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Sample records for quantum key distribution

  1. Quantum dense key distribution

    CERN Document Server

    Degiovanni, I P; Castelletto, S; Rastello, M L; Bovino, F A; Colla, A M; Castagnoli, G C

    2004-01-01

    This paper proposes a new protocol for quantum dense key distribution. This protocol embeds the benefits of a quantum dense coding and a quantum key distribution and is able to generate shared secret keys four times more efficiently than BB84 one. We hereinafter prove the security of this scheme against individual eavesdropping attacks, and we present preliminary experimental results, showing its feasibility.

  2. Quantum Key Distribution

    Science.gov (United States)

    Seshu, Ch.

    Quantum Key Distribution (QKD) uses Quantum Mechanics to guarantee secure communication. It enables two parties to produce a shared random bit string known only to them, which can be used as a key to encrypt and decrypt messages.

  3. Efficient Quantum Key Distribution

    CERN Document Server

    Ardehali, M; Chau, H F; Lo, H K

    1998-01-01

    We devise a simple modification that essentially doubles the efficiency of a well-known quantum key distribution scheme proposed by Bennett and Brassard (BB84). Our scheme assigns significantly different probabilities for the different polarization bases during both transmission and reception to reduce the fraction of discarded data. The actual probabilities used in the scheme are announced in public. As the number of transmitted signals increases, the efficiency of our scheme can be made to approach 100%. The security of our scheme (against single-photon eavesdropping strategies) is guaranteed by a refined analysis of accepted data which is employed to detect eavesdropping: Instead of lumping all the accepted data together to estimate a single error rate, we separate the accepted data into various subsets according to the basis employed and estimate an error rate for each subset individually. Our scheme is the first quantum key distribution with an efficiency greater than 50%. We remark that our idea is rath...

  4. Security of Quantum Key Distribution

    CERN Document Server

    Renner, R

    2005-01-01

    We propose various new techniques in quantum information theory, including a de Finetti style representation theorem for finite symmetric quantum states. As an application, we give a proof for the security of quantum key distribution which applies to arbitrary protocols.

  5. Quantum cryptography beyond quantum key distribution

    NARCIS (Netherlands)

    A. Broadbent (Anne); C. Schaffner (Christian)

    2016-01-01

    textabstractQuantum cryptography is the art and science of exploiting quantum mechanical effects in order to perform cryptographic tasks. While the most well-known example of this discipline is quantum key distribution (QKD), there exist many other applications such as quantum money, randomness

  6. Quantum cryptography beyond quantum key distribution

    NARCIS (Netherlands)

    Broadbent, A.; Schaffner, C.

    2016-01-01

    Quantum cryptography is the art and science of exploiting quantum mechanical effects in order to perform cryptographic tasks. While the most well-known example of this discipline is quantum key distribution (QKD), there exist many other applications such as quantum money, randomness generation,

  7. Quantum cryptography beyond quantum key distribution

    NARCIS (Netherlands)

    Broadbent, A.; Schaffner, C.

    2016-01-01

    Quantum cryptography is the art and science of exploiting quantum mechanical effects in order to perform cryptographic tasks. While the most well-known example of this discipline is quantum key distribution (QKD), there exist many other applications such as quantum money, randomness generation, secu

  8. Decoy State Quantum Key Distribution

    Science.gov (United States)

    Lo, Hoi-Kwong

    2005-10-01

    Quantum key distribution (QKD) allows two parties to communicate in absolute security based on the fundamental laws of physics. Up till now, it is widely believed that unconditionally secure QKD based on standard Bennett-Brassard (BB84) protocol is limited in both key generation rate and distance because of imperfect devices. Here, we solve these two problems directly by presenting new protocols that are feasible with only current technology. Surprisingly, our new protocols can make fiber-based QKD unconditionally secure at distances over 100km (for some experiments, such as GYS) and increase the key generation rate from O(η2) in prior art to O(η) where η is the overall transmittance. Our method is to develop the decoy state idea (first proposed by W.-Y. Hwang in "Quantum Key Distribution with High Loss: Toward Global Secure Communication", Phys. Rev. Lett. 91, 057901 (2003)) and consider simple extensions of the BB84 protocol. This part of work is published in "Decoy State Quantum Key Distribution", . We present a general theory of the decoy state protocol and propose a decoy method based on only one signal state and two decoy states. We perform optimization on the choice of intensities of the signal state and the two decoy states. Our result shows that a decoy state protocol with only two types of decoy states--a vacuum and a weak decoy state--asymptotically approaches the theoretical limit of the most general type of decoy state protocols (with an infinite number of decoy states). We also present a one-decoy-state protocol as a special case of Vacuum+Weak decoy method. Moreover, we provide estimations on the effects of statistical fluctuations and suggest that, even for long distance (larger than 100km) QKD, our two-decoy-state protocol can be implemented with only a few hours of experimental data. In conclusion, decoy state quantum key distribution is highly practical. This part of work is published in "Practical Decoy State for Quantum Key Distribution

  9. Symmetric autocompensating quantum key distribution

    Science.gov (United States)

    Walton, Zachary D.; Sergienko, Alexander V.; Levitin, Lev B.; Saleh, Bahaa E. A.; Teich, Malvin C.

    2004-08-01

    We present quantum key distribution schemes which are autocompensating (require no alignment) and symmetric (Alice and Bob receive photons from a central source) for both polarization and time-bin qubits. The primary benefit of the symmetric configuration is that both Alice and Bob may have passive setups (neither Alice nor Bob is required to make active changes for each run of the protocol). We show that both the polarization and the time-bin schemes may be implemented with existing technology. The new schemes are related to previously described schemes by the concept of advanced waves.

  10. Quantum Key Distribution over Probabilistic Quantum Repeaters

    CERN Document Server

    Amirloo, Jeyran; Majedi, A Hamed

    2010-01-01

    A feasible route towards implementing long-distance quantum key distribution (QKD) systems relies on probabilistic schemes for entanglement distribution and swapping as proposed in the work of Duan, Lukin, Cirac, and Zoller (DLCZ) [Nature 414, 413 (2001)]. Here, we calculate the conditional throughput and fidelity of entanglement for DLCZ quantum repeaters, by accounting for the DLCZ self-purification property, in the presence of multiple excitations in the ensemble memories as well as loss and other sources of inefficiency in the channel and measurement modules. We then use our results to find the generation rate of secure key bits for QKD systems that rely on DLCZ quantum repeaters. We compare the key generation rate per logical memory employed in the two cases of with and without a repeater node. We find the cross-over distance beyond which the repeater system outperforms the non-repeater one. That provides us with the optimum inter-node distancing in quantum repeater systems. We also find the optimal exci...

  11. Microwave Photonics Parallel Quantum Key Distribution

    CERN Document Server

    Mora, Jose; Amaya, Waldimar; Martinez, Alfonso; Munoz, Victor Garcia-; Calvo, David; Capmany, Jose

    2011-01-01

    The incorporation of multiplexing techniques used in Microwave Photonics to Quantum Key Distribution (QKD) systems bring important advantages enabling the simultaneous and parallel delivery of multiple keys between a central station and different end-users in the context of multipoint access and metropolitan networks, or by providing higher key distribution rates in point to point links by suitably linking the parallel distributed keys. It also allows the coexistence of classical information and quantum key distribution channels over a single optical fibre infrastructure. Here we show, for the first time to our knowledge, the successful operation of a two domain (subcarrier and wavelength division) multiplexed strong reference BB84 quantum key distribution system. A four independent channel QKD system featuring 10 kb/s/channel over an 11 km link with Quantum Bit Error Rate (QBER) < 2 % is reported. These results open the way for multi-quantum key distribution over optical fiber networks.

  12. Nonorthogonal Decoy-State Quantum Key Distribution

    Institute of Scientific and Technical Information of China (English)

    LI Jing-Bo; FANG Xi-Ming

    2006-01-01

    @@ In practical quantum key distribution (QKD), weak coherent states as the photon source have a limit in the secure key rate and transmission distance because of the existence of multi-photon pulses and heavy loss in transmission line.

  13. Quantum Key Distribution Protocol with Private-Public Key

    OpenAIRE

    Serna, Eduin H.

    2009-01-01

    A quantum cryptographic protocol based in public key cryptography combinations and private key cryptography is presented. Unlike the BB84 protocol [1] and its many variants [2,3] two quantum channels are used. The present research does not make reconciliation mechanisms of information to derive the key. A three related system of key distribution are described.

  14. Quantum Key Distribution Protocol with User Authentication

    CERN Document Server

    Lee, H; Lee, D; Lim, J; Yang, H J; Lee, Hwayean; Lee, Sangjin; Lee, Donghoon; Lim, Jongin; Yang, HyungJin

    2005-01-01

    We propose a quantum key distribution protocol with quantum based user authentication. User authentication is executed by validating the correlation of GHZ states. Alice and Bob can distribute a secure key using the remaining GHZ states after authentication. This secret key does not leak even to the arbitrator by the properties of the entanglement. We will show that our protocol is secure against the cloning attack.

  15. Failure of Kak quantum key distribution protocol

    Indian Academy of Sciences (India)

    Ching-Nung Yang; Su-Hsuan Chu; Bing-Ling Lu

    2005-01-01

    Kak's quantum key distribution (QKD) protocol provides not only the distribution but also the integrity of secret key simultaneously in quantum channel. Consequently the additional exchange of information, used to check whether an eavesdropper exists, is unnecessary. In this comment, we will point out the failure of Kak's protocol and show that Kak's protocol does not have the joint distribution and integration that the author declares in [1].

  16. Interactive simulations for quantum key distribution

    CERN Document Server

    Kohnle, Antje

    2016-01-01

    Secure communication protocols are becoming increasingly important, e.g. for internet-based communication. Quantum key distribution allows two parties, commonly called Alice and Bob, to generate a secret sequence of 0s and 1s called a key that is only known to themselves. Classically, Alice and Bob could never be certain that their communication was not compromised by a malicious eavesdropper. Quantum mechanics however makes secure communication possible. The fundamental principle of quantum mechanics that taking a measurement perturbs the system (unless the measurement is compatible with the quantum state) also applies to an eavesdropper. Using appropriate protocols to create the key, Alice and Bob can detect the presence of an eavesdropper by errors in their measurements. As part of the QuVis Quantum Mechanics Visualization Project, we have developed a suite of four interactive simulations that demonstrate the basic principles of three different quantum key distribution protocols. The simulations use either...

  17. Security of quantum key distribution source

    OpenAIRE

    Simonsen, Eivind Sjøtun

    2010-01-01

    Cryptography has begun its journey into the field of quantum information theory. Classical cryptography has shown weaknesses, which may be exploited in the future, either by development in mathematics, or by quantum computers. Quantum key distribution (QKD) is a promising path for cryptography to enable secure communication in the future. Although the theory of QKD promises absolute security, the reality is that current quantum crypto systems have flaws in them, as perfect devices have proven...

  18. Quantum key distribution network for multiple applications

    Science.gov (United States)

    Tajima, A.; Kondoh, T.; Ochi, T.; Fujiwara, M.; Yoshino, K.; Iizuka, H.; Sakamoto, T.; Tomita, A.; Shimamura, E.; Asami, S.; Sasaki, M.

    2017-09-01

    The fundamental architecture and functions of secure key management in a quantum key distribution (QKD) network with enhanced universal interfaces for smooth key sharing between arbitrary two nodes and enabling multiple secure communication applications are proposed. The proposed architecture consists of three layers: a quantum layer, key management layer and key supply layer. We explain the functions of each layer, the key formats in each layer and the key lifecycle for enabling a practical QKD network. A quantum key distribution-advanced encryption standard (QKD-AES) hybrid system and an encrypted smartphone system were developed as secure communication applications on our QKD network. The validity and usefulness of these systems were demonstrated on the Tokyo QKD Network testbed.

  19. Free-space quantum key distribution

    CERN Document Server

    Buttler, W T; Kwiat, P G; Luther, G G; Morgan, G L; Nordholt, J E; Peterson, C G; Simmons, C M

    1998-01-01

    A working free-space quantum key distribution (QKD) system has been developed and tested over a 205-m indoor optical path at Los Alamos National Laboratory under fluorescent lighting conditions. Results show that free-space QKD can provide secure real-time key distribution between parties who have a need to communicate secretly.

  20. Quantum key distribution using three basis states

    Indian Academy of Sciences (India)

    Subhash Kak

    2000-05-01

    This note presents a method of public key distribution using quantum communication of photons that simultaneously provides a high probability that the bits have not been tampered. It is a variant of the quantum method of Bennett and Brassard (BB84) where the transmission states have been decreased from 4 to 3 and the detector states have been increased from 2 to 3. Under certain assumptions regarding method of attack, it provides superior performance (in terms of the number of usable key bits) for < 18, where is the number of key bits used to verify the integrity of the process in the BB84-protocol.

  1. Frequency-coded quantum key distribution.

    Science.gov (United States)

    Bloch, Matthieu; McLaughlin, Steven W; Merolla, Jean-Marc; Patois, Frédéric

    2007-02-01

    We report an intrinsically stable quantum key distribution scheme based on genuine frequency-coded quantum states. The qubits are efficiently processed without fiber interferometers by fully exploiting the nonlinear interaction occurring in electro-optic phase modulators. The system requires only integrated off-the-shelf devices and could be used with a true single-photon source. Preliminary experiments have been performed with weak laser pulses and have demonstrated the feasibility of this new setup.

  2. Numerical approach for unstructured quantum key distribution

    Science.gov (United States)

    Coles, Patrick J.; Metodiev, Eric M.; Lütkenhaus, Norbert

    2016-05-01

    Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret key rate for a given protocol. Analytical formulas are known for protocols with symmetries, since symmetry simplifies the analysis. However, experimental imperfections break symmetries, hence the effect of imperfections on key rates is difficult to estimate. Furthermore, it is an interesting question whether (intentionally) asymmetric protocols could outperform symmetric ones. Here we develop a robust numerical approach for calculating the key rate for arbitrary discrete-variable QKD protocols. Ultimately this will allow researchers to study `unstructured' protocols, that is, those that lack symmetry. Our approach relies on transforming the key rate calculation to the dual optimization problem, which markedly reduces the number of parameters and hence the calculation time. We illustrate our method by investigating some unstructured protocols for which the key rate was previously unknown.

  3. Quantum Key Distribution Using Decoy State Protocol

    Directory of Open Access Journals (Sweden)

    Sellami Ali

    2009-01-01

    Full Text Available Problem statement: Quantum key distribution provides unconditional security guaranteed by the fundamental laws of quantum physics. Unfortunately, for real-life experimental set-ups, which mainly based on faint laser pulses, the occasional production of multi-photons and channel loss make it possible for sophisticated eavesdroppers to launch various subtle eavesdropping attacks including the Photon Number Splitting (PNS attack. The decoy state protocols recently proposed to beat PNS attack and to improve dramatically distance and secure key generation rate of Quantum Key Distribution (QKD. Approach: Objective of this study was experimental implementation of weak decoy + vacuum states QKD for increasing the performance of QKD system. To show conceptually how simple it was to apply the weak decoy + vacuum state idea to a commercial QKD system, we chosen ID-3000 commercial quantum key distribution system manufactured by id quantique. To implement the weak decoy + vacuum state protocol, we had to add some new optical and electronics components to id quantique and to attenuate each signal to the intensity of either signal state or weak decoy or vacuum state randomly. Results: In our implementation, the attenuation will be done by placing a VOA (variable optical attenuator in Alice’s side. Specifically, our QKD system required the polarizations of 2 pulses from the same signal to be orthogonal. Therefore the VOA must be polarization independent so as to attenuate the two pulses equally. The VOA utilized in experiment to attenuate signals dynamically was Intensity Modulator (IM. We had implemented weak + vacuum protocol on a modified commercial QKD system over a 25 km of telecom fibers with an unconditionally secure key rate of 6.2931x10-4 per pulse. Conclusion: By making simple modifications to a commercial quantum key distribution system, we could achieve much better performance with substantially higher key generation rate and longer distance than

  4. Two-Layer Quantum Key Distribution

    CERN Document Server

    Ramos, Rubens Viana

    2012-01-01

    Recently a new quantum key distribution protocol using coherent and thermal states was proposed. In this work this kind of two-layer QKD protocol is formalized and its security against the most common attacks, including external control and Trojan horse attacks, is discussed.

  5. Satellite-to-ground quantum key distribution

    Science.gov (United States)

    Liao, Sheng-Kai; Cai, Wen-Qi; Liu, Wei-Yue; Zhang, Liang; Li, Yang; Ren, Ji-Gang; Yin, Juan; Shen, Qi; Cao, Yuan; Li, Zheng-Ping; Li, Feng-Zhi; Chen, Xia-Wei; Sun, Li-Hua; Jia, Jian-Jun; Wu, Jin-Cai; Jiang, Xiao-Jun; Wang, Jian-Feng; Huang, Yong-Mei; Wang, Qiang; Zhou, Yi-Lin; Deng, Lei; Xi, Tao; Ma, Lu; Hu, Tai; Zhang, Qiang; Chen, Yu-Ao; Liu, Nai-Le; Wang, Xiang-Bin; Zhu, Zhen-Cai; Lu, Chao-Yang; Shu, Rong; Peng, Cheng-Zhi; Wang, Jian-Yu; Pan, Jian-Wei

    2017-09-01

    Quantum key distribution (QKD) uses individual light quanta in quantum superposition states to guarantee unconditional communication security between distant parties. However, the distance over which QKD is achievable has been limited to a few hundred kilometres, owing to the channel loss that occurs when using optical fibres or terrestrial free space that exponentially reduces the photon transmission rate. Satellite-based QKD has the potential to help to establish a global-scale quantum network, owing to the negligible photon loss and decoherence experienced in empty space. Here we report the development and launch of a low-Earth-orbit satellite for implementing decoy-state QKD—a form of QKD that uses weak coherent pulses at high channel loss and is secure because photon-number-splitting eavesdropping can be detected. We achieve a kilohertz key rate from the satellite to the ground over a distance of up to 1,200 kilometres. This key rate is around 20 orders of magnitudes greater than that expected using an optical fibre of the same length. The establishment of a reliable and efficient space-to-ground link for quantum-state transmission paves the way to global-scale quantum networks.

  6. Experimental quantum key distribution with source flaws

    Science.gov (United States)

    Xu, Feihu; Wei, Kejin; Sajeed, Shihan; Kaiser, Sarah; Sun, Shihai; Tang, Zhiyuan; Qian, Li; Makarov, Vadim; Lo, Hoi-Kwong

    2015-09-01

    Decoy-state quantum key distribution (QKD) is a standard technique in current quantum cryptographic implementations. Unfortunately, existing experiments have two important drawbacks: the state preparation is assumed to be perfect without errors and the employed security proofs do not fully consider the finite-key effects for general attacks. These two drawbacks mean that existing experiments are not guaranteed to be proven to be secure in practice. Here, we perform an experiment that shows secure QKD with imperfect state preparations over long distances and achieves rigorous finite-key security bounds for decoy-state QKD against coherent attacks in the universally composable framework. We quantify the source flaws experimentally and demonstrate a QKD implementation that is tolerant to channel loss despite the source flaws. Our implementation considers more real-world problems than most previous experiments, and our theory can be applied to general discrete-variable QKD systems. These features constitute a step towards secure QKD with imperfect devices.

  7. Multiple-Access Quantum Key Distribution Networks

    CERN Document Server

    Razavi, Mohsen

    2011-01-01

    This paper addresses multi-user quantum key distribution networks, in which any two users can mutually exchange a secret key without trusting any other nodes. The same network also supports conventional classical communications by assigning two different wavelength bands to quantum and classical signals. Time and code division multiple access (CDMA) techniques, within a passive star network, are considered. In the case of CDMA, it turns out that the optimal performance is achieved at a unity code weight. A listen-before-send protocol is then proposed to improve secret key generation rates in this case. Finally, a hybrid setup with wavelength routers and passive optical networks, which can support a large number of users, is considered and analyzed.

  8. Satellite-to-ground quantum key distribution.

    Science.gov (United States)

    Liao, Sheng-Kai; Cai, Wen-Qi; Liu, Wei-Yue; Zhang, Liang; Li, Yang; Ren, Ji-Gang; Yin, Juan; Shen, Qi; Cao, Yuan; Li, Zheng-Ping; Li, Feng-Zhi; Chen, Xia-Wei; Sun, Li-Hua; Jia, Jian-Jun; Wu, Jin-Cai; Jiang, Xiao-Jun; Wang, Jian-Feng; Huang, Yong-Mei; Wang, Qiang; Zhou, Yi-Lin; Deng, Lei; Xi, Tao; Ma, Lu; Hu, Tai; Zhang, Qiang; Chen, Yu-Ao; Liu, Nai-Le; Wang, Xiang-Bin; Zhu, Zhen-Cai; Lu, Chao-Yang; Shu, Rong; Peng, Cheng-Zhi; Wang, Jian-Yu; Pan, Jian-Wei

    2017-08-09

    Quantum key distribution (QKD) uses individual light quanta in quantum superposition states to guarantee unconditional communication security between distant parties. In practice, the achievable distance for QKD has been limited to a few hundred kilometres, owing to the channel loss of fibers or terrestrial free space that exponentially reduced the photon rate. Satellite-based QKD promises to establish a global-scale quantum network by exploiting the negligible photon loss and decoherence in the empty out space. Here we develop and launch a low-Earth-orbit satellite to implement decoy-state QKD with over kHz key rate from the satellite to ground over a distance of up to 1,200 km, which is up to 20 orders of magnitudes more efficient than that expected using an optical fiber (with 0.2 dB/km loss) of the same length. The establishment of a reliable and efficient space-to-ground link for faithful quantum state transmission paves the way to global-scale quantum networks.

  9. Unsymmetrical Quantum Key Distribution Using Tripartite Entanglement

    Institute of Scientific and Technical Information of China (English)

    XIONG Jin; ZHANG Zhe-Shen; ZHOU Nan-Run; PENG Jin-Ye; ZENG Gui-Hua

    2007-01-01

    An unsymmetrical quantum key distribution protocol is proposed,in which Greenberger-Horne-Zeilinger (GHZ) triplet states are used to obtain the secret key.Except the lost qubits due to the unperfectness of the physical devices,the unsymmetrical characteristic makes all transmitted qubits useful.This leads to an excellent efficiency,which reaches 100% in an ideal case.The security is studied from the aspect of information theory.By using the correlation of the GHZ tripartite entanglement state,eavesdropping can be easily checked out,which indicates that the presented protocol is more secure.

  10. Quantum key distribution without alternative measurements

    CERN Document Server

    Cabello, A

    2000-01-01

    Entanglement swapping between Einstein-Podolsky-Rosen (EPR) pairs can be used to generate the same sequence of random bits in two remote places. A quantum key distribution protocol based on this idea is described. The scheme exhibits the following features. (a) It does not require that Alice and Bob choose between alternative measurements, therefore improving the rate of generated bits by transmitted qubit. (b) It allows Alice and Bob to generate a key of arbitrary length using a single quantum system (three EPR pairs), instead of a long sequence of them. (c) Detecting Eve requires the comparison of fewer bits. (d) Entanglement is an essential ingredient. The scheme assumes reliable measurements of the Bell operator. (20 refs).

  11. Atmospheric Quantum Key Distribution in Daylight

    Science.gov (United States)

    Buttler, William; Hughes, Richard; Morgan, George; Nordholt, Jane; Peterson, Charles

    2001-05-01

    In quantum key distribution (QKD) single-photon transmissions generate the shared, secret random number sequences, known as cryptographic keys, that are used to encrypt and decrypt secret communications. Because the security of QKD is based on principles of quantum physics 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 an experimental QKD system that uses the four-state “BB84” protocol with non-orthogonal photon polarization states and lowest-order adaptive optics to generate shared key material over multi-kilometer atmospheric, line-of-sight paths. We will present results of a daylight demonstration of this system. Key material is built up using the transmission of a photon-pulse per bit of an initial secret random sequence. We will describe the design and operation of the system, present an analysis of the system's security, efficiency and error rate, and describe the prospects for longer-distance applications of free-space QKD.

  12. Progress in satellite quantum key distribution

    Science.gov (United States)

    Bedington, Robert; Arrazola, Juan Miguel; Ling, Alexander

    2017-08-01

    Quantum key distribution (QKD) is a family of protocols for growing a private encryption key between two parties. Despite much progress, all ground-based QKD approaches have a distance limit due to atmospheric losses or in-fibre attenuation. These limitations make purely ground-based systems impractical for a global distribution network. However, the range of communication may be extended by employing satellites equipped with high-quality optical links. This manuscript summarizes research and development which is beginning to enable QKD with satellites. It includes a discussion of protocols, infrastructure, and the technical challenges involved with implementing such systems, as well as a top level summary of on-going satellite QKD initiatives around the world.

  13. Reference frame independent quantum key distribution

    CERN Document Server

    Laing, Anthony; Rarity, John G; O'Brien, Jeremy L

    2010-01-01

    We describe a quantum key distribution protocol based on pairs of entangled qubits that generates a secure key between two partners in an environment of unknown and slowly varying reference frame. A direction of particle delivery is required, but the phases between the computational basis states need not be known or fixed. The protocol can simplify the operation of existing setups and has immediate applications to emerging scenarios such as earth-to-satellite links and the use of integrated photonic waveguides. We compute the asymptotic secret key rate for a two-qubit source, which coincides with the rate of the six-state protocol for white noise. We give the generalization of the protocol to higher-dimensional systems and detail a scheme for physical implementation in the three dimensional qutrit case.

  14. Security of practical quantum key distribution systems

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Nitin

    2015-02-24

    This thesis deals with practical security aspects of quantum key distribution (QKD) systems. At the heart of the theoretical model of any QKD system lies a quantum-mechanical security proof that guarantees perfect secrecy of messages - based on certain assumptions. However, in practice, deviations between the theoretical model and the physical implementation could be exploited by an attacker to break the security of the system. These deviations may arise from technical limitations and operational imperfections in the physical implementation and/or unrealistic assumptions and insufficient constraints in the theoretical model. In this thesis, we experimentally investigate in depth several such deviations. We demonstrate the resultant vulnerabilities via proof-of-principle attacks on a commercial QKD system from ID Quantique. We also propose countermeasures against the investigated loopholes to secure both existing and future QKD implementations.

  15. Quantum key distribution with two-segment quantum repeaters

    Energy Technology Data Exchange (ETDEWEB)

    Kampermann, Hermann; Abruzzo, Silvestre; Bruss, Dagmar [Theoretische Physik III, Heinrich-Heine-Universitaet Duesseldorf (Germany)

    2014-07-01

    Quantum repeaters represent one possible way to achieve long-distance quantum key distribution. One way of improving the repeater rate and decreasing the memory coherence time is the usage of multiplexing. Motivated by the experimental fact that long-range connections are practically demanding, we extend the analysis of the quantum repeater multiplexing protocol to the case of short-range connections. We derive formulas for the repeater rate and we show that short-range connections lead to most of the benefits of a full-range multiplexing protocol. A less demanding QKD-protocol without quantum memories was recently introduced by Lo et al. We generalize this measurement-device-independent quantum key Distribution protocol to the scenario where the repeater Station contains also heralded quantum memories. We assume either single-photon sources or weak coherent pulse sources plus decay states. We show that it is possible to significantly outperform the original proposal, even in presence of decoherence of the quantum memory. We give formulas in terms of device imperfections i.e., the quantum bit error rate and the repeater rate.

  16. Detector-device-independent quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Charles Ci Wen; Korzh, Boris; Martin, Anthony; Bussières, Félix; Thew, Rob; Zbinden, Hugo [Group of Applied Physics, University of Geneva, Chemin de Pinchat 22, CH-1211 Geneva 4 (Switzerland)

    2014-12-01

    Recently, a quantum key distribution (QKD) scheme based on entanglement swapping, called measurement-device-independent QKD (mdiQKD), was proposed to bypass all measurement side-channel attacks. While mdiQKD is conceptually elegant and offers a supreme level of security, the experimental complexity is challenging for practical systems. For instance, it requires interference between two widely separated independent single-photon sources, and the secret key rates are dependent on detecting two photons—one from each source. Here, we demonstrate a proof-of-principle experiment of a QKD scheme that removes the need for a two-photon system and instead uses the idea of a two-qubit single-photon to significantly simplify the implementation and improve the efficiency of mdiQKD in several aspects.

  17. Unconditional Security In Quantum Key Distribution

    CERN Document Server

    Yuen, Horace P

    2012-01-01

    It has been widely claimed and believed that many protocols in quantum key distribution, especially the single-photon BB84 protocol, have been proved unconditionally secure at least in principle, for both asymptotic and finite protocols with realistic bit lengths. In this paper it is pointed out that the only known quantitative justification for such claims is based on incorrect assertions. The precise security requirements are described in terms of the attacker's sequence and bit error probabilities in estimating the key. The extent to which such requirements can be met from a proper trace distance criterion is established. The results show that the quantitative security levels obtainable in concrete protocols with ideal devices do not rule out drastic breach of security unless privacy amplification is more properly applied.

  18. Quantum election scheme based on anonymous quantum key distribution

    Institute of Scientific and Technical Information of China (English)

    Zhou Rui-Rui; Yang Li

    2012-01-01

    An unconditionally secure authority-certified anonymous quantum key distribution scheme using conjugate coding is presented,based on which we construct a quantum election scheme without the help of an entanglement state.We show that this election scheme ensures the completeness,soundness,privacy,eligibility,unreusability,fairness,and verifiability of a large-scale election in which the administrator and counter are semi-honest.This election scheme can work even if there exist loss and errors in quantum channels.In addition,any irregularity in this scheme is sensible.

  19. Completely device-independent quantum key distribution

    Science.gov (United States)

    Aguilar, Edgar A.; Ramanathan, Ravishankar; Kofler, Johannes; Pawłowski, Marcin

    2016-08-01

    Quantum key distribution (QKD) is a provably secure way for two distant parties to establish a common secret key, which then can be used in a classical cryptographic scheme. Using quantum entanglement, one can reduce the necessary assumptions that the parties have to make about their devices, giving rise to device-independent QKD (DIQKD). However, in all existing protocols to date the parties need to have an initial (at least partially) random seed as a resource. In this work, we show that this requirement can be dropped. Using recent advances in the fields of randomness amplification and randomness expansion, we demonstrate that it is sufficient for the message the parties want to communicate to be (partially) unknown to the adversaries—an assumption without which any type of cryptography would be pointless to begin with. One party can use her secret message to locally generate a secret sequence of bits, which can then be openly used by herself and the other party in a DIQKD protocol. Hence our work reduces the requirements needed to perform secure DIQKD and establish safe communication.

  20. Finite-key security analysis for multilevel quantum key distribution

    Science.gov (United States)

    Brádler, Kamil; Mirhosseini, Mohammad; Fickler, Robert; Broadbent, Anne; Boyd, Robert

    2016-07-01

    We present a detailed security analysis of a d-dimensional quantum key distribution protocol based on two and three mutually unbiased bases (MUBs) both in an asymptotic and finite-key-length scenario. The finite secret key rates (in bits per detected photon) are calculated as a function of the length of the sifted key by (i) generalizing the uncertainly relation-based insight from BB84 to any d-level 2-MUB QKD protocol and (ii) by adopting recent advances in the second-order asymptotics for finite block length quantum coding (for both d-level 2- and 3-MUB QKD protocols). Since the finite and asymptotic secret key rates increase with d and the number of MUBs (together with the tolerable threshold) such QKD schemes could in principle offer an important advantage over BB84. We discuss the possibility of an experimental realization of the 3-MUB QKD protocol with the orbital angular momentum degrees of freedom of photons.

  1. Chip-based quantum key distribution

    Science.gov (United States)

    Sibson, P.; Erven, C.; Godfrey, M.; Miki, S.; Yamashita, T.; Fujiwara, M.; Sasaki, M.; Terai, H.; Tanner, M. G.; Natarajan, C. M.; Hadfield, R. H.; O'Brien, J. L.; Thompson, M. G.

    2017-02-01

    Improvement in secure transmission of information is an urgent need for governments, corporations and individuals. Quantum key distribution (QKD) promises security based on the laws of physics and has rapidly grown from proof-of-concept to robust demonstrations and deployment of commercial systems. Despite these advances, QKD has not been widely adopted, and large-scale deployment will likely require chip-based devices for improved performance, miniaturization and enhanced functionality. Here we report low error rate, GHz clocked QKD operation of an indium phosphide transmitter chip and a silicon oxynitride receiver chip--monolithically integrated devices using components and manufacturing processes from the telecommunications industry. We use the reconfigurability of these devices to demonstrate three prominent QKD protocols--BB84, Coherent One Way and Differential Phase Shift--with performance comparable to state-of-the-art. These devices, when combined with integrated single photon detectors, pave the way for successfully integrating QKD into future telecommunications networks.

  2. Chip-based quantum key distribution

    Science.gov (United States)

    Sibson, P.; Erven, C.; Godfrey, M.; Miki, S.; Yamashita, T.; Fujiwara, M.; Sasaki, M.; Terai, H.; Tanner, M. G.; Natarajan, C. M.; Hadfield, R. H.; O'Brien, J. L.; Thompson, M. G.

    2017-01-01

    Improvement in secure transmission of information is an urgent need for governments, corporations and individuals. Quantum key distribution (QKD) promises security based on the laws of physics and has rapidly grown from proof-of-concept to robust demonstrations and deployment of commercial systems. Despite these advances, QKD has not been widely adopted, and large-scale deployment will likely require chip-based devices for improved performance, miniaturization and enhanced functionality. Here we report low error rate, GHz clocked QKD operation of an indium phosphide transmitter chip and a silicon oxynitride receiver chip—monolithically integrated devices using components and manufacturing processes from the telecommunications industry. We use the reconfigurability of these devices to demonstrate three prominent QKD protocols—BB84, Coherent One Way and Differential Phase Shift—with performance comparable to state-of-the-art. These devices, when combined with integrated single photon detectors, pave the way for successfully integrating QKD into future telecommunications networks. PMID:28181489

  3. Quantum key distribution: vulnerable if imperfectly implemented

    Science.gov (United States)

    Leuchs, G.

    2013-10-01

    We report several vulnerabilities found in Clavis2, the flagship quantum key distribution (QKD) system from ID Quantique. We show the hacking of a calibration sequence run by Clavis2 to synchronize the Alice and Bob devices before performing the secret key exchange. This hack induces a temporal detection efficiency mismatch in Bob that can allow Eve to break the security of the cryptosystem using faked states. We also experimentally investigate the superlinear behaviour in the single-photon detectors (SPDs) used by Bob. Due to this superlinearity, the SPDs feature an actual multi-photon detection probability which is generally higher than the theoretically-modelled value. We show how this increases the risk of detector control attacks on QKD systems (including Clavis2) employing such SPDs. Finally, we review the experimental feasibility of Trojan-horse attacks. In the case of Clavis2, the objective is to read Bob's phase modulator to acquire knowledge of his basis choice as this information suffices for constructing the raw key in the Scarani-Acin-Ribordy-Gisin 2004 (SARG04) protocol. We work in close collaboration with ID Quantique and for all these loopholes, we notified them in advance. Wherever possible, we or ID Quantique proposed countermeasures and they implemented suitable patches and upgrade their systems.

  4. Quantum relay schemes for continuous-variable quantum key distribution

    Science.gov (United States)

    Guo, Ying; Liao, Qin; Huang, Duan; Zeng, Guihua

    2017-04-01

    We propose several concatenated quantum relay continuous-variable quantum key distribution schemes based on the parametric amplifier (PA) and the beam splitter (BS). Instead of using only one BS in the traditional relay scheme, the proposed schemes provide two operations that involve both PA and BS, activating the beam splitting and recombining operations in turn. These schemes would benefit the system performance improvement by providing signal amplification and establishing quantum correlations. We show that the different effects of the relay schemes will cause different system performances because of the varied signal-to-noise ratio (SNR) of output fields. The system's secret key rate will be increased when equipping with the PA-BS relay scheme, because the output fields of the PA are entangled with the correlated quantum noises while input fields of the BS are superimposed, subsequently leading to the quantum noise reduction of the total output fields of relay station, while the reversed BS-PA relay scheme has little advantage over the traditional counterpart that contains only one BS in relay data postprocessing because it will not cause any SNR improvement. Moreover, the reinforced PA-PA relay scheme results in a slight improvement due to the increased SNR. These quantum relay schemes can be performed through the beam splitting, the recombining operations, and the relay data postprocessing, such that it would be suitable for secret information exchange in complex networks with intermediate stations.

  5. Quantum hacking on quantum key distribution using homodyne detection

    Science.gov (United States)

    Huang, Jing-Zheng; Kunz-Jacques, Sébastien; Jouguet, Paul; Weedbrook, Christian; Yin, Zhen-Qiang; Wang, Shuang; Chen, Wei; Guo, Guang-Can; Han, Zheng-Fu

    2014-03-01

    Imperfect devices in commercial quantum key distribution systems open security loopholes that an eavesdropper may exploit. An example of one such imperfection is the wavelength-dependent coupling ratio of the fiber beam splitter. Utilizing this loophole, the eavesdropper can vary the transmittances of the fiber beam splitter at the receiver's side by inserting lights with wavelengths different from what is normally used. Here, we propose a wavelength attack on a practical continuous-variable quantum key distribution system using homodyne detection. By inserting light pulses at different wavelengths, this attack allows the eavesdropper to bias the shot-noise estimation even if it is done in real time. Based on experimental data, we discuss the feasibility of this attack and suggest a prevention scheme by improving the previously proposed countermeasures.

  6. Quantum Key Distribution with Fibonacci Orbital Angular Momentum States

    OpenAIRE

    Simon, David S.; Lawrence, Nate; Trevino, Jacob; Negro, Luca Dal; Sergienko, Alexander V.

    2012-01-01

    Quantum cryptography and quantum key distribution (QKD) have been the most successful applications of quantum information processing, highlighting the unique capability of quantum mechanics, through the no-cloning theorem, to protect the security of shared encryption keys. Here we present a new and fundamentally different approach to high-capacity, high-efficiency QKD by exploiting interplay between cross-disciplinary ideas from quantum information and light scattering of aperiodic photonic m...

  7. Trojan horse attacks on counterfactual quantum key distribution

    Science.gov (United States)

    Yang, Xiuqing; Wei, Kejin; Ma, Haiqiang; Sun, Shihai; Du, Yungang; Wu, Lingan

    2016-04-01

    There has been much interest in "counterfactual quantum cryptography" (T.-G. Noh, 2009 [10]). It seems that the counterfactual quantum key distribution protocol without any photon carrier through the quantum channel provides practical security advantages. However, we show that it is easy to break counterfactual quantum key distribution systems in practical situations. We introduce the two types of Trojan horse attacks that are available for the two-way protocol and become possible for practical counterfactual systems with our eavesdropping schemes.

  8. Single-quadrature continuous-variable quantum key distribution

    DEFF Research Database (Denmark)

    Gehring, Tobias; Jacobsen, Christian Scheffmann; Andersen, Ulrik Lund

    2016-01-01

    Most continuous-variable quantum key distribution schemes are based on the Gaussian modulation of coherent states followed by continuous quadrature detection using homodyne detectors. In all previous schemes, the Gaussian modulation has been carried out in conjugate quadratures thus requiring two...... commercialization of continuous-variable quantum key distribution, provided that the low noise requirement can be achieved....

  9. Security Proof for Quantum Key Distribution Using Qudit Systems

    CERN Document Server

    Sheridan, Lana

    2010-01-01

    We provide security bounds against coherent attacks for two families of quantum key distribution protocols that use $d$-dimensional quantum systems. In the asymptotic regime, both the secret key rate for fixed noise and the robustness to noise increase with $d$. The finite-key corrections are found to be almost insensitive to $d\\lesssim 20$.

  10. Continuous variable quantum key distribution with modulated entangled states

    DEFF Research Database (Denmark)

    Madsen, Lars S; Usenko, Vladyslav C.; Lassen, Mikael

    2012-01-01

    Quantum key distribution enables two remote parties to grow a shared key, which they can use for unconditionally secure communication over a certain distance. The maximal distance depends on the loss and the excess noise of the connecting quantum channel. Several quantum key distribution schemes...... based on coherent states and continuous variable measurements are resilient to high loss in the channel, but are strongly affected by small amounts of channel excess noise. Here we propose and experimentally address a continuous variable quantum key distribution protocol that uses modulated fragile...... entangled states of light to greatly enhance the robustness to channel noise. We experimentally demonstrate that the resulting quantum key distribution protocol can tolerate more noise than the benchmark set by the ideal continuous variable coherent state protocol. Our scheme represents a very promising...

  11. Simple Post Quantum Scheme for Higher Key Rate Multiparty Quantum Key Distribution

    Directory of Open Access Journals (Sweden)

    Abudhahir Buhari

    2012-10-01

    Full Text Available We propose a multi-party quantum key distribution protocol which enables all the receivers can converttheir respective private shared key into common secret key without use of entanglement. The maincomponent of our protocol is a simple post quantum scheme for achieving the higher secret key rate.Efficiency of the extracted key rate is almost 100%. We assume that sender established the pre-sharedprivate secret keys and a common secret number with the receivers. Our proposed scheme sends n stringsof number to n receivers in the public channel to convert their respective shared secret key into commonsecret key in the presence of Eve. We also analyze the complexity of attack by the adversary to guess thesecret key

  12. A System-Level Throughput Model for Quantum Key Distribution

    Science.gov (United States)

    2015-09-17

    quantum mechanics to generate and distribute shared secret keying material. QKD systems generate and distribute key by progressing through a number of...communicate a seed to prime random number generation to construct a very large matrix used in the calculation of Privacy Amplification. We assume that... generate a desired number of final key bits. RQ7: What are the implications of altering the amount of Alice’s memory allocated for Quantum Exchange

  13. Quantum hacking: attacking practical quantum key distribution systems

    Science.gov (United States)

    Qi, Bing; Fung, Chi-Hang Fred; Zhao, Yi; Ma, Xiongfeng; Tamaki, Kiyoshi; Chen, Christine; Lo, Hoi-Kwong

    2007-09-01

    Quantum key distribution (QKD) can, in principle, provide unconditional security based on the fundamental laws of physics. Unfortunately, a practical QKD system may contain overlooked imperfections and violate some of the assumptions in a security proof. Here, we report two types of eavesdropping attacks against a practical QKD system. The first one is "time-shift" attack, which is applicable to QKD systems with gated single photon detectors (SPDs). In this attack, the eavesdropper, Eve, exploits the time mismatch between the open windows of the two SPDs. She can acquire a significant amount of information on the final key by simply shifting the quantum signals forwards or backwards in time domain. Our experimental results in [9] with a commercial QKD system demonstrate that, under this attack, the original QKD system is breakable. This is the first experimental demonstration of a feasible attack against a commercial QKD system. This is a surprising result. The second one is "phase-remapping" attack [10]. Here, Eve exploits the fact that a practical phase modulator has a finite response time. In principle, Eve could change the encoded phase value by time-shifting the signal pulse relative to the reference pulse.

  14. Quantum key distribution using gaussian-modulated coherent states

    CERN Document Server

    Grosshans, F; Wenger, J; Brouri, R; Cerf, N J; Grangier, P; Grangier, Ph.

    2003-01-01

    Quantum continuous variables are being explored as an alternative means to implement quantum key distribution, which is usually based on single photon counting. The former approach is potentially advantageous because it should enable higher key distribution rates. Here we propose and experimentally demonstrate a quantum key distribution protocol based on the transmission of gaussian-modulated coherent states (consisting of laser pulses containing a few hundred photons) and shot-noise-limited homodyne detection; squeezed or entangled beams are not required. Complete secret key extraction is achieved using a reverse reconciliation technique followed by privacy amplification. The reverse reconciliation technique is in principle secure for any value of the line transmission, against gaussian individual attacks based on entanglement and quantum memories. Our table-top experiment yields a net key transmission rate of about 1.7 megabits per second for a loss-free line, and 75 kilobits per second for a line with loss...

  15. Polarization-Basis Tracking Scheme in Satellite Quantum Key Distribution

    Directory of Open Access Journals (Sweden)

    Morio Toyoshima

    2011-01-01

    Full Text Available Satellite quantum key distribution is a promising technique that overcomes the limited transmission distance in optical-fiber-based systems. The polarization tracking technique is one of the key techniques in the satellite quantum key distribution. With free-space quantum key distribution between an optical ground station and a satellite, the photon polarization state will be changed according to the satellite movement. To enable polarization based quantum key distribution between mobile terminals, we developed a polarization-basis tracking scheme allowing a common frame of reference to be shared. It is possible to orient two platforms along a common axis by detecting the reference optical signal only on the receiver side with no prior information about the transmitter's orientation. We developed a prototype system for free-space quantum key distribution with the polarization-basis tracking scheme. Polarization tracking performance was 0.092° by conducting quantum key distribution experiments over a 1 km free space between two buildings in a Tokyo suburb.

  16. Free-Space Quantum Key Distribution

    CERN Document Server

    Carrasco-Casado, Alberto; Denisenko, Natalia

    2016-01-01

    Based on the firm laws of physics rather than unproven foundations of mathematical complexity, quantum cryptography provides a radically different solution for encryption and promises unconditional security. Quantum cryptography systems are typically built between two nodes connected to each other through fiber optic. This chapter focuses on quantum cryptography systems operating over free-space optical channels as a cost-effective and license-free alternative to fiber optic counterparts. It provides an overview of the different parts of an experimental free-space quantum communication link developed in the Spanish National Research Council (Madrid, Spain).

  17. Practical free-space quantum key distribution over 1 km

    CERN Document Server

    Buttler, W T; Kwiat, P G; Lamoreaux, S K; Luther, G G; Morgan, G L; Nordholt, J E; Peterson, C G; Simmons, C M

    1998-01-01

    A working free-space quantum key distribution (QKD) system has been developed and tested over an outdoor optical path of ~1 km at Los Alamos National Laboratory under nighttime conditions. Results show that QKD can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, we examine the feasibility of surface to satellite QKD.

  18. Free space quantum key distribution: Towards a real life application

    Science.gov (United States)

    Weier, H.; Schmitt-Manderbach, T.; Regner, N.; Kurtsiefer, Ch.; Weinfurter, H.

    2006-08-01

    Quantum key distribution (QKD) [1] is the first method of quantum information science that will find its way into our everyday life. It employs fundamental laws of quantum physics to ensure provably secure symmetric key generation between two parties. The key can then be used to encrypt and decrypt sensitive data with unconditional security. Here, we report on a free space QKD implementation using strongly attenuated laser pulses over a distance of 480 m. It is designed to work continuously without human interaction. Until now, it produces quantum keys unattended at night for more than 12 hours with a sifted key rate of more than 50 kbit/s and a quantum bit error rate between 3% and 5%.

  19. Quantum Key Distribution Network Based on Differential Phase Shift

    Institute of Scientific and Technical Information of China (English)

    WANG Wan-Ying; WANG Chuan; WEN Kai; LONG Gui-Lu

    2007-01-01

    Using a series of quantum correlated photon pairs, we propose a theoretical scheme for any-to-any multi-user quantum key distribution network based on differential phase shift. The differential phase shift and the different detection time slots ensure the security of our scheme against eavesdropping. We discuss the security under the intercept-resend attack and the source replacement attack.

  20. 802.11i Encryption Key Distribution Using Quantum Cryptography

    Directory of Open Access Journals (Sweden)

    Thi Mai Trang Nguyen

    2006-10-01

    Full Text Available Quantum cryptography is a promising solution towards absolute security in long term cryptosystems. While the use of quantum cryptography in fiber optical networks gets significant advances, research on the application of quantum cryptography in mobile wireless network is still premature. In this paper, we analyze the interests of using quantum cryptography in 802.11 wireless networks, and propose a scheme integrating quantum cryptography in 802.11i security mechanisms for the distribution of the encryption keys. The use of an apparatus network to provide alternative line-of-sight paths is also discussed.

  1. Quantum key distribution with an entangled light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Dzurnak, B.; Stevenson, R. M.; Nilsson, J.; Dynes, J. F.; Yuan, Z. L.; Skiba-Szymanska, J.; Shields, A. J. [Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2015-12-28

    Measurements performed on entangled photon pairs shared between two parties can allow unique quantum cryptographic keys to be formed, creating secure links between users. An advantage of using such entangled photon links is that they can be adapted to propagate entanglement to end users of quantum networks with only untrusted nodes. However, demonstrations of quantum key distribution with entangled photons have so far relied on sources optically excited with lasers. Here, we realize a quantum cryptography system based on an electrically driven entangled-light-emitting diode. Measurement bases are passively chosen and we show formation of an error-free quantum key. Our measurements also simultaneously reveal Bell's parameter for the detected light, which exceeds the threshold for quantum entanglement.

  2. Dense Wavelength Division Multiplexed Quantum Key Distribution Using Entangled Photons

    CERN Document Server

    Mower, Jacob; Shapiro, Jeff H; Englund, Dirk

    2011-01-01

    Quantum key distribution (QKD) enables two parties to establish a secret key over a potentially hostile channel by exchanging photonic quantum states, relying on the fact that it is impossible for an eavesdropper to tap the quantum channel without disturbing these photons in a way that can be detected [1]. Here we introduce a large-alphabet QKD protocol that makes optimal use of temporal and spectral correlations of entangled photons, reaching the maximum number of inde- pendent basis states (the Schmidt number) and enabling extremely high information content per photon together with an optimal rate of secret key generation. This protocol, which we call 'Dense Wavelength Division Multiplexed Quantum Key Distribution' (DWDM-QKD), derives its security by the conjugate nature of the temporal and spectral entanglement of photon pairs generated by spontaneous parametric down conversion. By using a combination of spectral and temporal bases, we can adjust the protocol to be resource efficient. We show that DWDM-QKD...

