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Quantum Cryptography Based on Orthogonal States  [PDF]
Lior Goldenberg,Lev Vaidman
Physics , 1995, DOI: 10.1103/PhysRevLett.75.1239
Abstract: All existing quantum cryptosystems use non-orthogonal states as the carriers of information. Non-orthogonal states cannot be cloned (duplicated) by an eavesdropper. In result, any eavesdropping attempt must introduce errors in the transmission, and therefore, can be detected by the legal users of the communication channel. Orthogonal states are not used in quantum cryptography, since they can be faithfully cloned without altering the transmitted data. In this Letter we present a cryptographic scheme based on orthogonal states, which also assures the detection of any eavesdropper.
Reply to Comment: Quantum Cryptography Based on Orthogonal States?  [PDF]
Lior Goldenberg,Lev Vaidman
Physics , 1996,
Abstract: This is our Reply to Peres' Comment [quant-ph/9509003] to "Quantum Cryptography Based on Orthogonal States" [Phys. Rev. Lett. 75, 1239 (1995)].
Security of Quantum Cryptography Against Trojan Horse Attacking
特洛依木马攻击下的量子密码安全性

ZENG Gui-Hua,
曾贵华

软件学报 , 2004,
Abstract: Trojan horse attacking strategy on quantum cryptography is investigated. First, the fragility of the quantum cryptographic algorithm employing EPR (Einstein-Podosky-Rosen) pairs as a key against the Trojan horse attacking strategy is analyzed. To prevent the Trojan horse attacking, an improved scheme which makes use of the non-orthogonal entangled states is proposed. This scheme is robust to the Trojan horse attacking, without reducing the security on other kinds of attacking strategies.
Scheme for the implementation of optimal cloning of two pairs of orthogonal states  [PDF]
Zhuo-Liang Cao,Wei Song
Physics , 2004, DOI: 10.1016/j.physleta.2004.03.073
Abstract: We propose a feasible scheme to implement the 1-to-2 optimal cloning transformation for two pairs of orthogonal states of two-dimensional quantum systems in the context of cavity QED. The copied qubits are shown to be inseparable by using Peres-Horodecki criterion.
A novel quantum key distribution scheme with orthogonal product states  [PDF]
Guo-Ping Guo,Chuan-Feng Li,Bao-Sen Shi,Jian Li,Guang-Can Guo
Physics , 2001, DOI: 10.1103/PhysRevA.64.042301
Abstract: The general conditions for the orthogonal product states of the multi-state systems to be used in quantum key distribution (QKD) are proposed, and a novel QKD scheme with orthogonal product states in the 3x3 Hilbert space is presented. We show that this protocol has many distinct features such as great capacity, high efficiency. The generalization to nxn systems is also discussed and a fancy limitation for the eavesdropper's success probability is reached.
Teleportation of one ququat encoded in single mode superposition of coherent states  [PDF]
Hari Prakash,Manoj K Mishra
Physics , 2012,
Abstract: Superposition of optical coherent states (SCS) Ket(plus/minus alpha), possessing opposite phases, plays an important role as qubits in quantum information processing tasks like quantum computation, teleportation, cryptography etc. and are of fundamental importance in testing quantum mechanics. Recently, ququats and qutrits defined in four and three dimensional (D) Hilbert space, respectively, have attracted much more attention as they present advantage in secure quantum communication and also in researches on the foundation of quantum mechanics. Here, we show that superposition of four non-orthogonal coherent states Ket(plus/minus alpha) and Ket(plus/minus i alpha), that are 90 degrees out of phase, can be employed for encoding one ququat defined in a 4D Hilbert space spanned by four newly defined multi-photonic states, Ket(alpha subscript j) with 4n+j numbers of photons, where, j= 0, 1, 2, 3. We propose a scheme which generates states Ket(alpha subscript j). When these states fall on a 50-50 beam splitter, the result is bipartite four-component entangled coherent state which represents equivalently an entangled ququat. Finally, we propose a linear optical scheme that gives almost perfect teleportation (minimum average fidelity greater than or equal to 0.99) of single ququat encoded in SCS using entangled ququat based on coherent states with almost perfect success rate for coherent amplitude mod(alpha) greater than or equal to 3.2. The present theoretical investigation and teleportation protocol is important in the sense that ququat allows the quantum information to be encoded and processed much more compactly and efficiently using fewer coupled quantum system.
Optimal eavesdropping in cryptography with three-dimensional quantum states  [PDF]
D. Bruss,C. Macchiavello
Physics , 2001, DOI: 10.1103/PhysRevLett.88.127901
Abstract: We study optimal eavesdropping in quantum cryptography with three-dimensional systems, and show that this scheme is more secure than protocols using two-dimensional states. We generalize the according eavesdropping transformation to arbitrary dimensions, and discuss the connection with optimal quantum cloning.
No-cloning of Orthogonal States in Composite Systems  [PDF]
Tal Mor
Physics , 1998, DOI: 10.1103/PhysRevLett.80.3137
Abstract: The no-cloning principle tells us that non-orthogonal quantum states cannot be cloned, but it does not tell us that orthogonal states can always be cloned. We suggest a situation where the cloning transformations are restricted, leading to a novel type of no-cloning principle. In the case of a composite system made of two subsystems: if the subsystems are only available one after the other then there are various cases when orthogonal states cannot be cloned. Surprising examples are given, which give a radically better insight regarding the basic concepts of quantum cryptography.
Quantum Cryptography using entangled photons in energy-time Bell states  [PDF]
W. Tittel,J. Brendel,H. Zbinden,N. Gisin
Physics , 1999, DOI: 10.1103/PhysRevLett.84.4737
Abstract: We present a setup for quantum cryptography based on photon pairs in energy-time Bell states and show its feasability in a laboratory experiment. Our scheme combines the advantages of using photon pairs instead of faint laser pulses and the possibility to preserve energy-time entanglement over long distances. Moreover, using 4-dimensional energy-time states, no fast random change of bases is required in our setup : Nature itself decides whether to measure in the energy or in the time base.
Quantum Cryptography Using Single Particle Entanglement  [PDF]
Jae-Weon Lee,Eok Kyun Lee,Yong Wook Chung,Hai-Woong Lee,Jaewan Kim
Physics , 2003, DOI: 10.1103/PhysRevA.68.012324
Abstract: A quantum cryptography scheme based on entanglement between a single particle state and a vacuum state is proposed. The scheme utilizes linear optics devices to detect the superposition of the vacuum and single particle states. Existence of an eavesdropper can be detected by using a variant of Bell's inequality.
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