantum cryptography implementations by exploiting the presence of losses and the ability of the eavesdropper to tune detection efficiencies. We present a simple attack of this form that applies to any protocol in which the key is constructed from the results of untrusted measurements performed on particles coming from an insecure source or channel. Because of its generality, the attack applies to a large class of protocols, from standard prepare-and-measure to device-independent schemes. Our attack gives bounds on the critical detection efficiencies necessary for secure quantum distribution, which show that the implementation of most partly device independent solutions is, from the point of view of detection efficiency, almost as demanding as fully device-independent ones. We also show how our attack implies the existence of a form of bound randomness, namely non-local correlations in which a non-signalling eavesdropper can find out a posteriori the result of any implemented measurement.

Key Distribution using Dual Channel Technique for Ultimate Security

Background: A new approach for the implementation of Quantum Cryptography is proposed in this paper. Quantum Cryptography has practical weakness like lack of authentication, single photon generation and many real time implementation problems. This paper also explains how the drawback of BB84 protocol is eliminated by combining Classical Cryptography and Quantum techniques. Methods: We analyze the usage of Dual Channel Interferometer technique and thereby fusing Quantum techniques with classical technique. And their combination result in the feasibility of authentication, and hacker identification, thereby introducing a novel method of QKD transmission. A quantum digital authentication scheme based on hash function is proposed in this paper .The security of the quantum protocol lies on the existence of quantum one way function by fundamental quantum principle. The practical difficulties in quantum control and quantum computation made quantum protocol hard to implement. The lack of authentication made the quantum protocol vulnerable to hackers. Introducing two level quantum system authentications can be achieved with the help of hash function. To guarantee the authenticity, hash codes are split into two parts and exchange of code is made through two quantum channels. This scheme uses a programmable polarizer ensuring the quantum one way function and removing the practical difficulties of quantum control and quantum computation. The proposed scheme presents a novel method to construct secure quantum authentication for future communication. Result: Dual channel implementation helps in implementing authentication in quantum BB84 protocol. We combined the advantages of quantum techniques and classical techniques and tried to implement a novel technique to ensure secure communication. Application: People use the ATM for transactions such as cash withdrawal, money transfer and payment of electricity and telephone bills. ATM is the most convenient to access the accounts and funding transactions. Personal Identification Number (PIN) is an important aspect of the current ATM system in providing security and it is a commonly used method in protecting the transaction of one’s account.By implementing above technique ATM pin transfer can be successfully made.

Long-distance quantum communication over noisy networks without long-time quantum memory

The problem of sharing entanglement over large distances is crucial for implementations of quantum cryptography. A possible scheme for long-distance entanglement sharing and quantum communication exploits networks whose nodes share Einstein-Podolsky-Rosen (EPR) pairs. In Perseguers et al. [Phys. Rev. A 78, 062324 (2008)] the authors put forward an important isomorphism between storing quantum information in a dimension $D$ and transmission of quantum information in a $D+1$-dimensional network. We show that it is possible to obtain long-distance entanglement in a noisy two-dimensional (2D) network, even when taking into account that encoding and decoding of a state is exposed to an error. For 3D networks we propose a simple encoding and decoding scheme based solely on syndrome measurements on 2D Kitaev topological quantum memory. Our procedure constitutes an alternative scheme of state injection that can be used for universal quantum computation on 2D Kitaev code. It is shown that the encoding scheme is equivalent to teleporting the state, from a specific node into a whole two-dimensional network, through some virtual EPR pair existing within the rest of network qubits. We present an analytic lower bound on fidelity of the encoding and decoding procedure, using as our main tool a modified metric on space-time lattice, deviating from a taxicab metric at the first and the last time slices.

Security proof of counterfactual quantum cryptography against general intercept-resend attacks and its vulnerability

Counterfactual quantum cryptography, recently proposed by Noh, is featured with no transmission of signal particles. This exhibits evident security advantages, such as its immunity to the well-known photon-number-splitting attack. In this paper, the theoretical security of counterfactual quantum cryptography protocol against the general intercept-resend attacks is proved by bounding the information of an eavesdropper Eve more tightly than in Yin's proposal [Phys. Rev. A 82 042335 (2010)]. It is also shown that practical counterfactual quantum cryptography implementations may be vulnerable when equipped with imperfect apparatuses, by proving that a negative key rate can be achieved when Eve launches a time-shift attack based on imperfect detector efficiency.

Experimental implementation of higher dimensional time–energy entanglement

Qudit entangled states have proven to offer significant advantages with respect to qubit states regarding the implementation of quantum cryptography or computation schemes. Here we propose and experimentally implement a scalable scheme for preparing and analyzing these states in the time–energy degree of freedom of two-photon pairs. Using the scheme, the entanglement of (2×4)-dimensional states is demonstrated.

A spintronic source of circularly polarized single photons

We present a spintronic single photon source which emits circularly polarized light, where the helicity is determined by an applied magnetic field. Photons are emitted from an InGaAs quantum dot inside an electrically operated spin light-emitting diode, which comprises the diluted magnetic semiconductor ZnMnSe. The circular polarization degree of the emitted light is high, reaching 83% at an applied magnetic field of 2 T and 96% at 6 T. Autocorrelation traces recorded in pulsed operation mode prove the emitted light to be antibunched. The two circular polarization states could be used for representing quantum states |0⟩ and |1⟩ in quantum cryptography implementations.

Polarization states encoded by phase modulation for high bit rate quantum key distribution

We present implementation of quantum cryptography with polarization code by wave-guide type phase modulator. At four different low input voltages of the phase modulator, coder encodes pulses into four different polarization states, 45°, 135° linearly polarized or right, left circle polarized, while the decoder serves as the complementary polarizers.

Eavesdropping on practical QKD system based on six-state protocol

Based on practical implementations of quantum cryptography with the attenuated laser pulses as the signal source rather than single photon, as well as lossy channels, detection efficiency, dark count of singlephoton counter, and technological possibilities of a realistic eavesdropping, we discuss a combining eavesdropping strategy of Breidbart basis and beamsplitting, and give a bound on maximum disturbance for a given mean photon number and transmission length for which a secret key can be distilled.

Demonstration of a low-noise near-infrared photon counter with multiphoton discrimination

We have demonstrated a system capable of directly measuring the photon-number state of a single pulse of light using a superconducting transition-edge sensor microcalorimeter. We verify the photon-number distribution of a weak pulsed-laser source at 1550 nm. Such single-photon metrology at telecommunication wavelengths provides the foundation for ensuring the security of photon sources used in implementations of quantum cryptography. Additionally, this system has the lowest noise equivalent power of any single-photon detector and combines high efficiency near-infrared photon counting with the ability to resolve multiphoton absorption events.