  3. SECOQC White Paper on Quantum Key Distribution and Cryptography

    CERN Document Server

    Alleaume, R; Branciard, C; Debuisschert, T; Dianati, M; Gisin, N; Godfrey, M; Grangier, P; Langer, T; Leverrier, A; Lütkenhaus, N; Painchault, P; Peev, M; Poppe, A; Pornin, T; Rarity, J; Renner, R; Ribordy, G; Riguidel, M; Salvail, L; Shields, A; Weinfurter, H; Zeilinger, A; Alleaume, Romain; Bouda, Jan; Branciard, Cyril; Debuisschert, Thierry; Dianati, Mehrdad; Gisin, Nicolas; Godfrey, Mark; Grangier, Philippe; Langer, Thomas; Leverrier, Anthony; Lutkenhaus, Norbert; Painchault, Philippe; Peev, Momtchil; Poppe, Andreas; Pornin, Thomas; Rarity, John; Renner, Renato; Ribordy, Gregoire; Riguidel, Michel; Salvail, Louis; Shields, Andrew; Weinfurter, Harald; Zeilinger, Anton

    2007-01-01

    The SECOQC White Paper on Quantum Key Distribution and Cryptography is the outcome on a thorough consultation and discussion among the participants of the European project SECOQC (www.secoqc.net). This paper is a review article that attempts to position Quantum Key Distribution (QKD) in terms of cryptographic applications. A detailed comparison of QKD with the solutions currently in use to solve the key distribution problem, based on classical cryptography, is provided. We also detail how the work on QKD networks lead within SECOQC will allow the deployment of long-distance secure communication infrastructures based on quantum cryptography. The purpose of the White Paper is finally to promote closer collaboration between classical and quantum cryptographers. We believe that very fruitful research, involving both communities, could emerge in the future years and try to sketch what may be the next challenges in this direction.

  4. Practical Quantum Key Distribution with Polarization-Entangled Photons

    CERN Document Server

    Poppe, A; Lorünser, T; Maurhardt, O; Ursin, R; Boehm, H R; Peev, M; Suda, M; Jennewein, T; Zeilinger, Anton

    2004-01-01

    We present an entangled state quantum cryptography system that operated for the first time in a real world application scenario. The full key generation protocol was performed in real time between two distributed embedded hardware devices, which were connected by 1.45 km of optical fiber, installed for this experiment in the Vienna sewage system. The generated quantum key was immediately handed over and used by a secure communication application.

  5. Trojan horse attacks on counterfactual quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiuqing, E-mail: xqqyang@163.com [School of Science, Beijing Jiaotong University, Beijing 100044 (China); College of Science, Inner Mongolia University of Technology, 010051 Hohhot (China); Wei, Kejin; Ma, Haiqiang [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Sun, Shihai, E-mail: shsun@nudt.edu.cn [Department of Physics, National University of Defense Technology, Changsha 410073 (China); Du, Yungang [College of Science, Inner Mongolia University of Technology, 010051 Hohhot (China); Wu, Lingan [Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

    2016-04-22

    There has been much interest in “counterfactual quantum cryptography” (T.-G. Noh, 2009 [10]). It seems that the counterfactual quantum key distribution protocol without any photon carrier through the quantum channel provides practical security advantages. However, we show that it is easy to break counterfactual quantum key distribution systems in practical situations. We introduce the two types of Trojan horse attacks that are available for the two-way protocol and become possible for practical counterfactual systems with our eavesdropping schemes. - Highlights: • We find the attacks available for the two-way protocol become possible for the practical counterfactual systems. • It does not require the assumption that it works on the counterfactual systems only in a finite key scenario. • Compared to the other attack models, our scheme is relatively simple for an eavesdropper.

  6. A secure quantum key distribution scheme based on variable quantum encoding algorithms

    Institute of Scientific and Technical Information of China (English)

    Zhiwen Zhao; Yi Luo; Zhangji Zhao; Haiming Long

    2011-01-01

    The security of the quantum secret key plays a critical role in quantum communications. Thus far, one problem that still exists in existing protocols is the leakage of the length of the secret key. In this letter, based on variable quantum encoding algorithms, we propose a secure quantum key distribution scheme, which can overcome the security problem involving the leakage of the secret key. Security analysis shows that the proposed scheme is both secure and effective.%@@ The security of the quantum secret key plays a critical role in quantum communications.Thus far, one problem that still exists in existing protocols is the leakage of the length of the secret key.In this letter,based on variable quantum encoding algorithms, we propose a secure quantum key distribution scheme,which can overcome the security problem involving the leakage of the secret key.Security analysis shows that the proposed scheme is both secure and effective.

  7. Auto-compensating differential phase shift quantum key distribution

    CERN Document Server

    Han, X; Zhou, C; Zeng, H; Han, Xiaohong; Wu, Guang; Zhou, Chunyuan; Zeng, Heping

    2005-01-01

    We propose an auto-compensating differential phase shift scheme for quantum key distribution with a high key-creation efficiency, which skillfully makes use of automatic alignment of the photon polarization states in optical fiber with modified Michelson interferometers composed of unequal arms with Faraday mirrors at the ends. The Faraday-mirrors-based Michelson interferometers not only function as pulse splitters, but also enable inherent compensation of polarization mode dispersion in the optic-fiber paths at both Alice's and Bob's sites. The sequential pulses encoded by differential phase shifts pass through the quantum channel with the same polarization states, resulting in a stable key distribution immune to the polarization mode dispersion in the quantum channel. Such a system features perfect stability and higher key creation efficiency over traditional schemes.

  8. An Interactive Learning Tutorial on Quantum Key Distribution

    CERN Document Server

    DeVore, Seth

    2016-01-01

    We describe the development and evaluation of a Quantum Interactive Learning Tutorial (QuILT) on quantum key distribution, a context which involves an exciting application of quantum mechanics. The protocol used in the QuILT described here uses single photons with non-orthogonal polarization states to generate a random shared key over a public channel for encrypting and decrypting information. The QuILT helps upper-level undergraduate students learn quantum mechanics using a simple two state system. It actively engages students in the learning process and helps them build links between the formalism and the conceptual aspects of quantum physics without compromising the technical content. The evaluations suggest that the QuILT is helpful in improving students' understanding of relevant concepts.

  9. Development of an interactive tutorial on quantum key distribution

    CERN Document Server

    DeVore, Seth

    2016-01-01

    We describe the development of a Quantum Interactive Learning Tutorial (QuILT) on quantum key distribution, a context which involves a practical application of quantum mechanics. The QuILT helps upper-level undergraduate students learn quantum mechanics using a simple two state system and was developed based upon the findings of cognitive research and physics education research. One protocol used in the QuILT involves generating a random shared key over a public channel for encrypting and decrypting information using single photons with non-orthogonal polarization states, and another protocol makes use of two entangled spin-1/2 particles. The QuILT uses a guided approach and focuses on helping students build links between the formalism and conceptual aspects of quantum physics without compromising the technical content. We also discuss findings from a preliminary in-class evaluation.

  10. Toward Designing a Quantum Key Distribution Network Simulation Model

    Directory of Open Access Journals (Sweden)

    Miralem Mehic

    2016-01-01

    Full Text Available As research in quantum key distribution network technologies grows larger and more complex, the need for highly accurate and scalable simulation technologies becomes important to assess the practical feasibility and foresee difficulties in the practical implementation of theoretical achievements. In this paper, we described the design of simplified simulation environment of the quantum key distribution network with multiple links and nodes. In such simulation environment, we analyzed several routing protocols in terms of the number of sent routing packets, goodput and Packet Delivery Ratio of data traffic flow using NS-3 simulator.

  11. Quantum key distribution for composite dimensional finite systems

    Science.gov (United States)

    Shalaby, Mohamed; Kamal, Yasser

    2017-06-01

    The application of quantum mechanics contributes to the field of cryptography with very important advantage as it offers a mechanism for detecting the eavesdropper. The pioneering work of quantum key distribution uses mutually unbiased bases (MUBs) to prepare and measure qubits (or qudits). Weak mutually unbiased bases (WMUBs) have weaker properties than MUBs properties, however, unlike MUBs, a complete set of WMUBs can be constructed for systems with composite dimensions. In this paper, we study the use of weak mutually unbiased bases (WMUBs) in quantum key distribution for composite dimensional finite systems. We prove that the security analysis of using a complete set of WMUBs to prepare and measure the quantum states in the generalized BB84 protocol, gives better results than using the maximum number of MUBs that can be constructed, when they are analyzed against the intercept and resend attack.

  12. Quantum key distribution in 50-km optic fibers

    Institute of Scientific and Technical Information of China (English)

    ZHOU Chunyuan; WU Guang; CHEN Xiuliang; LI Hexiang; ZENG Heping

    2004-01-01

    In this paper, we report our recent experiment of long-distance fiber-optic "plug and play" quantum cryptography system wherein a Faraday-Mirror was used to compensate for the polarization mode dispersion and phase drifts. The pulse-biased coincident gate single-photon detection technique was used to effectively reduce the noises from the detrimental Rayleigh backscattering. We have achieved a quantum key distribution system with the working distance of 50 km, which was tested to be stable in more than 6 hours' continuous work. And we also demonstrated the practical quantum communication in a local area network using the TCP protocol.

  13. Quantum key distribution using gaussian-modulated coherent states.

    Science.gov (United States)

    Grosshans, Frédéric; Van Assche, Gilles; Wenger, Jérôme; Brouri, Rosa; Cerf, Nicolas J; Grangier, Philippe

    2003-01-16

    Quantum continuous variables are being explored as an alternative means to implement quantum key distribution, which is usually based on single photon counting. The former approach is potentially advantageous because it should enable higher key distribution rates. Here we propose and experimentally demonstrate a quantum key distribution protocol based on the transmission of gaussian-modulated coherent states (consisting of laser pulses containing a few hundred photons) and shot-noise-limited homodyne detection; squeezed or entangled beams are not required. Complete secret key extraction is achieved using a reverse reconciliation technique followed by privacy amplification. The reverse reconciliation technique is in principle secure for any value of the line transmission, against gaussian individual attacks based on entanglement and quantum memories. Our table-top experiment yields a net key transmission rate of about 1.7 megabits per second for a loss-free line, and 75 kilobits per second for a line with losses of 3.1 dB. We anticipate that the scheme should remain effective for lines with higher losses, particularly because the present limitations are essentially technical, so that significant margin for improvement is available on both the hardware and software.

  14. Performance of Photon-Pair Quantum Key Distribution Systems

    CERN Document Server

    Walton, Z D; Atatüre, M; Saleh, B E A; Teich, M C

    2001-01-01

    We analyze the quantitative improvement in performance provided by a novel quantum key distribution (QKD) system that employs a correlated photon source (CPS) and a photon-number resolving detector (PNR). Our calculations suggest that given current technology, the CPR implementation offers an improvement of several orders of magnitude in secure bit rate over previously described implementations.

  15. Long distance quantum key distribution with continuous variables

    CERN Document Server

    Leverrier, Anthony

    2010-01-01

    We present a continuous-variable quantum key distribution protocol combining a continuous but slightly non-Gaussian modulation together with a efficient reverse reconciliation scheme. At the price of requiring an heterodyne detection, this protocol outperforms all known practical protocols. In particular, longer distances can be achieved, even taking into account finite size effects.

  16. Continuous Variable Quantum Key Distribution with a Noisy Laser

    DEFF Research Database (Denmark)

    Jacobsen, Christian Scheffmann; Gehring, Tobias; Andersen, Ulrik Lund

    2015-01-01

    Existing experimental implementations of continuous-variable quantum key distribution require shot-noise limited operation, achieved with shot-noise limited lasers. However, loosening this requirement on the laser source would allow for cheaper, potentially integrated systems. Here, we implement ...

  17. Post-processing procedure for industrial quantum key distribution systems

    Science.gov (United States)

    Kiktenko, Evgeny; Trushechkin, Anton; Kurochkin, Yury; Fedorov, Aleksey

    2016-08-01

    We present algorithmic solutions aimed on post-processing procedure for industrial quantum key distribution systems with hardware sifting. The main steps of the procedure are error correction, parameter estimation, and privacy amplification. Authentication of classical public communication channel is also considered.

  18. Security of EPR-based Quantum Key Distribution

    CERN Document Server

    Inamori, H

    2000-01-01

    We propose a proof of the security of EPR-based quantum key distribution against enemies with unlimited computational power. The proof holds for a protocol using interactive error-reconciliation scheme. We assume in this paper that the legitimate parties receive a given number of single photon signals and that their measurement devices are perfect.

  19. Comment on "Quantum key distribution without alternative measurements"

    CERN Document Server

    Zhang Yu Shun; Guo Guang Can; Zhang, Yong-Sheng; Li, Chuan-Feng; Guo, Guang-Can

    2001-01-01

    In a recent paper [A. Cabello, Phys. Rev. A 61, 052312 (2000)], a quantum key distribution protocol based on entanglement swapping was proposed. However, in this comment, it is shown that this protocol is insecure if Eve use a special strategy to attack.

  20. Quantum key distribution using card, base station and trusted authority

    Science.gov (United States)

    Nordholt, Jane Elizabeth; Hughes, Richard John; Newell, Raymond Thorson; Peterson, Charles Glen; Rosenberg, Danna; McCabe, Kevin Peter; Tyagi, Kush T; Dallman, Nicholas

    2015-04-07

    Techniques and tools for quantum key distribution ("QKD") between a quantum communication ("QC") card, base station and trusted authority are described herein. In example implementations, a QC card contains a miniaturized QC transmitter and couples with a base station. The base station provides a network connection with the trusted authority and can also provide electric power to the QC card. When coupled to the base station, after authentication by the trusted authority, the QC card acquires keys through QKD with a trusted authority. The keys can be used to set up secure communication, for authentication, for access control, or for other purposes. The QC card can be implemented as part of a smart phone or other mobile computing device, or the QC card can be used as a fillgun for distribution of the keys.

  1. Quantum key distribution using card, base station and trusted authority

    Energy Technology Data Exchange (ETDEWEB)

    Nordholt, Jane E.; Hughes, Richard John; Newell, Raymond Thorson; Peterson, Charles Glen; Rosenberg, Danna; McCabe, Kevin Peter; Tyagi, Kush T.; Dallmann, Nicholas

    2017-06-14

    Techniques and tools for quantum key distribution ("QKD") between a quantum communication ("QC") card, base station and trusted authority are described herein. In example implementations, a QC card contains a miniaturized QC transmitter and couples with a base station. The base station provides a network connection with the trusted authority and can also provide electric power to the QC card. When coupled to the base station, after authentication by the trusted authority, the QC card acquires keys through QKD with a trust authority. The keys can be used to set up secure communication, for authentication, for access control, or for other purposes. The QC card can be implemented as part of a smart phone or other mobile computing device, or the QC card can be used as a fillgun for distribution of the keys.

  2. The queueing model for quantum key distribution network

    Institute of Scientific and Technical Information of China (English)

    Wen Hao; Han Zheng-Fu; Guo Guang-Can; Hong Pei-Lin

    2009-01-01

    This paper develops a QKD (quantum key distribution)-based queueing model to investigate the data delay on QKD link and network, especially that based on trusted relays. It shows the mean packet delay performance of the QKD system. Furthermore, it proposes a key buffering policy which could effectively improve the delay performance in practice. The results will be helpful for quality of service in practical QKD systems.

  3. Authenticated semi-quantum key distributions without classical channel

    Science.gov (United States)

    Li, Chuan-Ming; Yu, Kun-Fei; Kao, Shih-Hung; Hwang, Tzonelih

    2016-07-01

    Yu et al. have proposed the first authenticated semi-quantum key distribution (ASQKD) without using an authenticated classical channel. This study further proposes two advanced ASQKD protocols. Compared to Yu et al.'s schemes, the proposed protocols ensure better qubit efficiency and require fewer pre-shared keys. Security analyses show that the proposed ASQKD protocols also can be secure against several well-known outside eavesdropper's attacks.

  4. Free-space quantum key distribution with entangled photons

    CERN Document Server

    Marcikic, I; Kurtsiefer, C; Marcikic, Ivan; Lamas-Linares, Antia; Kurtsiefer, Christian

    2006-01-01

    We report on a complete experimental implementation of a quantum key distribution protocol through a free space link using polarization-entangled photon pairs from a compact parametric down-conversion source. Over 10 hours of uninterrupted communication between sites 1.5 km apart, we observe average key generation rates of 630 per second after error correction and privacy amplification. Our scheme requires no specific hardware channel for synchronization apart from a classical wireless link, and no explicit random number generator.

  5. Active phase compensation of quantum key distribution system

    Institute of Scientific and Technical Information of China (English)

    CHEN Wei; HAN ZhengFu; MO XiaoFan; XU FangXing; WEI Guo; GUO GuangCan

    2008-01-01

    Quantum key distribution (QKD) system must be robust enough in practical communication. Besides birefringence of fiber, system performance is notably affected by phase drift. The Faraday-Michelson QKD system can auto-compensate the birefringence of fiber, but phase shift is still a serious problem in its practical operation. In this paper, the major reason of phase drift and its effect on Faraday-Michel-son QKD system is analyzed and an effective active phase compensation scheme is proposed. By this means, we demonstrate a quantum key distribution system which can stably run over 37-km fiber in practical working condition with the long-time averaged quantum bit error rate of 1.59% and the stan-dard derivation of 0.46%. This result shows that the active phase compensation scheme is suitable to be used in practical QKD systems based on double asymmetric interferometers without additional de-vices and thermal controller.

  6. Quantum key distribution without detector vulnerabilities using optically seeded lasers

    Science.gov (United States)

    Comandar, L. C.; Lucamarini, M.; Fröhlich, B.; Dynes, J. F.; Sharpe, A. W.; Tam, S. W.-B.; Yuan, Z. L.; Penty, R. V.; Shields, A. J.

    2016-05-01

    Security in quantum cryptography is continuously challenged by inventive attacks targeting the real components of a cryptographic set-up, and duly restored by new countermeasures to foil them. Owing to their high sensitivity and complex design, detectors are the most frequently attacked components. It was recently shown that two-photon interference from independent light sources can be used to remove any vulnerability from detectors. This new form of detection-safe quantum key distribution (QKD), termed measurement-device-independent (MDI), has been experimentally demonstrated but with modest key rates. Here, we introduce a new pulsed laser seeding technique to obtain high-visibility interference from gain-switched lasers and thereby perform MDI-QKD with unprecedented key rates in excess of 1 megabit per second in the finite-size regime. This represents a two to six orders of magnitude improvement over existing implementations and supports the new scheme as a practical resource for secure quantum communications.

  7. High-capacity quantum Fibonacci coding for key distribution

    Science.gov (United States)

    Simon, David S.; Lawrence, Nate; Trevino, Jacob; Dal Negro, Luca; Sergienko, Alexander V.

    2013-03-01

    Quantum cryptography and quantum key distribution (QKD) have been the most successful applications of quantum information processing, highlighting the unique capability of quantum mechanics, through the no-cloning theorem, to securely share encryption keys between two parties. Here, we present an approach to high-capacity, high-efficiency QKD by exploiting cross-disciplinary ideas from quantum information theory and the theory of light scattering of aperiodic photonic media. We propose a unique type of entangled-photon source, as well as a physical mechanism for efficiently sharing keys. The key-sharing protocol combines entanglement with the mathematical properties of a recursive sequence to allow a realization of the physical conditions necessary for implementation of the no-cloning principle for QKD, while the source produces entangled photons whose orbital angular momenta (OAM) are in a superposition of Fibonacci numbers. The source is used to implement a particular physical realization of the protocol by randomly encoding the Fibonacci sequence onto entangled OAM states, allowing secure generation of long keys from few photons. Unlike in polarization-based protocols, reference frame alignment is unnecessary, while the required experimental setup is simpler than other OAM-based protocols capable of achieving the same capacity and its complexity grows less rapidly with increasing range of OAM used.

  8. A universal coherent source for quantum key distribution

    Institute of Scientific and Technical Information of China (English)

    ZHANG ShengLi; ZOU XuBo; LI ChuanFeng; JIN ChenHui; GUO GuangCan

    2009-01-01

    We propose a concept of universal coherent source for quantum key distribution. The weak coherent pulse (WCP) and heralded single photon source (HSPS) are the most common photon sources for state-of-art quantum key distribution (QKD). However, there exists a prominent crossover between the maximal secure distance and the secure key generating rate in short and middle distance if one applies these two sources in a practical decoy state quantum key distribution. It is shown that by combining the heralded pair coherent state (HPCS) photon source and the practical decoy state method together, one can not only strengthen the maximal secure transmission distance, but also improve key generat-ing rate at short and medium distance. Moreover, the advancement in key generating is not confined in the particular protocol utilized and can be easily checked for both BB84 and SARG protocol. Finally, we clearly demonstrate how the HPCS-based decoy method works effectively and feasibly by proposing an efficient HPCS-based "1 signal+2 decoy" state method.

  9. Autonomous open-source hardware apparatus for quantum key distribution

    Directory of Open Access Journals (Sweden)

    Ignacio H. López Grande

    2016-01-01

    Full Text Available We describe an autonomous, fully functional implementation of the BB84 quantum key distribution protocol using open source hardware microcontrollers for the synchronization, communication, key sifting and real-time key generation diagnostics. The quantum bits are prepared in the polarization of weak optical pulses generated with light emitting diodes, and detected using a sole single-photon counter and a temporally multiplexed scheme. The system generates a shared cryptographic key at a rate of 365 bps, with a raw quantum bit error rate of 2.7%. A detailed description of the peripheral electronics for control, driving and communication between stages is released as supplementary material. The device can be built using simple and reliable hardware and it is presented as an alternative for a practical realization of sophisticated, yet accessible quantum key distribution systems. Received: 11 Novembre 2015, Accepted: 7 January 2016; Edited by: O. Martínez; DOI: http://dx.doi.org/10.4279/PIP.080002 Cite as: I H López Grande, C T Schmiegelow, M A Larotonda, Papers in Physics 8, 080002 (2016

  10. The security and recent technology of quantum key distribution

    Institute of Scientific and Technical Information of China (English)

    WANG Xiang-bin; YING Hao; MA Huai-xing; PENG Cheng-zhi; YANG Tao; PAN Jian-wei

    2006-01-01

    In principle,quantum key distribution (QKD)can be used to make unconditionally secure private communication.However,the security of the existing real system for QKD needs to be carefully examined.Actually,the existing experiments based on weak coherent states are not secure under photon-number-splitting attack.Fortunately,the decoy-state method and the entanglement-distribution method can be used to realize the unconditionally secure QKD based on real-life systems with existing technology.

  11. Free-Space Quantum Key Distribution using Polarization Entangled Photons

    Science.gov (United States)

    Kurtsiefer, Christian

    2007-06-01

    We report on a complete experimental implementation of a quantum key distribution protocol through a free space link using polarization-entangled photon pairs from a compact parametric down-conversion source [1]. Based on a BB84-equivalent protocol, we generated without interruption over 10 hours a secret key free-space optical link distance of 1.5 km with a rate up to 950 bits per second after error correction and privacy amplification. Our system is based on two time stamp units and relies on no specific hardware channel for coincidence identification besides an IP link. For that, initial clock synchronization with an accuracy of better than 2 ns is achieved, based on a conventional NTP protocol and a tiered cross correlation of time tags on both sides. Time tags are used to servo a local clock, allowing a streamed measurement on correctly identified photon pairs. Contrary to the majority of quantum key distribution systems, this approach does not require a trusted large-bandwidth random number generator, but integrates that into the physical key generation process. We discuss our current progress of implementing a key distribution via an atmospherical link during daylight conditions, and possible attack scenarios on a physical timing information side channel to a entanglement-based key distribution system. [1] I. Marcikic, A. Lamas-Linares, C. Kurtsiefer, Appl. Phys. Lett. 89, 101122 (2006).

  12. Memory-assisted measurement-device-independent quantum key distribution

    Science.gov (United States)

    Panayi, Christiana; Razavi, Mohsen; Ma, Xiongfeng; Lütkenhaus, Norbert

    2014-04-01

    A protocol with the potential of beating the existing distance records for conventional quantum key distribution (QKD) systems is proposed. It borrows ideas from quantum repeaters by using memories in the middle of the link, and that of measurement-device-independent QKD, which only requires optical source equipment at the user's end. For certain memories with short access times, our scheme allows a higher repetition rate than that of quantum repeaters with single-mode memories, thereby requiring lower coherence times. By accounting for various sources of nonideality, such as memory decoherence, dark counts, misalignment errors, and background noise, as well as timing issues with memories, we develop a mathematical framework within which we can compare QKD systems with and without memories. In particular, we show that with the state-of-the-art technology for quantum memories, it is potentially possible to devise memory-assisted QKD systems that, at certain distances of practical interest, outperform current QKD implementations.

  13. Notes on a Continuous-Variable Quantum Key Distribution Scheme

    Science.gov (United States)

    Ichikawa, Tsubasa; Hirano, Takuya; Matsubara, Takuto; Ono, Motoharu; Namiki, Ryo

    2017-09-01

    We develop a physical model to describe the signal transmission for a continuous-variable quantum key distribution scheme and investigate its security against a couple of eavesdropping attacks assuming that the eavesdropper's power is partly restricted owing to today's technological limitations. We consider an eavesdropper performing quantum optical homodyne measurement on the signal obtained by a type of beamsplitting attack. We also consider the case in which the eavesdropper Eve is unable to access a quantum memory and she performs heterodyne measurement on her signal without performing a delayed measurement. Our formulation includes a model in which the receiver's loss and noise are unaccessible by the eavesdropper. This setup enables us to investigate the condition that Eve uses a practical fiber differently from the usual beamsplitting attack where she can deploy a lossless transmission channel. The secret key rates are calculated in both the direct and reverse reconciliation scenarios.

  14. Measurement-device-independent entanglement-based quantum key distribution

    Science.gov (United States)

    Yang, Xiuqing; Wei, Kejin; Ma, Haiqiang; Sun, Shihai; Liu, Hongwei; Yin, Zhenqiang; Li, Zuohan; Lian, Shibin; Du, Yungang; Wu, Lingan

    2016-05-01

    We present a quantum key distribution protocol in a model in which the legitimate users gather statistics as in the measurement-device-independent entanglement witness to certify the sources and the measurement devices. We show that the task of measurement-device-independent quantum communication can be accomplished based on monogamy of entanglement, and it is fairly loss tolerate including source and detector flaws. We derive a tight bound for collective attacks on the Holevo information between the authorized parties and the eavesdropper. Then with this bound, the final secret key rate with the source flaws can be obtained. The results show that long-distance quantum cryptography over 144 km can be made secure using only standard threshold detectors.

  15. Authenticated Quantum Key Distribution with Collective Detection using Single Photons

    Science.gov (United States)

    Huang, Wei; Xu, Bing-Jie; Duan, Ji-Tong; Liu, Bin; Su, Qi; He, Yuan-Hang; Jia, Heng-Yue

    2016-10-01

    We present two authenticated quantum key distribution (AQKD) protocols by utilizing the idea of collective (eavesdropping) detection. One is a two-party AQKD protocol, the other is a multiparty AQKD protocol with star network topology. In these protocols, the classical channels need not be assumed to be authenticated and the single photons are used as the quantum information carriers. To achieve mutual identity authentication and establish a random key in each of the proposed protocols, only one participant should be capable of preparing and measuring single photons, and the main quantum ability that the rest of the participants should have is just performing certain unitary operations. Security analysis shows that these protocols are free from various kinds of attacks, especially the impersonation attack and the man-in-the-middle (MITM) attack.

  16. Decoy State Quantum Key Distribution with Odd Coherent State

    Institute of Scientific and Technical Information of China (English)

    SUN Shi-Hai; GAO Ming; DAI Hong-Yi; CHEN Ping-Xing; LI Cheng-Zu

    2008-01-01

    We propose a decoy state quantum key distribution scheme with odd coherent state which follows sub-Poissonian distributed photon count and has low probability of the multi-photon event and vacuum event in each pulse. The numerical calculations show that our scheme can improve efficiently the key generation rate and secure communication distance. Furthermore, only one decoy state is necessary to approach to the perfect asymptotic limit with infinite decoy states in our scheme, but at least two decoy states are needed in other scheme.

  17. Long-distance quantum key distribution with imperfect devices

    Energy Technology Data Exchange (ETDEWEB)

    Lo Piparo, Nicoló; Razavi, Mohsen [School of Electronic and Electrical Engineering, University of Leeds (United Kingdom)

    2014-12-04

    Quantum key distribution over probabilistic quantum repeaters is addressed. We compare, under practical assumptions, two such schemes in terms of their secure key generation rate per memory, R{sub QKD}. The two schemes under investigation are the one proposed by Duan et al. in [Nat. 414, 413 (2001)] and that of Sangouard et al. proposed in [Phys. Rev. A 76, 050301 (2007)]. We consider various sources of imperfections in the latter protocol, such as a nonzero double-photon probability for the source, dark count per pulse, channel loss and inefficiencies in photodetectors and memories, to find the rate for different nesting levels. We determine the maximum value of the double-photon probability beyond which it is not possible to share a secret key anymore. We find the crossover distance for up to three nesting levels. We finally compare the two protocols.

  18. Orthogonal Frequency-Division Multiplexed Quantum Key Distribution

    Science.gov (United States)

    Bahrani, Sima; Razavi, Mohsen; Salehi, Jawad A.

    2015-12-01

    We propose orthogonal frequency division multiplexing (OFDM), as a spectrally efficient multiplexing technique, for quantum key distribution (QKD) at the core of trustednode quantum networks. Two main schemes are proposed and analyzed in detail, considering system imperfections, specifically, time misalignment issues. It turns out that while multiple service providers can share the network infrastructure using the proposed multiplexing techniques, no gain in the total secret key generation rate is obtained if one uses conventional all-optical passive OFDM decoders. To achieve a linear increase in the key rate with the number of channels, an alternative active setup for OFDM decoding is proposed, which employs an optical switch in addition to conventional passive circuits. We show that by using our proposed decoder the bandwidth utilization is considerably improved as compared to conventional wavelength division multiplexing techniques.

  19. Long-distance quantum key distribution with imperfect devices

    Science.gov (United States)

    Lo Piparo, Nicoló; Razavi, Mohsen

    2014-12-01

    Quantum key distribution over probabilistic quantum repeaters is addressed. We compare, under practical assumptions, two such schemes in terms of their secure key generation rate per memory, RQKD. The two schemes under investigation are the one proposed by Duan et al. in [Nat. 414, 413 (2001)] and that of Sangouard et al. proposed in [Phys. Rev. A 76, 050301 (2007)]. We consider various sources of imperfections in the latter protocol, such as a nonzero double-photon probability for the source, dark count per pulse, channel loss and inefficiencies in photodetectors and memories, to find the rate for different nesting levels. We determine the maximum value of the double-photon probability beyond which it is not possible to share a secret key anymore. We find the crossover distance for up to three nesting levels. We finally compare the two protocols.

  20. High-efficiency reconciliation for continuous variable quantum key distribution

    Science.gov (United States)

    Bai, Zengliang; Yang, Shenshen; Li, Yongmin

    2017-04-01

    Quantum key distribution (QKD) is the most mature application of quantum information technology. Information reconciliation is a crucial step in QKD and significantly affects the final secret key rates shared between two legitimate parties. We analyze and compare various construction methods of low-density parity-check (LDPC) codes and design high-performance irregular LDPC codes with a block length of 106. Starting from these good codes and exploiting the slice reconciliation technique based on multilevel coding and multistage decoding, we realize high-efficiency Gaussian key reconciliation with efficiency higher than 95% for signal-to-noise ratios above 1. Our demonstrated method can be readily applied in continuous variable QKD.

  1. Experimental demonstration of passive decoy state quantum key distribution

    Institute of Scientific and Technical Information of China (English)

    Zhang Yang; Wang Shuang; Yin Zhen-Qiang; Chen Wei; Liang Wen-Ye; Li Hong-Wei; Guo Guang-Can; Han Zheng-Fu

    2012-01-01

    Passive decoy state quantum key distribution (PDS-QKD) has advantages in high-speed scenarios.We propose a modified model to simulate the PDS-QKD with a weak coherent light source based on Curty's theory [Opt.Lett.343238 (2009)].The modified model can provide better performance in a practical PDS-QKD system.Moreover,we report an experimental demonstration of the PDS-QKD of over 22.0-dB channel loss.

  2. An efficient quantum key distribution protocol with orthogonal product states

    Institute of Scientific and Technical Information of China (English)

    Yang Yu-Guang; Wen Qiao-Yan

    2007-01-01

    An efficient quantum key distribution (QKD) protocol with orthogonal product states in the 3(×)3 Hilbert space is presented. The sender, Alice, disorders the orthogonal product state sequence and sends it to Bob. After Alice has published the matching information of the particle sequence, Bob recovers the correct correspondences and makes an orthogonal measurement on the orthogonal product states to obtain the information sent by Alice. Finally, security analysis is also made.

  3. Security analysis of continuous-variable quantum key distribution scheme

    Institute of Scientific and Technical Information of China (English)

    Zhu Jun; He Guang-Qiang; Zeng Gui-Hua

    2007-01-01

    In this paper security of the quantum key distribution scheme using correlations of continuous variable Einstein- Podolsky- Rosen (EPR) pairs is investigated. A new approach for calculating the secret information rate △I is proposed by using the Shannon information theory. Employing an available parameter F which is associated with the entanglement of the EPR pairs, one can detect easily the eavesdropping. Results show that the proposed scheme is secure against individual beam splitter attack strategy with a proper squeeze parameter.

  4. Conditional beam splitting attack on quantum key distribution

    OpenAIRE

    Calsamiglia, John; Barnett, Stephen M.; Lütkenhaus, Norbert

    2001-01-01

    We present a novel attack on quantum key distribution based on the idea of adaptive absorption [calsam01]. The conditional beam splitting attack is shown to be much more efficient than the conventional beam spitting attack, achieving a performance similar to the, powerful but currently unfeasible, photon number splitting attack. The implementation of the conditional beam splitting attack, based solely on linear optical elements, is well within reach of current technology.

  5. Long-distance practical quantum key distribution by entanglement swapping

    CERN Document Server

    Scherer, Artur; Tittel, Wolfgang

    2010-01-01

    We develop a model for practical, entanglement-based long-distance quantum key distribution employing entanglement swapping as a key building block. Relying only on existing off-the-shelf technology, we show how to optimize resources so as to maximize secret key distribution rates. The tools comprise lossy transmission links, such as telecom optical fibers or free space, parametric down-conversion sources of entangled photon pairs, and threshold detectors that are inefficient and have dark counts. Our analysis provides the optimal trade-off between detector efficiency and dark counts, which are usually competing, as well as the optimal source brightness that maximizes the secret key rate for specified distances (i.e. loss) between sender and receiver.

  6. Long-distance quantum key distribution in optical fiber

    CERN Document Server

    Hiskett, P A; Lita, A E; Miller, A J; Nam, S; Nordholt, J E; Peterson, C G; Rosenberg, D

    2006-01-01

    Use of low-noise detectors can both increase the secret bit rate of long-distance quantum key distribution (QKD) and dramatically extend the length of a fibre optic link over which secure key can be distributed. Previous work has demonstrated use of ultra-low-noise transition-edge sensors (TESs) in a QKD system with transmission over 50 km. In this work, we demonstrate the potential of the TESs by successfully generating error-corrected, privacy-amplified key over 148.7 km of dark optical fibre at a mean photon number mu = 0.1, or 184.6 km of dark optical fibre at a mean photon number of 0.5. We have also exchanged secret key over 67.5 km that is secure against powerful photon-number-splitting attacks.

  7. Deterministic Quantum Key Distribution Using Gaussian-Modulated Squeezed States

    Institute of Scientific and Technical Information of China (English)

    何广强; 朱俊; 曾贵华

    2011-01-01

    A continuous variable ping-pong scheme, which is utilized to generate deterministic private key, is proposed. The proposed scheme is implemented physically by using Ganssian-modulated squeezed states. The deterministic char- acteristic, i.e., no basis reconciliation between two parties, leads a nearly two-time efficiency comparing to the standard quantum key distribution schemes. Especially, the separate control mode does not need in the proposed scheme so that it is simpler and more available than previous ping-pong schemes. The attacker may be detected easily through the fidelity of the transmitted signal, and may not be successful in the beam splitter attack strategy.

  8. Security of practical phase-coding quantum key distribution

    CERN Document Server

    Li, Hong-Wei; Han, Zheng-Fu; Bao, Wan-Su; Guo, Guang-Can

    2009-01-01

    Security proof of practical quantum key distribution (QKD) has attracted a lot of attentions in recent years. Most of real-life QKD implementations are based on phase-coding BB84 protocol, which usually uses Unbalanced Mach-Zehnder Interferometer (UMZI) as the information coder and decoder. However, the long arm and short arm of UMZI will introduce different loss in practical experimental realizations, the state emitted by Alice's side is nolonger standard BB84 states. In this paper, we will give a security analysis in this situation. Counterintuitively, active compensation for this different loss will only lower the secret key bit rate.

  9. Alternative schemes for measurement-device-independent quantum key distribution

    CERN Document Server

    Ma, Xiongfeng

    2012-01-01

    A practical scheme for measurement-device-independent quantum key distribution using phase and path/time encoding is presented. In addition to immunity to existing loopholes in detection systems, our setup employs simple encoding and decoding modules without relying on polarization maintenance or optical switches. Moreover, by handling, with a modified sifting technique, the dead time limitations in single-photon detectors, our scheme can be run with only two single-photon detectors. With a phase-post-selection technique, a decoy-state variant of our scheme is also proposed, whose secret key generation rate scales linearly with the channel transmittance.

  10. Long distance decoy state quantum key distribution in optical fiber

    CERN Document Server

    Rosenberg, D; Hiskett, P A; Hughes, R J; Lita, A E; Nam, S W; Nordholt, J E; Peterson, C G; Rice, P R; Harrington, Jim W.; Hiskett, Philip A.; Hughes, Richard J.; Lita, Adriana E.; Nam, Sae Woo; Nordholt, Jane E.; Peterson, Charles G.; Rice, Patrick R.; Rosenberg, Danna

    2006-01-01

    The theoretical existence of photon-number-splitting attacks creates a security loophole for most quantum key distribution (QKD) demonstrations that use a highly attenuated laser source. Using ultra-low-noise, high-efficiency transition-edge sensor photo-detectors, we have implemented the first finite statistics version of a decoy state protocol in a one-way QKD system, enabling the creation of secure keys immune to both photon-number-splitting attacks and Trojan horse attacks over 107 km of optical fiber.

  11. Side Channel Passive Quantum Key Distribution with One Uninformative State

    Science.gov (United States)

    Kang, Guo-Dong; Zhou, Qing-Ping; Fang, Mao-Fa

    2017-03-01

    In most of quantum key distribution schemes, real random number generators are required on both sides for preparation and measurement bases choice. In this paper, via entangled photon pairs, we present a side channel passive quantum key distribution scheme, in which random number generator is unneeded on the receiver side. On the sender Alice side, along with massive of signal photons, small amount of uninformative photons are randomly sent to her partner Bob for eavesdropper-presence testing and error estimation. While on the other side channel, without using random number generator Bob do not actively measure the income signals randomly in two non-orthogonal bases. Instead, he just passively register photon click events, in two settled symmetric (i.e. X) bases, and the raw key(click events) is the probable outcomes of a special quantum measurement module constructed by Alice and Bob. Further, security analysis and formulas of security bounds for this scheme is also investigated under reasonable assumptions. Our work shows that the uninformative state employed in this paper is powerful to fight against eavesdropper Eve.

  12. Experimental passive decoy-state quantum key distribution

    Science.gov (United States)

    Sun, Qi-Chao; Wang, Wei-Long; Liu, Yang; Zhou, Fei; Pelc, Jason S.; Fejer, M. M.; Peng, Cheng-Zhi; Chen, Xianfeng; Ma, Xiongfeng; Zhang, Qiang; Pan, Jian-Wei

    2014-08-01

    The decoy-state method is widely used in practical quantum key distribution systems to replace ideal single photon sources with realistic light sources of varying intensities. Instead of active modulation, the passive decoy-state method employs built-in decoy states in a parametric down-conversion photon source, which can decrease the side channel information leakage in decoy-state preparation and hence increase the security. By employing low dark count up-conversion single photon detectors, we experimentally demonstrate the passive decoy-state method over a 50 km long optical fiber and obtain a key rate of about 100 bit s-1. Our result suggests that the passive decoy-state source is a practical candidate for future quantum communication implementation.

  13. Trustworthiness of detectors in quantum key distribution with untrusted detectors

    Science.gov (United States)

    Qi, Bing

    2015-02-01

    Measurement-device-independent quantum key distribution (MDI-QKD) protocol has been demonstrated as a viable solution to detector side-channel attacks. Recently, to bridge the strong security of MDI-QKD with the high efficiency of conventional QKD, the detector-device-independent (DDI) QKD has been proposed. One crucial assumption made in DDI-QKD is that the untrusted Bell state measurement (BSM) located inside the receiver's laboratory cannot send any unwanted information to the outside. Here, we show that if the BSM is completely untrusted, a simple scheme would allow the BSM to send information to the outside. Combined with Trojan horse attacks, this scheme could allow an eavesdropper to gain information of the quantum key without being detected. To prevent the above attack, either countermeasures to Trojan horse attacks or some trustworthiness to the "untrusted" BSM device is required.

  14. Long distance free-space quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt-Manderbach, T.

    2007-10-16

    The aim of the presented experiment was to investigate the feasibility of satellite-based global quantum key distribution. In this context, a free-space quantum key distribution experiment over a real distance of 144 km was performed. The transmitter and the receiver were situated in 2500 m altitude on the Canary Islands of La Palma and Tenerife, respectively. The small and compact transmitter unit generated attenuated laser pulses, that were sent to the receiver via a 15-cm optical telescope. The receiver unit for polarisation analysis and detection of the sent pulses was integrated into an existing mirror telescope designed for classical optical satellite communications. To ensure the required stability and efficiency of the optical link in the presence of atmospheric turbulence, the two telescopes were equipped with a bi-directional automatic tracking system. Still, due to stray light and high optical attenuation, secure key exchange would not be possible using attenuated pulses in connection with the standard BB84 protocol. The photon number statistics of attenuated pulses follows a Poissonian distribution. Hence, by removing a photon from all pulses containing two or more photons, an eavesdropper could measure its polarisation without disturbing the polarisation state of the remaining pulse. In this way, he can gain information about the key without introducing detectable errors. To protect against such attacks, the presented experiment employed the recently developed method of using additional 'decoy' states, i.e., the the intensity of the pulses created by the transmitter were varied in a random manner. By analysing the detection probabilities of the different pulses individually, a photon-number-splitting attack can be detected. Thanks to the decoy-state analysis, the secrecy of the resulting quantum key could be ensured despite the Poissonian nature of the emitted pulses. For a channel attenuation as high as 35 dB, a secret key rate of up to 250

  15. Simultaneous classical communication and quantum key distribution using continuous variables*

    Science.gov (United States)

    Qi, Bing

    2016-10-01

    Presently, classical optical communication systems employing strong laser pulses and quantum key distribution (QKD) systems working at single-photon levels are very different communication modalities. Dedicated devices are commonly required to implement QKD. In this paper, we propose a scheme which allows classical communication and QKD to be implemented simultaneously using the same communication infrastructure. More specially, we propose a coherent communication scheme where both the bits for classical communication and the Gaussian distributed random numbers for QKD are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Simulation results based on practical system parameters show that both deterministic classical communication with a bit error rate of 10-9 and secure key distribution could be achieved over tens of kilometers of single-mode fibers. It is conceivable that in the future coherent optical communication network, QKD will be operated in the background of classical communication at a minimal cost.

  16. A Composed Protocol of Quantum Identity Authentication Plus Quantum Key Distribution Based on Squeezed States

    Institute of Scientific and Technical Information of China (English)

    张盛; 王剑; 唐朝京; 张权

    2011-01-01

    It is established that a single quantum cryptography protocol usually cooperates with other cryptographic systems, such as an authentication system, in the real world. However, few protocols have been proposed on how to combine two or more quantum protocols. To fill this gap, we propose a composed quantum protocol, containing both quantum identity authentication and quantum key distribution, using squeezed states. Hence, not only the identity can be verified, but also a new private key can be generated by our new protocol. We also analyze the security under an optimal attack, and the efficiency, which is defined by the threshold of the tolerant error rate, using Gaussian error function.

  17. Statistical Quadrature Evolution for Continuous-Variable Quantum Key Distribution

    Science.gov (United States)

    Gyongyosi, Laszlo; Imre, Sandor

    2016-05-01

    We propose a statistical quadrature evolution (SQE) method for multicarrier continuous-variable quantum key distribution (CVQKD). A multicarrier CVQKD protocol utilizes Gaussian subcarrier quantum continuous variables (CV) for information transmission. The SQE framework provides a minimal error estimate of the quadratures of the CV quantum states from the discrete, measured noisy subcarrier variables. We define a method for the statistical modeling and processing of noisy Gaussian subcarrier quadratures. We introduce the terms statistical secret key rate and statistical private classical information, which quantities are derived purely by the statistical functions of our method. We prove the secret key rate formulas for a multiple access multicarrier CVQKD. The framework can be established in an arbitrary CVQKD protocol and measurement setting, and are implementable by standard low-complexity statistical functions, which is particularly convenient for an experimental CVQKD scenario. This work was partially supported by the GOP-1.1.1-11-2012-0092 project sponsored by the EU and European Structural Fund, by the Hungarian Scientific Research Fund - OTKA K-112125, and by the COST Action MP1006.

  18. Reverse reconciliation for continuous variable quantum key distribution

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    An efficient and practical post-processing technique based on reverse reconciliation for continuous variable quantum key distribution is proposed and simulated with low-density parity check (LDPC) codes. MultiLevel Coding/ MultiStage Decoding, which fully utilizes optimization technique such as vector quantization and iterative decoding and the optimal channel coding most close to the Shannon limit, was used to realize efficient reverse reconciliation algorithm. Simulation results showed that the proposed method can improve the secure key distribution rate to 2.2 kb/s and the coding efficiency to 0.89 over 20 km in single-mode optical fiber. Moreover, there still is room for much improvement.

  19. Finite-key analysis of a practical decoy-state high-dimensional quantum key distribution

    Science.gov (United States)

    Bao, Haize; Bao, Wansu; Wang, Yang; Zhou, Chun; Chen, Ruike

    2016-05-01

    Compared with two-level quantum key distribution (QKD), high-dimensional QKD enables two distant parties to share a secret key at a higher rate. We provide a finite-key security analysis for the recently proposed practical high-dimensional decoy-state QKD protocol based on time-energy entanglement. We employ two methods to estimate the statistical fluctuation of the postselection probability and give a tighter bound on the secure-key capacity. By numerical evaluation, we show the finite-key effect on the secure-key capacity in different conditions. Moreover, our approach could be used to optimize parameters in practical implementations of high-dimensional QKD.

  20. Numerical analysis of decoy state quantum key distribution protocols

    Energy Technology Data Exchange (ETDEWEB)

    Harrington, Jim W [Los Alamos National Laboratory; Rice, Patrick R [Los Alamos National Laboratory

    2008-01-01

    Decoy state protocols are a useful tool for many quantum key distribution systems implemented with weak coherent pulses, allowing significantly better secret bit rates and longer maximum distances. In this paper we present a method to numerically find optimal three-level protocols, and we examine how the secret bit rate and the optimized parameters are dependent on various system properties, such as session length, transmission loss, and visibility. Additionally, we show how to modify the decoy state analysis to handle partially distinguishable decoy states as well as uncertainty in the prepared intensities.

  1. Quantum key distribution based on phase encoding and polarization measurement

    CERN Document Server

    Ma, H Q; Zhao, J L; Ma, Hai-Qiang; Wu, Ling-An; Zhao, Jian-Ling

    2007-01-01

    A one-way quantum key distribution scheme based on intrinsically stable Faraday-mirror type Michelson interferometers with four-port polarizing beampslitters has been demonstrated which can compensate for birefringence effects automatically. The encoding is performed with phase modulators, but decoding is accomplished through measurement of the polarization state of Bob's photons. An extinction ratio of about 30dB was maintained for several hours over 50km of fiber at 1310nm without any adjustment to the setup, which shows its good potential for practical systems

  2. Decoy States and Two Way Quantum Key Distribution Schemes

    CERN Document Server

    Shaari, J S; Ali, Sellami

    2010-01-01

    We study the possible application of the decoy state method on a basic two way quantum key distribution (QKD) scheme to extend its distance. Noting the obvious advantage of such a QKD scheme in allowing for single as well as double photon contributions, we derive relevant lower-bounds on the corresponding gains in a practical decoy state implementation using two intensities for decoy states. We work with two different approaches in this vein and compare these with an ideal infinite decoy state case as well as the simulation of the original LM05.

  3. Self-referenced continuous-variable quantum key distribution

    Science.gov (United States)

    Soh, Daniel B. S.; Sarovar, Mohan; Camacho, Ryan

    2017-01-24

    Various technologies for continuous-variable quantum key distribution without transmitting a transmitter's local oscillator are described herein. A receiver on an optical transmission channel uses an oscillator signal generated by a light source at the receiver's location to perform interferometric detection on received signals. An optical reference pulse is sent by the transmitter on the transmission channel and the receiver computes a phase offset of the transmission based on quadrature measurements of the reference pulse. The receiver can then compensate for the phase offset between the transmitter's reference and the receiver's reference when measuring quadratures of received data pulses.

  4. Self-referenced continuous-variable quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Soh, Daniel B. S.; Sarovar, Mohan; Camacho, Ryan

    2017-01-24

    Various technologies for continuous-variable quantum key distribution without transmitting a transmitter's local oscillator are described herein. A receiver on an optical transmission channel uses an oscillator signal generated by a light source at the receiver's location to perform interferometric detection on received signals. An optical reference pulse is sent by the transmitter on the transmission channel and the receiver computes a phase offset of the transmission based on quadrature measurements of the reference pulse. The receiver can then compensate for the phase offset between the transmitter's reference and the receiver's reference when measuring quadratures of received data pulses.

  5. Trojan Horse attacks on Quantum Key Distribution systems

    CERN Document Server

    Gisin, Nicolas; Kraus, B; Zbinden, H; Ribordy, G

    2005-01-01

    General Trojan horse attacks on quantum key distribution systems are analyzed. We illustrate the power of such attacks with today's technology and conclude that all system must implement active counter-measures. In particular all systems must include an auxiliary detector that monitors any incoming light. We show that such counter-measures can be efficient, provided enough additional privacy amplification is applied to the data. We present a practical way to reduce the maximal information gain that an adversary can gain using Trojan horse attacks.

  6. Single Photon Detector at Telecom Wavelengths for Quantum Key Distribution

    Institute of Scientific and Technical Information of China (English)

    LIU Yun; WU Qing-Lin; HAN Zheng-Fu; DAI Yi-Min; QUO Guang-Can

    2006-01-01

    Using InGaAs/InP avalanche photodiodes as sensors and coaxial cables as reflection lines to reject spike signals, we have firstly employed the "timing filtering" gates to pick out avalanche signals and have realized the single photon detection at 1550 nm in the temperature range of thermoelectric cooling. A ratio of the dark count rate to the detection efficiency was obtained to be 9×10-5 at 223K. When the detector is applied to a practical quantum key distribution system, the transmission distance can reach 89.5km and the repetition rate can reach 0.33MHz.

  7. Continuous Variable Quantum Key Distribution with a Noisy Laser

    DEFF Research Database (Denmark)

    Jacobsen, Christian Scheffmann; Gehring, Tobias; Andersen, Ulrik Lund

    2015-01-01

    a theoretically proposed prepare-and-measure continuous-variable protocol and experimentally demonstrate the robustness of it against preparation noise stemming for instance from technical laser noise. Provided that direct reconciliation techniques are used in the post-processing we show that for small distances......Existing experimental implementations of continuous-variable quantum key distribution require shot-noise limited operation, achieved with shot-noise limited lasers. However, loosening this requirement on the laser source would allow for cheaper, potentially integrated systems. Here, we implement...

  8. Recent developments in quantum key distribution: Theory and practice

    Energy Technology Data Exchange (ETDEWEB)

    Mauerer, W.; Helwig, W.; Silberhorn, C. [Max Planck Research Group, Institute of Optics, Information and Photonics, Integrated Quantum Optics Group, University of Erlangen-Nuernberg, Guenther-Scharowsky-Strasse 1/Bau 24, 91058 Erlangen (Germany)

    2008-02-15

    Quantum key distribution is among the foremost applications of quantum mechanics, both in terms of fundamental physics and as a technology on the brink of commercial deployment. Starting from principal schemes and initial proofs of unconditional security for perfect systems, much effort has gone into providing secure schemes which can cope with numerous experimental imperfections unavoidable in real world implementations. In this paper, we provide a comparison of various schemes and protocols. We analyse their efficiency and performance when implemented with imperfect physical components. We consider how experimental faults are accounted for using effective parameters. We compare various recent protocols and provide guidelines as to which components propose best advances when being improved. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  9. Feasible attack on detector-device-independent quantum key distribution.

    Science.gov (United States)

    Wei, Kejin; Liu, Hongwei; Ma, Haiqiang; Yang, Xiuqing; Zhang, Yong; Sun, Yongmei; Xiao, Jinghua; Ji, Yuefeng

    2017-03-27

    Recently, to bridge the gap between security of Measurement-device-independent quantum key distribution (MDI-QKD) and a high key rate, a novel protocol, the so-called detector-device-independent QKD (DDI-QKD), has been independently proposed by several groups and has attracted great interest. A higher key rate is obtained, since a single photon bell state measurement (BSM) setup is applied to DDI-QKD. Subsequently, Qi has proposed two attacks for this protocol. However, the first attack, in which Bob's BSM setup is assumed to be completely a "black box", is easily prevented by using some additional monitoring devices or by specifically characterizing the BSM. The second attack, which combines the blinding attack and the detector wavelength-dependent efficiency, is not explicitly discussed, and its feasibility is not experimentally confirmed. Here, we show that the second attack is not technically viable because of an intrinsically wavelength-dependent property of a realistic beam splitter, which is an essential component in DDI-QKD. Moreover, we propose a feasible attack that combines a well-known attack-detector blinding attack with intrinsic imperfections of single-photon detectors. The experimental measurement and proof-of-principle test results confirm that our attack can allow Eve to get a copy of quantum keys without being detected and that it is feasible with current technology.

  10. The physical underpinning of security proofs for quantum key distribution

    Science.gov (United States)

    Boileau, Jean Christian

    The dawn of quantum technology unveils a plethora of new possibilities and challenges in the world of information technology, one of which is the quest for secure information transmission. A breakthrough in classical algorithm or the development of a quantum computer could threaten the security of messages encoded using public key cryptosystems based on one-way function such as RSA. Quantum key distribution (QKD) offers an unconditionally secure alternative to such schemes, even in the advent of a quantum computer, as it does not rely on mathematical or technological assumptions, but rather on the universality of the laws of quantum mechanics. Physical concepts associated with quantum mechanics, like the uncertainty principle or entanglement, paved the way to the first successful security proof for QKD. Ever since, further development in security proofs for QKD has been remarkable. But the connection between entanglement distillation and the uncertainty principle has remained hidden under a pile of mathematical burden. Our main goal is to dig the physics out of the new advances in security proofs for QKD. By introducing an alternative definition of private state, which elaborates the ideas of Mayers and Koashi, we explain how the security of all QKD protocols follows from an entropic uncertainty principle. We show explicitly how privacy amplification protocol can be reduced to a private state distillation protocol constructed from our observations about the uncertainty principle. We also derive a generic security proof for one-way permutation-invariant QKD protocols. Considering collective attack, we achieve the same secret key generation rate as the Devetak-Winter's bound. Generalizing an observation from Kraus, Branciard and Renner, we have provided an improved version of the secret key generation rates by considering a different symmetrization. In certain situations, we argue that Azuma's inequality can simplify the security proof considerably, and we explain

  11. Scheme for Robust Long-Distance Continuous Variable Quantum Key Distribution

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong-Sheng; QUO Guang-Can

    2006-01-01

    It is shown that the configuration of phase coding for quantum key distribution with single photon can also be used for continuous variable quantum key distribution. Therefore the robust long-distance high-speed quantum key distribution can be achieved with current technology.

  12. Eigenchannel decomposition for continuous-variable quantum key distribution

    Science.gov (United States)

    Gyongyosi, L.; Imre, S.

    2015-03-01

    We develop a singular layer transmission model for continuous-variable quantum key distribution (CVQKD). In CVQKD, the transmit information is carried by continuous-variable (CV) quantum states, particularly by Gaussian random distributed position and momentum quadratures. The reliable transmission of the quadrature components over a noisy link is a cornerstone of CVQKD protocols. The proposed singular layer uses the singular value decomposition of the Gaussian quantum channel, which yields an additional degree of freedom for the phase space transmission. This additional degree of freedom can further be exploited in a multiple-access scenario. The singular layer defines the eigenchannels of the Gaussian physical link, which can be used for the simultaneous reliable transmission of multiple user data streams. We demonstrate the results through the adaptive multicarrier quadrature division-multiuser quadrature allocation (AMQD-MQA) CVQKD multiple-access scheme. We define the singular model of AMQD-MQA and characterize the properties of the eigenchannel interference. The singular layer transmission provides improved simultaneous transmission rates for the users with unconditional security in a multiple-access scenario, particularly in crucial low signal-to-noise ratio regimes.

  13. Secret Key Distillation for Continuous Variable Quantum Key Distribution against Gaussian Classical Eve

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yi-Bo; HAN Zheng-Fu; CHEN Jin-Jian; GU You-Zhen; GUO Guang-Can

    2008-01-01

    The continuous variable quantum key distribution is expected to provide high secret key rate without single photon source and detector, while the lack of the effective key distillation method makes it unpractical under the high loss condition. Here we present a single-bit-reverse-reconciliation protocol against Gaussian classical Eve,which can distill the secret key through practical imperfect error correction with high efficiency. The simulation results show that this protocol can distill secret keys even when the transmission fibre is longer than 150 km,which may make the continuous variable scheme to outvie the single photon one.

  14. Experimental demonstration of subcarrier multiplexed quantum key distribution system.

    Science.gov (United States)

    Mora, José; Ruiz-Alba, Antonio; Amaya, Waldimar; Martínez, Alfonso; García-Muñoz, Víctor; Calvo, David; Capmany, José

    2012-06-01

    We provide, to our knowledge, the first experimental demonstration of the feasibility of sending several parallel keys by exploiting the technique of subcarrier multiplexing (SCM) widely employed in microwave photonics. This approach brings several advantages such as high spectral efficiency compatible with the actual secure key rates, the sharing of the optical fainted pulse by all the quantum multiplexed channels reducing the system complexity, and the possibility of upgrading with wavelength division multiplexing in a two-tier scheme, to increase the number of parallel keys. Two independent quantum SCM channels featuring a sifted key rate of 10 Kb/s/channel over a link with quantum bit error rate <2% is reported.

  15. Robust and Efficient Sifting-Less Quantum Key Distribution Protocols

    CERN Document Server

    Grosshans, Frédéric

    2009-01-01

    We show that replacing the usual sifting step of the standard quantum-key-distribution protocol BB84 by a one-way reverse reconciliation procedure increases its robustness against photon-number-splitting (PNS) attacks to the level of the SARG04 protocol while keeping the raw key-rate of BB84. This protocol, which uses the same state and detection than BB84, is the m=4 member of a protocol-family using m polarization states which we introduce here. We show that the robustness of these protocols against PNS attacks increases exponentially with m, and that the effective keyrate of optimized weak coherent pulses decreases with the transmission T like T^{1+1/(m-2)}.

  16. A passive transmitter for quantum key distribution with coherent light

    CERN Document Server

    Curty, Marcos; Pruneri, Valerio; Mitchell, Morgan W

    2011-01-01

    Signal state preparation in quantum key distribution schemes can be realized using either an active or a passive source. Passive sources might be valuable in some scenarios; for instance, in those experimental setups operating at high transmission rates, since no externally driven element is required. Typical passive transmitters involve parametric down-conversion. More recently, it has been shown that phase-randomized coherent pulses also allow passive generation of decoy states and Bennett-Brassard 1984 (BB84) polarization signals, though the combination of both setups in a single passive source is cumbersome. In this paper, we present a complete passive transmitter that prepares decoy-state BB84 signals using coherent light. Our method employs sum-frequency generation together with linear optical components and classical photodetectors. In the asymptotic limit of an infinite long experiment, the resulting secret key rate (per pulse) is comparable to the one delivered by an active decoy-state BB84 setup wit...

  17. Spin-orbit hybrid entanglement quantum key distribution scheme

    Institute of Scientific and Technical Information of China (English)

    ZHANG ChengXian; GUO BangHong; CHENG GuangMing; GUO JianJun; FAN RongHua

    2014-01-01

    We propose a novel quantum key distribution scheme by using the SAM-OAM hybrid entangled state as the physical resource.To obtain this state,the polarization entangled photon pairs are created by the spontaneous parametric down conversion process,and then,the q-plate acts as a SAM-to-OAM transverter to transform the polarization entangled pairs into the hybrid entangled pattern,which opens the possibility to exploit the features of the higher-dimensional space of OAM state to encode information.In the manipulation and encoding process,Alice performs the SAM measurement by modulating the polarization state |θ>π on one photon,whereas Bob modulates the OAM sector state |x>1 on the other photon to encode his key elements using the designed holograms which is implemented by the computer-controlled SLM.With coincidence measurement,Alice could extract the key information.It is showed that N-based keys can be encoded with each pair of entangled photon,and this scheme is robust against Eve's individual attack.Also,the MUBs are not used.Alice and Bob do not need the classical communication for the key recovery.

  18. Experimental multiplexing of quantum key distribution with classical optical communication

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liu-Jun; Chen, Luo-Kan; Ju, Lei [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Xu, Mu-Lan; Zhao, Yong [Quantum Communication Technology Co., Ltd., Anhui, Hefei, Anhui 230088 (China); Chen, Kai; Chen, Zeng-Bing; Chen, Teng-Yun, E-mail: tychen@ustc.edu.cn; Pan, Jian-Wei [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2015-02-23

    We demonstrate the realization of quantum key distribution (QKD) when combined with classical optical communication, and synchronous signals within a single optical fiber. In the experiment, the classical communication sources use Fabry-Pérot (FP) lasers, which are implemented extensively in optical access networks. To perform QKD, multistage band-stop filtering techniques are developed, and a wavelength-division multiplexing scheme is designed for the multi-longitudinal-mode FP lasers. We have managed to maintain sufficient isolation among the quantum channel, the synchronous channel and the classical channels to guarantee good QKD performance. Finally, the quantum bit error rate remains below a level of 2% across the entire practical application range. The proposed multiplexing scheme can ensure low classical light loss, and enables QKD over fiber lengths of up to 45 km simultaneously when the fibers are populated with bidirectional FP laser communications. Our demonstration paves the way for application of QKD to current optical access networks, where FP lasers are widely used by the end users.

  19. Key-rate enhancement using qutrit states for quantum key distribution with askew aligned sources

    Science.gov (United States)

    Jo, Yonggi; Son, Wonmin

    2016-11-01

    It is known that measurement-device-independent quantum key distribution (MDI-QKD) provides ultimate security from all types of side-channel attack on detectors at the expense of low key rate. In the present study, we propose MDI-QKD using three-dimensional quantum states and show that the protocol improves the secret key rate under the analysis of mismatched-basis statistics. Specifically, we analyze security of the 3 d -MDI-QKD protocol with askew aligned sources, meaning that the original sources contain unwanted states instead of the expected one. We evaluate the secret key rate of the protocol and identify the regime in which the key rate is higher than the protocol with the qubit MDI-QKD.

  20. High-dimensional quantum key distribution based on multicore fiber using silicon photonic integrated circuits

    DEFF Research Database (Denmark)

    Ding, Yunhong; Bacco, Davide; Dalgaard, Kjeld

    2017-01-01

    Quantum key distribution provides an efficient means to exchange information in an unconditionally secure way. Historically, quantum key distribution protocols have been based on binary signal formats, such as two polarization states, and the transmitted information efficiency of the quantum key...

  1. Decoy-state quantum key distribution with a leaky source

    Science.gov (United States)

    Tamaki, Kiyoshi; Curty, Marcos; Lucamarini, Marco

    2016-06-01

    In recent years, there has been a great effort to prove the security of quantum key distribution (QKD) with a minimum number of assumptions. Besides its intrinsic theoretical interest, this would allow for larger tolerance against device imperfections in the actual implementations. However, even in this device-independent scenario, one assumption seems unavoidable, that is, the presence of a protected space devoid of any unwanted information leakage in which the legitimate parties can privately generate, process and store their classical data. In this paper we relax this unrealistic and hardly feasible assumption and introduce a general formalism to tackle the information leakage problem in most of existing QKD systems. More specifically, we prove the security of optical QKD systems using phase and intensity modulators in their transmitters, which leak the setting information in an arbitrary manner. We apply our security proof to cases of practical interest and show key rates similar to those obtained in a perfectly shielded environment. Our work constitutes a fundamental step forward in guaranteeing implementation security of quantum communication systems.

  2. Subcarrier multiplexing multiple-input multiple-output quantum key distribution scheme with orthogonal quantum states

    Science.gov (United States)

    Xiao, Hailin; Zhang, Zhongshan

    2017-01-01

    Quantum key distribution (QKD) system is presently being developed for providing high-security transmission in future free-space optical communication links. However, current QKD technique restricts quantum secure communication to a low bit rate. To improve the QKD bit rate, we propose a subcarrier multiplexing multiple-input multiple-output quantum key distribution (SCM-MQKD) scheme with orthogonal quantum states. Specifically, we firstly present SCM-MQKD system model and drive symmetrical SCM-MQKD system into decoherence-free subspaces. We then utilize bipartite Werner and isotropic states to construct multiple parallel single photon with orthogonal quantum states that are invariant for unitary operations. Finally, we derive the density matrix and the capacity of SCM-MQKD system, respectively. Theoretical analysis and numerical results show that the capacity of SCM-MQKD system will increase {log _2}(N^2+1) times than that of single-photon QKD system.

  3. Quantum key management

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Richard John; Thrasher, James Thomas; Nordholt, Jane Elizabeth

    2016-11-29

    Innovations for quantum key management harness quantum communications to form a cryptography system within a public key infrastructure framework. In example implementations, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a Merkle signature scheme (using Winternitz one-time digital signatures or other one-time digital signatures, and Merkle hash trees) to constitute a cryptography system. More generally, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a hash-based signature scheme. This provides a secure way to identify, authenticate, verify, and exchange secret cryptographic keys. Features of the quantum key management innovations further include secure enrollment of users with a registration authority, as well as credential checking and revocation with a certificate authority, where the registration authority and/or certificate authority can be part of the same system as a trusted authority for quantum key distribution.

  4. Quantum key management

    Science.gov (United States)

    Hughes, Richard John; Thrasher, James Thomas; Nordholt, Jane Elizabeth

    2016-11-29

    Innovations for quantum key management harness quantum communications to form a cryptography system within a public key infrastructure framework. In example implementations, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a Merkle signature scheme (using Winternitz one-time digital signatures or other one-time digital signatures, and Merkle hash trees) to constitute a cryptography system. More generally, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a hash-based signature scheme. This provides a secure way to identify, authenticate, verify, and exchange secret cryptographic keys. Features of the quantum key management innovations further include secure enrollment of users with a registration authority, as well as credential checking and revocation with a certificate authority, where the registration authority and/or certificate authority can be part of the same system as a trusted authority for quantum key distribution.

  5. Device-independent quantum key distribution based on measurement inputs

    Science.gov (United States)

    Rahaman, Ramij; Parker, Matthew G.; Mironowicz, Piotr; Pawłowski, Marcin

    2015-12-01

    We provide an analysis of a family of device-independent quantum key distribution (QKD) protocols that has the following features. (a) The bits used for the secret key do not come from the results of the measurements on an entangled state but from the choices of settings. (b) Instead of a single security parameter (a violation of some Bell inequality) a set of them is used to estimate the level of trust in the secrecy of the key. The main advantage of these protocols is a smaller vulnerability to imperfect random number generators made possible by feature (a). We prove the security and the robustness of such protocols. We show that using our method it is possible to construct a QKD protocol which retains its security even if the source of randomness used by communicating parties is strongly biased. As a proof of principle, an explicit example of a protocol based on the Hardy's paradox is presented. Moreover, in the noiseless case, the protocol is secure in a natural way against any type of memory attack, and thus allows one to reuse the device in subsequent rounds. We also analyze the robustness of the protocol using semidefinite programming methods. Finally, we present a postprocessing method, and observe a paradoxical property that rejecting some random part of the private data can increase the key rate of the protocol.

  6. SYNCHRONIZATION SIGNAL DISTORTION IN SUBCARRIER WAVE QUANTUM KEY DISTRIBUTION SYSTEMS

    Directory of Open Access Journals (Sweden)

    Varvara D. Dubrovskaya

    2017-07-01

    Full Text Available Subject of Research. The paper deals with temperature effects dependence of the synchronization signal parameters in an optical fiber cable for a subcarrier wave quantum communication system. Two main causes of signal distortion are considered: the change in the refractive index as a function of the average daily temperature and the dispersion effects in the optical fiber, over which the signal is transmitted in the system. Method. To account for these effects, a temperature model has been created. The signal delay is calculated as a result of external influences in the system working with a standard fiber-optic cable. Real operational conditions are taken into account, including cable laying conditions, average daily temperature and wind speed. Main Results. The simulations were carried out on the standard single-mode fiber ITU-T G.652D. It was experimentally obtained that the maximum calculated phase mismatch of the synchronization signal for a system operating at a 100 km fiber length corresponds to a 1.7 ps signal time delay. The maximum operating intervals of the system without the use of phase adjustment are calculated. The obtained results are used to improve the parameters of the subcarrier wave quantum communication system. It is determined that the change in the refractive index in the fiber causes significant distortion of the signal. It is shown that stable operation is possible with adjustment every 158 ms. The additional phase delay resulting from the dispersion effects should be adjusted every 2.3 hours. Practical Relevance. The obtained results enable to optimize the parameters of the subcarrier wave quantum key distribution system to increase the overall key generation rate.

  7. Upconversion-based receivers for quantum hacking-resistant quantum key distribution

    Science.gov (United States)

    Jain, Nitin; Kanter, Gregory S.

    2016-07-01

    We propose a novel upconversion (sum frequency generation)-based quantum-optical system design that can be employed as a receiver (Bob) in practical quantum key distribution systems. The pump governing the upconversion process is produced and utilized inside the physical receiver, making its access or control unrealistic for an external adversary (Eve). This pump facilitates several properties which permit Bob to define and control the modes that can participate in the quantum measurement. Furthermore, by manipulating and monitoring the characteristics of the pump pulses, Bob can detect a wide range of quantum hacking attacks launched by Eve.

  8. Free-space quantum key distribution at night

    Energy Technology Data Exchange (ETDEWEB)

    Buttler, W.T.; Hughes, R.J.; Kwiat, P.G.; Lamoreaux, S.K.; Luther, G.G.; Morgan, G.L.; Nordholt, J.E.; Peterson, C.G.; Simmons, C.M.

    1998-09-01

    An experimental free-space quantum key distribution (QKD) system has been tested over an outdoor optical path of {approximately} 1 km under nighttime conditions at Los Alamos National Laboratory. This system employs the Bennett 92 protocol; in this paper, the authors give a brief overview of this protocol, and describe the experimental implementation of it. An analysis of the system efficiency is presented, as well as a description of the error detection protocol which employs a two-dimensional parity check scheme. Finally, the susceptibility of this system to eavesdropping by various techniques is determined, and the effectiveness of privacy amplification procedures is discussed. The conclusions are that free-space QKD is both effective and secure; possible applications include the rekeying of satellites in low earth orbit.

  9. Sifting attacks in finite-size quantum key distribution

    Science.gov (United States)

    Pfister, Corsin; Lütkenhaus, Norbert; Wehner, Stephanie; Coles, Patrick J.

    2016-05-01

    A central assumption in quantum key distribution (QKD) is that Eve has no knowledge about which rounds will be used for parameter estimation or key distillation. Here we show that this assumption is violated for iterative sifting, a sifting procedure that has been employed in some (but not all) of the recently suggested QKD protocols in order to increase their efficiency. We show that iterative sifting leads to two security issues: (1) some rounds are more likely to be key rounds than others, (2) the public communication of past measurement choices changes this bias round by round. We analyze these two previously unnoticed problems, present eavesdropping strategies that exploit them, and find that the two problems are independent. We discuss some sifting protocols in the literature that are immune to these problems. While some of these would be inefficient replacements for iterative sifting, we find that the sifting subroutine of an asymptotically secure protocol suggested by Lo et al (2005 J. Cryptol. 18 133-65), which we call LCA sifting, has an efficiency on par with that of iterative sifting. One of our main results is to show that LCA sifting can be adapted to achieve secure sifting in the finite-key regime. More precisely, we combine LCA sifting with a certain parameter estimation protocol, and we prove the finite-key security of this combination. Hence we propose that LCA sifting should replace iterative sifting in future QKD implementations. More generally, we present two formal criteria for a sifting protocol that guarantee its finite-key security. Our criteria may guide the design of future protocols and inspire a more rigorous QKD analysis, which has neglected sifting-related attacks so far.

  10. The SECOQC quantum key distribution network in Vienna

    Energy Technology Data Exchange (ETDEWEB)

    Peev, M; Pacher, C; Boxleitner, W; Happe, A; Hasani, Y [AIT Austrian Institute of Technology GmbH (formerly Austrian Research Centers GmbH-ARC), Donau-City-Strasse 1, 1220 Vienna (Austria); Alleaume, R; Diamanti, E [Telecom ParisTech and LTCI-CNRS, 37/39 rue Dareau, 75014 Paris (France); Barreiro, C; Fasel, S; Gautier, J-D; Gisin, N [Group of Applied Physics, University of Geneva, 1211, Geneva 4 (Switzerland); Bouda, J [Faculty of Informatics, Masaryk University, Botanicka 68a, 602 00, Brno (Czech Republic); Debuisschert, T; Fossier, S [Thales Research and Technology France, RD 128, 91767 Palaiseau Cedex (France); Dianati, M [University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Dynes, J F [Toshiba Research Europe Ltd, 208 Cambridge Science Park, Cambridge CB4 0GZ (United Kingdom); Fuerst, M [Department fuer Physik, Ludwig-Maximilians-Universitaet, 80799 Muenchen (Germany); Gay, O [id Quantique SA, Chemin de la Marberie 3, 1227 Carouge/Geneva (Switzerland); Grangier, P [Laboratoire Charles Fabry de l' Institut d' Optique - CNRS - University Paris-Sud, Campus Polytechnique, RD 128, 91127 Palaiseau Cedex (France); Hentschel, M [Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna (Austria)], E-mail: Momtchil.Peev@ait.ac.at (and others)

    2009-07-15

    In this paper, we present the quantum key distribution (QKD) network designed and implemented by the European project SEcure COmmunication based on Quantum Cryptography (SECOQC) (2004-2008), unifying the efforts of 41 research and industrial organizations. The paper summarizes the SECOQC approach to QKD networks with a focus on the trusted repeater paradigm. It discusses the architecture and functionality of the SECOQC trusted repeater prototype, which has been put into operation in Vienna in 2008 and publicly demonstrated in the framework of a SECOQC QKD conference held from October 8 to 10, 2008. The demonstration involved one-time pad encrypted telephone communication, a secure (AES encryption protected) video-conference with all deployed nodes and a number of rerouting experiments, highlighting basic mechanisms of the SECOQC network functionality. The paper gives an overview of the eight point-to-point network links in the prototype and their underlying technology: three plug and play systems by id Quantique, a one way weak pulse system from Toshiba Research in the UK, a coherent one-way system by GAP Optique with the participation of id Quantique and the AIT Austrian Institute of Technology (formerly ARC ), an entangled photons system by University of Vienna and the AIT, a continuous-variables system by Centre National de la Recherche Scientifique (CNRS) and THALES Research and Technology with the participation of Universite Libre de Bruxelles, and a free space link by the Ludwig Maximillians University in Munich connecting two nodes situated in adjacent buildings (line of sight 80 m). The average link length is between 20 and 30 km, the longest link being 83 km. The paper presents the architecture and functionality of the principal networking agent-the SECOQC node module, which enables the authentic classical communication required for key distillation, manages the generated key material, determines a communication path between any destinations in the network

  11. The SECOQC quantum key distribution network in Vienna

    Science.gov (United States)

    Peev, M.; Pacher, C.; Alléaume, R.; Barreiro, C.; Bouda, J.; Boxleitner, W.; Debuisschert, T.; Diamanti, E.; Dianati, M.; Dynes, J. F.; Fasel, S.; Fossier, S.; Fürst, M.; Gautier, J.-D.; Gay, O.; Gisin, N.; Grangier, P.; Happe, A.; Hasani, Y.; Hentschel, M.; Hübel, H.; Humer, G.; Länger, T.; Legré, M.; Lieger, R.; Lodewyck, J.; Lorünser, T.; Lütkenhaus, N.; Marhold, A.; Matyus, T.; Maurhart, O.; Monat, L.; Nauerth, S.; Page, J.-B.; Poppe, A.; Querasser, E.; Ribordy, G.; Robyr, S.; Salvail, L.; Sharpe, A. W.; Shields, A. J.; Stucki, D.; Suda, M.; Tamas, C.; Themel, T.; Thew, R. T.; Thoma, Y.; Treiber, A.; Trinkler, P.; Tualle-Brouri, R.; Vannel, F.; Walenta, N.; Weier, H.; Weinfurter, H.; Wimberger, I.; Yuan, Z. L.; Zbinden, H.; Zeilinger, A.

    2009-07-01

    In this paper, we present the quantum key distribution (QKD) network designed and implemented by the European project SEcure COmmunication based on Quantum Cryptography (SECOQC) (2004-2008), unifying the efforts of 41 research and industrial organizations. The paper summarizes the SECOQC approach to QKD networks with a focus on the trusted repeater paradigm. It discusses the architecture and functionality of the SECOQC trusted repeater prototype, which has been put into operation in Vienna in 2008 and publicly demonstrated in the framework of a SECOQC QKD conference held from October 8 to 10, 2008. The demonstration involved one-time pad encrypted telephone communication, a secure (AES encryption protected) video-conference with all deployed nodes and a number of rerouting experiments, highlighting basic mechanisms of the SECOQC network functionality. The paper gives an overview of the eight point-to-point network links in the prototype and their underlying technology: three plug and play systems by id Quantique, a one way weak pulse system from Toshiba Research in the UK, a coherent one-way system by GAP Optique with the participation of id Quantique and the AIT Austrian Institute of Technology (formerly ARCAustrian Research Centers GmbH—ARC is now operating under the new name AIT Austrian Institute of Technology GmbH following a restructuring initiative.), an entangled photons system by the University of Vienna and the AIT, a continuous-variables system by Centre National de la Recherche Scientifique (CNRS) and THALES Research and Technology with the participation of Université Libre de Bruxelles, and a free space link by the Ludwig Maximillians University in Munich connecting two nodes situated in adjacent buildings (line of sight 80 m). The average link length is between 20 and 30 km, the longest link being 83 km. The paper presents the architecture and functionality of the principal networking agent—the SECOQC node module, which enables the authentic

  12. Security of Quantum Key Distribution with Realistic Devices

    CERN Document Server

    Ma, X

    2005-01-01

    We simulate quantum key distribution (QKD) experimental setups and give out some improvement for QKD procedures. A new data post-processing protocol is introduced, mainly including error correction and privacy amplification. This protocol combines the ideas of GLLP and the decoy states, which essentially only requires to turn up and down the source power. We propose a practical way to perform the decoy state method, which mainly follows the idea of Lo's decoy state. A new data post-processing protocol is then developed for the QKD scheme with the decoy state. We first study the optimal expected photon number mu of the source for the improved QKD scheme. We get the new optimal mu=O(1) comparing with former mu=O(eta), where eta is the overall transmission efficiency. With this protocol, we can then improve the key generation rate from quadratic of transmission efficiency O(eta2) to O(eta). Based on the recent experimental setup, we obtain the maximum secure transmission distance of over 140 km.

  13. Quantum key distribution series network protocol with M-classical Bobs

    Institute of Scientific and Technical Information of China (English)

    Zhang Xian-Zhou; Gong Wei-Gui; Tan Yong-Gang; Ren Zhen-Zhong; Guo Xiao-Tian

    2009-01-01

    Secure key distribution among classical parties is impossible both between two parties and in a network. In this paper, we present a quantum key distribution (QKD) protocol to distribute secure key bits among one quantum party and numerous classical parties who have no quantum capacity. We prove that our protocol is completely robust, i.e.,any eavesdropping attack should be detected with nonzero probability. Our calculations show that our protocol may be secure against Eve's symmetrically individual attack.

  14. Floodlight quantum key distribution: A practical route to gigabit-per-second secret-key rates

    Science.gov (United States)

    Zhuang, Quntao; Zhang, Zheshen; Dove, Justin; Wong, Franco N. C.; Shapiro, Jeffrey H.

    2016-07-01

    The channel loss incurred in long-distance transmission places a significant burden on quantum key distribution (QKD) systems: they must defeat a passive eavesdropper who detects all the light lost in the quantum channel and does so without disturbing the light that reaches the intended destination. The current QKD implementation with the highest long-distance secret-key rate meets this challenge by transmitting no more than one photon per bit [M. Lucamarini et al., Opt. Express 21, 24550 (2013), 10.1364/OE.21.024550]. As a result, it cannot achieve the Gbps secret-key rate needed for one-time pad encryption of large data files unless an impractically large amount of multiplexing is employed. We introduce floodlight QKD (FL-QKD), which floods the quantum channel with a high number of photons per bit distributed over a much greater number of optical modes. FL-QKD offers security against the optimum frequency-domain collective attack by transmitting less than one photon per mode and using photon-coincidence channel monitoring, and it is completely immune to passive eavesdropping. More importantly, FL-QKD is capable of a 2-Gbps secret-key rate over a 50-km fiber link, without any multiplexing, using available equipment, i.e., no new technology need be developed. FL-QKD achieves this extraordinary secret-key rate by virtue of its unprecedented secret-key efficiency, in bits per channel use, which exceeds those of state-of-the-art systems by two orders of magnitude.

  15. Decoy State Quantum Key Distribution: Theory and Practice

    Science.gov (United States)

    Zhao, Yi; Lo, Hoi-Kwong; Ma, Xiongfeng; Qi, Bing; Chen, Kai; Qian, Li

    2007-03-01

    Decoy state quantum key distribution (QKD) has been proposed as a novel approach to improve dramatically both the security and the performance of practical QKD set-ups. We proved its security, and proposed the first practical decoy state QKD protocols, including the one-decoy protocol, the weak+vacuum protocol, and the general two-decoy protocol. Our further study shows that the two-way communication can effectively improve the performance of decoy state QKD. We performed the first experiments of decoy state QKD. Two protocols -- the one-decoy protocol and the weak+vacuum protocol -- were implemented with a maximum transmission distance of 60km. We implemented the decoy state method by adding commercial acousto-optic modulator to a commercial QKD system. Our theoretical and experimental studies show explicitly the power and the feasibility of decoy method, and brings it to our real- life. Our works are published in [1-5]. [1] H. -K. Lo, X. Ma, and K. Chen, Phys. Rev. Lett. 94 230504 (2005) [2] X. Ma et. al., Phys. Rev. A 72, 012326 (2005) [3] Y. Zhao et. al., Phys. Rev. Lett., 96, 070502 (2006) [4] Y. Zhao et. al., in Proceedings of IEEE ISIT (IEEE, 2006) pp. 2094-2098 [5] X. Ma et. al., Phys. Rev. A 74, 032330 (2006)

  16. Finite-key analysis for quantum key distribution with weak coherent pulses based on Bernoulli sampling

    Science.gov (United States)

    Kawakami, Shun; Sasaki, Toshihiko; Koashi, Masato

    2017-07-01

    An essential step in quantum key distribution is the estimation of parameters related to the leaked amount of information, which is usually done by sampling of the communication data. When the data size is finite, the final key rate depends on how the estimation process handles statistical fluctuations. Many of the present security analyses are based on the method with simple random sampling, where hypergeometric distribution or its known bounds are used for the estimation. Here we propose a concise method based on Bernoulli sampling, which is related to binomial distribution. Our method is suitable for the Bennett-Brassard 1984 (BB84) protocol with weak coherent pulses [C. H. Bennett and G. Brassard, Proceedings of the IEEE Conference on Computers, Systems and Signal Processing (IEEE, New York, 1984), Vol. 175], reducing the number of estimated parameters to achieve a higher key generation rate compared to the method with simple random sampling. We also apply the method to prove the security of the differential-quadrature-phase-shift (DQPS) protocol in the finite-key regime. The result indicates that the advantage of the DQPS protocol over the phase-encoding BB84 protocol in terms of the key rate, which was previously confirmed in the asymptotic regime, persists in the finite-key regime.

  17. Seaworthy Quantum Key Distribution Design and Validation (SEAKEY)

    Science.gov (United States)

    2016-03-10

    Technologies Kathryn Carson Program Manager Quantum Information Processing 2 | P a g e Approved for public release; distribution is...imbalance in the optical arms and the asymmetry in the differential amplifier of the detector. Detector is operating at wavelength = 1.55m...Technologies Section D. Financial Update 7 | P a g e Approved for public release; distribution is unlimited. ©2016 Raytheon BBN Technologies

  18. Quantum hacking of a continuous-variable quantum-key-distribution system using a wavelength attack

    Science.gov (United States)

    Huang, Jing-Zheng; Weedbrook, Christian; Yin, Zhen-Qiang; Wang, Shuang; Li, Hong-Wei; Chen, Wei; Guo, Guang-Can; Han, Zheng-Fu

    2013-06-01

    The security proofs of continuous-variable quantum key distribution are based on the assumptions that the eavesdropper can neither act on the local oscillator nor control Bob's beam splitter. These assumptions may be invalid in practice due to potential imperfections in the implementations of such protocols. In this paper, we consider the problem of transmitting the local oscillator in a public channel and propose a wavelength attack which allows the eavesdropper to control the intensity transmission of Bob's beam splitter by switching the wavelength of the input light. Specifically we target continuous-variable quantum key distribution systems that use the heterodyne detection protocol using either direct or reverse reconciliation. Our attack is proved to be feasible and renders all of the final keys shared between the legitimate parties insecure, even if they have monitored the intensity of the local oscillator. To prevent our attack on commercial systems, a simple wavelength filter should be randomly added before performing monitoring detection.

  19. Novel classical post-processing for quantum key distribution-based quantum private query

    Science.gov (United States)

    Yang, Yu-Guang; Liu, Zhi-Chao; Chen, Xiu-Bo; Cao, Wei-Feng; Zhou, Yi-Hua; Shi, Wei-Min

    2016-09-01

    Existing classical post-processing (CPP) schemes for quantum key distribution (QKD)-based quantum private queries (QPQs) including the kN→ N, N→ N, and rM→ N ones have been found imperfect in terms of communication efficiency and security. In this paper, we propose a novel CPP scheme for QKD-based QPQs. The proposed CPP scheme reduces the communication complexity and improves the security of QKD-based QPQ protocols largely. Furthermore, the proposed CPP scheme can provide a multi-bit query efficiently.

  20. Quantum key distribution system in standard telecommunications fiber using a short wavelength single-photon source

    CERN Document Server

    Collins, R J; Fernandez, V; Gordon, K J; Makhonin, M N; Timpson, J A; Tahraoui, A; Hopkinson, M; Fox, A M; Skolnick, M S; Buller, G S; 10.1063/1.3327427

    2010-01-01

    A demonstration of the principles of quantum key distribution is performed using a single-photon source in a proof of concept test-bed over a distance of 2 km in standard telecommunications optical fiber. The single-photon source was an optically-pumped quantum dot in a microcavity emitting at a wavelength of 895 nm. Characterization of the quantum key distribution parameters was performed at a range of different optical excitation powers. An investigation of the effect of varying the optical excitation power of the quantum dot microcavity on the quantum bit error rate and cryptographic key exchange rate of the system are presented.

  1. Finite-key analysis for time-energy high-dimensional quantum key distribution

    Science.gov (United States)

    Niu, Murphy Yuezhen; Xu, Feihu; Shapiro, Jeffrey H.; Furrer, Fabian

    2016-11-01

    Time-energy high-dimensional quantum key distribution (HD-QKD) leverages the high-dimensional nature of time-energy entangled biphotons and the loss tolerance of single-photon detection to achieve long-distance key distribution with high photon information efficiency. To date, the general-attack security of HD-QKD has only been proven in the asymptotic regime, while HD-QKD's finite-key security has only been established for a limited set of attacks. Here we fill this gap by providing a rigorous HD-QKD security proof for general attacks in the finite-key regime. Our proof relies on an entropic uncertainty relation that we derive for time and conjugate-time measurements that use dispersive optics, and our analysis includes an efficient decoy-state protocol in its parameter estimation. We present numerically evaluated secret-key rates illustrating the feasibility of secure and composable HD-QKD over metropolitan-area distances when the system is subjected to the most powerful eavesdropping attack.

  2. High-Speed Large-Alphabet Quantum Key Distribution Using Photonic Integrated Circuits

    Science.gov (United States)

    2014-01-28

    Lett., 93:010503, Jul 2004. [14] Irfan Ali-Khan, Curtis J. Broadbent , and John C. Howell. Large-Alphabet Quantum Key Distribution Using Energy-Time...Rev. Lett., 92:167903, Apr 2004. [20] Irfan Ali-Khan, Curtis J. Broadbent , and John C. Howell. Large-Alphabet Quantum Key Distribution Using Energy

  3. Two-dimensional distributed-phase-reference protocol for quantum key distribution

    DEFF Research Database (Denmark)

    Bacco, Davide; Christensen, Jesper Bjerge; Usuga Castaneda, Mario A.;

    2016-01-01

    Quantum key distribution (QKD) and quantum communication enable the secure exchange of information between remote parties. Currently, the distributed-phase-reference (DPR) protocols, which are based on weak coherent pulses, are among the most practical solutions for long-range QKD. During the last...... 10 years, long-distance fiber-based DPR systems have been successfully demonstrated, although fundamental obstacles such as intrinsic channel losses limit their performance. Here, we introduce the first two-dimensional DPR-QKD protocol in which information is encoded in the time and phase of weak...

  4. Quantum key distribution at telecom wavelengths with noise-free detectors

    CERN Document Server

    Rosenberg, D; Hiskett, P A; Peterson, C G; Hughes, R J; Nordholt, J E; Lita, A E; Miller, A J; Rosenberg, Danna; Nam, Sae Woo; Hiskett, Philip A.; Peterson, Charles G.; Hughes, Richard J.; Nordholt, Jane E.; Lita, Adriana E.; Miller, Aaron J.

    2005-01-01

    The length of a secure link over which a quantum key can be distributed depends on the efficiency and dark-count rate of the detectors used at the receiver. We report on the first demonstration of quantum key distribution using transition-edge sensors with high efficiency and negligible dark-count rates. Using two methods of synchronization, a bright optical pulse scheme and an electrical signal scheme, we have successfully distributed key material at 1,550 nm over 50 km of optical fiber. We discuss how use of these detectors in a quantum key distribution system can result in dramatic increases in range and performance.

  5. High-dimensional quantum key distribution based on multicore fiber using silicon photonic integrated circuits

    Science.gov (United States)

    Ding, Yunhong; Bacco, Davide; Dalgaard, Kjeld; Cai, Xinlun; Zhou, Xiaoqi; Rottwitt, Karsten; Oxenløwe, Leif Katsuo

    2017-06-01

    Quantum key distribution provides an efficient means to exchange information in an unconditionally secure way. Historically, quantum key distribution protocols have been based on binary signal formats, such as two polarization states, and the transmitted information efficiency of the quantum key is intrinsically limited to 1 bit/photon. Here we propose and experimentally demonstrate, for the first time, a high-dimensional quantum key distribution protocol based on space division multiplexing in multicore fiber using silicon photonic integrated lightwave circuits. We successfully realized three mutually unbiased bases in a four-dimensional Hilbert space, and achieved low and stable quantum bit error rate well below both the coherent attack and individual attack limits. Compared to previous demonstrations, the use of a multicore fiber in our protocol provides a much more efficient way to create high-dimensional quantum states, and enables breaking the information efficiency limit of traditional quantum key distribution protocols. In addition, the silicon photonic circuits used in our work integrate variable optical attenuators, highly efficient multicore fiber couplers, and Mach-Zehnder interferometers, enabling manipulating high-dimensional quantum states in a compact and stable manner. Our demonstration paves the way to utilize state-of-the-art multicore fibers for noise tolerance high-dimensional quantum key distribution, and boost silicon photonics for high information efficiency quantum communications.

  6. Measuring-basis-encrypted six-state quantum key distribution scheme

    Institute of Scientific and Technical Information of China (English)

    CHEN Pan; DENG Fuguo; WANG Pingxiao; LONG Guilu

    2006-01-01

    A six-state quantum key distribution scheme with measuring-basis encryption technique, which is based on the six-state protocol and the MBE protocol, is proposed. In this modified six-state quantum key distribution protocol, Alice and Bob use a control key to synchronize the use of their measuring-basis so that they always use the same measuring-basis. This modified six-state quantum key distribution protocol retains the advantage of higher security and at the same time has a higher efficiency.

  7. Implementation of a Wireless Time Distribution Testbed Protected with Quantum Key Distribution

    Energy Technology Data Exchange (ETDEWEB)

    Bonior, Jason D [ORNL; Evans, Philip G [ORNL; Sheets, Gregory S [ORNL; Jones, John P [ORNL; Flynn, Toby H [ORNL; O' Neil, Lori Ross [Pacific Northwest National Laboratory (PNNL); Hutton, William [Pacific Northwest National Laboratory (PNNL); Pratt, Richard [Pacific Northwest National Laboratory (PNNL); Carroll, Thomas E. [Pacific Northwest National Laboratory (PNNL)

    2017-01-01

    Secure time transfer is critical for many timesensitive applications. the Global Positioning System (GPS) which is often used for this purpose has been shown to be susceptible to spoofing attacks. Quantum Key Distribution offers a way to securely generate encryption keys at two locations. Through careful use of this information it is possible to create a system that is more resistant to spoofing attacks. In this paper we describe our work to create a testbed which utilizes QKD and traditional RF links. This testbed will be used for the development of more secure and spoofing resistant time distribution protocols.

  8. New passive decoy-state quantum key distribution with thermal distributed parametric down-conversion source

    Science.gov (United States)

    Wei, Jie; Zhang, Chun-Hui; Wang, Qin

    2017-02-01

    We present a new scheme on implementing the passive quantum key distribution with thermal distributed parametric down-conversion source. In this scheme, only one-intensity decoy state is employed, but we can achieve very precise estimation on the single-photon-pulse contribution by utilizing those built-in decoy states. Moreover, we compare the new scheme with other practical methods, i.e., the standard three-intensity decoy-state BB84 protocol using either weak coherent states or parametric down-conversion source. Through numerical simulations, we demonstrate that our new scheme can drastically improve both the secure transmission distance and the key generation rate.

  9. Subcarrier Wave Quantum Key Distribution in Telecommunication Network with Bitrate 800 kbit/s

    Directory of Open Access Journals (Sweden)

    Gleim A.V.

    2015-01-01

    Full Text Available In the course of work on creating the first quantum communication network in Russia we demonstrated quantum key distribution in metropolitan optical network infrastructure. A single-pass subcarrier wave quantum cryptography scheme was used in the experiments. BB84 protocol with strong reference was chosen for performing key distribution. The registered sifted key rate in an optical cable with 1.5 dB loss was 800 Kbit/s. Signal visibility exceeded 98%, and quantum bit error rate value was 1%. The achieved result is a record for this type of systems.

  10. Subcarrier Wave Quantum Key Distribution in Telecommunication Network with Bitrate 800 kbit/s

    Science.gov (United States)

    Gleim, A. V.; Nazarov, Yu. V.; Egorov, V. I.; Smirnov, S. V.; Bannik, O. I.; Chistyakov, V. V.; Kynev, S. M.; Anisimov, A. A.; Kozlov, S. A.; Vasiliev, V. N.

    2015-09-01

    In the course of work on creating the first quantum communication network in Russia we demonstrated quantum key distribution in metropolitan optical network infrastructure. A single-pass subcarrier wave quantum cryptography scheme was used in the experiments. BB84 protocol with strong reference was chosen for performing key distribution. The registered sifted key rate in an optical cable with 1.5 dB loss was 800 Kbit/s. Signal visibility exceeded 98%, and quantum bit error rate value was 1%. The achieved result is a record for this type of systems.

  11. Two-dimensional distributed-phase-reference protocol for quantum key distribution

    Science.gov (United States)

    Bacco, Davide; Christensen, Jesper Bjerge; Castaneda, Mario A. Usuga; Ding, Yunhong; Forchhammer, Søren; Rottwitt, Karsten; Oxenløwe, Leif Katsuo

    2016-12-01

    Quantum key distribution (QKD) and quantum communication enable the secure exchange of information between remote parties. Currently, the distributed-phase-reference (DPR) protocols, which are based on weak coherent pulses, are among the most practical solutions for long-range QKD. During the last 10 years, long-distance fiber-based DPR systems have been successfully demonstrated, although fundamental obstacles such as intrinsic channel losses limit their performance. Here, we introduce the first two-dimensional DPR-QKD protocol in which information is encoded in the time and phase of weak coherent pulses. The ability of extracting two bits of information per detection event, enables a higher secret key rate in specific realistic network scenarios. Moreover, despite the use of more dimensions, the proposed protocol remains simple, practical, and fully integrable.

  12. Key Distribution based on Three Player Quantum Games

    CERN Document Server

    Toyota, Norihito

    2010-01-01

    We study a new QKD that is different from the scheme proposed by \\cite{Ramz2}, though it essentially takes our ground on three-player quantum games and Greenberg-Horne-Zeilinger triplet entangled state (GHZ state) \\cite{Gree} is used. In our scheme proposed in this article, Bob and Charlie (and Alice also) that they are players in a game get some common key or information (applied strategies and their payoffs in the game) by knowing some results of the measurement made by Alice. There is not any arbiter in our scheme, since existence of an arbiter increase the risk of wiretapping. For it is difficult to detect wiretapping, when an arbiter repeatedly sends classical information. Lastly we discuss robustness for eavesdrop. We show that though maximally entangled case and non-entangled case provided essentially equivalent way in QKD, the latter is not available in the case there are some eavesdroppers.

  13. Seaworthy Quantum Key Distribution Design and Validation (SEAKEY)

    Science.gov (United States)

    2015-02-06

    subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE...as follows: 1. This document (containing minor programmatic points, organizational notes and summary of progress in Phase I); 2. A PPTX document...discretization of the full Gaussian distribution of amplitude and phase, that CV demonstrations use) should retrieve the optimal (R~η) key rate scaling

  14. Finite-key security analysis of quantum key distribution with imperfect light sources

    Science.gov (United States)

    Mizutani, Akihiro; Curty, Marcos; Lim, Charles Ci Wen; Imoto, Nobuyuki; Tamaki, Kiyoshi

    2015-09-01

    In recent years, the gap between theory and practice in quantum key distribution (QKD) has been significantly narrowed, particularly for QKD systems with arbitrarily flawed optical receivers. The status for QKD systems with imperfect light sources is however less satisfactory, in the sense that the resulting secure key rates are often overly dependent on the quality of state preparation. This is especially the case when the channel loss is high. Very recently, to overcome this limitation, Tamaki et al proposed a QKD protocol based on the so-called ‘rejected data analysis’, and showed that its security—in the limit of infinitely long keys—is almost independent of any encoding flaw in the qubit space, being this protocol compatible with the decoy state method. Here, as a step towards practical QKD, we show that a similar conclusion is reached in the finite-key regime, even when the intensity of the light source is unstable. More concretely, we derive security bounds for a wide class of realistic light sources and show that the bounds are also efficient in the presence of high channel loss. Our results strongly suggest the feasibility of long distance provably secure communication with imperfect light sources.

  15. Secure multi-party communication with quantum key distribution managed by trusted authority

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Richard John; Nordholt, Jane Elizabeth; Peterson, Charles Glen

    2017-06-14

    Techniques and tools for implementing protocols for secure multi-party communication after quantum key distribution ("QKD") are described herein. In example implementations, a trusted authority facilitates secure communication between multiple user devices. The trusted authority distributes different quantum keys by QKD under trust relationships with different users. The trusted authority determines combination keys using the quantum keys and makes the combination keys available for distribution (e.g., for non-secret distribution over a public channel). The combination keys facilitate secure communication between two user devices even in the absence of QKD between the two user devices. With the protocols, benefits of QKD are extended to multi-party communication scenarios. In addition, the protocols can retain benefit of QKD even when a trusted authority is offline or a large group seeks to establish secure communication within the group.

  16. Photon Counting and Super Homodyne Detection of Weak QPSK Signals for Quantum Key Distribution

    CERN Document Server

    XU, Q; Agnolini, S; Gallion, P; Mendieta, F J

    2006-01-01

    We compare the principles and experimental results of two different QPSK signal detection configurations, photon counting and super homodyning, for applications in fiber-optic Quantum Key Distribution (QKD) systems operating at telecom wavelength, using the BB84 protocol.

  17. Higher-dimensional orbital-angular-momentum-based quantum key distribution with mutually unbiased bases

    CSIR Research Space (South Africa)

    Mafu, M

    2013-09-01

    Full Text Available We present an experimental study of higher-dimensional quantum key distribution protocols based on mutually unbiased bases, implemented by means of photons carrying orbital angular momentum. We perform (d + 1) mutually unbiased measurements in a...

  18. Temporal steering and security of quantum key distribution with mutually unbiased bases against individual attacks

    Science.gov (United States)

    Bartkiewicz, Karol; Černoch, Antonín; Lemr, Karel; Miranowicz, Adam; Nori, Franco

    2016-06-01

    Temporal steering, which is a temporal analog of Einstein-Podolsky-Rosen steering, refers to temporal quantum correlations between the initial and final state of a quantum system. Our analysis of temporal steering inequalities in relation to the average quantum bit error rates reveals the interplay between temporal steering and quantum cloning, which guarantees the security of quantum key distribution based on mutually unbiased bases against individual attacks. The key distributions analyzed here include the Bennett-Brassard 1984 protocol and the six-state 1998 protocol by Bruss. Moreover, we define a temporal steerable weight, which enables us to identify a kind of monogamy of temporal correlation that is essential to quantum cryptography and useful for analyzing various scenarios of quantum causality.

  19. Security of quantum key distribution using two-mode squeezed states against optimal beam splitter attack

    Institute of Scientific and Technical Information of China (English)

    He Guang-Qiang; Zhu Si-Wei; Guo Hong-Bin; Zeng Gui-Hua

    2008-01-01

    For the beam splitter attack strategy against quantum key distribution using two-mode squeezed states, the analytical expression of the optimal beam splitter parameter is provided in this paper by applying the Shannon information theory. The theoretical secret information rate after error correction and privacy amplification is given in terms of the squeezed parameter and channel parameters. The results show that the two-mode squeezed state quantum key distribution is secure against an optimal beam splitter attack.

  20. Quantum hacking: Saturation attack on practical continuous-variable quantum key distribution

    Science.gov (United States)

    Qin, Hao; Kumar, Rupesh; Alléaume, Romain

    2016-07-01

    We identify and study a security loophole in continuous-variable quantum key distribution (CVQKD) implementations, related to the imperfect linearity of the homodyne detector. By exploiting this loophole, we propose an active side-channel attack on the Gaussian-modulated coherent-state CVQKD protocol combining an intercept-resend attack with an induced saturation of the homodyne detection on the receiver side (Bob). We show that an attacker can bias the excess noise estimation by displacing the quadratures of the coherent states received by Bob. We propose a saturation model that matches experimental measurements on the homodyne detection and use this model to study the impact of the saturation attack on parameter estimation in CVQKD. We demonstrate that this attack can bias the excess noise estimation beyond the null key threshold for any system parameter, thus leading to a full security break. If we consider an additional criterion imposing that the channel transmission estimation should not be affected by the attack, then the saturation attack can only be launched if the attenuation on the quantum channel is sufficient, corresponding to attenuations larger than approximately 6 dB. We moreover discuss the possible countermeasures against the saturation attack and propose a countermeasure based on Gaussian postselection that can be implemented by classical postprocessing and may allow one to distill the secret key when the raw measurement data are partly saturated.

  1. Quantum hacking: Experimental demonstration of time-shift attack against practical quantum-key-distribution systems

    Science.gov (United States)

    Zhao, Yi; Fung, Chi-Hang F.; Qi, Bing; Chen, Christine; Lo, Hoi-Kwong

    2009-03-01

    Quantum key distribution (QKD) systems can send signals over more than 100 km standard optical fiber and are widely believed to be secure. Here, we show experimentally for the first time a technologically feasible attack, namely the time-shift attack, against a commercial QKD system. Our result shows that, contrary to popular belief, an eavesdropper, Eve, has a non-negligible probability (˜4%) to break the security of the system. Eve's success is due to the well-known detection efficiency loophole in the experimental testing of Bell inequalities. Therefore, the detection efficiency loophole plays a key role not only in fundamental physics, but also in technological applications such as QKD. Our work is published in [1]. [4pt] [1] Y. Zhao, C.-H. F. Fung, B. Qi, C. Chen, and H.-K. Lo, Phys. Rev. A, 78:042333 (2008).

  2. Unconditional security proof of long-distance continuous-variable quantum key distribution with discrete modulation.

    Science.gov (United States)

    Leverrier, Anthony; Grangier, Philippe

    2009-05-08

    We present a continuous-variable quantum key distribution protocol combining a discrete modulation and reverse reconciliation. This protocol is proven unconditionally secure and allows the distribution of secret keys over long distances, thanks to a reverse reconciliation scheme efficient at very low signal-to-noise ratio.

  3. Superdense Coding with GHZ and Quantum Key Distribution with W in the ZX-calculus

    Directory of Open Access Journals (Sweden)

    Anne Hillebrand

    2012-10-01

    Full Text Available Quantum entanglement is a key resource in many quantum protocols, such as quantum teleportation and quantum cryptography. Yet entanglement makes protocols presented in Dirac notation difficult to verify. This is why Coecke and Duncan have introduced a diagrammatic language for quantum protocols, called the ZX-calculus. This diagrammatic notation is both intuitive and formally rigorous. It is a simple, graphical, high level language that emphasises the composition of systems and naturally captures the essentials of quantum mechanics. In the author's MSc thesis it has been shown for over 25 quantum protocols that the ZX-calculus provides a relatively easy and more intuitive presentation. Moreover, the author embarked on the task to apply categorical quantum mechanics on quantum security; earlier works did not touch anything but Bennett and Brassard's quantum key distribution protocol, BB84. Superdense coding with the Greenberger-Horne-Zeilinger state and quantum key distribution with the W-state are presented in the ZX-calculus in this paper.

  4. Practical quantum key distribution over a 48-km optical fiber network

    CERN Document Server

    Hughes, R J; Peterson, C G; Hughes, Richard J.; Morgan, George L.

    1999-01-01

    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 a new technique for secure key distribution with single-photon transmissions: Heisenberg'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 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. Here we report the most recent results...

  5. Two-step unsymmetrical quantum key distribution protocol using GHZ triplet states

    Institute of Scientific and Technical Information of China (English)

    HUANG Peng; LIU Ye; ZHOU Nan-run; ZENG Gui-hua

    2009-01-01

    The security, efficiency, transmission distance and error rate are important parameters of a quantum key distribution scheme. In this article, the former two parameters are focused on. To reach high efficiency, an unsymmetrical quantum key distribution scheme that employs Greenberger-Horne-Zeilinger (GHZ) triplet states and dense coding mechanism is proposed, in which a GHZ triplet state can be used to share two bits of classical information. The proposed scheme can be employed in a noisy or lossy quantum channel. In addition, a general approach to security analysis against general individual attacks is presented.

  6. Scintillation Has Minimal Impact On Far Field Quantum Key Distribution

    Science.gov (United States)

    2010-11-24

    provides spatial- mode discrimination against background light . APD: single-photon ( Geiger mode ) avalanche photodiode . governed by conditionally...employ identical singlc- photon avalanche photodiodes (APDs) , each of quantum efficiency 7) [7]. For a single photon arriving at Bob’s receiver...normal- mode decomposition for line-of-sight optical propagation through atmospheric turbulence [2] to obtain upper and lower bounds on t he sift and

  7. Seaworthy Quantum Key Distribution Design and Validation (SEAKEY)

    Science.gov (United States)

    2014-04-25

    2014 Raytheon BBN Technologies - We will also investigate the multiple quantum-well and InGaAs modulating retroreflectors developed by NRL for... properties - More detailed calculations of background power vs wavelength o Sky background, thermal background o Evaluate effects of filter bandwidth and...Washington DC (1985). 2. John Seinfeld and Spiros Pandis, Atmospheric Chemistry and Physics , Wiley, Hoboken, NJ (2006). 3. http://www.gps.caltech.edu

  8. Time-cost analysis of a quantum key distribution system clocked at 100 MHz

    CERN Document Server

    Mo, Xiaofan; Chan, Philip; Healey, Chris; Hosier, Steve; Tittel, Wolfgang

    2011-01-01

    We describe the realization of a quantum key distribution (QKD) system clocked at 100 MHz. The system includes classical postprocessing implemented via software, and is operated over a 12 km standard telecommunication dark fiber in a real-world environment. A time-cost analysis of the sifted, error-corrected, and secret key rates relative to the raw key rate is presented, and the scalability of our implementation with respect to higher secret key rates is discussed.

  9. Measurement device-independent quantum key distribution with heralded pair coherent state

    Science.gov (United States)

    Chen, Dong; Shang-Hong, Zhao; Lei, Shi

    2016-10-01

    The original measurement device-independent quantum key distribution is reviewed, and a modified protocol using heralded pair coherent state (HPCS) is proposed to overcome the quantum bit error rate associated with the dark count rate of the detectors in long-distance quantum key distribution. Our simulation indicates that the secure transmission distance can be improved evidently with HPCS owing to the lower probability of vacuum events when compared with weak coherent source scenario, while the secure key rate can be increased with HPCS due to the higher probability of single-photon events when compared with heralded single-photon source scenario. Furthermore, we apply the finite key analysis to the decoy state MDI-QKD with HPCS and obtain a practical key rate.

  10. Practical issues in decoy-state quantum key distribution based on the central limit theorem

    Science.gov (United States)

    Trushechkin, A. S.; Kiktenko, E. O.; Fedorov, A. K.

    2017-08-01

    Decoy-state quantum key distribution (QKD) is a standard tool for long-distance quantum communications. An important issue in this field is processing the decoy-state statistics taking into account statistical fluctuations (or "finite-key effects"). In this work, we propose and analyze an option for decoy statistics processing, which is based on the central limit theorem. We discuss such practical issues as inclusion of the failure probability of the decoy-state statistical estimates in the total failure probability of a QKD protocol and also taking into account the deviations of the binomially distributed random variables used in the estimations from the Gaussian distribution. The results of numerical simulations show that the obtained estimations are quite tight. The proposed technique can be used as a part of post-processing procedures for industrial quantum key distribution systems.

  11. Limitations on quantum key repeaters.

    Science.gov (United States)

    Bäuml, Stefan; Christandl, Matthias; Horodecki, Karol; Winter, Andreas

    2015-04-23

    A major application of quantum communication is the distribution of entangled particles for use in quantum key distribution. Owing to noise in the communication line, quantum key distribution is, in practice, limited to a distance of a few hundred kilometres, and can only be extended to longer distances by use of a quantum repeater, a device that performs entanglement distillation and quantum teleportation. The existence of noisy entangled states that are undistillable but nevertheless useful for quantum key distribution raises the question of the feasibility of a quantum key repeater, which would work beyond the limits of entanglement distillation, hence possibly tolerating higher noise levels than existing protocols. Here we exhibit fundamental limits on such a device in the form of bounds on the rate at which it may extract secure key. As a consequence, we give examples of states suitable for quantum key distribution but unsuitable for the most general quantum key repeater protocol.

  12. Continuous-variable Quantum Key Distribution protocols with a discrete modulation

    CERN Document Server

    Leverrier, Anthony

    2010-01-01

    In this paper, we consider continuous-variable quantum key distribution with a discrete modulation, either binary or quaternary. We establish the security of these protocols against collective attacks, which implies their security against arbitrary attacks in the asymptotic limit. We give lower bounds for the secret key rate using extremality properties of Gaussian states.

  13. A Secure Key Distribution System of Quantum Cryptography Based on the Coherent State

    Science.gov (United States)

    Guo, Guang-Can; Zhang, Xiao-Yu

    1996-01-01

    The cryptographic communication has a lot of important applications, particularly in the magnificent prospects of private communication. As one knows, the security of cryptographic channel depends crucially on the secrecy of the key. The Vernam cipher is the only cipher system which has guaranteed security. In that system the key must be as long as the message and most be used only once. Quantum cryptography is a method whereby key secrecy can be guaranteed by a physical law. So it is impossible, even in principle, to eavesdrop on such channels. Quantum cryptography has been developed in recent years. Up to now, many schemes of quantum cryptography have been proposed. Now one of the main problems in this field is how to increase transmission distance. In order to use quantum nature of light, up to now proposed schemes all use very dim light pulses. The average photon number is about 0.1. Because of the loss of the optical fiber, it is difficult for the quantum cryptography based on one photon level or on dim light to realize quantum key-distribution over long distance. A quantum key distribution based on coherent state is introduced in this paper. Here we discuss the feasibility and security of this scheme.

  14. Orthogonal frequency division multiplexed quantum key distribution in the presence of Raman noise

    Science.gov (United States)

    Bahrani, Sima; Razavi, Mohsen; Salehi, Jawad A.

    2016-04-01

    In this paper, we investigate the performance of orthogonal frequency division multiplexed quantum key distribution (OFDM-QKD) in an integrated quantum-classical wavelength-division-multiplexing system. The presence of an intense classical signal alongside the quantum one generates Raman background noise. Noise reduction techniques should, then, be carried out at the receiver to suppress this crosstalk noise. In this work, we show that OFDM-QKD enables efficient filtering, in time and frequency domains, making it an attractive solution for the high-rate links at the core of quantum-classical networks.

  15. Security bound of two-bases quantum key-distribution protocols using qudits

    CERN Document Server

    Nikolopoulos, G M; Nikolopoulos, Georgios M.; Alber, Gernot

    2005-01-01

    We investigate the security bounds of quantum cryptographic protocols using $d$-level systems. In particular, we focus on schemes that use two mutually unbiased bases, thus extending the BB84 quantum key distribution scheme to higher dimensions. Under the assumption of general coherent attacks, we derive an analytic expression for the ultimate upper security bound of such quantum cryptography schemes. This bound is well below the predictions of optimal cloning machines. The possibility of extraction of a secret key beyond entanglement distillation is discussed. In the case of qutrits we argue that any eavesdropping strategy is equivalent to a symmetric one. For higher dimensions such an equivalence is generally no longer valid.

  16. Provable entanglement and information cost for qubit-based quantum key-distribution protocols

    CERN Document Server

    Nikolopoulos, G M; Khalique, A

    2005-01-01

    Provable entanglement has been shown to be a necessary precondition for unconditionally secure key generation in the context of quantum cryptographic protocols. We estimate the maximal threshold disturbance up to which the two legitimate users can prove the presence of quantum correlations in their data, in the context of the four- and six-state quantum key-distribution protocols, under the assumption of coherent attacks. Moreover, we investigate the conditions under which an eavesdropper can saturate these bounds, by means of incoherent and two-qubit coherent attacks. A direct connection between entanglement distillation and classical advantage distillation is also presented.

  17. Gaussian-modulated coherent-state measurement-device-independent quantum key distribution

    Science.gov (United States)

    Ma, Xiang-Chun; Sun, Shi-Hai; Jiang, Mu-Sheng; Gui, Ming; Liang, Lin-Mei

    2014-04-01

    Measurement-device-independent quantum key distribution (MDI-QKD), leaving the detection procedure to the third partner and thus being immune to all detector side-channel attacks, is very promising for the construction of high-security quantum information networks. We propose a scheme to implement MDI-QKD, but with continuous variables instead of discrete ones, i.e., with the source of Gaussian-modulated coherent states, based on the principle of continuous-variable entanglement swapping. This protocol not only can be implemented with current telecom components but also has high key rates compared to its discrete counterpart; thus it will be highly compatible with quantum networks.

  18. Seaworthy Quantum Key Distribution Design and Validation (SEAKEY)

    Science.gov (United States)

    2015-08-07

    Kathryn Carson at 617.873.8144 (email: kcarson@bbn.com) if you would like to discuss this letter or have any other questions. Sincerely , Raytheon...achievable key rate of the aforementioned QKD link in realistic environmental conditions. This quarter we have evaluated literature which calculates

  19. Quantum Key Distribution in the Presence of the Intercept-Resend with Faked States Attack

    Directory of Open Access Journals (Sweden)

    Luis Adrian Lizama-Pérez

    2016-12-01

    Full Text Available Despite the unconditionally secure theory of the Quantum Key Distribution (Q K D, several attacks have been successfully implemented against commercial Q K D systems. Those systems have exhibited some flaws, as the secret key rate of corresponding protocols remains unaltered, while the eavesdropper obtains the entire secret key. We propose the negative acknowledgment state quantum key distribution protocol as a novel protocol capable of detecting the eavesdropping activity of the Intercept Resend with Faked Sates (I R F S attack without requiring additional optical components different from the B B 84 protocol because the system can be implemented as a high software module. In this approach, the transmitter interleaves pairs of quantum states, referred to here as parallel and orthogonal states, while the receiver uses active basis selection.

  20. Quantum Encoder and Decoder for Secret Key Distribution with Check Bits

    Directory of Open Access Journals (Sweden)

    T. Godhavari

    2013-12-01

    Full Text Available The focus of this study is to develop a novel method of encoding the qubits and use as secret key in public key cryptography. In BB 84 protocol, 50% of the random number (generated at source is used as secret key and the remaining bits are used as “check bits”. The check bits are used to detect the presence of eve as well as the nature of quantum channels. In this protocol, random qubits are encoded using different type of polarizations like horizontal, veritical and diagonal. In the proposed quantum encoder, basic quantum gates are used to encode the random secret key along with the check bits. Quantum key distribution, (a cryptographic mechanism relies on the inherent randomness of quantum mechanics and serves as an option to replace techniques made vulnerable by quantum computing. However, it is still subject to clever forms of eavesdropping and poses a significant challenge to implementation. To study the challenges, quantum circuits are first simulated using QCAD.

  1. Deterministic quantum key distribution based on Gaussian-modulated EPR correlations

    Institute of Scientific and Technical Information of China (English)

    He Guang-Qiang; Zeng Gui-Hua

    2006-01-01

    This paper proposes a deterministic quantum key distribution scheme based on Gaussian-modulated continuous variable EPR correlations. This scheme can implement fast and efficient key distribution. The security is guaranteed by continuous variable EPR entanglement correlations produced by nondegenerate optical parametric amplifier. For general beam splitter eavesdropping strategy, the secret information rate△I = I(α,β) - I(α,ε) is calculated in view of Shannon information theory. Finally the security analysis is presented.

  2. Feasibility of Double-Click Attack on a Passive Detection Quantum Key Distribution System

    Institute of Scientific and Technical Information of China (English)

    ZHANG Peng; LI Chao

    2011-01-01

    An eavesdropper (Eve) can exploit all the imperfections of a practical quantum key distribution (QKD) system to obtain some information about the secret key,no matter whether these imperfections are from the physical layer or from the post-processing layer.We propose a possible attack on a passive detection QKD system based on the imperfection from the software layer.The analysis shows that Eve can obtain all the information about the key without being discovered.

  3. Unbreakable distributed storage with quantum key distribution network and password-authenticated secret sharing.

    Science.gov (United States)

    Fujiwara, M; Waseda, A; Nojima, R; Moriai, S; Ogata, W; Sasaki, M

    2016-07-01

    Distributed storage plays an essential role in realizing robust and secure data storage in a network over long periods of time. A distributed storage system consists of a data owner machine, multiple storage servers and channels to link them. In such a system, secret sharing scheme is widely adopted, in which secret data are split into multiple pieces and stored in each server. To reconstruct them, the data owner should gather plural pieces. Shamir's (k, n)-threshold scheme, in which the data are split into n pieces (shares) for storage and at least k pieces of them must be gathered for reconstruction, furnishes information theoretic security, that is, even if attackers could collect shares of less than the threshold k, they cannot get any information about the data, even with unlimited computing power. Behind this scenario, however, assumed is that data transmission and authentication must be perfectly secure, which is not trivial in practice. Here we propose a totally information theoretically secure distributed storage system based on a user-friendly single-password-authenticated secret sharing scheme and secure transmission using quantum key distribution, and demonstrate it in the Tokyo metropolitan area (≤90 km).

  4. Unbreakable distributed storage with quantum key distribution network and password-authenticated secret sharing

    Science.gov (United States)

    Fujiwara, M.; Waseda, A.; Nojima, R.; Moriai, S.; Ogata, W.; Sasaki, M.

    2016-07-01

    Distributed storage plays an essential role in realizing robust and secure data storage in a network over long periods of time. A distributed storage system consists of a data owner machine, multiple storage servers and channels to link them. In such a system, secret sharing scheme is widely adopted, in which secret data are split into multiple pieces and stored in each server. To reconstruct them, the data owner should gather plural pieces. Shamir’s (k, n)-threshold scheme, in which the data are split into n pieces (shares) for storage and at least k pieces of them must be gathered for reconstruction, furnishes information theoretic security, that is, even if attackers could collect shares of less than the threshold k, they cannot get any information about the data, even with unlimited computing power. Behind this scenario, however, assumed is that data transmission and authentication must be perfectly secure, which is not trivial in practice. Here we propose a totally information theoretically secure distributed storage system based on a user-friendly single-password-authenticated secret sharing scheme and secure transmission using quantum key distribution, and demonstrate it in the Tokyo metropolitan area (≤90 km).

  5. Unbreakable distributed storage with quantum key distribution network and password-authenticated secret sharing

    Science.gov (United States)

    Fujiwara, M.; Waseda, A.; Nojima, R.; Moriai, S.; Ogata, W.; Sasaki, M.

    2016-01-01

    Distributed storage plays an essential role in realizing robust and secure data storage in a network over long periods of time. A distributed storage system consists of a data owner machine, multiple storage servers and channels to link them. In such a system, secret sharing scheme is widely adopted, in which secret data are split into multiple pieces and stored in each server. To reconstruct them, the data owner should gather plural pieces. Shamir’s (k, n)-threshold scheme, in which the data are split into n pieces (shares) for storage and at least k pieces of them must be gathered for reconstruction, furnishes information theoretic security, that is, even if attackers could collect shares of less than the threshold k, they cannot get any information about the data, even with unlimited computing power. Behind this scenario, however, assumed is that data transmission and authentication must be perfectly secure, which is not trivial in practice. Here we propose a totally information theoretically secure distributed storage system based on a user-friendly single-password-authenticated secret sharing scheme and secure transmission using quantum key distribution, and demonstrate it in the Tokyo metropolitan area (≤90 km). PMID:27363566

  6. Quantum Key Distribution (QKD) and Commodity Security Protocols: Introduction and Integration

    CERN Document Server

    Mink, Alan; Perlner, Ray

    2010-01-01

    We present an overview of quantum key distribution (QKD), a secure key exchange method based on the quantum laws of physics rather than computational complexity. We also provide an overview of the two most widely used commodity security protocols, IPsec and TLS. Pursuing a key exchange model, we propose how QKD could be integrated into these security applications. For such a QKD integration we propose a support layer that provides a set of common QKD services between the QKD protocol and the security applications

  7. Quantum Key Distribution in a Multi-User Network at Gigahertz Clock rates

    CERN Document Server

    Fernández, V; Collins, R J; Townsend, P D; Cova, S D; Rech, I; Buller, G S; Fernandez, Veronica; Gordon, Karen J.; Collins, Robert J.; Townsend, Paul D.; Cova, Sergio D.; Rech, Ivan; Buller, Gerald S.

    2005-01-01

    In recent years quantum information research has lead to the discovery of a number of remarkable new paradigms for information processing and communication. These developments include quantum cryptography schemes that offer unconditionally secure information transport guaranteed by quantum-mechanical laws. Such potentially disruptive security technologies could be of high strategic and economic value in the future. Two major issues confronting researchers in this field are the transmission range (typically <100km) and the key exchange rate, which can be as low as a few bits per second at long optical fiber distances. This paper describes further research of an approach to significantly enhance the key exchange rate in an optical fiber system at distances in the range of 1-20km. We will present results on a number of application scenarios, including point-to-point links and multi-user networks. Quantum key distribution systems have been developed, which use standard telecommunications optical fiber, and whi...

  8. Multi-user quantum key distribution with entangled photons from an AlGaAs chip

    Science.gov (United States)

    Autebert, C.; Trapateau, J.; Orieux, A.; Lemaître, A.; Gomez-Carbonell, C.; Diamanti, E.; Zaquine, I.; Ducci, S.

    2016-12-01

    In view of real-world applications of quantum information technologies, the combination of miniature quantum resources with existing fibre networks is a crucial issue. Among such resources, on-chip entangled photon sources play a central role for applications spanning quantum communications, computing and metrology. Here, we use a semiconductor source of entangled photons operating at room temperature in conjunction with standard telecom components to demonstrate multi-user quantum key distribution, a core protocol for securing communications in quantum networks. The source consists of an AlGaAs chip-emitting polarisation entangled photon pairs over a large bandwidth in the main telecom band around 1550 nm without the use of any off-chip compensation or interferometric scheme; the photon pairs are directly launched into a dense wavelength division multiplexer (DWDM) and secret keys are distributed between several pairs of users communicating through different channels. We achieve a visibility measured after the DWDM of 87% and show long-distance key distribution using a 50-km standard telecom fibre link between two network users. These results illustrate a promising route to practical, resource-efficient implementations adapted to quantum network infrastructures.

  9. Field test of a continuous-variable quantum key distribution prototype

    Energy Technology Data Exchange (ETDEWEB)

    Fossier, S; Debuisschert, T [Thales Research and Technology France, RD 128, 91767 Palaiseau Cedex (France); Diamanti, E; Villing, A; Tualle-Brouri, R; Grangier, P [Laboratoire Charles Fabry de l' Institut d' Optique-CNRS-Univ. Paris-Sud, Campus Polytechnique, RD 128, 91127 Palaiseau Cedex (France)], E-mail: simon.fossier@institutoptique.fr

    2009-04-15

    We have designed and realized a prototype that implements a continuous-variable quantum key distribution (QKD) protocol based on coherent states and reverse reconciliation. The system uses time and polarization multiplexing for optimal transmission and detection of the signal and phase reference, and employs sophisticated error-correction codes for reconciliation. The security of the system is guaranteed against general coherent eavesdropping attacks. The performance of the prototype was tested over preinstalled optical fibres as part of a quantum cryptography network combining different QKD technologies. The stable and automatic operation of the prototype over 57 h yielded an average secret key distribution rate of 8 kbit s{sup -1} over a 3 dB loss optical fibre, including the key extraction process and all quantum and classical communication. This system is therefore ideal for securing communications in metropolitan size networks with high-speed requirements.

  10. Faked state attacks on realistic round robin DPS quantum key distribution systems and countermeasure

    Science.gov (United States)

    Iwakoshi, T.

    2015-05-01

    In May 2014, a new quantum key distribution protocol named "Round Robin Differential-Phase-Shift Quantum Key Distribution (RR DPS QKD)" was proposed. It has a special feature that the key consumption via privacy amplification is a small constant because RR DPS QKD guarantees its security by information causality, not by information-disturbance trade-off. Therefore, the authors claimed that RR DPS QKD systems does not need to monitor the disturbance by an attacker in the quantum channel. However, this study shows that a modified Faked-State Attack (or so-called bright illumination attack) can hack a RR DPS QKD system almost perfectly if it is implemented with realistic detectors even information-causality guarantees the security of RR DPS QKD protocol. Therefore, this study also proposes a possible Measurement-Device-Independent RR DPS QKD system to avoid the modified Faked-State Attack.

  11. Misinterpretation of statistical distance in security of quantum key distribution shown by simulation

    Science.gov (United States)

    Iwakoshi, Takehisa; Hirota, Osamu

    2014-10-01

    This study will test an interpretation in quantum key distribution (QKD) that trace distance between the distributed quantum state and the ideal mixed state is a maximum failure probability of the protocol. Around 2004, this interpretation was proposed and standardized to satisfy both of the key uniformity in the context of universal composability and operational meaning of the failure probability of the key extraction. However, this proposal has not been verified concretely yet for many years while H. P. Yuen and O. Hirota have thrown doubt on this interpretation since 2009. To ascertain this interpretation, a physical random number generator was employed to evaluate key uniformity in QKD. In this way, we calculated statistical distance which correspond to trace distance in quantum theory after a quantum measurement is done, then we compared it with the failure probability whether universal composability was obtained. As a result, the degree of statistical distance of the probability distribution of the physical random numbers and the ideal uniformity was very large. It is also explained why trace distance is not suitable to guarantee the security in QKD from the view point of quantum binary decision theory.

  12. High-speed free-space quantum key distribution system for urban daylight applications.

    Science.gov (United States)

    García-Martínez, M J; Denisenko, N; Soto, D; Arroyo, D; Orue, A B; Fernandez, V

    2013-05-10

    We report a free-space quantum key distribution system designed for high-speed key transmission in urban areas. Clocking the system at gigahertz frequencies and efficiently filtering background enables higher secure key rates than those previously achieved by similar systems. The transmitter and receiver are located in two separate buildings 300 m apart in downtown Madrid and they exchange secure keys at rates up to 1 Mbps. The system operates in full bright daylight conditions with an average secure key rate of 0.5 Mbps and 24 h stability without human intervention.

  13. Secure Quantum Key Distribution Network with Bell States and Local Unitary Operations

    Institute of Scientific and Technical Information of China (English)

    LI Chun-Yan; ZHOU Hong-Yu; WANG Yan; DENG Fu-Guo

    2005-01-01

    @@ We propose a theoretical scheme for secure quantum key distribution network following the ideas in quantum dense coding. In this scheme, the server of the network provides the service for preparing and measuring the Bell states,and the users encode the states with local unitary operations. For preventing the server from eavesdropping, we design a decoy when the particle is transmitted between the users. The scheme has high capacity as one particle carries two bits of information and its efficiency for qubits approaches 100%. Moreover, it is unnecessary for the users to store the quantum states, which makes this scheme more convenient in applications than others.

  14. Quantum key distribution by swapping the entanglement of {chi}-type state

    Energy Technology Data Exchange (ETDEWEB)

    Gao Gan, E-mail: gaogan0556@163.co [Department of Electrical Engineering, Tongling University, Tongling 244000 (China)

    2010-06-01

    We propose a quantum key distribution protocol using entanglement swapping of {chi}-type state; in this protocol, Alice and Bob transmit a particle sequence to each other and perform {chi}-type state measurements. Alice's and Bob's roles are completely symmetric.

  15. Measuring-Basis Encrypted Quantum Key Distribution with Four-State Systems

    Institute of Scientific and Technical Information of China (English)

    CHEN Pan; LI Yan-Song; DENG Fu-Guo; LONG Gui-Lu

    2007-01-01

    A measuring-basis encrypted quantum key distribution scheme is proposed by using twelve nonorthogonal states in a four-state system and the measuring-basis encryption technique. In this scheme, two bits of classical information can be encoded on one four-state particle and the transmitted particles can be fully used.

  16. A Modified Protocol of Quantum Key Distribution Based on Entanglement Swapping

    Institute of Scientific and Technical Information of China (English)

    HUANG Xin; LI Shu-Min; WANG An-Min

    2007-01-01

    By comparing Cabello's addendum to his quantum key distribution protocol [Phys. Rev. A 64 (2001) 024301],we propose a more convenient modified protocol based on the entanglement swapping which is secure against the eavesdropping strategy addressed by Zhang et al. [Phys. Rev. A 63 (2001)036301] and other existing types of attack.

  17. Security of EPR-based Quantum Key Distribution using three bases

    CERN Document Server

    Inamori, H

    2000-01-01

    Modifications to a previous proof of the security of EPR-based quantum key distribution are proposed. This modified version applies to a protocol using three conjugate measurement bases rather than two. A higher tolerable error rate is obtained for the three-basis protocol.

  18. Multiplexing scheme for simplified entanglement-based large-alphabet quantum key distribution

    CERN Document Server

    Dada, Adetunmise C

    2015-01-01

    We propose a practical quantum cryptographic scheme which combines high information capacity, such as provided by high-dimensional quantum entanglement, with the simplicity of a two-dimensional Clauser-Horne-Shimony-Holt (CHSH) Bell test for security verification. By applying a state combining entanglement in a two-dimensional degree of freedom, such as photon polarization, with high-dimensional correlations in another degree of freedom, such as photon orbital angular momentum (OAM) or path, the scheme provides a considerably simplified route towards security verification in quantum key distribution (QKD) aimed at exploiting high-dimensional quantum systems for increased secure key rates. It also benefits from security against collective attacks and is feasible using currently available technologies.

  19. Quantum Flows for Secret Key Distribution in the Presence of the Photon Number Splitting Attack

    Directory of Open Access Journals (Sweden)

    Luis A. Lizama-Pérez

    2014-06-01

    Full Text Available Physical implementations of quantum key distribution (QKD protocols, like the Bennett-Brassard (BB84, are forced to use attenuated coherent quantum states, because the sources of single photon states are not functional yet for QKD applications. However, when using attenuated coherent states, the relatively high rate of multi-photonic pulses introduces vulnerabilities that can be exploited by the photon number splitting (PNS attack to brake the quantum key. Some QKD protocols have been developed to be resistant to the PNS attack, like the decoy method, but those define a single photonic gain in the quantum channel. To overcome this limitation, we have developed a new QKD protocol, called ack-QKD, which is resistant to the PNS attack. Even more, it uses attenuated quantum states, but defines two interleaved photonic quantum flows to detect the eavesdropper activity by means of the quantum photonic error gain (QPEG or the quantum bit error rate (QBER. The physical implementation of the ack-QKD is similar to the well-known BB84 protocol.

  20. Differential-phase-shift quantum key distribution using heralded narrow-band single photons.

    Science.gov (United States)

    Liu, Chang; Zhang, Shanchao; Zhao, Luwei; Chen, Peng; Fung, C-H F; Chau, H F; Loy, M M T; Du, Shengwang

    2013-04-22

    We demonstrate the first proof of principle differential phase shift (DPS) quantum key distribution (QKD) using narrow-band heralded single photons with amplitude-phase modulations. In the 3-pulse case, we obtain a quantum bit error rate (QBER) as low as 3.06% which meets the unconditional security requirement. As we increase the pulse number up to 15, the key creation efficiency approaches 93.4%, but with a cost of increasing the QBER. Our result suggests that narrow-band single photons maybe a promising source for the DPS-QKD protocol.

  1. High performance frame synchronization for continuous variable quantum key distribution systems.

    Science.gov (United States)

    Lin, Dakai; Huang, Peng; Huang, Duan; Wang, Chao; Peng, Jinye; Zeng, Guihua

    2015-08-24

    Considering a practical continuous variable quantum key distribution(CVQKD) system, synchronization is of significant importance as it is hardly possible to extract secret keys from unsynchronized strings. In this paper, we proposed a high performance frame synchronization method for CVQKD systems which is capable to operate under low signal-to-noise(SNR) ratios and is compatible with random phase shift induced by quantum channel. A practical implementation of this method with low complexity is presented and its performance is analysed. By adjusting the length of synchronization frame, this method can work well with large range of SNR values which paves the way for longer distance CVQKD.

  2. Suppression of dark-count effects in practical quantum key-distribution

    CERN Document Server

    Khalique, A; Alber, G; Khalique, Aeysha; Nikolopoulos, Georgios M.; Alber, Gernot

    2006-01-01

    The influence of imperfections on achievable secret-key generation rates of quantum key distribution protocols is investigated. As examples of relevant imperfections, we consider tagging of Alice's qubits and dark counts at Bob's detectors. It is demonstrated that error correction and privacy amplification based on a combination of a two-way classical communication protocol and asymmetric Calderbank-Shor-Steane codes may significantly suppress the disastrous influence of dark counts. As a result, the distances are increased considerably over which a secret key can be distributed in optical fibres reliably. Results are presented for the four-state, the six-state, and the decoy-state protocols.

  3. Measurement-device-independent quantum key distribution with source state errors and statistical fluctuation

    Science.gov (United States)

    Jiang, Cong; Yu, Zong-Wen; Wang, Xiang-Bin

    2017-03-01

    We show how to calculate the secure final key rate in the four-intensity decoy-state measurement-device-independent quantum key distribution protocol with both source errors and statistical fluctuations with a certain failure probability. Our results rely only on the range of only a few parameters in the source state. All imperfections in this protocol have been taken into consideration without assuming any specific error patterns of the source.

  4. Experimental study for Yuen-Kim protocol of quantum key distribution with unconditional secure

    OpenAIRE

    Hirota, O.; Kato, K; Sohma, M.

    2002-01-01

    In this report, we simulate practical feature of Yuen-Kim protocol for quantum key distribution with unconditional secure. In order to demonstrate them experimentally by intensity modulation/direct detection(IMDD) optical fiber communication system, we use simplified encoding scheme to guarantee security for key information(1 or 0). That is, pairwise M-ary intensity modulation scheme is employed. Furthermore, we give an experimental implementation of YK protocol based on IMDD.

  5. Proof-of-principle field test of quantum key distribution immune to detector attacks

    CERN Document Server

    Rubenok, A; Chan, P; Lucio-Martinez, I; Tittel, W

    2012-01-01

    Quantum key distribution (QKD) promises the distribution of cryptographic keys whose secrecy is guaranteed by fundamental laws of quantum physics. After more than two decades devoted to the improvement of theoretical understanding and experimental realization, recent results in quantum hacking have reminded us that the information theoretic security of QKD protocols does not necessarily imply the same level of security for actual implementations. Of particular concern are attacks that exploit vulnerabilities of single photon detectors. Here we report the first proof-of-principle demonstration of a QKD protocol that removes the threat of any such attack. Our fiber-based implementation took advantage of three different locations within the city of Calgary. Its simplicity and robustness to environment-induced property variations of deployed optical fibers, along with the enhanced level of security offered by the protocol, confirms QKD as a viable technology for safeguarding secrets in transmission.

  6. High Efficient Quantum Key Distribution by Random Using Classified Signal Coherent States

    Institute of Scientific and Technical Information of China (English)

    XI Jing-Bo; FANG Xi-Ming

    2006-01-01

    The decoy-state method is a useful method in resisting the attacks on quantum key distribution. However, how to choose the intensities of decoy states and the ratio of the decoy states and the signal state is still an open question. We present a simple formula to analyse the problem. We also give a simple method to derive the bounds of the necessary counting rates and quantum bit error rates for BB84 and SARG04; the latter was previously proposed by Scarani et al. [Phys. Rev. Lett. 92 (2004) 057901] We then propose a multi-signal-state method which employs different coherent states either as the decoy state or as the signal state to carry out quantum key distribution. We find our protocol more efficient and feasible.

  7. Making the decoy-state measurement-device-independent quantum key distribution practically useful

    Science.gov (United States)

    Zhou, Yi-Heng; Yu, Zong-Wen; Wang, Xiang-Bin

    2016-04-01

    The relatively low key rate seems to be the major barrier to its practical use for the decoy-state measurement-device-independent quantum key distribution (MDI-QKD). We present a four-intensity protocol for the decoy-state MDI-QKD that hugely raises the key rate, especially in the case in which the total data size is not large. Also, calculations show that our method makes it possible for secure private communication with fresh keys generated from MDI-QKD with a delay time of only a few seconds.

  8. Controlling excess noise in fiber optics continuous variables quantum key distribution

    OpenAIRE

    Lodewyck, Jérôme; Debuisschert, Thierry; Tualle-Brouri, Rosa; Grangier, Philippe

    2005-01-01

    5 pages, 4 figures; International audience; We describe a continuous variables coherent states quantum key distribution system working at 1550 nm, and entirely made of standard fiber optics and telecom components, such as integrated-optics modulators, couplers and fast InGaAs photodiodes. The setup is composed of an emitter randomly modulating a coherent state in the complex plane with a doubly Gaussian distribution, and a receiver based on a shot noise limited time-resolved homodyne detector...

  9. High-dimensional quantum key distribution with the entangled single-photon-added coherent state

    Science.gov (United States)

    Wang, Yang; Bao, Wan-Su; Bao, Hai-Ze; Zhou, Chun; Jiang, Mu-Sheng; Li, Hong-Wei

    2017-04-01

    High-dimensional quantum key distribution (HD-QKD) can generate more secure bits for one detection event so that it can achieve long distance key distribution with a high secret key capacity. In this Letter, we present a decoy state HD-QKD scheme with the entangled single-photon-added coherent state (ESPACS) source. We present two tight formulas to estimate the single-photon fraction of postselected events and Eve's Holevo information and derive lower bounds on the secret key capacity and the secret key rate of our protocol. We also present finite-key analysis for our protocol by using the Chernoff bound. Our numerical results show that our protocol using one decoy state can perform better than that of previous HD-QKD protocol with the spontaneous parametric down conversion (SPDC) using two decoy states. Moreover, when considering finite resources, the advantage is more obvious.

  10. Measurement-Device-Independent Quantum Key Distribution Over a 404 km Optical Fiber

    Science.gov (United States)

    Yin, Hua-Lei; Chen, Teng-Yun; Yu, Zong-Wen; Liu, Hui; You, Li-Xing; Zhou, Yi-Heng; Chen, Si-Jing; Mao, Yingqiu; Huang, Ming-Qi; Zhang, Wei-Jun; Chen, Hao; Li, Ming Jun; Nolan, Daniel; Zhou, Fei; Jiang, Xiao; Wang, Zhen; Zhang, Qiang; Wang, Xiang-Bin; Pan, Jian-Wei

    2016-11-01

    Measurement-device-independent quantum key distribution (MDIQKD) with the decoy-state method negates security threats of both the imperfect single-photon source and detection losses. Lengthening the distance and improving the key rate of quantum key distribution (QKD) are vital issues in practical applications of QKD. Herein, we report the results of MDIQKD over 404 km of ultralow-loss optical fiber and 311 km of a standard optical fiber while employing an optimized four-intensity decoy-state method. This record-breaking implementation of the MDIQKD method not only provides a new distance record for both MDIQKD and all types of QKD systems but also, more significantly, achieves a distance that the traditional Bennett-Brassard 1984 QKD would not be able to achieve with the same detection devices even with ideal single-photon sources. This work represents a significant step toward proving and developing feasible long-distance QKD.

  11. Protocol of Secure Key Distribution Using Hash Functions and Quantum Authenticated Channels (KDP-6DP

    Directory of Open Access Journals (Sweden)

    Mohammed M.A. Majeed

    2010-01-01

    Full Text Available Problem statement: In previous researches, we investigated the security of communication channels, which utilizes authentication, key distribution between two parties, error corrections and cost establishment. In the present work, we studied new concepts of Quantum Authentication (QA and sharing key according to previous points. Approach: This study presented a new protocol concept that allows the session and key generation on-site by independently applying a cascade of two hash functions on a random string of bits at the sender and receiver sides. This protocol however, required a reliable method of authentication. It employed an out-of-band authentication methodology based on quantum theory, which uses entangled pairs of photons. Results: The proposed quantum-authenticated channel is secure in the presence of eavesdropper who has access to both the classical and the quantum channels. Conclusion/Recommendations: The key distribution process using cascaded hash functions provides better security. The concepts presented by this protocol represent a valid approach to the communication security problem.

  12. Improved two-way six-state protocol for quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Shaari, J.S., E-mail: jesni_shamsul@yahoo.com [Faculty of Science, International Islamic University Malaysia (IIUM), Jalan Sultan Ahmad Shah, Bandar Indera Mahkota, 25200 Kuantan, Pahang (Malaysia); Bahari, Asma' Ahmad [Faculty of Science, International Islamic University Malaysia (IIUM), Jalan Sultan Ahmad Shah, Bandar Indera Mahkota, 25200 Kuantan, Pahang (Malaysia)

    2012-10-01

    A generalized version for a qubit based two-way quantum key distribution scheme was first proposed in the paper [Phys. Lett. A 358 (2006) 85] capitalizing on the six quantum states derived from three mutually unbiased bases. While boasting of a higher level of security, the protocol was not designed for ease of practical implementation. In this work, we propose modifications to the protocol, resulting not only in improved security but also in a more efficient and practical setup. We provide comparisons for calculated secure key rates for the protocols in noisy and lossy channels. -- Highlights: ► Modification for efficient generalized two-way QKD is proposed. ► Calculations include secure key rates in noisy and lossy channels for selected attack scenario. ► Resulting proposal provides for higher secure key rate in selected attack scheme.

  13. Hacking on decoy-state quantum key distribution system with partial phase randomization

    Science.gov (United States)

    Sun, Shi-Hai; Jiang, Mu-Sheng; Ma, Xiang-Chun; Li, Chun-Yan; Liang, Lin-Mei

    2014-04-01

    Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a hybrid measurement attack, with only linear optics, homodyne detection, and single photon detection, to the widely used vacuum + weak decoy state QKD system when the phase of source is partially randomized. Our analysis shows that, in some parameter regimes, the proposed attack would result in an entanglement breaking channel but still be able to trick the legitimate users to believe they have transmitted secure keys. That is, the eavesdropper is able to steal all the key information without discovered by the users. Thus, our proposal reveals that partial phase randomization is not sufficient to guarantee the security of phase-encoding QKD systems with weak coherent states.

  14. Quantum Hash function and its application to privacy amplification in quantum key distribution, pseudo-random number generation and image encryption.

    Science.gov (United States)

    Yang, Yu-Guang; Xu, Peng; Yang, Rui; Zhou, Yi-Hua; Shi, Wei-Min

    2016-01-29

    Quantum information and quantum computation have achieved a huge success during the last years. In this paper, we investigate the capability of quantum Hash function, which can be constructed by subtly modifying quantum walks, a famous quantum computation model. It is found that quantum Hash function can act as a hash function for the privacy amplification process of quantum key distribution systems with higher security. As a byproduct, quantum Hash function can also be used for pseudo-random number generation due to its inherent chaotic dynamics. Further we discuss the application of quantum Hash function to image encryption and propose a novel image encryption algorithm. Numerical simulations and performance comparisons show that quantum Hash function is eligible for privacy amplification in quantum key distribution, pseudo-random number generation and image encryption in terms of various hash tests and randomness tests. It extends the scope of application of quantum computation and quantum information.

  15. Quantum Hash function and its application to privacy amplification in quantum key distribution, pseudo-random number generation and image encryption

    Science.gov (United States)

    Yang, Yu-Guang; Xu, Peng; Yang, Rui; Zhou, Yi-Hua; Shi, Wei-Min

    2016-01-01

    Quantum information and quantum computation have achieved a huge success during the last years. In this paper, we investigate the capability of quantum Hash function, which can be constructed by subtly modifying quantum walks, a famous quantum computation model. It is found that quantum Hash function can act as a hash function for the privacy amplification process of quantum key distribution systems with higher security. As a byproduct, quantum Hash function can also be used for pseudo-random number generation due to its inherent chaotic dynamics. Further we discuss the application of quantum Hash function to image encryption and propose a novel image encryption algorithm. Numerical simulations and performance comparisons show that quantum Hash function is eligible for privacy amplification in quantum key distribution, pseudo-random number generation and image encryption in terms of various hash tests and randomness tests. It extends the scope of application of quantum computation and quantum information.

  16. Quantum Hash function and its application to privacy amplification in quantum key distribution, pseudo-random number generation and image encryption

    Science.gov (United States)

    Yang, Yu-Guang; Xu, Peng; Yang, Rui; Zhou, Yi-Hua; Shi, Wei-Min

    2016-01-01

    Quantum information and quantum computation have achieved a huge success during the last years. In this paper, we investigate the capability of quantum Hash function, which can be constructed by subtly modifying quantum walks, a famous quantum computation model. It is found that quantum Hash function can act as a hash function for the privacy amplification process of quantum key distribution systems with higher security. As a byproduct, quantum Hash function can also be used for pseudo-random number generation due to its inherent chaotic dynamics. Further we discuss the application of quantum Hash function to image encryption and propose a novel image encryption algorithm. Numerical simulations and performance comparisons show that quantum Hash function is eligible for privacy amplification in quantum key distribution, pseudo-random number generation and image encryption in terms of various hash tests and randomness tests. It extends the scope of application of quantum computation and quantum information. PMID:26823196

  17. W-state Analyzer and Multi-party Measurement-device-independent Quantum Key Distribution

    Science.gov (United States)

    Zhu, Changhua; Xu, Feihu; Pei, Changxing

    2015-12-01

    W-state is an important resource for many quantum information processing tasks. In this paper, we for the first time propose a multi-party measurement-device-independent quantum key distribution (MDI-QKD) protocol based on W-state. With linear optics, we design a W-state analyzer in order to distinguish the four-qubit W-state. This analyzer constructs the measurement device for four-party MDI-QKD. Moreover, we derived a complete security proof of the four-party MDI-QKD, and performed a numerical simulation to study its performance. The results show that four-party MDI-QKD is feasible over 150 km standard telecom fiber with off-the-shelf single photon detectors. This work takes an important step towards multi-party quantum communication and a quantum network.

  18. Implementation of continuous-variable quantum key distribution with composable and one-sided-device-independent security against coherent attacks

    DEFF Research Database (Denmark)

    Gehring, Tobias; Haendchen, Vitus; Duhme, Joerg

    2015-01-01

    Secret communication over public channels is one of the central pillars of a modern information society. Using quantum key distribution this is achieved without relying on the hardness of mathematical problems, which might be compromised by improved algorithms or by future quantum computers. State......-of-the-art quantum key distribution requires composable security against coherent attacks for a finite number of distributed quantum states as well as robustness against implementation side channels. Here we present an implementation of continuous-variable quantum key distribution satisfying these requirements. Our...... with conventional optical communication technology, our work is a step towards practical implementations of quantum key distribution with state-of-the-art security based solely on telecom components....

  19. 2 GHz clock quantum key distribution over 260 km of standard telecom fiber.

    Science.gov (United States)

    Wang, Shuang; Chen, Wei; Guo, Jun-Fu; Yin, Zhen-Qiang; Li, Hong-Wei; Zhou, Zheng; Guo, Guang-Can; Han, Zheng-Fu

    2012-03-15

    We report a demonstration of quantum key distribution (QKD) over a standard telecom fiber exceeding 50 dB in loss and 250 km in length. The differential phase shift QKD protocol was chosen and implemented with a 2 GHz system clock rate. By careful optimization of the 1 bit delayed Faraday-Michelson interferometer and the use of the superconducting single photon detector (SSPD), we achieved a quantum bit error rate below 2% when the fiber length was no more than 205 km, and of 3.45% for a 260 km fiber with 52.9 dB loss. We also improved the quantum efficiency of SSPD to obtain a high key rate for 50 km length.

  20. 2-GHz clock quantum key distribution over 260 km of standard telecom fiber

    CERN Document Server

    Wang, Shuang; Guo, Jun-Fu; Yin, Zhen-Qiang; Li, Hong-Wei; Zhou, Zheng; Guo, Guang-Can; Han, Zheng-Fu; 10.1364/OL.37.001008

    2012-01-01

    We report a demonstration of quantum key distribution (QKD) over a standard telecom fiber exceeding 50 dB in loss and 250 km in length. The differential phase shift QKD protocol was chosen and implemented with 2 GHz system clock rate. By careful optimization of the 1-bit delayed Faraday-Michelson interferometer and the use of the super-conducting single photon detector (SSPD), we achieved a quantum bit error rate below 2% when the fiber length was no more than 205 km, and of 3.45% for the 260 km length fiber with 52.9 dB loss. We also improved the quantum efficiency of SSPD to obtain high key rate for 50 km length.

  1. Measurement-Device-Independent Quantum Key Distribution over Untrustful Metropolitan Network

    Directory of Open Access Journals (Sweden)

    Yan-Lin Tang

    2016-03-01

    Full Text Available Quantum cryptography holds the promise to establish an information-theoretically secure global network. All field tests of metropolitan-scale quantum networks to date are based on trusted relays. The security critically relies on the accountability of the trusted relays, which will break down if the relay is dishonest or compromised. Here, we construct a measurement-device-independent quantum key distribution (MDIQKD network in a star topology over a 200-square-kilometer metropolitan area, which is secure against untrustful relays and against all detection attacks. In the field test, our system continuously runs through one week with a secure key rate 10 times larger than previous results. Our results demonstrate that the MDIQKD network, combining the best of both worlds—security and practicality, constitutes an appealing solution to secure metropolitan communications.

  2. Experimental Study on Practical Quantum Key Distribution Scheme with Time-Multiplexed Technique

    Institute of Scientific and Technical Information of China (English)

    HUANG Yu-Xian; HU Hua-Peng; LIANG Rui-Sheng; LU Yi-Qun; WANG Jin-Dong; LU Wei

    2008-01-01

    We present a scheme that is capable of detecting photon numbers during the quantum key distribution (QKD) based on an improved differential phase shift (DPS) system without Trojan horse attack. A time-multiplexed detector (TMD) is set in for the photon-number resolution. Two fibre loops are used for detecting photon numbers as well as distributing keys. The long-term stabilization is guaranteed by two Faraday mirrors (FM) at Bob's site to automatically compensate for polarization defect. Our experimental study (90km QKD is completed) indicates that such a system is stable and secure which nearly reaches the performance of a single photon scheme.

  3. Phase-remapping attack in practical quantum-key-distribution systems

    Science.gov (United States)

    Fung, Chi-Hang Fred; Qi, Bing; Tamaki, Kiyoshi; Lo, Hoi-Kwong

    2007-03-01

    Quantum key distribution (QKD) can be used to generate secret keys between two distant parties. Even though QKD has been proven unconditionally secure against eavesdroppers with unlimited computation power, practical implementations of QKD may contain loopholes that may lead to the generated secret keys being compromised. In this paper, we propose a phase-remapping attack targeting two practical bidirectional QKD systems (the “plug-and-play” system and the Sagnac system). We showed that if the users of the systems are unaware of our attack, the final key shared between them can be compromised in some situations. Specifically, we showed that, in the case of the Bennett-Brassard 1984 (BB84) protocol with ideal single-photon sources, when the quantum bit error rate (QBER) is between 14.6% and 20%, our attack renders the final key insecure, whereas the same range of QBER values has been proved secure if the two users are unaware of our attack; also, we demonstrated three situations with realistic devices where positive key rates are obtained without the consideration of Trojan horse attacks but in fact no key can be distilled. We remark that our attack is feasible with only current technology. Therefore, it is very important to be aware of our attack in order to ensure absolute security. In finding our attack, we minimize the QBER over individual measurements described by a general POVM, which has some similarity with the standard quantum state discrimination problem.

  4. High speed and adaptable error correction for megabit/s rate quantum key distribution.

    Science.gov (United States)

    Dixon, A R; Sato, H

    2014-12-02

    Quantum Key Distribution is moving from its theoretical foundation of unconditional security to rapidly approaching real world installations. A significant part of this move is the orders of magnitude increases in the rate at which secure key bits are distributed. However, these advances have mostly been confined to the physical hardware stage of QKD, with software post-processing often being unable to support the high raw bit rates. In a complete implementation this leads to a bottleneck limiting the final secure key rate of the system unnecessarily. Here we report details of equally high rate error correction which is further adaptable to maximise the secure key rate under a range of different operating conditions. The error correction is implemented both in CPU and GPU using a bi-directional LDPC approach and can provide 90-94% of the ideal secure key rate over all fibre distances from 0-80 km.

  5. Quantum hacking of two-way continuous-variable quantum key distribution using Trojan-horse attack

    Science.gov (United States)

    Ma, Hong-Xin; Bao, Wan-Su; Li, Hong-Wei; Chou, Chun

    2016-08-01

    We present a Trojan-horse attack on the practical two-way continuous-variable quantum key distribution system. Our attack mainly focuses on the imperfection of the practical system that the modulator has a redundancy of modulation pulse-width, which leaves a loophole for the eavesdropper inserting a Trojan-horse pulse. Utilizing the unique characteristics of two-way continuous-variable quantum key distribution that Alice only takes modulation operation on the received mode without any measurement, this attack allows the eavesdropper to render all of the final keys shared between the legitimate parties insecure without being detected. After analyzing the feasibility of the attack, the corresponding countermeasures are put forward. Project supported by the National Basic Research Program of China (Grant No. 2013CB338002) and the National Natural Science Foundation of China (Grant Nos. 11304397 and 61505261).

  6. Continuous-variable quantum key distribution protocols with a non-Gaussian modulation

    CERN Document Server

    Leverrier, Anthony

    2011-01-01

    In this paper, we consider continuous-variable quantum key distribution (QKD) protocols which use non-Gaussian modulations. These specific modulation schemes are compatible with very efficient error correction procedures, hence allowing the protocols to outperform previous protocols in terms of achievable range. In their simplest implementation, these protocols are secure for any linear quantum channels (hence against Gaussian attacks). We also show how the use of decoy states makes the protocols secure against arbitrary collective attacks, which implies their unconditional security in the asymptotic limit.

  7. High-Rate Field Demonstration of Large-Alphabet Quantum Key Distribution

    Science.gov (United States)

    2016-10-12

    by controlling excess noise. Sci. Rep. 6, 19201 (2016). [30] Treiber, A. et al. A fully automated entanglement-based quantum cryptography system for telecom fiber networks . New J. Phys. 11, 045013 (2009). ...research has focused on extending the range of QKD links well beyond 100 km [13–15], deployed QKD networks will include a variety of link lengths with...2009). [14] Wang, S. et al. 2 GHz clock quantum key distribution over 260 km of standard telecom fiber. Opt. Lett. 37, 1008–1010 (2012). [15] Korzh, B

  8. Quantum Key Distribution Based on a Weak-Coupling Cavity QED Regime

    Institute of Scientific and Technical Information of China (English)

    李春燕; 李岩松

    2011-01-01

    We present a quantum key distribution scheme using a weak-coupling cavity QED regime based on quantum dense coding.Hybrid entanglement states of photons and electrons are used to distribute information.We just need to transmit photons without storing them in the scheme.The electron confined in a quantum dot,which is embedded in a microcavity,is held by one of the legitimate users throughout the whole communication process.Only the polarization of a single photon and spin of electron measurements are applied in this protocol,which are easier to perform than collective-Bell state measurements.Linear optical apparatus,such as a special polarizing beam splitter in a circular basis and single photon operations,make it more flexible to realize under current technology.Its efficiency will approach 100% in the ideal case.The security of the scheme is also discussed.%We present a quantum key distribution scheme using a weak-coupling cavity QED regime based on quantum dense coding. Hybrid entanglement states of photons and electrons are used to distribute information. We just need to transmit photons without storing them in the scheme. The electron confined in a quantum dot, which is embedded in a microcavity, is held by one of the legitimate users throughout the whole communication process. Only the polarization of a single photon and spin of electron measurements are applied in this protocol, which are easier to perform than collective-Bell state measurements. Linear optical apparatus, such as a speciai polarizing beam splitter in a circular basis and single photon operations, make it more flexible to realize under current technology. Its efficiency will approach 100% in the ideal case. The security of the scheme is also discussed.

  9. Efficient bit sifting scheme of post-processing in quantum key distribution

    Science.gov (United States)

    Li, Qiong; Le, Dan; Wu, Xianyan; Niu, Xiamu; Guo, Hong

    2015-10-01

    Bit sifting is an important step in the post-processing of quantum key distribution (QKD). Its function is to sift out the undetected original keys. The communication traffic of bit sifting has essential impact on the net secure key rate of a practical QKD system. In this paper, an efficient bit sifting scheme is presented, of which the core is a lossless source coding algorithm. Both theoretical analysis and experimental results demonstrate that the performance of the scheme is approaching the Shannon limit. The proposed scheme can greatly decrease the communication traffic of the post-processing of a QKD system, which means the proposed scheme can decrease the secure key consumption for classical channel authentication and increase the net secure key rate of the QKD system, as demonstrated by analyzing the improvement on the net secure key rate. Meanwhile, some recommendations on the application of the proposed scheme to some representative practical QKD systems are also provided.

  10. Unconditional security of time-energy entanglement quantum key distribution using dual-basis interferometry.

    Science.gov (United States)

    Zhang, Zheshen; Mower, Jacob; Englund, Dirk; Wong, Franco N C; Shapiro, Jeffrey H

    2014-03-28

    High-dimensional quantum key distribution (HDQKD) offers the possibility of high secure-key rate with high photon-information efficiency. We consider HDQKD based on the time-energy entanglement produced by spontaneous parametric down-conversion and show that it is secure against collective attacks. Its security rests upon visibility data-obtained from Franson and conjugate-Franson interferometers-that probe photon-pair frequency correlations and arrival-time correlations. From these measurements, an upper bound can be established on the eavesdropper's Holevo information by translating the Gaussian-state security analysis for continuous-variable quantum key distribution so that it applies to our protocol. We show that visibility data from just the Franson interferometer provides a weaker, but nonetheless useful, secure-key rate lower bound. To handle multiple-pair emissions, we incorporate the decoy-state approach into our protocol. Our results show that over a 200-km transmission distance in optical fiber, time-energy entanglement HDQKD could permit a 700-bit/sec secure-key rate and a photon information efficiency of 2 secure-key bits per photon coincidence in the key-generation phase using receivers with a 15% system efficiency.

  11. An efficient two-step quantum key distribution protocol with orthogonal product states

    Institute of Scientific and Technical Information of China (English)

    Yang Yu-Guang; Wen Qiao-Yan; Zhu Fu-Chen

    2007-01-01

    An efficient two-step quantum key distribution (QKD) protocol with orthogonal product states in the n( )n(n ≥ 3) Hilbert space is presented. In this protocol, the particles in the orthogonal product states form two particle sequences.The sender, Alice, first sends one sequence to the receiver, Bob. After Bob receives the first particle sequence, Alice and Bob check eavesdropping by measuring a fraction of particles randomly chosen. After ensuring the security of the quantum channel, Alice sends the other particle sequence to Bob. By making an orthogonal measurement on the two particle sequences, Bob can obtain the information of the orthogonal product states sent by Alice. This protocol has many distinct features such as great capacity, high efficiency in that it uses all orthogonal product states in distributing the key except those chosen for checking eavesdroppers.

  12. Improvement of two-way continuous-variable quantum key distribution with virtual photon subtraction

    Science.gov (United States)

    Zhao, Yijia; Zhang, Yichen; Li, Zhengyu; Yu, Song; Guo, Hong

    2017-08-01

    We propose a method to improve the performance of two-way continuous-variable quantum key distribution protocol by virtual photon subtraction. The virtual photon subtraction implemented via non-Gaussian post-selection not only enhances the entanglement of two-mode squeezed vacuum state but also has advantages in simplifying physical operation and promoting efficiency. In two-way protocol, virtual photon subtraction could be applied on two sources independently. Numerical simulations show that the optimal performance of renovated two-way protocol is obtained with photon subtraction only used by Alice. The transmission distance and tolerable excess noise are improved by using the virtual photon subtraction with appropriate parameters. Moreover, the tolerable excess noise maintains a high value with the increase in distance so that the robustness of two-way continuous-variable quantum key distribution system is significantly improved, especially at long transmission distance.

  13. Implementation of continuous-variable quantum key distribution with discrete modulation

    Science.gov (United States)

    Hirano, Takuya; Ichikawa, Tsubasa; Matsubara, Takuto; Ono, Motoharu; Oguri, Yusuke; Namiki, Ryo; Kasai, Kenta; Matsumoto, Ryutaroh; Tsurumaru, Toyohiro

    2017-06-01

    We have developed a continuous-variable quantum key distribution (CV-QKD) system that employs discrete quadrature-amplitude modulation and homodyne detection of coherent states of light. We experimentally demonstrated automated secure key generation with a rate of 50 kbps when a quantum channel is a 10 km optical fibre. The CV-QKD system utilises a four-state and post-selection protocol and generates a secure key against the entangling cloner attack. We used a pulsed light source of 1550 nm wavelength with a repetition rate of 10 MHz. A commercially available balanced receiver is used to realise shot-noise-limited pulsed homodyne detection. We used a non-binary LDPC code for error correction (reverse reconciliation) and the Toeplitz matrix multiplication for privacy amplification. A graphical processing unit card is used to accelerate the software-based post-processing.

  14. Practical Quantum Private Database Queries Based on Passive Round-Robin Differential Phase-shift Quantum Key Distribution

    Science.gov (United States)

    Li, Jian; Yang, Yu-Guang; Chen, Xiu-Bo; Zhou, Yi-Hua; Shi, Wei-Min

    2016-08-01

    A novel quantum private database query protocol is proposed, based on passive round-robin differential phase-shift quantum key distribution. Compared with previous quantum private database query protocols, the present protocol has the following unique merits: (i) the user Alice can obtain one and only one key bit so that both the efficiency and security of the present protocol can be ensured, and (ii) it does not require to change the length difference of the two arms in a Mach-Zehnder interferometer and just chooses two pulses passively to interfere with so that it is much simpler and more practical. The present protocol is also proved to be secure in terms of the user security and database security.

  15. Improving the maximum transmission distance of continuous-variable quantum key distribution using a noiseless amplifier

    CERN Document Server

    Blandino, Rémi; Barbieri, Marco; Etesse, Jean; Grangier, Philippe; Tualle-Brouri, Rosa

    2012-01-01

    We show that the maximum transmission distance of continuous-variable quantum key distribution in presence of a Gaussian noisy lossy channel can be arbitrarily increased using a linear noiseless amplifier. We explicitly consider a protocol using amplitude and phase modulated coherent states with reverse reconciliation. We find that a noiseless amplifier with amplitude gain g can increase the maximum admissible losses by a factor 1/g^2.

  16. Detector dead-time effects and paralyzability in high-speed quantum key distribution

    OpenAIRE

    Rogers, Daniel J.; Bienfang, Joshua C.; Nakassis, Anastase; Xu,Hai; Clark, Charles W.

    2007-01-01

    Recent advances in quantum key distribution (QKD) have given rise to systems that operate at transmission periods significantly shorter than the dead times of their component single-photon detectors. As systems continue to increase in transmission rate, security concerns associated with detector dead times can limit the production rate of sifted bits. We present a model of high-speed QKD in this limit that identifies an optimum transmission rate for a system with given link loss and detector ...

  17. Quantum cryptography: Theoretical protocols for quantum key distribution and tests of selected commercial QKD systems in commercial fiber networks

    Science.gov (United States)

    Jacak, Monika; Jacak, Janusz; Jóźwiak, Piotr; Jóźwiak, Ireneusz

    2016-06-01

    The overview of the current status of quantum cryptography is given in regard to quantum key distribution (QKD) protocols, implemented both on nonentangled and entangled flying qubits. Two commercial R&D platforms of QKD systems are described (the Clavis II platform by idQuantique implemented on nonentangled photons and the EPR S405 Quelle platform by AIT based on entangled photons) and tested for feasibility of their usage in commercial TELECOM fiber metropolitan networks. The comparison of systems efficiency, stability and resistivity against noise and hacker attacks is given with some suggestion toward system improvement, along with assessment of two models of QKD.

  18. Entanglement-distillation attack on continuous-variable quantum key distribution in a turbulent atmospheric channel

    Science.gov (United States)

    Guo, Ying; Xie, Cailang; Liao, Qin; Zhao, Wei; Zeng, Guihua; Huang, Duan

    2017-08-01

    The survival of Gaussian quantum states in a turbulent atmospheric channel is of crucial importance in free-space continuous-variable (CV) quantum key distribution (QKD), in which the transmission coefficient will fluctuate in time, thus resulting in non-Gaussian quantum states. Different from quantum hacking of the imperfections of practical devices, here we propose a different type of attack by exploiting the security loopholes that occur in a real lossy channel. Under a turbulent atmospheric environment, the Gaussian states are inevitably afflicted by decoherence, which would cause a degradation of the transmitted entanglement. Therefore, an eavesdropper can perform an intercept-resend attack by applying an entanglement-distillation operation on the transmitted non-Gaussian mixed states, which allows the eavesdropper to bias the estimation of the parameters and renders the final keys shared between the legitimate parties insecure. Our proposal highlights the practical CV QKD vulnerabilities with free-space quantum channels, including the satellite-to-earth links, ground-to-ground links, and a link from moving objects to ground stations.

  19. Measurement-device-independent quantum key distribution with nitrogen vacancy centers in diamond

    Science.gov (United States)

    Lo Piparo, Nicoló; Razavi, Mohsen; Munro, William J.

    2017-02-01

    Memory-assisted measurement-device-independent quantum key distribution (MA-MDI-QKD) has recently been proposed as a possible intermediate step towards the realization of quantum repeaters. Despite its relaxing some of the requirements on quantum memories, the choice of memory in relation to the layout of the setup and the protocol has a stark effect on our ability to beat existing no-memory systems. Here, we investigate the suitability of nitrogen vacancy (NV) centers, as quantum memories, in MA-MDI-QKD. We particularly show that moderate cavity enhancement is required for NV centers if we want to outperform no-memory QKD systems. Using system parameters mostly achievable by today's state of the art, we then anticipate some total key rate advantage in the distance range between 300 and 500 km for cavity-enhanced NV centers. Our analysis accounts for major sources of error including the dark current, the channel loss, and the decoherence of the quantum memories.

  20. High-dimensional decoy-state quantum key distribution over multicore telecommunication fibers

    Science.gov (United States)

    Cañas, G.; Vera, N.; Cariñe, J.; González, P.; Cardenas, J.; Connolly, P. W. R.; Przysiezna, A.; Gómez, E. S.; Figueroa, M.; Vallone, G.; Villoresi, P.; da Silva, T. Ferreira; Xavier, G. B.; Lima, G.

    2017-08-01

    Multiplexing is a strategy to augment the transmission capacity of a communication system. It consists of combining multiple signals over the same data channel and it has been very successful in classical communications. However, the use of enhanced channels has only reached limited practicality in quantum communications (QC) as it requires the manipulation of quantum systems of higher dimensions. Considerable effort is being made towards QC using high-dimensional quantum systems encoded into the transverse momentum of single photons, but so far no approach has been proven to be fully compatible with the existing telecommunication fibers. Here we overcome such a challenge and demonstrate a secure high-dimensional decoy-state quantum key distribution session over a 300-m-long multicore optical fiber. The high-dimensional quantum states are defined in terms of the transverse core modes available for the photon transmission over the fiber, and theoretical analyses show that positive secret key rates can be achieved through metropolitan distances.

  1. Experimental Passive Round-Robin Differential Phase-Shift Quantum Key Distribution

    Science.gov (United States)

    Guan, Jian-Yu; Cao, Zhu; Liu, Yang; Shen-Tu, Guo-Liang; Pelc, Jason S.; Fejer, M. M.; Peng, Cheng-Zhi; Ma, Xiongfeng; Zhang, Qiang; Pan, Jian-Wei

    2015-05-01

    In quantum key distribution (QKD), the bit error rate is used to estimate the information leakage and hence determines the amount of privacy amplification—making the final key private by shortening the key. In general, there exists a threshold of the error rate for each scheme, above which no secure key can be generated. This threshold puts a restriction on the environment noises. For example, a widely used QKD protocol, the Bennett-Brassard protocol, cannot tolerate error rates beyond 25%. A new protocol, round-robin differential phase-shifted (RRDPS) QKD, essentially removes this restriction and can in principle tolerate more environment disturbance. Here, we propose and experimentally demonstrate a passive RRDPS QKD scheme. In particular, our 500 MHz passive RRDPS QKD system is able to generate a secure key over 50 km with a bit error rate as high as 29%. This scheme should find its applications in noisy environment conditions.

  2. Generating the Local Oscillator "Locally" in Continuous-Variable Quantum Key Distribution Based on Coherent Detection

    Science.gov (United States)

    Qi, Bing; Lougovski, Pavel; Pooser, Raphael; Grice, Warren; Bobrek, Miljko

    2015-10-01

    Continuous-variable quantum key distribution (CV-QKD) protocols based on coherent detection have been studied extensively in both theory and experiment. In all the existing implementations of CV-QKD, both the quantum signal and the local oscillator (LO) are generated from the same laser and propagate through the insecure quantum channel. This arrangement may open security loopholes and limit the potential applications of CV-QKD. In this paper, we propose and demonstrate a pilot-aided feedforward data recovery scheme that enables reliable coherent detection using a "locally" generated LO. Using two independent commercial laser sources and a spool of 25-km optical fiber, we construct a coherent communication system. The variance of the phase noise introduced by the proposed scheme is measured to be 0.04 (rad2 ), which is small enough to enable secure key distribution. This technology also opens the door for other quantum communication protocols, such as the recently proposed measurement-device-independent CV-QKD, where independent light sources are employed by different users.

  3. Experimental demonstration on the deterministic quantum key distribution based on entangled photons

    Science.gov (United States)

    Chen, Hua; Zhou, Zhi-Yuan; Zangana, Alaa Jabbar Jumaah; Yin, Zhen-Qiang; Wu, Juan; Han, Yun-Guang; Wang, Shuang; Li, Hong-Wei; He, De-Yong; Tawfeeq, Shelan Khasro; Shi, Bao-Sen; Guo, Guang-Can; Chen, Wei; Han, Zheng-Fu

    2016-02-01

    As an important resource, entanglement light source has been used in developing quantum information technologies, such as quantum key distribution(QKD). There are few experiments implementing entanglement-based deterministic QKD protocols since the security of existing protocols may be compromised in lossy channels. In this work, we report on a loss-tolerant deterministic QKD experiment which follows a modified “Ping-Pong”(PP) protocol. The experiment results demonstrate for the first time that a secure deterministic QKD session can be fulfilled in a channel with an optical loss of 9 dB, based on a telecom-band entangled photon source. This exhibits a conceivable prospect of ultilizing entanglement light source in real-life fiber-based quantum communications.

  4. Principle of Quantum Key Distribution on an Optical Fiber Based on Time Shifts of TB Qubits

    Science.gov (United States)

    Zadorin, A. S.; Makhorin, D. A.

    2016-07-01

    The possibility of the physical realization of a quantum key distribution scheme in an optical-fiber communication channel based on time coding of two- and three-level single-photon quantum states is demonstrated. It is proposed to employ shifts of TB qubits (time-bin qubits) as protected code combinations, transmitted over a quantum channel, and for registering individual photons - the corresponding qutrits prepared in unbalanced Mach-Zehnder interferometers. The possibility of enhancing the level of protection of the code combinations as a result of taking into account information about qubit basis states and their statistics is indicated. A computer model of the time coding of TB qubits based on the BB84 protocol is developed, and results of calculations confirming the realizability of the indicated principle are presented.

  5. Field test of classical symmetric encryption with continuous variables quantum key distribution.

    Science.gov (United States)

    Jouguet, Paul; Kunz-Jacques, Sébastien; Debuisschert, Thierry; Fossier, Simon; Diamanti, Eleni; Alléaume, Romain; Tualle-Brouri, Rosa; Grangier, Philippe; Leverrier, Anthony; Pache, Philippe; Painchault, Philippe

    2012-06-18

    We report on the design and performance of a point-to-point classical symmetric encryption link with fast key renewal provided by a Continuous Variable Quantum Key Distribution (CVQKD) system. Our system was operational and able to encrypt point-to-point communications during more than six months, from the end of July 2010 until the beginning of February 2011. This field test was the first demonstration of the reliability of a CVQKD system over a long period of time in a server room environment. This strengthens the potential of CVQKD for information technology security infrastructure deployments.

  6. Field Test of Classical Symmetric Encryption with Continuous Variable Quantum Key Distribution

    CERN Document Server

    Jouguet, Paul; Debuisschert, Thierry; Fossier, Simon; Diamanti, Eleni; Alléaume, Romain; Tualle-Brouri, Rosa; Grangier, Philippe; Leverrier, Anthony; Pache, Philippe; Painchault, Philippe

    2012-01-01

    We report on the design and performance of a point-to-point classical symmetric encryption link with fast key renewal provided by a Continuous Variable Quantum Key Distribution (CVQKD) system. Our system was operational and able to encrypt point-to-point communications during more than six months, from the end of July 2010 until the beginning of February 2011. This field test was the first demonstration of the reliability of a CVQKD system over a long period of time in a server room environment. This strengthens the potential of CVQKD for information technology security infrastructure deployments.

  7. Improving the maximum transmission distance of continuous-variable quantum key distribution using a noiseless amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Blandino, Rémi; Etesse, Jean; Grangier, Philippe [Laboratoire Charles Fabry, Institut d' Optique, CNRS, Université Paris-Sud, 2 avenue Augustin Fresnel, 91127 Palaiseau Cedex (France); Leverrier, Anthony [Institute for Theoretical Physics, ETH Zurich, 8093 Zurich, Switzerland and INRIA Paris-Rocquencourt, 78153 Le Chesnay Cedex (France); Barbieri, Marco [Laboratoire Charles Fabry, Institut d' Optique, CNRS, Université Paris-Sud, 2 avenue Augustin Fresnel, 91127 Palaiseau Cedex, France and Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU (United Kingdom); Tualle-Brouri, Rosa [Laboratoire Charles Fabry, Institut d' Optique, CNRS, Université Paris-Sud, 2 avenue Augustin Fresnel, 91127 Palaiseau Cedex, France and Institut Universitaire de France, 103 boulevard St. Michel, 75005, Paris (France)

    2014-12-04

    We show that the maximum transmission distance of continuous-variable quantum key distribution in presence of a Gaussian noisy lossy channel can be arbitrarily increased using a heralded noiseless linear amplifier. We explicitly consider a protocol using amplitude and phase modulated coherent states with reverse reconciliation. Assuming that the secret key rate drops to zero for a line transmittance T{sub lim}, we find that a noiseless amplifier with amplitude gain g can improve this value to T{sub lim}/g{sup 2}, corresponding to an increase in distance proportional to log g. We also show that the tolerance against noise is increased.

  8. Intrinsic-Stabilization Uni-Directional Quantum Key Distribution Between Beijing and Tianjin

    CERN Document Server

    Mo, X; Han, Z; Gui, Y; Guo, G; Mo, Xiao-fan; Zhu, Bing; Han, Zheng-fu; Gui, You-zhen; Guo, Guang-can

    2004-01-01

    Quantum key distribution provides unconditional security for communication. Unfortunately, current experiment schemes are not suitable for long-distance fiber transmission because of instability or backscattering. We present a uni-directional intrinsic-stabilization scheme that is based on Michelson-Faraday interferometers, in which reflectors are replaced with 90 degree Faraday mirrors. With the scheme, key exchange from Beijing to Tianjin over 125 kilometers with an average error rate is below 6% has been achieved and its limited distance exceeds 150 kilometers. Experimental result shows the system is insensitive to environment and can run over day and night without any break even in the noise workshop.

  9. An enhanced proposal on decoy-state measurement device-independent quantum key distribution

    Science.gov (United States)

    Wang, Qin; Zhang, Chun-Hui; Luo, Shunlong; Guo, Guang-Can

    2016-09-01

    By employing pulses involving three-intensity, we propose a scheme for the measurement device-independent quantum key distribution with heralded single-photon sources. We make a comparative study of this scheme with the standard three-intensity decoy-state scheme using weak coherent sources or heralded single-photon sources. The advantage of this scheme is illustrated through numerical simulations: It can approach very closely the asymptotic case of using an infinite number of decoy-states and exhibits excellent behavior in both the secure transmission distance and the final key generation rate.

  10. Field test of the wavelength-saving quantum key distribution network

    CERN Document Server

    Wang, Shuang; Yin, Zhen-Qiang; Zhang, Yang; Zhang, Tao; Li, Hong-Wei; Xu, Fang-Xing; Zhou, Zheng; Yang, Yang; Huang, Da-Jun; Zhang, Li-Jun; Li, Fang-Yi; Liu, Dong; Wang, Yong-Gang; Guo, Guang-Can; Han, Zheng-Fu

    2012-01-01

    We propose a wavelength-saving topology of quantum key distribution(QKD) network based on passive optical elements, and report the field test of this network on the commercial telecom optical fiber. In this network, 5 nodes are supported with 2 wavelengths, and every two nodes can share secure keys directly at the same time. All QKD links in the network operate at the frequency of 20 MHz. We also characterized the insertion loss and crosstalk effects on the point-to-point QKD system after introducing this QKD network.

  11. Analysis of detector performance in a gigahertz clock rate quantum key distribution system

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Patrick J; Collins, Robert J; Hiskett, Philip A; GarcIa-MartInez, MarIa-Jose; Krichel, Nils J; McCarthy, Aongus; Tanner, Michael G; O' Connor, John A; Natarajan, Chandra M; Hadfield, Robert H; Buller, Gerald S [Scottish Universities Physics Alliance and School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Miki, Shigehito; Sasaki, Masahide; Wang, Zhen; Fujiwara, Mikio [National Institute of Information and Communications Technology (NICT), 4-2-1 Nukui-kitamachi, Koganei, Tokyo 184-8795 (Japan); Rech, Ivan; Ghioni, Massimo; Gulinatti, Angelo [Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Townsend, Paul D, E-mail: G.S.Buller@hw.ac.uk [Tyndall National Institute and Department of Physics, University College Cork, Cork (Ireland)

    2011-07-15

    We present a detailed analysis of a gigahertz clock rate environmentally robust phase-encoded quantum key distribution (QKD) system utilizing several different single-photon detectors, including the first implementation of an experimental resonant cavity thin-junction silicon single-photon avalanche diode. The system operates at a wavelength of 850 nm using standard telecommunications optical fibre. A general-purpose theoretical model for the performance of QKD systems is presented with reference to these experimental results before predictions are made about realistic detector developments in this system. We discuss, with reference to the theoretical model, how detector operating parameters can be further optimized to maximize key exchange rates.

  12. "Pretty good" private queries based on a quantum key distribution protocol

    CERN Document Server

    Jakobi, Markus; Gisin, Nicolas; Branciard, Cyril; Bancal, Jean-Daniel; Walenta, Nino; Zbinden, Hugo

    2010-01-01

    Private queries allow a user to learn an element of a database without revealing which element she was interested in, while limiting her information about the other elements. We propose to implement private queries based on a quantum key distribution protocol, with changes only in the classical post-processing of the key. This approach makes our scheme both easy to implement and loss-tolerant. While unconditionally secure private queries are known to be impossible, we argue that an interesting degree of security can be achieved, with fundamental physical principles protecting both user and database.

  13. Integrated quantum key distribution sender unit for daily-life implementations

    Science.gov (United States)

    Mélen, Gwenaelle; Vogl, Tobias; Rau, Markus; Corrielli, Giacomo; Crespi, Andrea; Osellame, Roberto; Weinfurter, Harald

    2016-03-01

    Unlike currently implemented encryption schemes, Quantum Key Distribution provides a secure way of generating and distributing a key among two parties. Although a multitude of research platforms has been developed, the integration of QKD units within classical communication systems remains a tremendous challenge. The recently achieved maturity of integrated photonic technologies could be exploited to create miniature QKD add-ons that could extend the primary function of various existing systems such as mobile devices or optical stations. In this work we report on an integrated optics module enabling secure short-distance communication for, e.g., quantum access schemes. Using BB84-like protocols, Alice's mobile low-cost device can exchange secure key and information everywhere within a trusted node network. The new optics platform (35×20×8mm) compatible with current smartphone's technology generates NIR faint polarised laser pulses with 100MHz repetition rate. Fully automated beam tracking and live basis-alignment on Bob's side ensure user-friendly operation with a quantum link efficiency as high as 50% stable over a few seconds.

  14. Experimental implementation of non-Gaussian attacks on a continuous-variable quantum key distribution system

    CERN Document Server

    Lodewyck, J; Garcia-Patron, R; Tualle-Brouri, R; Cerf, N J; Grangier, P; Lodewyck, Jerome; Debuisschert, Thierry; Garcia-Patron, Raul; Tualle-Brouri, Rosa; Cerf, Nicolas J.; Grangier, Philippe

    2007-01-01

    An intercept-resend attack on a continuous-variable quantum-key-distribution protocol is investigated experimentally. By varying the interception fraction, one can implement a family of attacks where the eavesdropper totally controls the channel parameters. In general, such attacks add excess noise in the channel, and may also result in non-Gaussian output distributions. We implement and characterize the measurements needed to detect these attacks, and evaluate experimentally the information rates available to the legitimate users and the eavesdropper. The results are consistent with the optimality of Gaussian attacks resulting from the security proofs.

  15. Noiseless Linear Amplifiers in Entanglement-Based Continuous-Variable Quantum Key Distribution

    Directory of Open Access Journals (Sweden)

    Yichen Zhang

    2015-06-01

    Full Text Available We propose a method to improve the performance of two entanglement-based continuous-variable quantum key distribution protocols using noiseless linear amplifiers. The two entanglement-based schemes consist of an entanglement distribution protocol with an untrusted source and an entanglement swapping protocol with an untrusted relay. Simulation results show that the noiseless linear amplifiers can improve the performance of these two protocols, in terms of maximal transmission distances, when we consider small amounts of entanglement, as typical in realistic setups.

  16. Improvement of continuous-variable quantum key distribution systems by using optical preamplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Fossier, S; Debuisschert, T [Thales Research and Technology France, RD 128, 91767 Palaiseau Cedex (France); Diamanti, E; Tualle-Brouri, R; Grangier, P [Laboratoire Charles Fabry de l' Institut d' Optique, CNRS, Univ. Paris-Sud, Campus Polytechnique, RD 128, 91127 Palaiseau Cedex (France)

    2009-06-14

    Continuous-variable quantum key distribution protocols have been implemented recently, based on Gaussian modulation of the quadratures of coherent states. A present limitation of such systems is the finite efficiency of the detectors, that can in principle be compensated for by the use of classical optical preamplifiers. Here we study this possibility in detail, by deriving the modified secret key generation rates when an optical parametric amplifier is placed at the output of the quantum channel. After presenting a general set of security proofs, we show that the use of preamplifiers does compensate all the imperfections of the detectors when the amplifier is optimal in terms of gain and noise. Imperfect amplifiers can also enhance the system performance, under conditions which are generally satisfied in practice.

  17. Experimental long-distance decoy-state quantum key distribution based on polarization encoding.

    Science.gov (United States)

    Peng, Cheng-Zhi; Zhang, Jun; Yang, Dong; Gao, Wei-Bo; Ma, Huai-Xin; Yin, Hao; Zeng, He-Ping; Yang, Tao; Wang, Xiang-Bin; Pan, Jian-Wei

    2007-01-05

    We demonstrate the decoy-state quantum key distribution (QKD) with one-way quantum communication in polarization space over 102 km. Further, we simplify the experimental setup and use only one detector to implement the one-way decoy-state QKD over 75 km, with the advantage to overcome the security loopholes due to the efficiency mismatch of detectors. Our experimental implementation can really offer the unconditionally secure final keys. We use 3 different intensities of 0, 0.2, and 0.6 for the light sources in our experiment. In order to eliminate the influences of polarization mode dispersion in the long-distance single-mode optical fiber, an automatic polarization compensation system is utilized to implement the active compensation.

  18. Experimental Long-Distance Decoy-State Quantum Key Distribution Based On Polarization Encoding

    CERN Document Server

    Peng, C Z; Ma, H X; Pan, J W; Wang, X B; Yang, D; Yang, T; Yin, H; Zeng, H P; Zhang, J; Gao, Wei-Bo; Ma, Huai-Xin; Pan, Jian-Wei; Peng, Cheng-Zhi; Wang, Xiang-Bin; Yang, Dong; Yang, Tao; Yin, Hao; Zeng, He-Ping; Zhang, Jun

    2006-01-01

    We demonstrate the decoy-state quantum key distribution (QKD) with one-way quantum communication in polarization space over 75 km. So far, our experimental implementation is the only one that really offers the unconditionally secure final keys among all the implementations of long-distance QKD with weak coherent states. We use 3 different intensities of 0, 0.2 and 0.6 for the pulses of source in our experiment. In order to eliminate the influences of polarization mode dispersion in the long-distance single-mode optical fiber, an automatic polarization compensation system is utilized to implement the active compensation. Only one detector is used in our experiment. The secure distance can be raised to 120 km given 4 detectors.

  19. Composable Security Proof for Continuous-Variable Quantum Key Distribution with Coherent States

    Science.gov (United States)

    Leverrier, Anthony

    2015-02-01

    We give the first composable security proof for continuous-variable quantum key distribution with coherent states against collective attacks. Crucially, in the limit of large blocks the secret key rate converges to the usual value computed from the Holevo bound. Combining our proof with either the de Finetti theorem or the postselection technique then shows the security of the protocol against general attacks, thereby confirming the long-standing conjecture that Gaussian attacks are optimal asymptotically in the composable security framework. We expect that our parameter estimation procedure, which does not rely on any assumption about the quantum state being measured, will find applications elsewhere, for instance, for the reliable quantification of continuous-variable entanglement in finite-size settings.

  20. Continuous variable quantum key distribution with two-mode squeezed states

    CERN Document Server

    Madsen, Lars S; Lassen, Mikael; Filip, Radim; Andersen, Ulrik L

    2011-01-01

    Quantum key distribution (QKD) enables two remote parties to grow a shared key which they can use for unconditionally secure communication [1]. The applicable distance of a QKD protocol depends on the loss and the excess noise of the connecting quantum channel [2-10]. Several QKD schemes based on coherent states and continuous variable (CV) measurements are resilient to high loss in the channel, but strongly affected by small amounts of channel excess noise [2-6]. Here we propose and experimentally address a CV QKD protocol which uses fragile squeezed states combined with a large coherent modulation to greatly enhance the robustness to channel noise. As a proof of principle we experimentally demonstrate that the resulting QKD protocol can tolerate more noise than the benchmark set by the ideal CV coherent state protocol. Our scheme represents a very promising avenue for extending the distance for which secure communication is possible.

  1. Experimental quantum key distribution with simulated ground-to-satellite photon losses and processing limitations

    Science.gov (United States)

    Bourgoin, Jean-Philippe; Gigov, Nikolay; Higgins, Brendon L.; Yan, Zhizhong; Meyer-Scott, Evan; Khandani, Amir K.; Lütkenhaus, Norbert; Jennewein, Thomas

    2015-11-01

    Quantum key distribution (QKD) has the potential to improve communications security by offering cryptographic keys whose security relies on the fundamental properties of quantum physics. The use of a trusted quantum receiver on an orbiting satellite is the most practical near-term solution to the challenge of achieving long-distance (global-scale) QKD, currently limited to a few hundred kilometers on the ground. This scenario presents unique challenges, such as high photon losses and restricted classical data transmission and processing power due to the limitations of a typical satellite platform. Here we demonstrate the feasibility of such a system by implementing a QKD protocol, with optical transmission and full post-processing, in the high-loss regime using minimized computing hardware at the receiver. Employing weak coherent pulses with decoy states, we demonstrate the production of secure key bits at up to 56.5 dB of photon loss. We further illustrate the feasibility of a satellite uplink by generating a secure key while experimentally emulating the varying losses predicted for realistic low-Earth-orbit satellite passes at 600 km altitude. With a 76 MHz source and including finite-size analysis, we extract 3374 bits of a secure key from the best pass. We also illustrate the potential benefit of combining multiple passes together: while one suboptimal "upper-quartile" pass produces no finite-sized key with our source, the combination of three such passes allows us to extract 165 bits of a secure key. Alternatively, we find that by increasing the signal rate to 300 MHz it would be possible to extract 21 570 bits of a secure finite-sized key in just a single upper-quartile pass.

  2. Practical round-robin differential-phase-shift quantum key distribution

    Science.gov (United States)

    Zhang, Zhen; Yuan, Xiao; Cao, Zhu; Ma, Xiongfeng

    2017-03-01

    The security of quantum key distribution (QKD) relies on the Heisenberg uncertainty principle, with which legitimate users are able to estimate information leakage by monitoring the disturbance of the transmitted quantum signals. Normally, the disturbance is reflected as bit flip errors in the sifted key; thus, privacy amplification, which removes any leaked information from the key, generally depends on the bit error rate. Recently, a round-robin differential-phase-shift QKD protocol for which privacy amplification does not rely on the bit error rate (Sasaki et al 2014 Nature 509 475) was proposed. The amount of leaked information can be bounded by the sender during the state-preparation stage and hence, is independent of the behavior of the unreliable quantum channel. In our work, we apply the tagging technique to the protocol and present a tight bound on the key rate and employ a decoy-state method. The effects of background noise and misalignment are taken into account under practical conditions. Our simulation results show that the protocol can tolerate channel error rates close to 50% within a typical experiment setting. That is, there is a negligible restriction on the error rate in practice.

  3. Finite-key security against coherent attacks in quantum key distribution

    CERN Document Server

    Sheridan, Lana; Scarani, Valerio

    2010-01-01

    The work by Christandl, K\\"onig and Renner [Phys. Rev. Lett. 102, 020504 (2009)] provides in particular the possibility of studying unconditional security in the finite-key regime for all discrete-variable protocols. We spell out this bound from their general formalism. Then we apply it to the study of a recently proposed protocol [Laing et al., Phys. Rev. A 82, 012304 (2010)]. This protocol is meaningful when the alignment of Alice's and Bob's reference frames is not monitored and may vary with time. In this scenario, the notion of asymptotic key rate has hardly any operational meaning, because if one waits too long time, the average correlations are smeared out and no security can be inferred. Therefore, finite-key analysis is necessary to find the maximal achievable secret key rate and the corresponding optimal number of signals.

  4. Practical security of continuous-variable quantum key distribution with finite sampling bandwidth effects

    Science.gov (United States)

    Wang, Chao; Huang, Peng; Huang, Duan; Lin, Dakai; Zeng, Guihua

    2016-02-01

    Practical security of the continuous-variable quantum key distribution (CVQKD) system with finite sampling bandwidth of analog-to-digital converter (ADC) at the receiver's side is investigated. We find that the finite sampling bandwidth effects may decrease the lower bound of secret key rate without awareness of the legitimate communicators. This leaves security loopholes for Eve to attack the system. In addition, this effect may restrains the linear relationship of secret key bit rate with repetition rate of the system; subsequently, there is a saturation value for the secret key bit rate with the repetition rate. To resist such kind of effects, we propose a dual sampling detection approach in which two ADCs are employed so that the finite sampling bandwidth effects are removed.

  5. Practical non-orthogonal decoy state quantum key distribution with heralded single photon source

    Institute of Scientific and Technical Information of China (English)

    Mi Jing-Long; Wang Fa-Qiang; Lin Qing-Qun; Liang Rui-Sheng

    2008-01-01

    Recently the performance of the quantum key distribution (QKD) is substantially improved by the decoy state method and the non-orthogonal encoding protocol, separately. In this paper, a practical non-orthogonal decoy state protocol with a heralded single photon source (HSPS) for QKD is presented. The protocol is based on 4 states with different intensities, i.e. one signal state and three decoy states. The signal state is for generating keys; the decoy states arc for detecting the eavesdropping and estimating the fraction of single-photon and two-photon pulses. We have discussed three cases of this protocol, i.e. the general case, the optimal case and the special case. Moreover, the final key rate over transmission distance is simulated. For the low dark count of the HSPS and the utilization of the two-photon pulses, our protocol has a higher key rate and a longer transmission distance than any other decoy state protocol.

  6. Quantum circuit for security proof of quantum key distribution without encryption of error syndrome and noisy processing

    CERN Document Server

    Tamaki, Kiyoshi

    2010-01-01

    One of the simplest security proofs of quantum key distribution is based on the so-called complementarity scenario, which involves the complementarity control of an actual protocol and a virtual protocol [M. Koashi, e-print arXiv:0704.3661 (2007)]. The existing virtual protocol has a limitation in classical postprocessing, i.e., the syndrome for the error-correction step has to be encrypted. In this paper, we remove this limitation by constructing a quantum circuit for the virtual protocol. Moreover, our circuit with a shield system gives an intuitive proof of why adding noise to the sifted key increases the bit error rate threshold in the general case in which one of the parties does not possess a qubit. Thus, our circuit bridges the simple proof and the use of wider classes of classical postprocessing.

  7. Round-robin differential quadrature phase-shift quantum key distribution

    Science.gov (United States)

    Zhou, Chun; Zhang, Ying-Ying; Bao, Wan-Su; Li, Hong-Wei; Wang, Yang; Jiang, Mu-Sheng

    2017-02-01

    Recently, a round-robin differential phase-shift (RRDPS) protocol was proposed [Nature 509, 475 (2014)], in which the amount of leakage is bounded without monitoring the signal disturbance. Introducing states of the phase-encoded Bennett–Brassard 1984 protocol (PE-BB84) to the RRDPS, this paper presents another quantum key distribution protocol called round-robin differential quadrature phase-shift (RRDQPS) quantum key distribution. Regarding a train of many pulses as a single packet, the sender modulates the phase of each pulse by one of {0, π/2, π, 3π/2}, then the receiver measures each packet with a Mach–Zehnder interferometer having a phase basis of 0 or π/2. The RRDQPS protocol can be implemented with essential similar hardware to the PE-BB84, so it has great compatibility with the current quantum system. Here we analyze the security of the RRDQPS protocol against the intercept-resend attack and the beam-splitting attack. Results show that the proposed protocol inherits the advantages arising from the simplicity of the RRDPS protocol and is more robust against these attacks than the original protocol. Project supported by the National Natural Science Foundation of China (Grant Nos. 61505261 and 11304397) and the National Basic Research Program of China (Grant No. 2013CB338002)

  8. Long-distance copropagation of quantum key distribution and terabit classical optical data channels

    Science.gov (United States)

    Wang, Liu-Jun; Zou, Kai-Heng; Sun, Wei; Mao, Yingqiu; Zhu, Yi-Xiao; Yin, Hua-Lei; Chen, Qing; Zhao, Yong; Zhang, Fan; Chen, Teng-Yun; Pan, Jian-Wei

    2017-01-01

    Quantum key distribution (QKD) generates symmetric keys between two remote parties and guarantees the keys are not accessible to any third party. Wavelength-division multiplexing between QKD and classical optical communications by sharing the existing fiber-optics infrastructure is highly desired in order to reduce the cost of QKD applications. However, comparing to the light for classical transmission, quantum signals are very weak and easily affected by impairments from classical light, such as the spontaneous Raman-scattering effect. Here, by selecting an optimal wavelength of quantum signals, we significantly reduce the influence of the Raman-scattering effect. In addition, through coherent optical communication technology, we achieve high-speed classical data transmission with relatively low launch powers, thereby further reducing the impairments from classical light. As a result, we realize the multiplexing and long-distance copropagation of QKD and terabit classical data transmission up to 80 km. The data capacity is two orders of magnitude larger than the existing results. Our demonstration verifies the feasibility of QKD and classical communication to share the resources of backbone fiber links and thus taking the utility of QKD a great step forward.

  9. A new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology for practical quantum key distribution system

    Institute of Scientific and Technical Information of China (English)

    Zhong Ping-Ping; Zhang Hua-Ni; Wang Jin-Dong; Qin Xiao-Juan; Wei zheng-Jun; Chen Shuai; Liu Song-Hao

    2011-01-01

    Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in the quantum key distribution system is analysed to propose a new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology to reduce quantum bits error rates under some transmission rate conditions.The proposed synchronization scheme can not only completely eliminate noise photons from the bright background light of the the clock signal, but also suppress the fibre nonlinear crosstalk.

  10. Controlling excess noise in fiber optics continuous variables quantum key distribution

    CERN Document Server

    Lodewyck, J; Grangier, P; Tualle-Brouri, R; Debuisscher, Thierry; Grangier, Philippe; Tualle-Brouri, Rosa

    2005-01-01

    We describe a continuous variables coherent states quantum key distribution system working at 1550 nm, and entirely made of standard fiber optics and telecom components, such as integrated-optics modulators, couplers and fast InGaAs photodiodes. The setup is composed of an emitter randomly modulating a coherent state in the complex plane with a doubly Gaussian distribution, and a receiver based on a shot noise limited time-resolved homodyne detector. By using a reverse reconciliation protocol, the device can transfer a raw key rate up to 1 Mb/s, with a proven security against Gaussian or non-Gaussian attacks. The dependence of the secret information rate of the present fiber set-up is studied as a function of the line transmission and excess noise.

  11. Quantum key distribution using vacuum-one-photon qubits: maximum number of transferable bits per particle

    CERN Document Server

    Lee, Su-Yong; Lee, Hai-Woong; Lee, Jae-Weon; Bergou, Janos A

    2009-01-01

    Quantum key distribution schemes which employ encoding on vacuum-one-photon qubits are capable of transferring more information bits per particle than the standard schemes employing polarization or phase coding. We calculate the maximum number of classical bits per particle that can be securely transferred when the key distribution is performed with the BB84 and B92 protocols, respectively, using the vacuum-one-photon qubits. In particular, we show that for a generalized B92 protocol with the vacuum-one-photon qubits, a maximum of two bits per particle can be securely transferred. We also demonstrate the advantage brought about by performing a generalized measurement that is optimized for unambiguous discrimination of the encoded states: the parameter range where the transfer of two bits per particle can be achieved is dramatically enhanced as compared to the corresponding parameter range of projective measurements.

  12. Practical round-robin differential phase-shift quantum key distribution

    Science.gov (United States)

    Zhang, Ying-Ying; Bao, Wan-Su; Zhou, Chun; Li, Hong-Wei; Wang, Yang; Jiang, Mu-Sheng

    2016-09-01

    To overcome the signal disturbance from the transmission process, recently, a new type of protocol named round-robin differential-phase-shift(RRDPS) quantum key distribution[Nature 509, 475(2014)] is proposed. It can estimate how much information has leaked to eavesdropper without monitoring bit error rates. In this paper, we compare the performance of RRDPS using different sources without and with decoy-state method, such as weak coherent pulses(WCPs) and heralded single photon source(HSPS). For practical implementations, we propose finite decoy-state method for RRDPS, the performance of which is close to the infinite one. Taking WCPs as an example, the three-intensity decoystate protocol can distribute secret keys over a distance of 128 km when the length of pulses packet is 32, which confirms the great practical interest of our method.

  13. Quantum Key Distribution using Continuous-variable non-Gaussian States

    CERN Document Server

    Borelli, L F M; Roversi, J A; Vidiella-Barranco, A

    2016-01-01

    In this work we present a quantum key distribution protocol using continuous-variable non-Gaussian states, homodyne detection and post-selection. The employed signal states are the Photon Added then Subtracted Coherent States (PASCS) in which one photon is added and subsequently one photon is subtracted. We analyze the performance of our protocol, compared to a coherent state based protocol, for two different attacks that could be carried out by the eavesdropper (Eve). We calculate the secret key rate transmission in a lossy line for a superior channel (beam-splitter) attack, and we show that we may increase the secret key generation rate by using the non-Gaussian PASCS rather than coherent states. We also consider the simultaneous quadrature measurement (intercept-resend) attack and we show that the efficiency of Eve's attack is substantially reduced if PASCS are used as signal states.

  14. High-capacity quantum key distribution using Chebyshev-map values corresponding to Lucas numbers coding

    Science.gov (United States)

    Lai, Hong; Orgun, Mehmet A.; Pieprzyk, Josef; Li, Jing; Luo, Mingxing; Xiao, Jinghua; Xiao, Fuyuan

    2016-08-01

    We propose an approach that achieves high-capacity quantum key distribution using Chebyshev-map values corresponding to Lucas numbers coding. In particular, we encode a key with the Chebyshev-map values corresponding to Lucas numbers and then use k-Chebyshev maps to achieve consecutive and flexible key expansion and apply the pre-shared classical information between Alice and Bob and fountain codes for privacy amplification to solve the security of the exchange of classical information via the classical channel. Consequently, our high-capacity protocol does not have the limitations imposed by orbital angular momentum and down-conversion bandwidths, and it meets the requirements for longer distances and lower error rates simultaneously.

  15. Finite-size analysis of continuous-variable quantum key distribution

    CERN Document Server

    Leverrier, Anthony; Grangier, Philippe

    2010-01-01

    The goal of this paper is to extend the framework of finite size analysis recently developed for quantum key distribution to continuous-variable protocols. We do not solve this problem completely here, and we mainly consider the finite size effects on the parameter estimation procedure. Despite the fact that some questions are left open, we are able to give an estimation of the secret key rate for protocols which do not contain a postselection procedure. As expected, these results are significantly more pessimistic than the ones obtained in the asymptotic regime. However, we show that recent continuous-variable protocols are able to provide fully secure secret keys in the finite size scenario, over distances larger than 50 km.

  16. A practical two-way system of quantum key distribution with untrusted source

    Institute of Scientific and Technical Information of China (English)

    Chen Ming-Juan; Liu Xiang

    2011-01-01

    The most severe problem of a two-way “plug-and-play” (p & p) quantum key distribution system is that the source can be controlled by the eavesdropper.This kind of source is defined as an “untrusted source”.This paper discusses the effects of the fluctuation of internal transmittance on the final key generation rate and the transmission distance.The security of the standard BB84 protocol,one-decoy state protocol,and weak+vacuum decoy state protocol,with untrusted sources and the fluctuation of internal transmittance are studied.It is shown that the one-decoy state is sensitive to the statistical fluctuation but weak+vacuum decoy state is only slightly affected by the fluctuation.It is also shown that both the maximum secure transmission distance and final key generation rate are reduced when Alice's laboratory transmittance fluctuation is considered.

  17. Continuous-variable quantum key distribution with random intensity fluctuation of the local oscillator

    Science.gov (United States)

    Gui, Ming; Huang, Ming-Qiu; Liang, Lin-Mei

    2016-10-01

    In practical continuous-variable quantum key distribution (CVQKD) systems, due to environmental disturbance or some intrinsic imperfections of devices, inevitably the local oscillator (LO) employed in a coherent detection always fluctuates arbitrarily over time, which compromises the security and performance of practical CVQKD systems. In this paper, we investigate the performance of practical CVQKD systems with LO fluctuating randomly. By revising the measurement result of balanced homodyne detection and embedding fluctuation parameters into security analysis, we find that in addition to the average LO intensity, the fluctuation variance also severely affects the secret key rate. No secret key can be obtained if fluctuation variance is relatively large. This indicates that in a practical CVQKD, LO intensity should be well monitored and stabilized. Our research can be directly applied to improve the robustness of a practical CVQKD system as well as be used to optimize CVQKD protocols.

  18. High-capacity quantum key distribution using Chebyshev-map values corresponding to Lucas numbers coding

    Science.gov (United States)

    Lai, Hong; Orgun, Mehmet A.; Pieprzyk, Josef; Li, Jing; Luo, Mingxing; Xiao, Jinghua; Xiao, Fuyuan

    2016-11-01

    We propose an approach that achieves high-capacity quantum key distribution using Chebyshev-map values corresponding to Lucas numbers coding. In particular, we encode a key with the Chebyshev-map values corresponding to Lucas numbers and then use k-Chebyshev maps to achieve consecutive and flexible key expansion and apply the pre-shared classical information between Alice and Bob and fountain codes for privacy amplification to solve the security of the exchange of classical information via the classical channel. Consequently, our high-capacity protocol does not have the limitations imposed by orbital angular momentum and down-conversion bandwidths, and it meets the requirements for longer distances and lower error rates simultaneously.

  19. Security of high speed quantum key distribution with finite detector dead time

    CERN Document Server

    Burenkov, Viacheslav; Fortescue, Ben; Lo, Hoi-Kwong

    2010-01-01

    The security of a high speed quantum key distribution system with finite detector dead time \\tau is analyzed. When the transmission rate becomes higher than the maximum count rate of the individual detectors (1/\\tau ), security issues affect the algorithm for sifting bits. Analytical calculations and numerical simulations of the Bennett-Brassard BB84 protocol are performed. We study Rogers et al.'s protocol (introduced in "Detector dead-time effects and paralyzability in high-speed quantum key distribution," New J. Phys. 9 (2007) 319) in the presence of an active eavesdropper Eve who has the power to perform an intercept-resend attack. It is shown that Rogers et al.'s protocol is no longer secure. More specifically, Eve can induce a basis-dependent detection efficiency at the receiver's end. Modified key sifting schemes that are secure in the presence of dead time and an active eavesdropper are then introduced. We analyze and compare these secure sifting schemes for this active Eve scenario, and calculate and...

  20. Photon counting for quantum key distribution with Peltier cooled InGaAs/InP APD's

    CERN Document Server

    Stucki, D; Stefanov, A; Zbinden, H; Rarity, J G; Wall, T; Stucki, Damien; Ribordy, Gr\\'{e}goire; Stefanov, Andr\\'{e}; Zbinden, Hugo; Rarity, John G.; Wall, Tom

    2001-01-01

    The performance of three types of InGaAs/InP avalanche photodiodes is investigated for photon counting at 1550 nm in the temperature range of thermoelectric cooling. The best one yields a dark count probability of $% 2.8\\cdot 10^{-5}$ per gate (2.4 ns) at a detection efficiency of 10% and a temperature of -60C. The afterpulse probability and the timing jitter are also studied. The results obtained are compared with those of other papers and applied to the simulation of a quantum key distribution system. An error rate of 10% would be obtained after 54 kilometers.

  1. Experimental open-air quantum key distribution with a single-photon source

    Energy Technology Data Exchange (ETDEWEB)

    Alleaume, R [Laboratoire de Photonique Quantique et Moleculaire, UMR 8537 du CNRS, ENS Cachan, 61 avenue du President Wilson, 94235 Cachan Cedex (France); Treussart, F [Laboratoire de Photonique Quantique et Moleculaire, UMR 8537 du CNRS, ENS Cachan, 61 avenue du President Wilson, 94235 Cachan Cedex (France); Messin, G [Laboratoire Charles Fabry de l' Institut d' Optique, UMR 8501 du CNRS, F-91403 Orsay (France); Dumeige, Y [Laboratoire de Photonique Quantique et Moleculaire, UMR 8537 du CNRS, ENS Cachan, 61 avenue du President Wilson, 94235 Cachan Cedex (France); Roch, J-F [Laboratoire de Photonique Quantique et Moleculaire, UMR 8537 du CNRS, ENS Cachan, 61 avenue du President Wilson, 94235 Cachan Cedex (France); Beveratos, A [Laboratoire Charles Fabry de l' Institut d' Optique, UMR 8501 du CNRS, F-91403 Orsay (France); Brouri-Tualle, R [Laboratoire Charles Fabry de l' Institut d' Optique, UMR 8501 du CNRS, F-91403 Orsay (France); Poizat, J-P [Laboratoire Charles Fabry de l' Institut d' Optique, UMR 8501 du CNRS, F-91403 Orsay (France); Grangier, P [Laboratoire Charles Fabry de l' Institut d' Optique, UMR 8501 du CNRS, F-91403 Orsay (France)

    2004-07-01

    We describe the implementation of a quantum key distribution (QKD) system using a single-photon source, operating at night in open air. The single-photon source at the heart of the functional and reliable set-up relies on the pulsed excitation of a single nitrogen-vacancy colour centre in a diamond nanocrystal. We tested the effect of attenuation on the polarized encoded photons for inferring the longer distance performance of our system. For strong attenuation, the use of pure single-photon states gives measurable advantage over systems relying on weak attenuated laser pulses. The results are in good agreement with theoretical models developed to assess QKD security.

  2. Narrow-band single-photon emission in the near infrared for quantum key distribution.

    Science.gov (United States)

    Wu, E; Jacques, Vincent; Zeng, Heping; Grangier, Philippe; Treussart, François; Roch, Jean-François

    2006-02-06

    We present a detailed study of photophysical properties of single color centers in natural diamond samples emitting in the near infrared under optical excitation. Photoluminescence of these single emitters has several striking features, including narrow-band (FWHM 2 nm) fully polarized emission around 780 nm, a short excited-state lifetime of about 2 ns, and perfect photostability at room temperature under our excitation conditions. Development of a triggered single-photon source relying on this single color center is discussed for application to quantum key distribution.

  3. Narrow-band single-photon emission in the near infrared for quantum key distribution

    CERN Document Server

    Wu, E; Jacques, V; Zeng, H; Grangier, Philippe; Jacques, Vincent; Zeng, Heping

    2005-01-01

    We report on the observation of single colour centers in natural diamond samples emitting in the near infrared region when optically excited. Photoluminescence of these single emitters have several striking features, such as a narrow-band fully polarized emission (FWHM 2 nm) around 780 nm, a short excited-state lifetime of about 2 ns, and perfect photostability at room temperature under our excitation conditions. We present a detailed study of their photophysical properties. Development of a triggered single-photon source relying on this single colour centre is discussed in the prospect of its application to quantum key distribution.

  4. Experimental open air quantum key distribution with a single photon source

    CERN Document Server

    Alleaume, R; Brouri-Tualle, R; Dumeige, Y; Messin, G; Poizat, J P; Roch, J F; Treussart, F; Alleaume, Romain; Beveratos, Alexios; Brouri-Tualle, Rosa; Dumeige, Yannick; Messin, Gaetan; Poizat, Jean-Philippe; Proxy, Philippe Grangier; Roch, Jean-Francois; Treussart, Francois; ccsd-00001148, ccsd

    2004-01-01

    We present a full implementation of a quantum key distribution (QKD) system with a single photon source, operating at night in open air. The single photon source at the heart of the functional and reliable setup relies on the pulsed excitation of a single nitrogen-vacancy color center in diamond nanocrystal. We tested the effect of attenuation on the polarized encoded photons for inferring longer distance performance of our system. For strong attenuation, the use of pure single photon states gives measurable advantage over systems relying on weak attenuated laser pulses. The results are in good agreement with theoretical models developed to assess QKD security.

  5. Four-state continuous-variable quantum key distribution with long secure distance

    Science.gov (United States)

    Yang, Jian; Xu, Bingjie; Peng, Xiang; Guo, Hong

    2012-05-01

    The four-state continuous-variable quantum key distribution protocol has a long practical secure distance [A. Leverrier and P. Grangier, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.180504 102, 180504 (2009)], while it poses the difficulty of parameter estimation. We propose an improved four-state protocol where the covariance matrix can be estimated from experimental data without using the linear channel assumption, thus ensuring its unconditional security in the asymptotical limit. Our scheme maintains the advantage of high reconciliation efficiency of the four-state protocol, which ensures long practical secure distance its. Our scheme can be implemented with the current technology.

  6. Room temperature single-photon detectors for high bit rate quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Comandar, L. C.; Patel, K. A. [Toshiba Research Europe Ltd., 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Engineering Department, Cambridge University, 9 J J Thomson Ave., Cambridge CB3 0FA (United Kingdom); Fröhlich, B., E-mail: bernd.frohlich@crl.toshiba.co.uk; Lucamarini, M.; Sharpe, A. W.; Dynes, J. F.; Yuan, Z. L.; Shields, A. J. [Toshiba Research Europe Ltd., 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Penty, R. V. [Engineering Department, Cambridge University, 9 J J Thomson Ave., Cambridge CB3 0FA (United Kingdom)

    2014-01-13

    We report room temperature operation of telecom wavelength single-photon detectors for high bit rate quantum key distribution (QKD). Room temperature operation is achieved using InGaAs avalanche photodiodes integrated with electronics based on the self-differencing technique that increases avalanche discrimination sensitivity. Despite using room temperature detectors, we demonstrate QKD with record secure bit rates over a range of fiber lengths (e.g., 1.26 Mbit/s over 50 km). Furthermore, our results indicate that operating the detectors at room temperature increases the secure bit rate for short distances.

  7. Trojan horse attack free fault-tolerant quantum key distribution protocols

    Science.gov (United States)

    Yang, Chun-Wei; Hwang, Tzonelih

    2013-11-01

    This work proposes two quantum key distribution (QKD) protocols—each of which is robust under one kind of collective noises—collective-dephasing noise and collective-rotation noise. Due to the use of a new coding function which produces error-robust codewords allowing one-time transmission of quanta, the proposed QKD schemes are fault-tolerant and congenitally free from Trojan horse attacks without having to use any extra hardware. Moreover, by adopting two Bell state measurements instead of a 4-GHZ state joint measurement for decoding, the proposed protocols are practical in combating collective noises.

  8. Trustworthiness of measurement devices in round-robin differential-phase-shift quantum key distribution

    Science.gov (United States)

    Cao, Zhu; Yin, Zhen-Qiang; Han, Zheng-Fu

    2016-02-01

    Round-robin differential-phase-shift quantum key distribution (RRDPS QKD) has been proposed to raise the noise tolerability of the channel. However, in practice, the measurement device in RRDPS QKD may be imperfect. Here, we show that, with these imperfections, the security of RRDPS may be damaged by proposing two attacks for RRDPS systems with uncharacterized measurement devices. One is valid even for a system with unit total efficiency, while the other is valid even when a single-photon state is sent. To prevent these attacks, either security arguments need to be fundamentally revised or further practical assumptions on the measurement device should be put.

  9. Multiple stochastic paths scheme on partially-trusted relay quantum key distribution network

    Institute of Scientific and Technical Information of China (English)

    WEN Hao; HAN ZhengFui; ZHAO YiBo; GUO GuangCan; HONG PeiLin

    2009-01-01

    Quantum key distribution (QKD) technology provides proven unconditional point-to-point security based on fundamental quantum physics. A QKD network also holds promise for secure multi-user communications over long distances at high-speed transmission rates. Although many schemes have been proposed so far, the trusted relay QKD network is still the most practical and flexible scenario. In reality, the insecurity of certain relay sections cannot be ignored, so to solve the fatal security problems of partially-trusted relay networks we suggest a multiple stochastic paths scheme. Its features are- (i) a safe probability model that may be more practical for real applications; (ii) a multi-path scheme with an upper bound for the overall safe probability; (iii) an adaptive stochastic routing algorithm to generate sufficient different paths and hidden routes. Simulation results for a typical partially-trusted relay QKD network show that this generalized scheme is effective.

  10. Experimental asymmetric plug-and-play measurement-device-independent quantum key distribution

    Science.gov (United States)

    Tang, Guang-Zhao; Sun, Shi-Hai; Xu, Feihu; Chen, Huan; Li, Chun-Yan; Liang, Lin-Mei

    2016-09-01

    Measurement-device-independent quantum key distribution (MDI-QKD) is immune to all security loopholes on detection. Previous experiments on MDI-QKD required spatially separated signal lasers and complicated stabilization systems. In this paper, we perform a proof-of-principle experimental demonstration of plug-and-play MDI-QKD over an asymmetric channel setting with a single signal laser in which the whole system is automatically stabilized in spectrum, polarization, arrival time, and phase reference. Both the signal laser and the single-photon detectors are in the possession of a common server. A passive timing-calibration technique is applied to ensure the precise and stable overlap of signal pulses. The results pave the way for the realization of a quantum network in which the users only need the encoding devices.

  11. Virtual noiseless amplification and Gaussian post-selection in continuous-variable quantum key distribution

    CERN Document Server

    Fiurasek, Jaromir

    2012-01-01

    The noiseless amplification or attenuation are two heralded filtering operations that enable respectively to increase or decrease the mean field of any quantum state of light with no added noise, at the cost of a small success probability. We show that inserting such noiseless operations in a transmission line improves the performance of continuous-variable quantum key distribution over this line. Remarkably, these noiseless operations do not need to be physically implemented but can simply be simulated in the data post-processing stage. Hence, virtual noiseless amplification or attenuation amounts to perform a Gaussian post-selection, which enhances the secure range or tolerable excess noise while keeping the benefits of Gaussian security proofs.

  12. Security of continuous-variable quantum key distribution against general attacks

    Science.gov (United States)

    Leverrier, Anthony

    2013-03-01

    We prove the security of Gaussian continuous-variable quantum key distribution with coherent states against arbitrary attacks in the finite-size regime. In contrast to previously known proofs of principle (based on the de Finetti theorem), our result is applicable in the practically relevant finite-size regime. This is achieved using a novel proof approach, which exploits phase-space symmetries of the protocols as well as the postselection technique introduced by Christandl, Koenig and Renner (Phys. Rev. Lett. 102, 020504 (2009)). This work was supported by the SNF through the National Centre of Competence in Research ``Quantum Science and Technology'' and through Grant No. 200020-135048, the ERC (grant No. 258932), the Humbolt foundation and the F.R.S.-FNRS under project HIPERCOM.

  13. Attacks on practical quantum key distribution systems (and how to prevent them)

    Science.gov (United States)

    Jain, Nitin; Stiller, Birgit; Khan, Imran; Elser, Dominique; Marquardt, Christoph; Leuchs, Gerd

    2016-07-01

    With the emergence of an information society, the idea of protecting sensitive data is steadily gaining importance. Conventional encryption methods may not be sufficient to guarantee data protection in the future. Quantum key distribution (QKD) is an emerging technology that exploits fundamental physical properties to guarantee perfect security in theory. However, it is not easy to ensure in practice that the implementations of QKD systems are exactly in line with the theoretical specifications. Such theory-practice deviations can open loopholes and compromise security. Several such loopholes have been discovered and investigated in the last decade. These activities have motivated the proposal and implementation of appropriate countermeasures, thereby preventing future attacks and enhancing the practical security of QKD. This article introduces the so-called field of quantum hacking by summarising a variety of attacks and their prevention mechanisms.

  14. Photon-monitoring attack on continuous-variable quantum key distribution with source in middle

    Science.gov (United States)

    Wang, Yijun; Huang, Peng; Guo, Ying; Huang, Dazu

    2014-12-01

    Motivated by a fact that the non-Gaussian operation may increase entanglement of an entangled system, we suggest a photon-monitoring attack strategy in the entanglement-based (EB) continuous-variable quantum key distribution (CVQKD) using the photon subtraction operations, where the entangled source originates from the center instead of one of the legal participants. It shows that an eavesdropper, Eve, can steal large information from participants after intercepting the partial beams with the photon-monitoring attach strategy. The structure of the proposed CVQKD protocol is useful in simply analyzing how quantum loss in imperfect channels can decrease the performance of the CVQKD protocol. The proposed attack strategy can be implemented under current technology, where a newly developed and versatile no-Gaussian operation can be well employed with the entangled source in middle in order to access to mass information in the EB CVQKD protocol, as well as in the prepare-and-measure (PM) CVQKD protocol.

  15. N-dimensional measurement-device-independent quantum key distribution with N + 1 un-characterized sources: zero quantum-bit-error-rate case.

    Science.gov (United States)

    Hwang, Won-Young; Su, Hong-Yi; Bae, Joonwoo

    2016-01-01

    We study N-dimensional measurement-device-independent quantum-key-distribution protocol where one checking state is used. Only assuming that the checking state is a superposition of other N sources, we show that the protocol is secure in zero quantum-bit-error-rate case, suggesting possibility of the protocol. The method may be applied in other quantum information processing.

  16. Attacks exploiting deviation of mean photon number in quantum key distribution and coin tossing

    Science.gov (United States)

    Sajeed, Shihan; Radchenko, Igor; Kaiser, Sarah; Bourgoin, Jean-Philippe; Pappa, Anna; Monat, Laurent; Legré, Matthieu; Makarov, Vadim

    2015-03-01

    The security of quantum communication using a weak coherent source requires an accurate knowledge of the source's mean photon number. Finite calibration precision or an active manipulation by an attacker may cause the actual emitted photon number to deviate from the known value. We model effects of this deviation on the security of three quantum communication protocols: the Bennett-Brassard 1984 (BB84) quantum key distribution (QKD) protocol without decoy states, Scarani-Acín-Ribordy-Gisin 2004 (SARG04) QKD protocol, and a coin-tossing protocol. For QKD we model both a strong attack using technology possible in principle and a realistic attack bounded by today's technology. To maintain the mean photon number in two-way systems, such as plug-and-play and relativistic quantum cryptography schemes, bright pulse energy incoming from the communication channel must be monitored. Implementation of a monitoring detector has largely been ignored so far, except for ID Quantique's commercial QKD system Clavis2. We scrutinize this implementation for security problems and show that designing a hack-proof pulse-energy-measuring detector is far from trivial. Indeed, the first implementation has three serious flaws confirmed experimentally, each of which may be exploited in a cleverly constructed Trojan-horse attack. We discuss requirements for a loophole-free implementation of the monitoring detector.

  17. Device-dependent and device-independent quantum key distribution without a shared reference frame

    Science.gov (United States)

    Slater, Joshua A.; Branciard, Cyril; Brunner, Nicolas; Tittel, Wolfgang

    2014-04-01

    Standard quantum key distribution (QKD) protocols typically assume that the distant parties share a common reference frame. In practice, however, establishing and maintaining a good alignment between distant observers is rarely a trivial issue, which may significantly restrain the implementation of long-distance quantum communication protocols. Here we propose simple QKD protocols that do not require the parties to share any reference frame, and study their security and feasibility in both the usual device-dependent (DD) case—in which the two parties use well characterized measurement devices—as well as in the device-independent (DI) case—in which the measurement devices can be untrusted, and the security relies on the violation of a Bell inequality. To illustrate the practical relevance of these ideas, we present a proof-of-principle demonstration of our protocols using polarization entangled photons distributed over a coiled 10-km long optical fiber. We consider two situations, in which either the fiber spool's polarization transformation freely drifts, or randomly chosen polarization transformations are applied. The correlations obtained from measurements allow, with high probability, to generate positive asymptotic secret key rates in both the DD and DI scenarios (under the fair-sampling assumption for the latter case).

  18. Fast optical source for quantum key distribution based on semiconductor optical amplifiers

    CERN Document Server

    Jofre, M; Anzolin, G; Amaya, W; Capmany, J; Ursin, R; Peñate, L; Lopez, D; Juan, J L San; Carrasco, J A; Garcia, F; Torcal-Milla, F J; Sanchez-Brea, L M; Bernabeu, E; Perdigues, J M; Jennewein, T; Torres, J P; Mitchell, M W; Pruneri, V; 10.1364/OE.19.003825

    2011-01-01

    A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor optical amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level of indistinguishability in time and spectrum of the pulses for the four different polarizations and three different levels of intensity. The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state BB84 protocol. We achieved a lower bound secure key rate of the order of 3.64 Mbps and a quantum bit error ratio as low as $1.14\\times 10^{-2}$ while the lower bound secure key rate became 187 bps for an equivalent attenuation of 35 dB. To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size,...

  19. Fast optical source for quantum key distribution based on semiconductor optical amplifiers.

    Science.gov (United States)

    Jofre, M; Gardelein, A; Anzolin, G; Amaya, W; Capmany, J; Ursin, R; Peñate, L; Lopez, D; San Juan, J L; Carrasco, J A; Garcia, F; Torcal-Milla, F J; Sanchez-Brea, L M; Bernabeu, E; Perdigues, J M; Jennewein, T; Torres, J P; Mitchell, M W; Pruneri, V

    2011-02-28

    A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor optical amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level of indistinguishability in time and spectrum of the pulses for the four different polarizations and three different levels of intensity. The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state BB84 protocol. We achieved a lower bound secure key rate of the order of 3.64 Mbps and a quantum bit error ratio as low as 1.14×10⁻² while the lower bound secure key rate became 187 bps for an equivalent attenuation of 35 dB. To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size, low power consumption and the fact that the components used can be space qualified make the source particularly suitable for secure satellite communication.

  20. Continuous operation of four-state continuous-variable quantum key distribution system

    Science.gov (United States)

    Matsubara, Takuto; Ono, Motoharu; Oguri, Yusuke; Ichikawa, Tsubasa; Hirano, Takuya; Kasai, Kenta; Matsumoto, Ryutaroh; Tsurumaru, Toyohiro

    2016-10-01

    We report on the development of continuous-variable quantum key distribution (CV-QKD) system that are based on discrete quadrature amplitude modulation (QAM) and homodyne detection of coherent states of light. We use a pulsed light source whose wavelength is 1550 nm and repetition rate is 10 MHz. The CV-QKD system can continuously generate secret key which is secure against entangling cloner attack. Key generation rate is 50 kbps when the quantum channel is a 10 km optical fiber. The CV-QKD system we have developed utilizes the four-state and post-selection protocol [T. Hirano, et al., Phys. Rev. A 68, 042331 (2003).]; Alice randomly sends one of four states {|+/-α⟩,|+/-𝑖α⟩}, and Bob randomly performs x- or p- measurement by homodyne detection. A commercially available balanced receiver is used to realize shot-noise-limited pulsed homodyne detection. GPU cards are used to accelerate the software-based post-processing. We use a non-binary LDPC code for error correction (reverse reconciliation) and the Toeplitz matrix multiplication for privacy amplification.

  1. Free-space Quantum Key Distribution over 10 km in Daylight and at Night

    Science.gov (United States)

    Hughes, Richard; Nordholt, Jane; Peterson, Charles

    2002-05-01

    In quantum key distribution (QKD) single-photon transmissions transfer the shared, secret random number sequences, known as cryptographic keys that are used to encrypt and decrypt secret communications. Because the security of QKD is based on principles of quantum physics and information theory an adversary can neither successfully tap the key transmissions, nor evade detection. We have performed QKD using the four-state Â"BB84Â" protocol with non-orthogonal photon polarization states across a 10-km line-of-sight path in daylight and at night [1]. We transferred secret, cryptographic quality random numbers at practical rates with security against technologically feasible eavesdropping strategies. By relating the secrecy capacity (secret bits transferred per transmitted bit), which had values up to 10-3, to properties of the atmospheric channel we are able to infer the secrecy capacity of free-space QKD under other atmospheric conditions and over other, longer transmission distances. 1. R. J. Hughes, J. E. Nordholt, D. Derkacs and C. G. Peterson, Los Alamos report LA-UR-02-449.

  2. Long-distance continuous-variable quantum key distribution with advanced reconciliation of a Gaussian modulation

    Science.gov (United States)

    Gyongyosi, L.; Imre, S.

    2014-02-01

    The two-way continuous-variable quantum key distribution (CVQKD) systems allow higher key rates and improved transmission distances over standard telecommunication networks in comparison to the one-way CVQKD protocols. To exploit the real potential of two-way CVQKD systems a robust reconciliation technique is needed. It is currently unavailable, which makes it impossible to reach the real performance of a two-way CVQKD system. The reconciliation process of correlated Gaussian variables is a complex problem that requires either tomography in the physical layer that is intractable in a practical scenario, or high-cost calculations in the multidimensional spherical space with strict dimensional limitations. To avoid these issues, we propose an efficient logical layer-based reconciliation method for two-way CVQKD to extract binary information from correlated Gaussian variables. We demonstrate that by operating on the raw-data level, the noise of the quantum channel can be corrected in the scalar space and the reconciliation can be extended to arbitrary high dimensions. We prove that the error probability of scalar reconciliation is zero in any practical CVQKD scenario, and provides unconditional security. The results allow to significantly improve the currently available key rates and transmission distances of two-way CVQKD. The proposed scalar reconciliation can also be applied in oneway systems as well, to replace the existing reconciliation schemes.

  3. Proof-of-principle experiment of reference-frame-independent quantum key distribution with phase coding

    Science.gov (United States)

    Liang, Wen-Ye; Wang, Shuang; Li, Hong-Wei; Yin, Zhen-Qiang; Chen, Wei; Yao, Yao; Huang, Jing-Zheng; Guo, Guang-Can; Han, Zheng-Fu

    2014-01-01

    We have demonstrated a proof-of-principle experiment of reference-frame-independent phase coding quantum key distribution (RFI-QKD) over an 80-km optical fiber. After considering the finite-key bound, we still achieve a distance of 50 km. In this scenario, the phases of the basis states are related by a slowly time-varying transformation. Furthermore, we developed and realized a new decoy state method for RFI-QKD systems with weak coherent sources to counteract the photon-number-splitting attack. With the help of a reference-frame-independent protocol and a Michelson interferometer with Faraday rotator mirrors, our system is rendered immune to the slow phase changes of the interferometer and the polarization disturbances of the channel, making the procedure very robust.

  4. Experimental measurement-device-independent quantum key distribution with uncharacterized encoding.

    Science.gov (United States)

    Wang, Chao; Wang, Shuang; Yin, Zhen-Qiang; Chen, Wei; Li, Hong-Wei; Zhang, Chun-Mei; Ding, Yu-Yang; Guo, Guang-Can; Han, Zheng-Fu

    2016-12-01

    Measurement-device-independent quantum key distribution (MDI QKD) is an efficient way to share secrets using untrusted measurement devices. However, the assumption on the characterizations of encoding states is still necessary in this promising protocol, which may lead to unnecessary complexity and potential loopholes in realistic implementations. Here, by using the mismatched-basis statistics, we present the first proof-of-principle experiment of MDI QKD with uncharacterized encoding sources. In this demonstration, the encoded states are only required to be constrained in a two-dimensional Hilbert space, and two distant parties (Alice and Bob) are resistant to state preparation flaws even if they have no idea about the detailed information of their encoding states. The positive final secure key rates of our system exhibit the feasibility of this novel protocol, and demonstrate its value for the application of secure communication with uncharacterized devices.

  5. The enhanced measurement-device-independent quantum key distribution with two-intensity decoy states

    Science.gov (United States)

    Zhu, Jian-Rong; Zhu, Feng; Zhou, Xing-Yu; Wang, Qin

    2016-09-01

    We put forward a new scheme for implementing the measurement-device-independent quantum key distribution (QKD) with weak coherent source, while using only two different intensities. In the new scheme, we insert a beam splitter and a local detector at both Alice's and Bob's side, and then all the triggering and non-triggering signals could be employed to process parameter estimations, resulting in very precise estimations for the two-single-photon contributions. Besides, we compare its behavior with two other often used methods, i.e., the conventional standard three-intensity decoy-state measurement-device-independent QKD and the passive measurement-device-independent QKD. Through numerical simulations, we demonstrate that our new approach can exhibit outstanding characteristics not only in the secure transmission distance, but also in the final key generation rate.

  6. Three-intensity decoy-state method for measurement-device-independent quantum key distribution

    Science.gov (United States)

    Yu, Zong-Wen; Zhou, Yi-Heng; Wang, Xiang-Bin

    2013-12-01

    We study the measurement-device-independent quantum key distribution (MDI-QKD) in practice with limited resources, when there are only three different states in implementing the decoy-state method. We present a tighter explicit formula to estimate the lower bound of the yield of two-single-photon pulses sent by Alice and Bob. Moreover, we show that the bounding of this yield and phase flip error of single-photon pulse pairs can be further improved by using other constraints which can be solved by a simple and explicit program. Our methods here can significantly improve the key rate and the secure distance of MDI-QKD with only three intensities.

  7. Performance analysis of information reconciliation with interceptor in Quantum Key distribution

    Directory of Open Access Journals (Sweden)

    Gouri Rani Barai,

    2011-04-01

    Full Text Available Information reconciliation is a step of Quantum Key Distribution (QKD which involves error detection and correction. If Alice (sender and Bob (receiver use an optical channel to exchange bits to form a secret key, some errors can occur in the bit string on the way of transmission due to interceptor. The performance comparison of error detection and correction for two situations with Eve (interceptor and without Eve has been presented in this paper. Here, not only the effect of Eve is analyzed like the existing works but also the simulation is shown for the very first time. The system model follows the BB84 protocol. Cascade algorithm has been applied for this work. The simulation is done using MATLAB.

  8. Implementation of continuous-variable quantum key distribution with composable and one-sided-device-independent security against coherent attacks

    Science.gov (United States)

    Gehring, Tobias; Händchen, Vitus; Duhme, Jörg; Furrer, Fabian; Franz, Torsten; Pacher, Christoph; Werner, Reinhard F.; Schnabel, Roman

    2015-10-01

    Secret communication over public channels is one of the central pillars of a modern information society. Using quantum key distribution this is achieved without relying on the hardness of mathematical problems, which might be compromised by improved algorithms or by future quantum computers. State-of-the-art quantum key distribution requires composable security against coherent attacks for a finite number of distributed quantum states as well as robustness against implementation side channels. Here we present an implementation of continuous-variable quantum key distribution satisfying these requirements. Our implementation is based on the distribution of continuous-variable Einstein-Podolsky-Rosen entangled light. It is one-sided device independent, which means the security of the generated key is independent of any memoryfree attacks on the remote detector. Since continuous-variable encoding is compatible with conventional optical communication technology, our work is a step towards practical implementations of quantum key distribution with state-of-the-art security based solely on telecom components.

  9. Differential phase shift quantum key distribution experiment over 105 km fibre

    CERN Document Server

    Takesue, H; Honjo, T; Langrock, C; Fejer, M M; Inoue, K; Yamamoto, Y

    2005-01-01

    Since several papers appeared in 2000, the quantum key distribution (QKD) community has been well aware that photon number splitting (PNS) attack by Eve severely limits the secure key distribution distance in BB84 QKD systems with Poissonian photon sources. In attempts to solve this problem, entanglement-based QKD, single-photon based QKD, and entanglement swapping-based QKD, have been studied in recent years. However, there are many technological difficulties that must be overcome before these schemes can become practical systems. Here we report a very simple QKD system, in which secure keys were generated over >100 km fibre for the first time. We used an alternative protocol of differential phase shift keying (DPSK) but with a Poissonian source. We analysed the security of the DPSK protocol and showed that it is robust even against hybrid attacks including collective PNS attack over consecutive pulses, intercept-and-resend (I-R) attack and beamsplitting (BS) attack, because of the non-deterministic collapse...

  10. Self-coherent phase reference sharing for continuous-variable quantum key distribution

    Science.gov (United States)

    Marie, Adrien; Alléaume, Romain

    2017-01-01

    We develop a comprehensive framework to model and optimize the performance of continuous-variable quantum key distribution (CV-QKD) with a local local oscillator (LLO), when phase reference sharing and QKD are jointly implemented. We first analyze the limitations of the only existing approach, called LLO-sequential, and show that it requires high modulation dynamics and can only tolerate small phase noise. Our main contribution is to introduce two designs to perform LLO CV-QKD, respectively called LLO-delayline and LLO-displacement, and to study their performance. Both designs rely on a self-coherent approach, in which phase reference information and quantum information are coherently obtained from a single optical wavefront. We show that these designs can lift some limitations of the existing LLO-sequential approach. The LLO-delayline design can in particular tolerate much stronger phase noise and thus appears to be an appealing alternative to LLO-sequential in terms of network integrability. We also investigate, with the LLO-displacement design, how phase reference information and quantum information can be multiplexed within a single optical pulse. By studying the trade-off between phase reference recovery and phase noise induced by displacement, we, however, demonstrate that this design can only tolerate low phase noise. On the other hand, the LLO-displacement design has the advantage of minimal hardware requirements and provides a simple approach to multiplex classical and quantum communications, opening a practical path towards the development of ubiquitous coherent classical-quantum communications systems compatible with next-generation network requirements.

  11. Enhancing the performance of the measurement-device-independent quantum key distribution with heralded pair-coherent sources

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Feng; Zhang, Chun-Hui; Liu, Ai-Ping [Institute of Signal Processing Transmission, Nanjing University of Posts and Telecommunications, Nanjing 210003 (China); Key Lab of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunications, Ministry of Education, Nanjing 210003 (China); Wang, Qin, E-mail: qinw@njupt.edu.cn [Institute of Signal Processing Transmission, Nanjing University of Posts and Telecommunications, Nanjing 210003 (China); Key Lab of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunications, Ministry of Education, Nanjing 210003 (China); Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026 (China)

    2016-04-01

    In this paper, we propose to implement the heralded pair-coherent source into the measurement-device-independent quantum key distribution. By comparing its performance with other existing schemes, we demonstrate that our new scheme can overcome many shortcomings existing in current schemes, and show excellent behavior in the quantum key distribution. Moreover, even when taking the statistical fluctuation into account, we can still obtain quite high key generation rate at very long transmission distance by using our new scheme. - Highlights: • Implement the heralded pair-coherent source into the measurement-device-independent quantum key distribution. • Overcome many shortcomings existing in current schemes and show excellent behavior. • Obtain quite high key generation rate even when taking statistical fluctuation into account.

  12. Symmetric extension of bipartite quantum states and its use in quantum key distribution with two-way postprocessing

    Energy Technology Data Exchange (ETDEWEB)

    Myhr, Geir Ove

    2010-11-08

    Just like we can divide the set of bipartite quantum states into separable states and entangled states, we can divide it into states with and without a symmetric extension. The states with a symmetric extension - which includes all the separable states - behave classically in many ways, while the states without a symmetric extension - which are all entangled - have the potential to exhibit quantum effects. The set of states with a symmetric extension is closed under local quantum operations assisted by one-way classical communication (1-LOCC) just like the set of separable states is closed under local operations assisted by two-way classical communication (LOCC). Because of this, states with a symmetric extension often play the same role in a one-way communication setting as the separable states play in a two-way communication setting. We show that any state with a symmetric extension can be decomposed into a convex combination of states that have a pure symmetric extension. A necessary condition for a state to have a pure symmetric extension is that the spectra of the local and global density matrices are equal. This condition is also sufficient for two qubits, but not for any larger systems. We present a conjectured necessary and sufficient condition for two-qubit states with a symmetric extension. Proofs are provided for some classes of states: rank-two states, states on the symmetric subspace, Bell-diagonal states and states that are invariant under S x S, where S is a phase gate. We also show how the symmetric extension problem for multi-qubit Bell-diagonal states can be simplified and the simplified problem implemented as a semidefinite program. Quantum key distribution protocols such as the six-state protocol and the BB84 protocol effectively gives Alice and Bob Bell-diagonal states that they measure in the standard basis to obtain a raw key which they may then process further to obtain a secret error-free key. When the raw key has a high error rate, the

  13. Apply current exponential de Finetti theorem to realistic quantum key distribution

    Science.gov (United States)

    Zhao, Yi-Bo; Yin, Zhen-Qiang

    2014-09-01

    In the realistic quantum key distribution (QKD), Alice and Bob respectively get a quantum state from an unknown channel, whose dimension may be unknown. However, while discussing the security, sometime we need to know exact dimension, since current exponential de Finetti theorem, crucial to the information-theoretical security proof, is deeply related with the dimension and can only be applied to finite dimensional case. Here we address this problem in detail. We show that if POVM elements corresponding to Alice and Bob's measured results can be well described in a finite dimensional subspace with sufficiently small error, then dimensions of Alice and Bob's states can be almost regarded as finite. Since the security is well defined by the smooth entropy, which is continuous with the density matrix, the small error of state actually means small change of security. Then the security of unknown-dimensional system can be solved. Finally we prove that for heterodyne detection continuous variable QKD and differential phase shift QKD, the collective attack is optimal under the infinite key size case.

  14. Necessary detection efficiencies for secure quantum key distribution and bound randomness

    Science.gov (United States)

    Acín, Antonio; Cavalcanti, Daniel; Passaro, Elsa; Pironio, Stefano; Skrzypczyk, Paul

    2016-01-01

    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 key 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 nonlocal correlations in which a nonsignalling eavesdropper can find out a posteriori the result of any implemented measurement.

  15. Quantum key distribution with hacking countermeasures and long term field trial.

    Science.gov (United States)

    Dixon, A R; Dynes, J F; Lucamarini, M; Fröhlich, B; Sharpe, A W; Plews, A; Tam, W; Yuan, Z L; Tanizawa, Y; Sato, H; Kawamura, S; Fujiwara, M; Sasaki, M; Shields, A J

    2017-05-16

    Quantum key distribution's (QKD's) central and unique claim is information theoretic security. However there is an increasing understanding that the security of a QKD system relies not only on theoretical security proofs, but also on how closely the physical system matches the theoretical models and prevents attacks due to discrepancies. These side channel or hacking attacks exploit physical devices which do not necessarily behave precisely as the theory expects. As such there is a need for QKD systems to be demonstrated to provide security both in the theoretical and physical implementation. We report here a QKD system designed with this goal in mind, providing a more resilient target against possible hacking attacks including Trojan horse, detector blinding, phase randomisation and photon number splitting attacks. The QKD system was installed into a 45 km link of a metropolitan telecom network for a 2.5 month period, during which time the system operated continuously and distributed 1.33 Tbits of secure key data with a stable secure key rate over 200 kbit/s. In addition security is demonstrated against coherent attacks that are more general than the collective class of attacks usually considered.

  16. Demonstration of free-space reference frame independent quantum key distribution

    Science.gov (United States)

    Wabnig, J.; Bitauld, D.; Li, H. W.; Laing, A.; O'Brien, J. L.; Niskanen, A. O.

    2013-07-01

    Quantum key distribution (QKD) is moving from research laboratories towards applications. As computing becomes more mobile, cashless as well as cardless payment solutions are introduced. A possible route to increase the security of wireless communications is to incorporate QKD in a mobile device. Handheld devices present a particular challenge as the orientation and the phase of a qubit will depend on device motion. This problem is addressed by the reference frame independent (RFI) QKD scheme. The scheme tolerates an unknown phase between logical states that vary slowly compared to the rate of particle repetition. Here we experimentally demonstrate the feasibility of RFI QKD over a free-space link in a prepare and measure scheme using polarization encoding. We extend the security analysis of the RFI QKD scheme to be able to deal with uncalibrated devices and a finite number of measurements. Together these advances are an important step towards mass production of handheld QKD devices.

  17. Trojan-horse attacks on quantum key distribution with classical Bob

    Science.gov (United States)

    Yang, Yu-Guang; Sun, Si-Jia; Zhao, Qian-Qian

    2015-02-01

    Recently, Boyer et al. (Phys Rev Lett 99:140501, 2007) introduced a conceptually novel semi-quantum key distribution scheme (BKM07). Tan et al. (Phys Rev Lett 102:098901, 2009) showed that classical Bob is unable to detect Eve's eavesdropping by giving a special implementation of BKM07 protocol. In the reply, Boyer et al. (Phys Rev Lett 102:098902, 2009) gave a solution against the eavesdropping, i.e., Bob may place a filter that allows only photons with approximately specific frequency to pass just at the expected time . However, their improvement contradicts the descriptions about "classical." If the assumption of "classical" is not considered, we give a delay-photon Trojan-horse attack on BKM07 protocol and its improvement and further present a possible improvement.

  18. Ultra fast quantum key distribution over a 97 km installed telecom fiber with wavelength division multiplexing clock synchronization.

    Science.gov (United States)

    Tanaka, Akihiro; Fujiwara, Mikio; Nam, Sae W; Nambu, Yoshihiro; Takahashi, Seigo; Maeda, Wakako; Yoshino, Ken-ichiro; Miki, Shigehito; Baek, Burm; Wang, Zhen; Tajima, Akio; Sasaki, Masahide; Tomita, Akihisa

    2008-07-21

    We demonstrated ultra fast BB84 quantum key distribution (QKD) transmission at 625 MHz clock rate through a 97 km field-installed fiber using practical clock synchronization based on wavelength-division multiplexing (WDM). We succeeded in over-one-hour stable key generation at a high sifted key rate of 2.4 kbps and a low quantum bit error rate (QBER) of 2.9%. The asymptotic secure key rate was estimated to be 0.78- 0.82 kbps from the transmission data with the decoy method of average photon numbers 0, 0.15, and 0.4 photons/pulse.

  19. Experimental round-robin differential phase-shift quantum key distribution

    Science.gov (United States)

    Li, Yu-Huai; Cao, Yuan; Dai, Hui; Lin, Jin; Zhang, Zhen; Chen, Wei; Xu, Yu; Guan, Jian-Yu; Liao, Sheng-Kai; Yin, Juan; Zhang, Qiang; Ma, Xiongfeng; Peng, Cheng-Zhi; Pan, Jian-Wei

    2016-03-01

    In conventional quantum key distribution (QKD) protocols, security is guaranteed by estimating the amount of leaked information. Such estimation tends to overrate, leading to a fundamental threshold of the bit error rate, which becomes a bottleneck of practical QKD development. This bottleneck is broken through by the recent work of round-robin differential phase-shift (RRDPS) protocol, which eliminates the fundamental threshold of the bit error rate. The key challenge for the implementation of the RRDPS scheme lies in the realization of a variable-delay Mach-Zehnder interferometer, which requires active and random choice of many delays. By designing an optical system with multiple switches and employing an active phase stabilization technology, we successfully construct a variable-delay interferometer with 127 actively selectable delays. With this measurement, we experimentally demonstrate the RRDPS protocol and obtain a final key rate of 15.54 bps with a total loss of 18 dB and an error rate of 8.9%.

  20. Round-robin differential-phase-shift quantum key distribution with heralded pair-coherent sources

    Science.gov (United States)

    Wang, Le; Zhao, Shengmei

    2017-04-01

    Round-robin differential-phase-shift (RRDPS) quantum key distribution (QKD) scheme provides an effective way to overcome the signal disturbance from the transmission process. However, most RRDPS-QKD schemes use weak coherent pulses (WCPs) as the replacement of the perfect single-photon source. Considering the heralded pair-coherent source (HPCS) can efficiently remove the shortcomings of WCPs, we propose a RRDPS-QKD scheme with HPCS in this paper. Both infinite-intensity decoy-state method and practical three-intensity decoy-state method are adopted to discuss the tight bound of the key rate of the proposed scheme. The results show that HPCS is a better candidate for the replacement of the perfect single-photon source, and both the key rate and the transmission distance are greatly increased in comparison with those results with WCPs when the length of the pulse trains is small. Simultaneously, the performance of the proposed scheme using three-intensity decoy states is close to that result using infinite-intensity decoy states when the length of pulse trains is small.

  1. Round-robin differential-phase-shift quantum key distribution with a passive decoy state method

    Science.gov (United States)

    Liu, Li; Guo, Fen-Zhuo; Qin, Su-Juan; Wen, Qiao-Yan

    2017-02-01

    Recently, a new type of protocol named Round-robin differential-phase-shift quantum key distribution (RRDPS QKD) was proposed, where the security can be guaranteed without monitoring conventional signal disturbances. The active decoy state method can be used in this protocol to overcome the imperfections of the source. But, it may lead to side channel attacks and break the security of QKD systems. In this paper, we apply the passive decoy state method to the RRDPS QKD protocol. Not only can the more environment disturbance be tolerated, but in addition it can overcome side channel attacks on the sources. Importantly, we derive a new key generation rate formula for our RRDPS protocol using passive decoy states and enhance the key generation rate. We also compare the performance of our RRDPS QKD to that using the active decoy state method and the original RRDPS QKD without any decoy states. From numerical simulations, the performance improvement of the RRDPS QKD by our new method can be seen.

  2. Security of six-state quantum key distribution protocol with threshold detectors.

    Science.gov (United States)

    Kato, Go; Tamaki, Kiyoshi

    2016-07-22

    The security of quantum key distribution (QKD) is established by a security proof, and the security proof puts some assumptions on the devices consisting of a QKD system. Among such assumptions, security proofs of the six-state protocol assume the use of photon number resolving (PNR) detector, and as a result the bit error rate threshold for secure key generation for the six-state protocol is higher than that for the BB84 protocol. Unfortunately, however, this type of detector is demanding in terms of technological level compared to the standard threshold detector, and removing the necessity of such a detector enhances the feasibility of the implementation of the six-state protocol. Here, we develop the security proof for the six-state protocol and show that we can use the threshold detector for the six-state protocol. Importantly, the bit error rate threshold for the key generation for the six-state protocol (12.611%) remains almost the same as the one (12.619%) that is derived from the existing security proofs assuming the use of PNR detectors. This clearly demonstrates feasibility of the six-state protocol with practical devices.

  3. Phase-noise limitations in continuous-variable quantum key distribution with homodyne detection

    Science.gov (United States)

    Corvaja, Roberto

    2017-02-01

    In continuous-variables quantum key distribution with coherent states, the advantage of performing the detection by using standard telecoms components is counterbalanced by the lack of a stable phase reference in homodyne detection due to the complexity of optical phase-locking circuits and to the unavoidable phase noise of lasers, which introduces a degradation on the achievable secure key rate. Pilot-assisted phase-noise estimation and postdetection compensation techniques are used to implement a protocol with coherent states where a local laser is employed and it is not locked to the received signal, but a postdetection phase correction is applied. Here the reduction of the secure key rate determined by the laser phase noise, for both individual and collective attacks, is analytically evaluated and a scheme of pilot-assisted phase estimation proposed, outlining the tradeoff in the system design between phase noise and spectral efficiency. The optimal modulation variance as a function of the phase-noise amount is derived.

  4. Quantum-Locked Key Distribution at Nearly the Classical Capacity Rate

    Science.gov (United States)

    Lupo, Cosmo; Lloyd, Seth

    2014-10-01

    Quantum data locking is a protocol that allows for a small secret key to (un)lock an exponentially larger amount of information, hence yielding the strongest violation of the classical one-time pad encryption in the quantum setting. This violation mirrors a large gap existing between two security criteria for quantum cryptography quantified by two entropic quantities: the Holevo information and the accessible information. We show that the latter becomes a sensible security criterion if an upper bound on the coherence time of the eavesdropper's quantum memory is known. Under this condition, we introduce a protocol for secret key generation through a memoryless qudit channel. For channels with enough symmetry, such as the d-dimensional erasure and depolarizing channels, this protocol allows secret key generation at an asymptotic rate as high as the classical capacity minus one bit.

  5. Research on measurement-device-independent quantum key distribution based on an air-water channel

    Science.gov (United States)

    Zhou, Yuan-yuan; Zhou, Xue-jun; Xu, Hua-bin; Cheng, Kang

    2016-11-01

    A measurement-device-independent quantum key distribution (MDI-QKD) method with an air-water channel is researched. In this method, the underwater vehicle and satellite are the legitimate parties, and the third party is at the airwater interface in order to simplify the unilateral quantum channel to water or air. Considering the condition that both unilateral transmission distance and transmission loss coefficient are unequal, a perfect model of the asymmetric channel is built. The influence of asymmetric channel on system loss tolerance and secure transmission distance is analyzed. The simulation results show that with the increase of the channel's asymmetric degree, the system loss tolerance will descend, one transmission distance will be reduced while the other will be increased. When the asymmetric coefficient of channel is between 0.068 and 0.171, MDI-QKD can satisfy the demand of QKD with an air-water channel, namely the underwater transmission distance and atmospheric transmission distance are not less than 60 m and 12 km, respectively.

  6. Security of Continuous-Variable Quantum Key Distribution via a Gaussian de Finetti Reduction

    Science.gov (United States)

    Leverrier, Anthony

    2017-05-01

    Establishing the security of continuous-variable quantum key distribution against general attacks in a realistic finite-size regime is an outstanding open problem in the field of theoretical quantum cryptography if we restrict our attention to protocols that rely on the exchange of coherent states. Indeed, techniques based on the uncertainty principle are not known to work for such protocols, and the usual tools based on de Finetti reductions only provide security for unrealistically large block lengths. We address this problem here by considering a new type of Gaussian de Finetti reduction, that exploits the invariance of some continuous-variable protocols under the action of the unitary group U (n ) (instead of the symmetric group Sn as in usual de Finetti theorems), and by introducing generalized S U (2 ,2 ) coherent states. Crucially, combined with an energy test, this allows us to truncate the Hilbert space globally instead as at the single-mode level as in previous approaches that failed to provide security in realistic conditions. Our reduction shows that it is sufficient to prove the security of these protocols against Gaussian collective attacks in order to obtain security against general attacks, thereby confirming rigorously the widely held belief that Gaussian attacks are indeed optimal against such protocols.

  7. Feasibility of quantum key distribution through dense wavelength division multiplexing network

    CERN Document Server

    Qi, Bing; Qian, Li; Lo, Hoi-Kwong

    2010-01-01

    In this paper, we study the feasibility of conducting quantum key distribution (QKD) together with classical communication through the same optical fiber by employing dense-wavelength-division-multiplexing (DWDM) technology at telecom wavelength. The impact of the classical channels to the quantum channel has been investigated for both QKD based on single photon detection and QKD based on homodyne detection. Our studies show that the latter can tolerate a much higher level of contamination from the classical channels than the former. This is because the local oscillator used in the homodyne detector acts as a "mode selector" which can suppress noise photons effectively. We have performed simulations based on both the decoy BB84 QKD protocol and the Gaussian modulated coherent state (GMCS) QKD protocol. While the former cannot tolerate even one classical channel (with a power of 0dBm), the latter can be multiplexed with 38 classical channels (0dBm power each channel) and still has a secure distance around 10km...

  8. Field and long-term demonstration of a wide area quantum key distribution network

    CERN Document Server

    Wang, Shuang; Yin, Zhen-Qiang; Li, Hong-Wei; He, De-Yong; Li, Yu-Hu; Zhou, Zheng; Song, Xiao-Tian; Li, Fang-Yi; Wang, Dong; Chen, Hua; Han, Yun-Guang; Huang, Jing-Zheng; Guo, Jun-Fu; Hao, Peng-Lei; Li, Mo; Zhang, Chun-Mei; Liu, Dong; Liang, Wen-Ye; Miao, Chun-Hua; Wu, Ping; Guo, Guang-Can; Han, Zheng-Fu

    2014-01-01

    A wide area quantum key distribution (QKD) network deployed on communication infrastructures provided by China Mobile Ltd. is demonstrated. Three cities and two metropolitan area QKD networks were linked up to form the Hefei-Chaohu-Wuhu wide area QKD network with over 150 kilometers coverage area, in which Hefei metropolitan area QKD network was a typical full-mesh core network to offer all-to-all interconnections, and Wuhu metropolitan area QKD network was a representative quantum access network with point-to-multipoint configuration. The whole wide area QKD network ran for more than 5000 hours, from 21 December 2011 to 19 July 2012, and part of the network stopped until last December. To adapt to the complex and volatile field environment, the Faraday-Michelson QKD system with several stability measures was adopted when we designed QKD devices. Through standardized design of QKD devices, resolution of symmetry problem of QKD devices, and seamless switching in dynamic QKD network, we realized the effective i...

  9. Continuous-variable quantum enigma machines for long-distance key distribution

    Science.gov (United States)

    Lupo, Cosmo; Lloyd, Seth

    2015-12-01

    Quantum physics allows for unconditionally secure communication through insecure communication channels. The achievable rates of quantum-secured communication are fundamentally limited by the laws of quantum physics and in particular by the properties of entanglement. For a lossy communication line, this implies that the secret-key generation rate vanishes at least exponentially with the communication distance. We show that this fundamental limitation can be violated in a realistic scenario where the eavesdropper can store quantum information for only a finite, yet arbitrarily long, time. We consider communication through a lossy bononic channel (modeling linear loss in optical fibers) and we show that it is in principle possible to achieve a constant rate of key generation of one bit per optical mode over arbitrarily long communication distances.

  10. Operational tools for moment characterization, entanglement verification and quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Moroder, Tobias

    2009-07-31

    security analysis of an idealized quantum key distribution protocol to the real experiment. We develop a formalism to check whether a given realistic measurement device has such a squash model or not and provide relevant detection schemes with and without this particular property. We also address an experimental option which equally well provides security of a realistic quantum key distribution experiment by just using the idealized version of it. We exploit the idea that one can combine a variable beam splitter with a simple click/no-click detector in order to achieve the statistics of a photon number resolving detector. Via this hardware change it is straightforward to estimate the crucial parameters for the security statement. Lastly we focus on experimental entanglement verification. Considering the mere question of entanglement verification this practicality issue occurs since one often uses - because of various reasons - an oversimplified model for the performed measurements. We show that via such a misinterpretation of the measurement results one can indeed make mistakes, nevertheless we are more interested in conditions under which such errors can be excluded. For that we introduce and investigate a similar, but less restrictive, concept of the squash model. As an application we show that the usual tomography entanglement test, typically used in parametric down-conversion or even multipartite photonic experiments, can easily be made error-free. (orig.)

  11. Efficient and universal quantum key distribution based on chaos and middleware

    Science.gov (United States)

    Jiang, Dong; Chen, Yuanyuan; Gu, Xuemei; Xie, Ling; Chen, Lijun

    2017-01-01

    Quantum key distribution (QKD) promises unconditionally secure communications, however, the low bit rate of QKD cannot meet the requirements of high-speed applications. Despite the many solutions that have been proposed in recent years, they are neither efficient to generate the secret keys nor compatible with other QKD systems. This paper, based on chaotic cryptography and middleware technology, proposes an efficient and universal QKD protocol that can be directly deployed on top of any existing QKD system without modifying the underlying QKD protocol and optical platform. It initially takes the bit string generated by the QKD system as input, periodically updates the chaotic system, and efficiently outputs the bit sequences. Theoretical analysis and simulation results demonstrate that our protocol can efficiently increase the bit rate of the QKD system as well as securely generate bit sequences with perfect statistical properties. Compared with the existing methods, our protocol is more efficient and universal, it can be rapidly deployed on the QKD system to increase the bit rate when the QKD system becomes the bottleneck of its communication system.

  12. Passive decoy-state quantum key distribution using weak coherent pulses with modulator attenuation

    Institute of Scientific and Technical Information of China (English)

    李源; 鲍皖苏; 李宏伟; 周淳; 汪洋

    2015-01-01

    Passive decoy-state quantum key distribution is more desirable than the active one in some scenarios. It is also affected by the imperfections of the devices. In this paper, the influence of modulator attenuation on the passive decoy-state method is considered. We introduce and analyze the unbalanced Mach–Zehnder interferometer, briefly, and combining with the virtual source and imaginary unitary transformation, we characterize the passive decoy-state method using a weak coherent photon source with modulator attenuation. According to the attenuation parameterδ, the pass efficiencies are given. Then, the key generation rate can be acquired. From numerical simulations, it can be seen that modulator attenuation has a non-negligible influence on the performance of passive-state QKD protocol. Based on the research, the analysis method of virtual source and imaginary unitary transformation are preferred in analyzing passive decoy state protocol, and the passive decoy-state method is better than the active one and is close to the active vacuum+weak decoy state under the condition of having the same modulator attenuation.

  13. Passive decoy-state quantum key distribution using weak coherent pulses with modulator attenuation

    Science.gov (United States)

    Li, Yuan; Bao, Wan-Su; Li, Hong-Wei; Zhou, Chun; Wang, Yang

    2015-11-01

    Passive decoy-state quantum key distribution is more desirable than the active one in some scenarios. It is also affected by the imperfections of the devices. In this paper, the influence of modulator attenuation on the passive decoy-state method is considered. We introduce and analyze the unbalanced Mach-Zehnder interferometer, briefly, and combining with the virtual source and imaginary unitary transformation, we characterize the passive decoy-state method using a weak coherent photon source with modulator attenuation. According to the attenuation parameter δ, the pass efficiencies are given. Then, the key generation rate can be acquired. From numerical simulations, it can be seen that modulator attenuation has a nonnegligible influence on the performance of passive-state QKD protocol. Based on the research, the analysis method of virtual source and imaginary unitary transformation are preferred in analyzing passive decoy state protocol, and the passive decoy-state method is better than the active one and is close to the active vacuum + weak decoy state under the condition of having the same modulator attenuation. Project supported by the National Natural Science Foundation of China (Grant No. 11304397).

  14. Experimental demonstration of passive-decoy-state quantum key distribution with two independent lasers

    Science.gov (United States)

    Sun, Shi-Hai; Tang, Guang-Zhao; Li, Chun-Yan; Liang, Lin-Mei

    2016-09-01

    The decoy-state method could effectively enhance the performance of quantum key distribution (QKD) with a practical phase randomized weak coherent source. Although active modulation of the source intensity is effective and has been implemented in many experiments, passive preparation of decoy states is also an important addition to the family of decoy-state QKD protocols. In this paper, following the theory of Curty et al. [Phys. Rev. A 81, 022310 (2010), 10.1103/PhysRevA.81.022310], we experimentally demonstrate the phase-encoding passive-decoy-state QKD with only linear optical setups and threshold single-photon detectors. In our experiment, two homemade independent pulsed lasers, with visibility of Hong-Ou-Mandel interference 0.53 (±0.003 ) , have been implemented and used to passively generate the different decoy states. Finally, a secret key rate of 1.5 ×10-5 /pulse is obtained with 10-km commercial fiber between Alice and Bob.

  15. A New Quantum Key Distribution Scheme Based on Frequency and Time Coding

    Institute of Scientific and Technical Information of China (English)

    ZHU Chang-Hua; PEI Chang-Xing; QUAN Dong-Xiao; GAO Jing-Liang; CHEN Nan; YI Yun-Hui

    2010-01-01

    @@ A new scheme of quantum key distribution (QKD) using frequency and time coding is proposed,in which the security is based on the frequency-time uncertainty relation.In this scheme,the binary information sequence is encoded randomly on either the central frequency or the time delay of the optical pulse at the sender.The central frequency of the single photon pulse is set as ω1 for bit 0 and set as ω2 for bit 1 when frequency coding is selected.However,the single photon pulse is not delayed for bit 0 and is delayed in T for 1 when time coding is selected.At the receiver,either the frequency or the time delay of the pulse is measured randomly,and the final key is obtained after basis comparison,data reconciliation and privacy amplification.With the proposed method,the effect of the noise in the fiber channel and environment on the QKD system can be reduced effectively.

  16. An improved proposal on the practical quantum key distribution with biased basis

    Science.gov (United States)

    Mao, Chen-Chen; Li, Jian; Zhu, Jian-Rong; Zhang, Chun-Mei; Wang, Qin

    2017-10-01

    In this manuscript, we propose an improved scheme on the decoy-state quantum key distribution (QKD) under practical experimental conditions with biased basis. Compared with the standard decoy-state method with biased basis (prepare signal pulses in both X and Z basis with certain probabilities, and weak decoy pulses as well), the difference here is, we prepare signal pulses in both X and Z basis, but the weak decoy state in only X basis. In the follow-up, we adopt this scheme to conducting numerical simulations on the QKD with the mostly often used source, i.e., weak coherent source by taking statistical fluctuations into account. Furthermore, we carry out full parameter optimization on it. Numerical simulation results demonstrate that our new scheme can present a higher key generation rate and a longer transmission distance compared with standard three-intensity decoy-state method with biased basis. Moreover, it shows drastically improved performance by conducting full parameter optimization in our new scheme compared with partial optimization.

  17. Experimental transmission of quantum digital signatures over 90 km of installed optical fiber using a differential phase shift quantum key distribution system

    Science.gov (United States)

    Collins, Robert J.; Amiri, Ryan; Fujiwara, Mikio; Honjo, Toshimori; Shimizu, Kaoru; Tamaki, Kiyoshi; Takeoka, Masahiro; Andersson, Erika; Buller, Gerald S.; Sasaki, Masahide

    2016-11-01

    Quantum digital signatures apply quantum mechanics to the problem of guaranteeing message integrity and non-repudiation with information-theoretical security, which are complementary to the confidentiality realized by quantum key distribution. Previous experimental demonstrations have been limited to transmission distances of less than 5-km of optical fiber in a laboratory setting. Here we report the first demonstration of quantum digital signatures over installed optical fiber as well as the longest transmission link reported to date. This demonstration used a 90-km long differential phase shift quantum key distribution system to achieve approximately one signed bit per second - an increase in the signature generation rate of several orders of magnitude over previous optical fiber demonstrations.

  18. Aerospace laser communications technology as enabler for worldwide quantum key distribution

    Science.gov (United States)

    Moll, Florian; Weinfurter, Harald; Rau, Markus; Schmidt, Christopher; Melén, Gwen; Vogl, Tobias; Nauerth, Sebastian; Fuchs, Christian

    2016-04-01

    A worldwide growing interest in fast and secure data communications pushes technology development along two lines. While fast communications can be realized using laser communications in fiber and free-space, inherently secure communications can be achieved using quantum key distribution (QKD). By combining both technologies in a single device, many synergies can be exploited, therefore reducing size, weight and power of future systems. In recent experiments we demonstrated quantum communications over large distances as well as between an aircraft and a ground station which proved the feasibility of QKD between moving partners. Satellites thus may be used as trusted nodes in combination with QKD receiver stations on ground, thereby enabling fast and secure communications on a global scale. We discuss the previous experiment with emphasis on necessary developments to be done and corresponding ongoing research work of German Aerospace Center (DLR) and Ludwig Maximilians University Munich (LMU). DLR is performing research on satellite and ground terminals for the high-rate laser communication component, which are enabling technologies for the QKD link. We describe the concept and hardware of three generations of OSIRIS (Optical High Speed Infrared Link System) laser communication terminals for low Earth orbiting satellites. The first type applies laser beam pointing solely based on classical satellite control, the second uses an optical feedback to the satellite bus and the third, currently being in design phase, comprises of a special coarse pointing assembly to control beam direction independent of satellite orientation. Ongoing work also targets optical terminals for CubeSats. A further increase of beam pointing accuracy can be achieved with a fine pointing assembly. Two ground stations will be available for future testing, an advanced stationary ground station and a transportable ground station. In parallel the LMU QKD source size will be reduced by more than an

  19. Two Methods for Extending Quantum Key Warehouse

    Institute of Scientific and Technical Information of China (English)

    WU Min; LIAO Chang-jun; LIU Song-hao

    2006-01-01

    Because the rates of quantum key distribution systems are too low,the interleaving technique and interpolation technique are used to extend the capacity of the quantum key warehouse to increase the quantum key rates of quantum secure communication systems. the simulation technique can extend random sequences and that their randomness are invariable. The correlative theory and technique of digital singal processing is an effective method of extending the quantum dey warehouse.

  20. Efficient Quantum Key Distribution Scheme And Proof of Its Unconditional Security

    CERN Document Server

    Lo, H K; Ardehali, M; Lo, Hoi-Kwong

    2000-01-01

    We devise a simple modification that essentially doubles the efficiency of the BB84 quantum key distribution scheme proposed by Bennett and Brassard. We also prove the security of our modified scheme against the most general eavesdropping attack that is allowed by the laws of physics. The first major ingredient of our scheme is the assignment of significantly different probabilities to the different polarization bases during both transmission and reception, thus reducing the fraction of discarded data. A second major ingredient of our scheme is a refined analysis of accepted data: We separate the accepted data into various subsets according to the basis employed and estimate an error rate for each subset {\\em separately}. We then show that such a refined data analysis guarantees the security of our scheme against the most general eavesdropping strategy, thus generalizing Shor and Preskill's proof of security of BB84 to our new scheme. Up till now, most proposed proofs of security of single-particle type quant...

  1. Simulation and Implementation of Decoy State Quantum Key Distribution over 60km Telecom Fiber

    CERN Document Server

    Zhao, Y; Ma, X; Qi, B; Qian, L; Lo, Hoi-Kwong; Ma, Xiongfeng; Qi, Bing; Qian, Li; Zhao, Yi

    2006-01-01

    Decoy state quantum key distribution (QKD) has been proposed as a novel approach to improve dramatically both the security and the performance of practical QKD set-ups. Recently, many theoretical efforts have been made on this topic and have theoretically predicted the high performance of decoy method. However, the gap between theory and experiment remains open. In this paper, we report the first experiments on decoy state QKD, thus bridging the gap. Two protocols of decoy state QKD are implemented: one-decoy protocol over 15km of standard telecom fiber, and weak+vacuum protocol over 60km of standard telecom fiber. We implemented the decoy state method on a modified commercial QKD system. The modification we made is simply adding commercial acousto-optic modulator (AOM) on the QKD system. The AOM is used to modulate the intensity of each signal individually, thus implementing the decoy state method. As an important part of implementation, numerical simulation of our set-up is also performed. The simulation sh...

  2. Increasing operational command and control security by the implementation of device independent quantum key distribution

    Science.gov (United States)

    Bovino, Fabio Antonio; Messina, Angelo

    2016-10-01

    In a very simplistic way, the Command and Control functions can be summarized as the need to provide the decision makers with an exhaustive, real-time, situation picture and the capability to convey their decisions down to the operational forces. This two-ways data and information flow is vital to the execution of current operations and goes far beyond the border of military operations stretching to Police and disaster recovery as well. The availability of off-the shelf technology has enabled hostile elements to endanger the security of the communication networks by violating the traditional security protocols and devices and hacking sensitive databases. In this paper an innovative approach based to implementing Device Independent Quantum Key Distribution system is presented. The use of this technology would prevent security breaches due to a stolen crypto device placed in an end-to-end communication chain. The system, operating with attenuated laser, is practical and provides the increasing of the distance between the legitimate users.

  3. Implementation of quantum key distribution network simulation module in the network simulator NS-3

    Science.gov (United States)

    Mehic, Miralem; Maurhart, Oliver; Rass, Stefan; Voznak, Miroslav

    2017-10-01

    As the research in quantum key distribution (QKD) technology grows larger and becomes more complex, the need for highly accurate and scalable simulation technologies becomes important to assess the practical feasibility and foresee difficulties in the practical implementation of theoretical achievements. Due to the specificity of the QKD link which requires optical and Internet connection between the network nodes, to deploy a complete testbed containing multiple network hosts and links to validate and verify a certain network algorithm or protocol would be very costly. Network simulators in these circumstances save vast amounts of money and time in accomplishing such a task. The simulation environment offers the creation of complex network topologies, a high degree of control and repeatable experiments, which in turn allows researchers to conduct experiments and confirm their results. In this paper, we described the design of the QKD network simulation module which was developed in the network simulator of version 3 (NS-3). The module supports simulation of the QKD network in an overlay mode or in a single TCP/IP mode. Therefore, it can be used to simulate other network technologies regardless of QKD.

  4. Reply to: Discrete-variable measurement-device-independent quantum key distribution suitable for metropolitan networks

    CERN Document Server

    Pirandola, Stefano; Spedalieri, Gaetana; Weedbrook, Christian; Braunstein, Samuel L; Lloyd, Seth; Gehring, Tobias; Jacobsen, Christian S; Andersen, Ulrik L

    2015-01-01

    In a recent comment, Xu et al. claimed that discrete-variable (DV) measurement-device-independent (MDI) quantum key distribution (QKD) would compete with its continuous-variable (CV) counterpart at metropolitan distances. Actually, Xu et al.'s analysis supports the opposite by showing that the experimental rate of our CV protocol (achieved with practical room-temperature devices) remains one order of magnitude higher than their purely-numerical and over-optimistic extrapolation for qubits, based on nearly-ideal parameters and cryogenic detectors (clearly unsuitable for the construction of a realistic, cheap and scalable high-rate network, e.g., including mobile devices). The experimental rate of our protocol (bits per relay use) is confirmed to be two-three orders of magnitude higher than the rate of any realistic simulation of practical DV-MDI-QKD over short-medium distances. Of course this does not mean that DV-MDI-QKD networks should not be investigated or built, but increasing their rate is a non-trivial ...

  5. On conclusive eavesdropping and measures of mutual information in quantum key distribution

    Science.gov (United States)

    Rastegin, Alexey E.

    2016-03-01

    We address the question of quantifying eavesdropper's information gain in an individual attack on systems of quantum key distribution. It is connected with the concept of conclusive eavesdropping introduced by Brandt. Using the BB84 protocol, we examine the problem of estimating a performance of conclusive entangling probe. The question of interest depends on the choice of a quantitative measure of eavesdropper's information about the error-free sifted bits. The Fuchs-Peres-Brandt probe realizes a very powerful individual attack on the BB84 scheme. In the usual formulation, Eve utilizes the Helstrom scheme in distinguishing between the two output probe states. In conclusive eavesdropping, the unambiguous discrimination is used. Comparing these two versions allows to demonstrate serious distinctions between widely used quantifiers of mutual information. In particular, the so-called Rényi mutual information does not seem to be a completely legitimate measure of an amount of mutual information. It is brightly emphasized with the example of conclusive eavesdropping.

  6. Realization of error correction and reconciliation of continuous quantum key distribution in detail

    Institute of Scientific and Technical Information of China (English)

    QIAN XuDong; HE GuangQiang; ZENG GuiHua

    2009-01-01

    The efficiency of reconciliation In the continuous key distribution is the main factor which limits the ratio of secret key distribution.However,the efficiency depends on the computational complexity of the algorithm.This paper optimizes the two main aspects of the reconciliation process of the continuous key distribution:the partition of Interval and the estimation of bit.We use Gaussian approximation to effectively speed up the convergence of algorithm.We design the estimation function as the estimator of the SEC (sliced error correction) algorithm.Therefore,we lower the computational complexity and simplify the core problem of the reconciliation algorithm.Thus we increase the efficiency of the reconciliation process in the continuous key distribution and then the ratio of the secret key distribution is also increased.

  7. Revealing of photon-number splitting attack on quantum key distribution system by photon-number resolving devices

    Science.gov (United States)

    Gaidash, A. A.; Egorov, V. I.; Gleim, A. V.

    2016-08-01

    Quantum cryptography allows distributing secure keys between two users so that any performed eavesdropping attempt would be immediately discovered. However, in practice an eavesdropper can obtain key information from multi-photon states when attenuated laser radiation is used as a source of quantum states. In order to prevent actions of an eavesdropper, it is generally suggested to implement special cryptographic protocols, like decoy states or SARG04. In this paper, we describe an alternative method based on monitoring photon number statistics after detection. We provide a useful rule of thumb to estimate approximate order of difference of expected distribution and distribution in case of attack. Formula for calculating a minimum value of total pulses or time-gaps to resolve attack is shown. Also formulas for actual fraction of raw key known to Eve were derived. This method can therefore be used with any system and even combining with mentioned special protocols.

  8. Attacking a practical quantum-key-distribution system with wavelength-dependent beam-splitter and multiwavelength sources

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hong-Wei [Key Laboratory of Quantum Information,University of Science and Technology of China, Hefei, 230026 (China); Zhengzhou Information Science and Technology Institute, Zhengzhou, 450004 (China); Wang, Shuang; Huang, Jing-Zheng; Chen, Wei; Yin, Zhen-Qiang; Li, Fang-Yi; Zhou, Zheng; Liu, Dong; Zhang, Yang; Guo, Guang-Can; Han, Zheng-Fu [Key Laboratory of Quantum Information,University of Science and Technology of China, Hefei, 230026 (China); Bao, Wan-Su [Zhengzhou Information Science and Technology Institute, Zhengzhou, 450004 (China)

    2011-12-15

    It is well known that the unconditional security of quantum-key distribution (QKD) can be guaranteed by quantum mechanics. However, practical QKD systems have some imperfections, which can be controlled by the eavesdropper to attack the secret key. With current experimental technology, a realistic beam splitter, made by fused biconical technology, has a wavelength-dependent property. Based on this fatal security loophole, we propose a wavelength-dependent attacking protocol, which can be applied to all practical QKD systems with passive state modulation. Moreover, we experimentally attack a practical polarization encoding QKD system to obtain all the secret key information at the cost of only increasing the quantum bit error rate from 1.3 to 1.4%.

  9. Controlling Continuous-Variable Quantum Key Distribution with Entanglement in the Middle Using Tunable Linear Optics Cloning Machines

    Science.gov (United States)

    Wu, Xiao Dong; Chen, Feng; Wu, Xiang Hua; Guo, Ying

    2016-11-01

    Continuous-variable quantum key distribution (CVQKD) can provide detection efficiency, as compared to discrete-variable quantum key distribution (DVQKD). In this paper, we demonstrate a controllable CVQKD with the entangled source in the middle, contrast to the traditional point-to-point CVQKD where the entanglement source is usually created by one honest party and the Gaussian noise added on the reference partner of the reconciliation is uncontrollable. In order to harmonize the additive noise that originates in the middle to resist the effect of malicious eavesdropper, we propose a controllable CVQKD protocol by performing a tunable linear optics cloning machine (LOCM) at one participant's side, say Alice. Simulation results show that we can achieve the optimal secret key rates by selecting the parameters of the tuned LOCM in the derived regions.

  10. Controlling Continuous-Variable Quantum Key Distribution with Entanglement in the Middle Using Tunable Linear Optics Cloning Machines

    Science.gov (United States)

    Wu, Xiao Dong; Chen, Feng; Wu, Xiang Hua; Guo, Ying

    2017-02-01

    Continuous-variable quantum key distribution (CVQKD) can provide detection efficiency, as compared to discrete-variable quantum key distribution (DVQKD). In this paper, we demonstrate a controllable CVQKD with the entangled source in the middle, contrast to the traditional point-to-point CVQKD where the entanglement source is usually created by one honest party and the Gaussian noise added on the reference partner of the reconciliation is uncontrollable. In order to harmonize the additive noise that originates in the middle to resist the effect of malicious eavesdropper, we propose a controllable CVQKD protocol by performing a tunable linear optics cloning machine (LOCM) at one participant's side, say Alice. Simulation results show that we can achieve the optimal secret key rates by selecting the parameters of the tuned LOCM in the derived regions.

  11. A simple proof that Gaussian attacks are optimal among collective attacks against continuous-variable quantum key distribution with a Gaussian modulation

    CERN Document Server

    Leverrier, Anthony

    2009-01-01

    In this paper, we give a simple proof of the fact that the optimal collective attacks against continous-variable quantum key distribution with a Gaussian modulation are Gaussian attacks. Our proof makes use of symmetry properties of the quantum key distribution protocol in phase-space.

  12. Impact of Raman Scattered Noise from Multiple Telecom Channels on Fiber-Optic Quantum Key Distribution Systems

    Science.gov (United States)

    2014-07-01

    In this paper we analyze the impact of the spontaneous Raman scattered noise generated from multiple optical classical channels on a single quantum key distribution channel, all within the telecom C-band. We experimentally measure the noise generated from up to 14 continuous lasers with different wavelengths using the dense wavelength division multiplexing (DWDM) standard, in both propagation directions in respect to the QKD channel, over different standard SMF-28 fiber lengths. We then simulate the expected secure key generation rate for a decoy-states-based system as a function of distance under the presence of simultaneous telecom traffic with different modulation techniques, and show a severe penalty growing with the number of classical channels present. Our results show that, for in-band coexistence, the telecom channels should be distributed as close as possible from the quantum channel to avoid the Raman noise peaks. Operation far from the zero dispersion wavelength of the fiber is also beneficial as it greatly reduces the generation of four-wave mixing inside the quantum channel. Furthermore, narrow spectral filtering on the quantum channels is required due to the harsh limitations of performing QKD under real telecom environments, with the quantum and several classical channels coexisting in the same ITU-T C-band.

  13. An optimized encoding method for secure key distribution by swapping quantum entanglement and its extension

    Science.gov (United States)

    Gao, Gan

    2015-08-01

    Song [Song D 2004 Phys. Rev. A 69 034301] first proposed two key distribution schemes with the symmetry feature. We find that, in the schemes, the private channels which Alice and Bob publicly announce the initial Bell state or the measurement result through are not needed in discovering keys, and Song’s encoding methods do not arrive at the optimization. Here, an optimized encoding method is given so that the efficiencies of Song’s schemes are improved by 7/3 times. Interestingly, this optimized encoding method can be extended to the key distribution scheme composed of generalized Bell states. Project supported by the National Natural Science Foundation of China (Grant No. 11205115), the Program for Academic Leader Reserve Candidates in Tongling University (Grant No. 2014tlxyxs30), and the 2014-year Program for Excellent Youth Talents in University of Anhui Province, China.

  14. Security of continuous-variable quantum key distribution: towards a de Finetti theorem for rotation symmetry in phase space

    Energy Technology Data Exchange (ETDEWEB)

    Leverrier, A [Institut Telecom/Telecom ParisTech, CNRS LTCI, 46, rue Barrault, 75634 Paris Cedex 13 (France); Karpov, E; Cerf, N J [Quantum Information and Communication, Ecole Polytechnique, CP 165/59, Universite Libre de Bruxelles, 50 avenue F D Roosevelt, B-1050 Brussels (Belgium); Grangier, P [Laboratoire Charles Fabry, Institut d' Optique, CNRS, Universite Paris-Sud, Campus Polytechnique, RD 128, 91127 Palaiseau Cedex (France)], E-mail: anthony.leverrier@enst.fr

    2009-11-15

    Proving the unconditional security of quantum key distribution (QKD) is a highly challenging task as one needs to determine the most efficient attack compatible with experimental data. This task is even more demanding for continuous-variable QKD as the Hilbert space where the protocol is described is infinite dimensional. A possible strategy to address this problem is to make an extensive use of the symmetries of the protocol. In this paper, we investigate a rotation symmetry in phase space that is particularly relevant to continuous-variable QKD, and explore the way towards a new quantum de Finetti theorem that would exploit this symmetry and provide a powerful tool to assess the security of continuous-variable protocols. As a first step, a single-party asymptotic version of this quantum de Finetti theorem in phase space is derived.

  15. Security of continuous-variable quantum key distribution: towards a de Finetti theorem for rotation symmetry in phase space

    Science.gov (United States)

    Leverrier, A.; Karpov, E.; Grangier, P.; Cerf, N. J.

    2009-11-01

    Proving the unconditional security of quantum key distribution (QKD) is a highly challenging task as one needs to determine the most efficient attack compatible with experimental data. This task is even more demanding for continuous-variable QKD as the Hilbert space where the protocol is described is infinite dimensional. A possible strategy to address this problem is to make an extensive use of the symmetries of the protocol. In this paper, we investigate a rotation symmetry in phase space that is particularly relevant to continuous-variable QKD, and explore the way towards a new quantum de Finetti theorem that would exploit this symmetry and provide a powerful tool to assess the security of continuous-variable protocols. As a first step, a single-party asymptotic version of this quantum de Finetti theorem in phase space is derived.

  16. Intercept-resend attack on six-state quantum key distribution over collective-rotation noise channels

    Institute of Scientific and Technical Information of China (English)

    Kevin Garapo; Mhlambululi Mafu; Francesco Petruccione

    2016-01-01

    We investigate the effect of collective-rotation noise on the security of the six-state quantum key distribution. We study the case where the eavesdropper, Eve, performs an intercept-resend attack on the quantum communication between Alice, the sender, and Bob, the receiver. We first derive the collective-rotation noise model for the six-state protocol and then parameterize the mutual information between Alice and Eve. We then derive quantum bit error rate for three intercept-resend attack scenarios. We observe that the six-state protocol is robust against intercept-resend attacks on collective rotation noise channels when the rotation angle is kept within certain bounds.

  17. Intercept-resend attack on six-state quantum key distribution over collective-rotation noise channels

    Science.gov (United States)

    Kevin, Garapo; Mhlambululi, Mafu; Francesco, Petruccione

    2016-07-01

    We investigate the effect of collective-rotation noise on the security of the six-state quantum key distribution. We study the case where the eavesdropper, Eve, performs an intercept-resend attack on the quantum communication between Alice, the sender, and Bob, the receiver. We first derive the collective-rotation noise model for the six-state protocol and then parameterize the mutual information between Alice and Eve. We then derive quantum bit error rate for three intercept-resend attack scenarios. We observe that the six-state protocol is robust against intercept-resend attacks on collective rotation noise channels when the rotation angle is kept within certain bounds. Project supported by the South African Research Chair Initiative of the Department of Science and Technology and National Research Foundation.

  18. Experimental implementation of non-Gaussian attacks on a continuous-variable quantum-key-distribution system.

    Science.gov (United States)

    Lodewyck, Jérôme; Debuisschert, Thierry; García-Patrón, Raúl; Tualle-Brouri, Rosa; Cerf, Nicolas J; Grangier, Philippe

    2007-01-19

    An intercept-resend attack on a continuous-variable quantum-key-distribution protocol is investigated experimentally. By varying the interception fraction, one can implement a family of attacks where the eavesdropper totally controls the channel parameters. In general, such attacks add excess noise in the channel, and may also result in non-Gaussian output distributions. We implement and characterize the measurements needed to detect these attacks, and evaluate experimentally the information rates available to the legitimate users and the eavesdropper. The results are consistent with the optimality of Gaussian attacks resulting from the security proofs.

  19. Correction of beam wander for a free-space quantum key distribution system operating in urban environment

    CERN Document Server

    Carrasco-Casado, Alberto; Fernandez, Veronica

    2014-01-01

    Free-space quantum key distribution links in urban environment have demanding operating needs, such as functioning in daylight and under atmospheric turbulence, which can dramatically impact their performance. Both effects are usually mitigated with a careful design of the field of view of the receiver. However, a trade-off is often required, since a narrow field of view improves background noise rejection but it is linked to an increase in turbulence-related losses. In this paper, we present a high-speed automatic tracking system to overcome these limitations. Both a reduction in the field-of-view to decrease the background noise and the mitigation of the losses caused by atmospheric turbulence are addressed. Two different designs are presented and discussed, along with technical considerations for the experimental implementation. Finally, preliminary experimental results of beam wander correction are used to estimate the potential improvement of both the quantum bit error rate and secret key rate of a free ...

  20. Efficient heralding of O-band passively spatial-multiplexed photons for noise-tolerant quantum key distribution.

    Science.gov (United States)

    Liu, Mao Tong; Lim, Han Chuen

    2014-09-22

    When implementing O-band quantum key distribution on optical fiber transmission lines carrying C-band data traffic, noise photons that arise from spontaneous Raman scattering or insufficient filtering of the classical data channels could cause the quantum bit-error rate to exceed the security threshold. In this case, a photon heralding scheme may be used to reject the uncorrelated noise photons in order to restore the quantum bit-error rate to a low level. However, the secure key rate would suffer unless one uses a heralded photon source with sufficiently high heralding rate and heralding efficiency. In this work we demonstrate a heralded photon source that has a heralding efficiency that is as high as 74.5%. One disadvantage of a typical heralded photon source is that the long deadtime of the heralding detector results in a significant drop in the heralding rate. To counter this problem, we propose a passively spatial-multiplexed configuration at the heralding arm. Using two heralding detectors in this configuration, we obtain an increase in the heralding rate by 37% and a corresponding increase in the heralded photon detection rate by 16%. We transmit the O-band photons over 10 km of noisy optical fiber to observe the relation between quantum bit-error rate and noise-degraded second-order correlation function of the transmitted photons. The effects of afterpulsing when we shorten the deadtime of the heralding detectors are also observed and discussed.

  1. Informatic analysis for hidden pulse attack exploiting spectral characteristics of optics in plug-and-play quantum key distribution system

    Science.gov (United States)

    Ko, Heasin; Lim, Kyongchun; Oh, Junsang; Rhee, June-Koo Kevin

    2016-10-01

    Quantum channel loopholes due to imperfect implementations of practical devices expose quantum key distribution (QKD) systems to potential eavesdropping attacks. Even though QKD systems are implemented with optical devices that are highly selective on spectral characteristics, information theory-based analysis about a pertinent attack strategy built with a reasonable framework exploiting it has never been clarified. This paper proposes a new type of trojan horse attack called hidden pulse attack that can be applied in a plug-and-play QKD system, using general and optimal attack strategies that can extract quantum information from phase-disturbed quantum states of eavesdropper's hidden pulses. It exploits spectral characteristics of a photodiode used in a plug-and-play QKD system in order to probe modulation states of photon qubits. We analyze the security performance of the decoy-state BB84 QKD system under the optimal hidden pulse attack model that shows enormous performance degradation in terms of both secret key rate and transmission distance.

  2. 一种量子密钥分配方案的研究%Research on Quantum Key Distribution Scheme

    Institute of Scientific and Technical Information of China (English)

    刘辛涛

    2013-01-01

      The quantum cryptography system has been proved to unconditionally secure based on Heisenberg uncertainty principle and quantum non-cloning law. Because single-photon are not easy to be generated and detected, and based on discrete variable it is difficult for the quantum key distribution to obtain high transmission rate of information. The paper puts forward that the two parts of communication get the same initial system parameters and state of chaotic systems from initial key;it can obtain the expanded key quantity. And the security of the scheme is discussed.%  利用海森堡测不准原理和量子不可克隆定律的量子密码体制被证明是无条件安全。由于产生和检测单光子比较困难,且基于离散变量的量子密钥分配难以获得高的信息传输速率,本文介绍了利用混沌系统的特性,通过初始密钥使通信双方设置相同的系统参数和初始状态,从而获得密钥量的扩展,并讨论了方案的安全性。

  3. Method and apparatus for free-space quantum key distribution in daylight

    Science.gov (United States)

    Hughes, Richard J.; Buttler, William T.; Lamoreaux, Steve K.; Morgan, George L.; Nordholt, Jane E.; Peterson, C. Glen; Kwiat, Paul G.

    2004-06-08

    A quantum cryptography apparatus securely generates a key to be used for secure transmission between a sender and a receiver connected by an atmospheric transmission link. A first laser outputs a timing bright light pulse; other lasers output polarized optical data pulses after having been enabled by a random bit generator. Output optics transmit output light from the lasers that is received by receiving optics. A first beam splitter receives light from the receiving optics, where a received timing bright light pulse is directed to a delay circuit for establishing a timing window for receiving light from the lasers and where an optical data pulse from one of the lasers has a probability of being either transmitted by the beam splitter or reflected by the beam splitter. A first polarizer receives transmitted optical data pulses to output one data bit value and a second polarizer receives reflected optical data pulses to output a second data bit value. A computer receives pulses representing receipt of a timing bright timing pulse and the first and second data bit values, where receipt of the first and second data bit values is indexed by the bright timing pulse.

  4. Robustness of the round-robin differential-phase-shift quantum-key-distribution protocol against source flaws

    Science.gov (United States)

    Mizutani, Akihiro; Imoto, Nobuyuki; Tamaki, Kiyoshi

    2015-12-01

    Recently, a new type of quantum key distribution, called the round-robin differential-phase-shift (RRDPS) protocol [T. Sasaki et al., Nature (London) 509, 475 (2014), 10.1038/nature13303], was proposed, where the security can be guaranteed without monitoring any statistics. In this Rapid Communication, we investigate source imperfections and side-channel attacks on the source of this protocol. We show that only three assumptions are needed for the security, and no detailed characterizations of the source or the side-channel attacks are needed. This high robustness is another striking advantage of the RRDPS protocol over other protocols.

  5. Experimental transmission of quantum digital signatures over 90  km of installed optical fiber using a differential phase shift quantum key distribution system.

    Science.gov (United States)

    Collins, Robert J; Amiri, Ryan; Fujiwara, Mikio; Honjo, Toshimori; Shimizu, Kaoru; Tamaki, Kiyoshi; Takeoka, Masahiro; Andersson, Erika; Buller, Gerald S; Sasaki, Masahide

    2016-11-01

    Quantum digital signatures (QDSs) apply quantum mechanics to the problem of guaranteeing message integrity and non-repudiation with information-theoretical security, which are complementary to the confidentiality realized by quantum key distribution (QKD). Previous experimental demonstrations have been limited to transmission distances of less than 5 km of optical fiber in a laboratory setting. Here we report, to the best of our knowledge, the first demonstration of QDSs over installed optical fiber, as well as the longest transmission link reported to date. This demonstration used a 90 km long differential phase shift QKD to achieve approximately one signed bit per second, an increase in the signature generation rate of several orders of magnitude over previous optical fiber demonstrations.

  6. Proof-of-principle test of coherent-state continuous variable quantum key distribution through turbulent atmosphere (Conference Presentation)

    Science.gov (United States)

    Derkach, Ivan D.; Peuntinger, Christian; Ruppert, László; Heim, Bettina; Gunthner, Kevin; Usenko, Vladyslav C.; Elser, Dominique; Marquardt, Christoph; Filip, Radim; Leuchs, Gerd

    2016-10-01

    Continuous-variable quantum key distribution is a practical application of quantum information theory that is aimed at generation of secret cryptographic key between two remote trusted parties and that uses multi-photon quantum states as carriers of key bits. Remote parties share the secret key via a quantum channel, that presumably is under control of of an eavesdropper, and which properties must be taken into account in the security analysis. Well-studied fiber-optical quantum channels commonly possess stable transmittance and low noise levels, while free-space channels represent a simpler, less demanding and more flexible alternative, but suffer from atmospheric effects such as turbulence that in particular causes a non-uniform transmittance distribution referred to as fading. Nonetheless free-space channels, providing an unobstructed line-of-sight, are more apt for short, mid-range and potentially long-range (using satellites) communication and will play an important role in the future development and implementation of QKD networks. It was previously theoretically shown that coherent-state CV QKD should be in principle possible to implement over a free-space fading channel, but strong transmittance fluctuations result in the significant modulation-dependent channel excess noise. In this regime the post-selection of highly transmitting sub-channels may be needed, which can even restore the security of the protocol in the strongly turbulent channels. We now report the first proof-of-principle experimental test of coherent state CV QKD protocol using different levels Gaussian modulation over a mid-range (1.6-kilometer long) free-space atmospheric quantum channel. The transmittance of the link was characterized using intensity measurements for the reference but channel estimation using the modulated coherent states was also studied. We consider security against Gaussian collective attacks, that were shown to be optimal against CV QKD protocols . We assumed a

  7. High-speed free-space quantum key distribution with automatic tracking for short-distance urban links

    CERN Document Server

    Carrasco-Casado, Alberto; Denisenko, Natalia; Fernandez, Veronica

    2015-01-01

    High-speed free-space quantum key distribution located in urban environment offers an interesting alternative to public key encryption - whose security strength is yet to be mathematically proven. To achieve this, three main objectives need to be accomplished: both the emitter and receiver have to be capable of transmitting and receiving at high speed - with the selection of the source's wavelength and detectors being of especial importance - the error rate needs to be kept at a minimum, especially that due to solar background radiation; and finally, a fast automatic tracking system, capable of compensating for atmospheric turbulence effects, is needed. Regarding to sky background and atmospheric turbulence, two different tracking techniques involving the beam wander compensation in the emitter or the receiver are presented and one of them is selected for our system, based on the link propagation distance and the atmospheric turbulence regime.

  8. Parameter optimization in biased decoy-state quantum key distribution with both source errors and statistical fluctuations

    Science.gov (United States)

    Zhu, Jian-Rong; Li, Jian; Zhang, Chun-Mei; Wang, Qin

    2017-10-01

    The decoy-state method has been widely used in commercial quantum key distribution (QKD) systems. In view of the practical decoy-state QKD with both source errors and statistical fluctuations, we propose a universal model of full parameter optimization in biased decoy-state QKD with phase-randomized sources. Besides, we adopt this model to carry out simulations of two widely used sources: weak coherent source (WCS) and heralded single-photon source (HSPS). Results show that full parameter optimization can significantly improve not only the secure transmission distance but also the final key generation rate. And when taking source errors and statistical fluctuations into account, the performance of decoy-state QKD using HSPS suffered less than that of decoy-state QKD using WCS.

  9. Enhancing the secure key rate in a quantum-key-distribution system using discrete-variable, high-dimensional, time-frequency states

    Science.gov (United States)

    Islam, Nurul T.; Cahall, Clinton; Aragoneses, Andrés.; Lim, Charles Ci Wen; Allman, Michael S.; Verma, Varun; Nam, Sae Woo; Kim, Jungsang; Gauthier, Daniel J.

    2016-10-01

    High-dimensional (dimension d > 2) quantum key distribution (QKD) protocols that encode information in the temporal degree of freedom promise to overcome some of the challenges of qubit-based (d = 2) QKD systems. In particular, the long recovery time of single-photon detectors and large channel noise at long distance both limit the rate at which a final secure key can be generated in a low-dimension QKD system. We propose and demonstrate a practical discrete-variable time-frequency protocol with d = 4 at a wavelength of 1550 nm, where the temporal states are secured by transmitting and detecting their dual states under Fourier transformation, known as the frequency-basis states, augmented by a decoy-state protocol. We show that the discrete temporal and frequency states can be generated and detected using commercially-available equipment with high timing and spectral efficiency. In our initial experiments, we only have access to detectors that have low efficiency (1%) at 1550 nm. Together with other component losses, our system is equivalent to a QKD system with ideal components and a 50-km-long optical-fiber quantum channel. We find that our system maintains a spectral visibility of over 99.0% with a quantum bit error rate of 2.3%, which is largely due to the finite extinction ratio of the intensity modulators used in the transmitter. The estimated secure key rate of this system is 7.7×104 KHz, which should improve drastically when we use detectors optimized for 1550 nm.

  10. Performance improvement of continuous-variable quantum key distribution with an entangled source in the middle via photon subtraction

    Science.gov (United States)

    Guo, Ying; Liao, Qin; Wang, Yijun; Huang, Duan; Huang, Peng; Zeng, Guihua

    2017-03-01

    A suitable photon-subtraction operation can be exploited to improve the maximal transmission of continuous-variable quantum key distribution (CVQKD) in point-to-point quantum communication. Unfortunately, the photon-subtraction operation faces solving the improvement transmission problem of practical quantum networks, where the entangled source is located in the third part, which may be controlled by a malicious eavesdropper, instead of in one of the trusted parts, controlled by Alice or Bob. In this paper, we show that a solution can come from using a non-Gaussian operation, in particular, the photon-subtraction operation, which provides a method to enhance the performance of entanglement-based (EB) CVQKD. Photon subtraction not only can lengthen the maximal transmission distance by increasing the signal-to-noise rate but also can be easily implemented with existing technologies. Security analysis shows that CVQKD with an entangled source in the middle (ESIM) from applying photon subtraction can well increase the secure transmission distance in both direct and reverse reconciliations of the EB-CVQKD scheme, even if the entangled source originates from an untrusted part. Moreover, it can defend against the inner-source attack, which is a specific attack by an untrusted entangled source in the framework of ESIM.

  11. Error tolerance of two-basis quantum key-distribution protocols using qudits and two-way classical communication

    CERN Document Server

    Nikolopoulos, G M; Ranade, K S; Alber, Gernot; Nikolopoulos, Georgios M.; Ranade, Kedar S.

    2006-01-01

    We investigate the error tolerance of quantum cryptographic protocols using $d$-level systems. In particular, we focus on prepare-and-measure schemes that use two mutually unbiased bases and a key-distillation procedure with two-way classical communication. For arbitrary quantum channels, we obtain a sufficient condition for secret-key distillation which, in the case of isotropic quantum channels, yields an analytic expression for the maximally tolerable error rate of the cryptographic protocols under consideration. The difference between the tolerable error rate and its theoretical upper bound tends slowly to zero for sufficiently large dimensions of the information carriers.

  12. 2.23 GHz gating InGaAs/InP single-photon avalanche diode for quantum key distribution

    CERN Document Server

    Zhang, Jun; Walenta, Nino; Barreiro, Claudio; Thew, Rob; Zbinden, Hugo

    2010-01-01

    We implement an InGaAs/InP single-photon avalanche diode (SPAD) for single-photon detection with the fastest gating frequency reported so far, of 2.23 GHz, which approaches the limit given by the bandwidth of the SPAD - 2.5 GHz. We propose a useful way to characterize the afterpulsing distribution for rapid gating that allows for easy comparison with conventional gating regimes. We compare the performance of this rapid gating scheme with free-running detector and superconducting single-photon detector (SSPD) for the coherent one-way quantum key distribution (QKD) protocol. The rapid gating system is well suited for both high-rate and long-distance QKD applications, in which Mbps key rates can be achieved for distances less than 40 km with 50 ns deadtime and the maximum distance is limited to ~190km with 5 $\\mu$s deadtime. These results illustrate that the afterpulsing is no longer a limiting factor for QKD.

  13. Hacking the Bell test using classical light in energy-time entanglement–based quantum key distribution

    Science.gov (United States)

    Jogenfors, Jonathan; Elhassan, Ashraf Mohamed; Ahrens, Johan; Bourennane, Mohamed; Larsson, Jan-Åke

    2015-01-01

    Photonic systems based on energy-time entanglement have been proposed to test local realism using the Bell inequality. A violation of this inequality normally also certifies security of device-independent quantum key distribution (QKD) so that an attacker cannot eavesdrop or control the system. We show how this security test can be circumvented in energy-time entangled systems when using standard avalanche photodetectors, allowing an attacker to compromise the system without leaving a trace. We reach Bell values up to 3.63 at 97.6% faked detector efficiency using tailored pulses of classical light, which exceeds even the quantum prediction. This is the first demonstration of a violation-faking source that gives both tunable violation and high faked detector efficiency. The implications are severe: the standard Clauser-Horne-Shimony-Holt inequality cannot be used to show device-independent security for energy-time entanglement setups based on Franson’s configuration. However, device-independent security can be reestablished, and we conclude by listing a number of improved tests and experimental setups that would protect against all current and future attacks of this type. PMID:26824059

  14. Hacking the Bell test using classical light in energy-time entanglement-based quantum key distribution.

    Science.gov (United States)

    Jogenfors, Jonathan; Elhassan, Ashraf Mohamed; Ahrens, Johan; Bourennane, Mohamed; Larsson, Jan-Åke

    2015-12-01

    Photonic systems based on energy-time entanglement have been proposed to test local realism using the Bell inequality. A violation of this inequality normally also certifies security of device-independent quantum key distribution (QKD) so that an attacker cannot eavesdrop or control the system. We show how this security test can be circumvented in energy-time entangled systems when using standard avalanche photodetectors, allowing an attacker to compromise the system without leaving a trace. We reach Bell values up to 3.63 at 97.6% faked detector efficiency using tailored pulses of classical light, which exceeds even the quantum prediction. This is the first demonstration of a violation-faking source that gives both tunable violation and high faked detector efficiency. The implications are severe: the standard Clauser-Horne-Shimony-Holt inequality cannot be used to show device-independent security for energy-time entanglement setups based on Franson's configuration. However, device-independent security can be reestablished, and we conclude by listing a number of improved tests and experimental setups that would protect against all current and future attacks of this type.

  15. Perfect random number generator is unnecessary for secure quantum key distribution

    CERN Document Server

    Wang, X B

    2004-01-01

    Game G: Clare passes a string s which is either from perfect random number generator R0 or from good imperfect number generator R1, with equal probability. Alice's information about whether it is from R0 or R1 is bounded by small value h. Alice use s as the input random numbers for QKD protocol with Bob. Suppose Eve may have very small information about the final key if s is from R0 and Eve has large information if s is from R1, then after the protocol, Alice announce the final key, Eve's information about whether s is from R0 or R1 is unreasonablly large, i.e., breaks the known bound, h. Explicit formulas are given in the article.

  16. High-Rate Field Demonstration of Large-Alphabet Quantum Key Distribution

    Science.gov (United States)

    2016-12-13

    allowing secure communication in the presence of an eaves- dropper. It commonly relies on detecting single photons, but the secret-key generation rates...such large-alphabet schemes can encode more secure information per detected photon, boosting secure communication rates, and also provide increased...energy encoding is appeal- ing for its compatibility with existing telecommunications infrastructure — which lowers the barriers to widespread adoption

  17. Trojan Horse Attack Free Fault-Tolerant Quantum Key Distribution Protocols Using GHZ States

    Science.gov (United States)

    Chang, Chih-Hung; Yang, Chun-Wei; Hwang, Tzonelih

    2016-09-01

    Recently, Yang and Hwang (Quantum Inf. Process. 13(3): 781-794, 19) proposed two fault-tolerant QKD protocols based on their proposed coding functions for resisting the collective noise, and their QKD protocols are free from Trojan horse attack without employing any specific detecting devices (e.g., photon number splitter (PNS) and wavelength filter). By using four-particle Greenberger-Horne-Zeilinger (GHZ) state and four-particle GHZ-like state in their proposed coding functions, Yang and Hwang's QKD protocols can resist each kind of the collective noise-collective-dephasing noise, collective-rotation noise. However, their proposed coding function can be improved by the utilization of three-particle GHZ state (three-particle GHZ-like state) instead of four-particle GHZ state (four-particle GHZ-like state) that will eventually reduce the consumption of the qubits. As a result, this study proposed the improved version of Yang and Hwang's coding functions to enhance the qubit efficiency of their schemes from 20 % to 22 %.

  18. Quantum Public-Key Cryptosystem

    Science.gov (United States)

    Luo, Ming-Xing; Chen, Xiu-Bo; Yun, Deng; Yang, Yi-Xian

    2012-03-01

    Quantum one-way functions play a fundamental role in cryptography because of its necessity for the secure encryption schemes taking into account the quantum computer. In this paper our purpose is to establish a theoretical framework for a candidate of the quantum one-way functions and quantum trapdoor functions based on one-parameter unitary groups. The dynamics of parameterized unitary groups ensure the one-wayness and quantum undistinguishability in different levels, and the physical feasibility are derived from the simultaneous approximation of its infinitesimal generators. Moreover, these special functions are used to construct new cryptosystems-the quantum public-key cryptosystems for encrypting both the classical and quantum information.

  19. Free-space measurement-device-independent quantum-key-distribution protocol using decoy states with orbital angular momentum

    Science.gov (United States)

    Wang, Le; Zhao, Sheng-Mei; Gong, Long-Yan; Cheng, Wei-Wen

    2015-12-01

    In this paper, we propose a measurement-device-independent quantum-key-distribution (MDI-QKD) protocol using orbital angular momentum (OAM) in free space links, named the OAM-MDI-QKD protocol. In the proposed protocol, the OAM states of photons, instead of polarization states, are used as the information carriers to avoid the reference frame alignment, the decoy-state is adopted to overcome the security loophole caused by the weak coherent pulse source, and the high efficient OAM-sorter is adopted as the measurement tool for Charlie to obtain the output OAM state. Here, Charlie may be an untrusted third party. The results show that the authorized users, Alice and Bob, could distill a secret key with Charlie’s successful measurements, and the key generation performance is slightly better than that of the polarization-based MDI-QKD protocol in the two-dimensional OAM cases. Simultaneously, Alice and Bob can reduce the number of flipping the bits in the secure key distillation. It is indicated that a higher key generation rate performance could be obtained by a high dimensional OAM-MDI-QKD protocol because of the unlimited degree of freedom on OAM states. Moreover, the results show that the key generation rate and the transmission distance will decrease as the growth of the strength of atmospheric turbulence (AT) and the link attenuation. In addition, the decoy states used in the proposed protocol can get a considerable good performance without the need for an ideal source. Project supported by the National Natural Science Foundation of China (Grant Nos. 61271238 and 61475075), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20123223110003), the Natural Science Research Foundation for Universities of Jiangsu Province of China (Grant No. 11KJA510002), the Open Research Fund of Key Laboratory of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, China (Grant No. NYKL2015011), and the

  20. Quantum walks public key cryptographic system

    OpenAIRE

    Vlachou, C; Rodrigues, J.; Mateus, P.; Paunković, N.; Souto, A.

    2016-01-01

    Quantum Cryptography is a rapidly developing field of research that benefits from the properties of Quantum Mechanics in performing cryptographic tasks. Quantum walks are a powerful model for quantum computation and very promising for quantum information processing. In this paper, we present a quantum public-key cryptographic system based on quantum walks. In particular, in the proposed protocol the public key is given by a quantum state generated by performing a quantum walk. We show that th...

  1. Free-Space Quantum Key Distribution with a High Generation Rate Potassium Titanyl Phosphate Waveguide Photon-Pair Source

    Science.gov (United States)

    Wilson, Jeffrey D.; Chaffee, Dalton W.; Wilson, Nathaniel C.; Lekki, John D.; Tokars, Roger P.; Pouch, John J.; Roberts, Tony D.; Battle, Philip; Floyd, Bertram M.; Lind, Alexander J.; hide

    2016-01-01

    A high generation rate photon-pair source using a dual element periodically-poled potassium titanyl phosphate (PP KTP) waveguide is described. The fully integrated photon-pair source consists of a 1064-nanometer pump diode laser, fiber-coupled to a dual element waveguide within which a pair of 1064-nanometer photons are up-converted to a single 532-nanometer photon in the first stage. In the second stage, the 532-nanometer photon is down-converted to an entangled photon-pair at 800 nanometer and 1600 nanometer which are fiber-coupled at the waveguide output. The photon-pair source features a high pair generation rate, a compact power-efficient package, and continuous wave (CW) or pulsed operation. This is a significant step towards the long term goal of developing sources for high-rate Quantum Key Distribution (QKD) to enable Earth-space secure communications. Characterization and test results are presented. Details and preliminary results of a laboratory free-space QKD experiment with the B92 protocol are also presented.

  2. A Narrow-Linewidth Atomic Line Filter for Free Space Quantum Key Distribution under Daytime Atmospheric Conditions

    Science.gov (United States)

    Brown, Justin; Woolf, David; Hensley, Joel

    2016-05-01

    Quantum key distribution can provide secure optical data links using the established BB84 protocol, though solar backgrounds severely limit the performance through free space. Several approaches to reduce the solar background include time-gating the photon signal, limiting the field of view through geometrical design of the optical system, and spectral rejection using interference filters. Despite optimization of these parameters, the solar background continues to dominate under daytime atmospheric conditions. We demonstrate an improved spectral filter by replacing the interference filter (Δν ~ 50 GHz) with an atomic line filter (Δν ~ 1 GHz) based on optical rotation of linearly polarized light through a warm Rb vapor. By controlling the magnetic field and the optical depth of the vapor, a spectrally narrow region can be transmitted between crossed polarizers. We find that the transmission is more complex than a single peak and evaluate peak transmission as well as a ratio of peak transmission to average transmission of the local spectrum. We compare filters containing a natural abundance of Rb with those containing isotopically pure 87 Rb and 85 Rb. A filter providing > 95 % transmission and Δν ~ 1.1 GHz is achieved.

  3. Quantum key distribution with delayed privacy amplification and its application to the security proof of a two-way deterministic protocol

    OpenAIRE

    Chau, HF; Fung, CHF; X.; Ma; Cai, QY

    2012-01-01

    Privacy amplification (PA) is an essential postprocessing step in quantum key distribution (QKD) for removing any information an eavesdropper may have on the final secret key. In this paper, we consider delaying PA of the final key after its use in one-time pad encryption and prove its security. We prove that the security and the key generation rate are not affected by delaying PA. Delaying PA has two applications: it serves as a tool for significantly simplifying the security proof of QKD wi...

  4. Quantum Message Distribution

    Institute of Scientific and Technical Information of China (English)

    LUO Ming-Xing; CHEN Xiu-Bo; DENG Yun; Yang Yi-Xian

    2013-01-01

    The semiquantum techniques have been explored recently to bridge the classical communications and the quantum communications.In this paper,we present one scheme to distribute the messages from one quantum participate to one weak quantum participate who can only measure the quantum states.It is proved to be robust by combining the classical coding encryption,quantum coding and other quantum techniques.

  5. Finite key analysis in quantum cryptography

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, T.

    2007-10-31

    In view of experimental realization of quantum key distribution schemes, the study of their efficiency becomes as important as the proof of their security. The latter is the subject of most of the theoretical work about quantum key distribution, and many important results such as the proof of unconditional security have been obtained. The efficiency and also the robustness of quantum key distribution protocols against noise can be measured by figures of merit such as the secret key rate (the fraction of input signals that make it into the key) and the threshold quantum bit error rate (the maximal error rate such that one can still create a secret key). It is important to determine these quantities because they tell us whether a certain quantum key distribution scheme can be used at all in a given situation and if so, how many secret key bits it can generate in a given time. However, these figures of merit are usually derived under the ''infinite key limit'' assumption, that is, one assumes that an infinite number of quantum states are send and that all sub-protocols of the scheme (in particular privacy amplification) are carried out on these infinitely large blocks. Such an assumption usually eases the analysis, but also leads to (potentially) too optimistic values for the quantities in question. In this thesis, we are explicitly avoiding the infinite key limit for the analysis of the privacy amplification step, which plays the most important role in a quantum key distribution scheme. We still assume that an optimal error correction code is applied and we do not take into account any statistical errors that might occur in the parameter estimation step. Renner and coworkers derived an explicit formula for the obtainable key rate in terms of Renyi entropies of the quantum states describing Alice's, Bob's, and Eve's systems. This results serves as a starting point for our analysis, and we derive an algorithm that efficiently computes

  6. Quantum walk public-key cryptographic system

    Science.gov (United States)

    Vlachou, C.; Rodrigues, J.; Mateus, P.; Paunković, N.; Souto, A.

    2015-12-01

    Quantum Cryptography is a rapidly developing field of research that benefits from the properties of Quantum Mechanics in performing cryptographic tasks. Quantum walks are a powerful model for quantum computation and very promising for quantum information processing. In this paper, we present a quantum public-key cryptographic system based on quantum walks. In particular, in the proposed protocol the public-key is given by a quantum state generated by performing a quantum walk. We show that the protocol is secure and analyze the complexity of public key generation and encryption/decryption procedures.

  7. Experimental study for Yuen-Kim protocol of quantum key distribution with unconditional secure Bell's Theorem Without Inequalities for two Maximally Entangled Particles

    CERN Document Server

    Hirota, O; Sohma, M; Li Ming Wei; Tang, Z L; Liao, C C

    2002-01-01

    In this report, we simulate practical feature of Yuen-Kim protocol for quantum key distribution with unconditional secure. In order to demonstrate them experimentally by intensity modulation/direct detection(IMDD) optical fiber communication system, we use simplified encoding scheme to guarantee security for key information(1 or 0). That is, pairwise M-ary intensity modulation scheme is employed. Furthermore, we give an experimental implementation of YK protocol based on IMDD. A proof of Bell's theorem without inequalities for two maximally entangled particles is proposed using the technique of quantum teleportation. It follows Hardy's arguments for a non-maximally entangled state with the help of two auxiliary particles without correlation. The present proof can be tested by measurements with 100% probability.

  8. High-rate quantum key distribution over 100 km using ultra-low-noise, 2-GHz sinusoidally gated InGaAs/InP avalanche photodiodes.

    Science.gov (United States)

    Namekata, N; Takesue, H; Honjo, T; Tokura, Y; Inoue, S

    2011-05-23

    We have demonstrated quantum key distribution (QKD) over 100 km using single-photon detectors based on InGaAs/InP avalanche photodiodes (APDs). We implemented the differential phase shift QKD (DPS-QKD) protocol with electrically cooled and 2-GHz sinusoidally gated APDs. The single-photon detector has a dark count probability of 2.8 × 10(-8) (55 counts per second) with a detection efficiency of 6 %, which enabled us to achieve 24 kbit/s secure key rate over 100 km of optical fiber. The DPS-QKD system offers better performances in a practical way than those achieved using superconducting single-photon detectors. Moreover, the distance that secure keys against the general individual attacks can be distributed has been extended to 160 km.

  9. Optimal experimental scheme for practical BB84 quantum key distribution protocol with weak coherent sources, noises, and high losses

    CERN Document Server

    Cai, Q

    2005-01-01

    It is the first scheme which allows the detection apparatus to achieve the photon number of arriving signals. Moreover, quantum bit error rates (QBERs) of multiphoton pulses can also be achieved precisely. Thus, our method is sensitive to the photon number splitting and resending (PNSR) attack, i.e., the eavesdropper (Eve) replaces one photon of the multiphoton pulse by a false one and forwards the pulse to the receiver, while the decoy-state protocols are not. In our scheme, Eve's whatever attacks will be limited by using the $improved$ decoy-state protocols and by checking the QBERs. Based on our multiphoton pulses detection apparatus, a quasi-single-photon protocol is presented to improve the security of the communication and the rate of the final key. We analyze that our scheme is optimal under today's technology. PACS: 03.67.Dd

  10. Key distribution in PKC through Quantas

    CERN Document Server

    Goel, Aditya

    2010-01-01

    Cryptography literally means "The art & science of secret writing & sending a message between two parties in such a way that its contents cannot be understood by someone other than the intended recipient". and Quantum word is related with "Light". Thus, Quantum Cryptography is a way of descripting any information in the form of quantum particles. There are no classical cryptographic systems which are perfectly secure. In contrast to Classical cryptography which depends upon Mathematics, Quantum Cryptography utilizes the concepts of Quantum Physics which provides us the security against the cleverest marauders of the present age. In the view of increasing need of Network and Information Security, we do require methods to overcome the Molecular Computing technologies (A future technology) and other techniques of the various codebrakers. Both the parts i.e. Quantum Key distribution and Information transference from Sender to Receiver are much efficient and secure. It is based upon BB84 protocol. It can b...

  11. Quantum key distribution over 120 km using ultrahigh purity single-photon source and superconducting single-photon detectors

    Science.gov (United States)

    Takemoto, Kazuya; Nambu, Yoshihiro; Miyazawa, Toshiyuki; Sakuma, Yoshiki; Yamamoto, Tsuyoshi; Yorozu, Shinichi; Arakawa, Yasuhiko

    2015-09-01

    Advances in single-photon sources (SPSs) and single-photon detectors (SPDs) promise unique applications in the field of quantum information technology. In this paper, we report long-distance quantum key distribution (QKD) by using state-of-the-art devices: a quantum-dot SPS (QD SPS) emitting a photon in the telecom band of 1.5 μm and a superconducting nanowire SPD (SNSPD). At the distance of 100 km, we obtained the maximal secure key rate of 27.6 bps without using decoy states, which is at least threefold larger than the rate obtained in the previously reported 50-km-long QKD experiment. We also succeeded in transmitting secure keys at the rate of 0.307 bps over 120 km. This is the longest QKD distance yet reported by using known true SPSs. The ultralow multiphoton emissions of our SPS and ultralow dark count of the SNSPD contributed to this result. The experimental results demonstrate the potential applicability of QD SPSs to practical telecom QKD networks.

  12. Experimentally feasible quantum-key-distribution scheme using qubit-like qudits and its comparison with existing qubit- and qudit-based protocols

    Science.gov (United States)

    Chau, H. F.; Wang, Qinan; Wong, Cardythy

    2017-02-01

    Recently, Chau [Phys. Rev. A 92, 062324 (2015), 10.1103/PhysRevA.92.062324] introduced an experimentally feasible qudit-based quantum-key-distribution (QKD) scheme. In that scheme, one bit of information is phase encoded in the prepared state in a 2n-dimensional Hilbert space in the form (|i > ±|j >) /√{2 } with n ≥2 . For each qudit prepared and measured in the same two-dimensional Hilbert subspace, one bit of raw secret key is obtained in the absence of transmission error. Here we show that by modifying the basis announcement procedure, the same experimental setup can generate n bits of raw key for each qudit prepared and measured in the same basis in the noiseless situation. The reason is that in addition to the phase information, each qudit also carries information on the Hilbert subspace used. The additional (n -1 ) bits of raw key comes from a clever utilization of this extra piece of information. We prove the unconditional security of this modified protocol and compare its performance with other existing provably secure qubit- and qudit-based protocols on market in the one-way classical communication setting. Interestingly, we find that for the case of n =2 , the secret key rate of this modified protocol using nondegenerate random quantum code to perform one-way entanglement distillation is equal to that of the six-state scheme.

  13. Development of the experimental setup for investigation of latching of superconducting single-photon detector caused by blinding attack on the quantum key distribution system

    Science.gov (United States)

    Elezov, M. S.; Ozhegov, R. V.; Goltsman, G. N.; Makarov, V.

    2017-01-01

    Recently bright-light control of the SSPD has been demonstrated. This attack employed a "backdoor" in the detector biasing scheme. Under bright-light illumination, SSPD becomes resistive and remains "latched" in the resistive state even when the light is switched off. While the SSPD is latched, Eve can simulate SSPD single-photon response by sending strong light pulses, thus deceiving Bob. We developed the experimental setup for investigation of a dependence on latching threshold of SSPD on optical pulse length and peak power. By knowing latching threshold it is possible to understand essential requirements for development countermeasures against blinding attack on quantum key distribution system with SSPDs.

  14. Anonymous-key quantum cryptography and unconditionally secure quantum bit commitment

    CERN Document Server

    Yuen, H P

    2000-01-01

    A new cryptographic tool, anonymous quantum key technique, is introduced that leads to unconditionally secure key distribution and encryption schemes that can be readily implemented experimentally in a realistic environment. If quantum memory is available, the technique would have many features of public-key cryptography; an identification protocol that does not require a shared secret key is provided as an illustration. The possibility is also indicated for obtaining unconditionally secure quantum bit commitment protocols with this technique.

  15. Multiparty Quantum Key Agreement Based on Quantum Search Algorithm.

    Science.gov (United States)

    Cao, Hao; Ma, Wenping

    2017-03-23

    Quantum key agreement is an important topic that the shared key must be negotiated equally by all participants, and any nontrivial subset of participants cannot fully determine the shared key. To date, the embed modes of subkey in all the previously proposed quantum key agreement protocols are based on either BB84 or entangled states. The research of the quantum key agreement protocol based on quantum search algorithms is still blank. In this paper, on the basis of investigating the properties of quantum search algorithms, we propose the first quantum key agreement protocol whose embed mode of subkey is based on a quantum search algorithm known as Grover's algorithm. A novel example of protocols with 5 - party is presented. The efficiency analysis shows that our protocol is prior to existing MQKA protocols. Furthermore it is secure against both external attack and internal attacks.

  16. TASQC Quantum Key Transfer Program

    Energy Technology Data Exchange (ETDEWEB)

    2016-11-04

    Securely transferring timing information in the electrical grid is a critical component of securing the nation's infrastructure from cyber attacks. One solution to this problem is to use quantum information to securely transfer the timing information across sites. This software provides such an infrastructure using a standard Java webserver that pulls the quantum information from associated hardware.

  17. Modified Novel Quantum Key Exchange using BB84 Algorithm

    Directory of Open Access Journals (Sweden)

    N.Vivek Chetty

    2013-06-01

    Full Text Available With the increasing number of eavesdroppers on communication channels, securing the reliability of digital communication has become a herculean task. For any communication and information exchange the most important step of securing the data is encryption and decryption (cryptography. The primary step involved in any efficient cryptographic system is Key Distribution. The paper deals with an efficient Key Distribution Technique based on Quantum Mechanics. The concept of Heisenberg’s Uncertainty Principle and quantum indeterminacy property are used to detect the presence of eavesdropper and secure the process of Key Distribution.

  18. Development of the experimental setup for investigation of latching of superconducting single-photon detector caused by blinding attack on the quantum key distribution system

    Directory of Open Access Journals (Sweden)

    Elezov M.S.

    2017-01-01

    Full Text Available Recently bright-light control of the SSPD has been demonstrated. This attack employed a “backdoor” in the detector biasing scheme. Under bright-light illumination, SSPD becomes resistive and remains “latched” in the resistive state even when the light is switched off. While the SSPD is latched, Eve can simulate SSPD single-photon response by sending strong light pulses, thus deceiving Bob. We developed the experimental setup for investigation of a dependence on latching threshold of SSPD on optical pulse length and peak power. By knowing latching threshold it is possible to understand essential requirements for development countermeasures against blinding attack on quantum key distribution system with SSPDs.

  19. Quantum attacks on public-key cryptosystems

    CERN Document Server

    Yan, Song Y

    2013-01-01

    The cryptosystems based on the Integer Factorization Problem (IFP), the Discrete Logarithm Problem (DLP) and the Elliptic Curve Discrete Logarithm Problem (ECDLP) are essentially the only three types of practical public-key cryptosystems in use. The security of these cryptosystems relies heavily on these three infeasible problems, as no polynomial-time algorithms exist for them so far. However, polynomial-time quantum algorithms for IFP, DLP and ECDLP do exist, provided that a practical quantum computer exists.Quantum Attacks on Public-Key Cryptosystems presemts almost all?known quantum comput

  20. Novel High-Speed Polarization Source for Decoy-State BB84 Quantum Key Distribution over Free Space and Satellite Links

    CERN Document Server

    Yan, Zhizhong; Bourgoin, Jean-Philippe; Higgins, Brendon L; Gigov, Nikolay; MacDonald, Allison; Hübel, Hannes; Jennewein, Thomas

    2012-01-01

    To implement the BB84 decoy-state quantum key distribution (QKD) protocol over a lossy ground-satellite quantum uplink requires a source that has high repetition rate of short laser pulses, long term stability, and no phase correlations between pulses. We present a new type of telecom optical polarization and amplitude modulator, based on a balanced Mach-Zehnder interferometer configuration, coupled to a polarization-preserving sum-frequency generation (SFG) optical setup, generating 532 nm photons with modulated polarization and amplitude states. The weak coherent pulses produced by SFG meet the challenging requirements for long range QKD, featuring a high clock rate of 76 MHz, pico-second pulse width, phase randomization, and 98% polarization visibility for all states. Successful QKD has been demonstrated using this apparatus with full system stability up to 160 minutes and channel losses as high 57 dB [Phys. Rev. A, Vol. 84, p.062326]. We present the design and simulation of the hardware through the Muelle...

  1. Quantum asymmetric cryptography with symmetric keys

    Science.gov (United States)

    Gao, Fei; Wen, Qiaoyan; Qin, Sujuan; Zhu, Fuchen

    2009-12-01

    Based on quantum encryption, we present a new idea for quantum public-key cryptography (QPKC) and construct a whole theoretical framework of a QPKC system. We show that the quantum-mechanical nature renders it feasible and reasonable to use symmetric keys in such a scheme, which is quite different from that in conventional public-key cryptography. The security of our scheme is analyzed and some features are discussed. Furthermore, the state-estimation attack to a prior QPKC scheme is demonstrated.

  2. Quantum asymmetric cryptography with symmetric keys

    OpenAIRE

    Gao, Fei; Wen, Qiao-Yan; Qin, Su-Juan; Zhu, Fu-Chen

    2008-01-01

    Based on quantum encryption, we present a new idea for quantum public-key cryptography (QPKC) and construct a whole theoretical framework of a QPKC system. We show that the quantum-mechanical nature renders it feasible and reasonable to use symmetric keys in such a scheme, which is quite different from that in conventional public-key cryptography. The security of our scheme is analyzed and some features are discussed. Furthermore, the state-estimation attack to a prior QPKC scheme is demonstr...

  3. Quantum asymmetric cryptography with symmetric keys

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on quantum encryption,we present a new idea for quantum public-key cryptography (QPKC) and construct a whole theoretical framework of a QPKC system. We show that the quantum-mechanical nature renders it feasible and reasonable to use symmetric keys in such a scheme,which is quite different from that in conventional public-key cryptography. The security of our scheme is analyzed and some features are discussed. Furthermore,the state-estimation attack to a prior QPKC scheme is demonstrated.

  4. Quantum asymmetric cryptography with symmetric keys

    Institute of Scientific and Technical Information of China (English)

    GAO Fei; WEN QiaoYan; QIN SuJuan; ZHU FuChen

    2009-01-01

    Based on quantum encryption, we present a new idea for quantum public-key cryptography (QPKC) and construct a whole theoretical framework of a QPKC system. We show that the quantum-mechanical nature renders it feasible and reasonable to use symmetric keys in such a scheme, which is quite different from that in conventional public-key cryptography. The security of our scheme is analyzed and some features are discussed. Furthermore, the state-estimation attack to a prior QPKC scheme is demonstrated.

  5. Experimental demonstration of quantum digital signatures over 43 dB channel loss using differential phase shift quantum key distribution.

    Science.gov (United States)

    Collins, Robert J; Amiri, Ryan; Fujiwara, Mikio; Honjo, Toshimori; Shimizu, Kaoru; Tamaki, Kiyoshi; Takeoka, Masahiro; Sasaki, Masahide; Andersson, Erika; Buller, Gerald S

    2017-06-12

    Ensuring the integrity and transferability of digital messages is an important challenge in modern communications. Although purely mathematical approaches exist, they usually rely on the computational complexity of certain functions, in which case there is no guarantee of long-term security. Alternatively, quantum digital signatures offer security guaranteed by the physical laws of quantum mechanics. Prior experimental demonstrations of quantum digital signatures in optical fiber have typically been limited to operation over short distances and/or operated in a laboratory environment. Here we report the experimental transmission of quantum digital signatures over channel losses of up to 42.8 ± 1.2 dB in a link comprised of 90 km of installed fiber with additional optical attenuation introduced to simulate longer distances. The channel loss of 42.8 ± 1.2 dB corresponds to an equivalent distance of 134.2 ± 3.8 km and this represents the longest effective distance and highest channel loss that quantum digital signatures have been shown to operate over to date. Our theoretical model indicates that this represents close to the maximum possible channel attenuation for this quantum digital signature protocol, defined as the loss for which the signal rate is comparable to the dark count rate of the detectors.

  6. Reverse Reconciliation of Quantum Gaussian Distributed Key%量子高斯密钥分发的逆向数据协调

    Institute of Scientific and Technical Information of China (English)

    郭大波; 刘纲; 张宁; 蔡虹

    2013-01-01

    The party Alice in a cryptograph system transmits coherent quantum signals to the party Bob,obtaining a series of correlated continuous Gaussian variables.The process to distill a binary key out of the correlated Gaussian variables that they share is called continuous-variable quantum key distribution (CVQKD).Reconciliation in CVQKD,i.e.,to correct differences between the correlated variables,is the key issue discussed in the paper.Based on both sliced error correction (SEC) protocol and multilevel coding/multistage decoding (MLC/MSD),reconciliation is implemented by LDPC code-based Slepian-Wolf CODEC.According to the proposed multilevel Tanner graph which depicts message transition of information,multistage iterative intrinsic and extrinsic information belief-propagation (LLR-BP) update formulae are derived.Three decoding modes of MSD are compared experimentally in convergence and performance.Simulation results show that the proposed algorithm can reconcile reliably 10000 continuous quantum variables with efficiency of 92.3 % when SNR of the channel is above 2.5 dB.%加密系统中Alice端通过光纤传送相干态量子信号给Bob端,得到的一系列相关的高斯连续变量,然后从中提取出二进制密钥,这一过程称作高斯连续变量量子密钥分发.其中的数据协调步骤,即对相关连续变量的错误校正,是本文的研究问题.本文在分层错误校正协议(SEC)和多电平编码/多级解码(MLC/MSD)协议的基础上,用基于LDPC码的Slepian-Wolf编译码器实现协调.根据连续变量的多级Tanner信息传输流图,本文推导了多级迭代的内信息和外信息置信传播(LLR-BP)更新公式,并用实验比较了MSD三种译码模式的收敛性质及性能.仿真结果表明该算法可在信道信噪比2.5 dB以上实现10000个连续变量序列的可靠协调,协调效率可达92.3%.

  7. A novel protocol for multiparty quantum key management

    Science.gov (United States)

    Xu, Gang; Chen, Xiu-Bo; Dou, Zhao; Yang, Yi-Xian; Li, Zongpeng

    2015-08-01

    Key management plays a fundamental role in the field of cryptography. In this paper, we propose a novel multiparty quantum key management (QKM) protocol. Departing from single-function quantum cryptography protocols, our protocol has a salient feature in that it accomplishes a complete QKM process. In this process, we can simultaneously realize the functions of key generation, key distribution and key backup by executing the protocol once. Meanwhile, for the first time, we propose the idea of multi-function QKM. Firstly, the secret key is randomly generated by managers via the quantum measurements in -level Bell basis. Then, through entanglement swapping, the secret key is successfully distributed to users. Under circumstances of urgent requirement, all managers can cooperate to recover the users' secret key, but neither of them can recover it unilaterally. Furthermore, this protocol is further generalized into the multi-manager and multi-user QKM scenario. It has clear advantages in the burgeoning area of quantum security group communication. In this system, all group members share the same group key, and group key management is the foundation of secure group communication and hence an important subject of study.

  8. Secure Communication Mechanism for Smart Distribution Network Integrated With Subcarrier Multiplexed Quantum Key Distribution%融合副载波复用量子密钥分配的智能配电网安全通信机制

    Institute of Scientific and Technical Information of China (English)

    马永红; 王秀玉; 崔丹丹

    2013-01-01

    Firstly, the risk of information security of the passive optical network (PON) based communication platform for smart distribution grid (SDG) is analyzed, and on this basis a technical thinking of integrating the high efficient subcarrier multiplexed quantum key distribution (SCM-QKD) with PON-SDG is proposed. Secondly, as for the three typical topological forms, namely the tree-form, hand-in-hand form and the chain form, the quantum bit-error-rate (QBER) for PON utilizing SCM-QKD technology and the parameters of quantum sifted-key-generation-rate are theoretically calculated. Calculation and analysis results show that under typical link length of PON and power-split-ratio parameters the SCM-QKD technology can meet the demand on information security of PON-SDG communication service. Finally, the method to share the quantum key distribution between the optical line terminal (OLT) in PON and the optical network unit (ONU) at the user side is given, and based on the key the concrete implementation of the two-way identity authentication and the generation process of the session key between OLT and ONU are given.%针对基于无源光网络(passive optical network,PON)的智能配电网(smart distribution grid,SDG)通信平台,首先深入分析其信息安全风险,在此基础上提出了将高效的副载波复用量子密钥分配(subcarrier multiplexed quantum key distribution,SCM-QKD)技术融合于PON-SDG的技术构想。针对树形、手拉手和链状3种典型拓扑,对采用SCM-QKD技术的 PON 的量子密钥差错率(quantum bit-error-rate , QBER)和筛选成钥率参数进行了理论计算。计算和分析结果表明,在典型的PON链路长度和分光比参数下,SCM-QKD技术能够满足SDG业务的信息安全需求。最后给出了融合SCM-QKD 技术实现 PON 中光线路终端(optical line terminal,OLT)和用户侧光网络单元(optical network unit, ONU)共享量子密钥的分配,以及基于该密钥实现 OLT

  9. Design considerations of high-performance InGaAs/InP single-photon avalanche diodes for quantum key distribution

    CERN Document Server

    Ma, Jian; Wang, Liu-Jun; Tong, Cun-Zhu; Jin, Ge; Zhang, Jun; Pan, Jian-Wei

    2016-01-01

    InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in practical applications requiring near-infrared photon counting such as quantum key distribution (QKD). Photon detection efficiency and dark count rate are the intrinsic parameters of InGaAs/InP SPADs, due to the fact that their performances cannot be improved using different quenching electronics given the same operation conditions. After modeling these parameters and developing a simulation platform for InGaAs/InP SPADs, we investigate the semiconductor structure design and optimization. The parameters of photon detection efficiency and dark count rate highly depend on the variables of absorption layer thickness, multiplication layer thickness, excess bias voltage and temperature. By evaluating the decoy-state QKD performance, the variables for SPAD design and operation can be globally optimized. Such optimization from the perspective of specific applications can provide an effective approach to design high-performance InGaAs/InP SPADs.

  10. Robust entanglement distribution via quantum network coding

    Science.gov (United States)

    Epping, Michael; Kampermann, Hermann; Bruß, Dagmar

    2016-10-01

    Many protocols of quantum information processing, like quantum key distribution or measurement-based quantum computation, ‘consume’ entangled quantum states during their execution. When participants are located at distant sites, these resource states need to be distributed. Due to transmission losses quantum repeater become necessary for large distances (e.g. ≳ 300 {{km}}). Here we generalize the concept of the graph state repeater to D-dimensional graph states and to repeaters that can perform basic measurement-based quantum computations, which we call quantum routers. This processing of data at intermediate network nodes is called quantum network coding. We describe how a scheme to distribute general two-colourable graph states via quantum routers with network coding can be constructed from classical linear network codes. The robustness of the distribution of graph states against outages of network nodes is analysed by establishing a link to stabilizer error correction codes. Furthermore we show, that for any stabilizer error correction code there exists a corresponding quantum network code with similar error correcting capabilities.

  11. Secret key generation via a modified quantum secret sharing protocol

    Science.gov (United States)

    Smith, A. M.; Evans, P. G.; Lawrie, B.; Legré, M.; Lougovski, P.; Ray, W.; Williams, B. P.; Qi, B.; Grice, W. P.

    2015-05-01

    We present and experimentally show a novel protocol for distributing secret information between two and only two parties in a N-party single-qubit Quantum Secret Sharing (QSS) system. We demonstrate this new algorithm with N = 3 active parties over ~6km of telecom. fiber. Our experimental device is based on the Clavis2 Quantum Key Distribution (QKD) system built by ID Quantique but is generalizable to any implementation. We show that any two out of the N parties can build secret keys based on partial information from each other and with collaboration from the remaining N - 2 parties. This algorithm allows for the creation of two-party secret keys were standard QSS does not and significantly reduces the number of resources needed to implement QKD on a highly connected network such as the electrical grid.

  12. Secret Key Generation via a Modified Quantum Secret Sharing Protocol

    Energy Technology Data Exchange (ETDEWEB)

    Smith IV, Amos M [ORNL; Evans, Philip G [ORNL; Lawrie, Benjamin J [ORNL; Legre, Matthieu [ID Quantique, Inc.; Lougovski, Pavel [ORNL; Ray, William R [ORNL; Williams, Brian P [ORNL; Qi, Bing [ORNL; Grice, Warren P [ORNL

    2015-01-01

    We present and experimentally show a novel protocol for distributing secret information between two and only two parties in a N-party single-qubit Quantum Secret Sharing (QSS) system. We demonstrate this new algorithm with N = 3 active parties over 6km of telecom. ber. Our experimental device is based on the Clavis2 Quantum Key Distribution (QKD) system built by ID Quantique but is generalizable to any implementation. We show that any two out of the N parties can build secret keys based on partial information from each other and with collaboration from the remaining N > 2 parties. This algorithm allows for the creation of two-party secret keys were standard QSS does not and signicantly reduces the number of resources needed to implement QKD on a highly connected network such as the electrical grid.

  13. Quantum coherence: Reciprocity and distribution

    Science.gov (United States)

    Kumar, Asutosh

    2017-03-01

    Quantum coherence is the outcome of the superposition principle. Recently, it has been theorized as a quantum resource, and is the premise of quantum correlations in multipartite systems. It is therefore interesting to study the coherence content and its distribution in a multipartite quantum system. In this work, we show analytically as well as numerically the reciprocity between coherence and mixedness of a quantum state. We find that this trade-off is a general feature in the sense that it is true for large spectra of measures of coherence and of mixedness. We also study the distribution of coherence in multipartite systems by looking at monogamy-type relation-which we refer to as additivity relation-between coherences of different parts of the system. We show that for the Dicke states, while the normalized measures of coherence violate the additivity relation, the unnormalized ones satisfy the same.

  14. Verifiable Quantum ( k, n)-threshold Secret Key Sharing

    Science.gov (United States)

    Yang, Yu-Guang; Teng, Yi-Wei; Chai, Hai-Ping; Wen, Qiao-Yan

    2011-03-01

    Based on Lagrange interpolation formula and the post-verification mechanism, we show how to construct a verifiable quantum ( k, n) threshold secret key sharing scheme. Compared with the previous secret sharing protocols, ours has the merits: (i) it can resist the fraud of the dealer who generates and distributes fake shares among the participants during the secret distribution phase; Most importantly, (ii) It can check the cheating of the dishonest participant who provides a false share during the secret reconstruction phase such that the authorized group cannot recover the correct secret.

  15. Tight finite-key analysis for quantum cryptography.

    Science.gov (United States)

    Tomamichel, Marco; Lim, Charles Ci Wen; Gisin, Nicolas; Renner, Renato

    2012-01-17

    Despite enormous theoretical and experimental progress in quantum cryptography, the security of most current implementations of quantum key distribution is still not rigorously established. One significant problem is that the security of the final key strongly depends on the number, M, of signals exchanged between the legitimate parties. Yet, existing security proofs are often only valid asymptotically, for unrealistically large values of M. Another challenge is that most security proofs are very sensitive to small differences between the physical devices used by the protocol and the theoretical model used to describe them. Here we show that these gaps between theory and experiment can be simultaneously overcome by using a recently developed proof technique based on the uncertainty relation for smooth entropies.

  16. Security Notions for Quantum Public-Key Cryptography

    OpenAIRE

    Koshiba, Takeshi

    2007-01-01

    It is well known that Shor's quantum algorithm for integer factorization can break down the RSA public-key cryptosystem, which is widely used in many cryptographic applications. Thus, public-key cryptosystems in the quantum computational setting are longed for cryptology. In order to define the security notions of public-key cryptosystems, we have to model the power of the sender, receiver, adversary and channel. While we may consider a setting where quantum computers are available only to ad...

  17. Direct Use of Secret Key in Quantum Cryptography

    CERN Document Server

    Yuen, H P

    2006-01-01

    For single-photon quantum key generation between two users, it is shown that for collective attacks the use of a shared secret key extended via a pseudo-random number generator may simultaneously enhance the security and efficiency of the cryptosystem. This effect arises from the intrinsic performance difference between quantum detectors with versus without knowledge of the key, a purely quantum effect and a new principle for key generation. No intrusion level estimation is needed and the method is directly applicable to realistic systems involving multi-photon sources, losses, noises, and finite-sequence statistical fluctuations. It is suggested that such use of a secret key be routinely incorporated in a quantum key generation system. The use of a secret key in quantum direct encryption is also indicated.

  18. Nonorthogonal decoy-state quantum key distribution based on coherent-state sup erp ositions%基于相干叠加态的非正交编码诱骗态量子密钥分发∗

    Institute of Scientific and Technical Information of China (English)

    孙伟; 尹华磊; 孙祥祥; 陈腾云

    2016-01-01

    the case of a limited number of decoy states by using matlab. The parameters are given according to the GYS experiment too. When the N is 1010, the safety transmission distance achieves 144 km;when the N is 109, the safety transmission distance achieves 139 km;when the N is 108, the safety transmission distance achieves 125.9 km. In this paper, we propose the use of CSS as the light source. Combining SARG04 agreements and decoy state, the scheme has the following advantages: first, the scheme which combines SARG04 agreements and decoy state method can effectively resist PNS; second, nonorthogonal decoy-state quantum key distribution based on coherent-state super-positions has a longer safety transmission distance and higher secure key generation rate than nonorthogonal decoy-state quantum key distribution based on weak coherent pulse and nonorthogonal decoy-state quantum key distribution based on conditionally prepared down-conversion source;third, nonorthogonal decoy-state quantum key distribution based on coherent-state superpositions is easier to prepare, which just needs one decoy state, than other schemes that require several decoy states. Obviously, our scheme can enhance the performance of quantum key distribution. Nonorthogonal decoy-state quantum key distribution based on coherent-state superpositions will have a very good application with the further development of preparation technology of CSS.

  19. Security Notions for Quantum Public-Key Cryptography

    CERN Document Server

    Koshiba, T

    2007-01-01

    It is well known that Shor's quantum algorithm for integer factorization can break down the RSA public-key cryptosystem, which is widely used in many cryptographic applications. Thus, public-key cryptosystems in the quantum computational setting are longed for cryptology. In order to define the security notions of public-key cryptosystems, we have to model the power of the sender, receiver, adversary and channel. While we may consider a setting where quantum computers are available only to adversaries, we generally discuss what are the right security notions for (quantum) public-key cryptosystems in the quantum computational setting. Moreover, we consider the security of quantum public-key cryptosystems known so far.

  20. Practical Quantum Cryptography: the Q-KeyMaker

    CERN Document Server

    Bovino, Fabio A

    2011-01-01

    In the next years the data transmission connections will constitute one of the principal tools of communication among cities, enterprises and public administration. With their enhanced connectivity, the systems and nets of information are now exposed to an increased vulnerability and new safety problems are emerging. Insofar Quantum Key Distribution (QKD) has matured to real world applications and can enhance the safety of the communication nets. In this paper we present the QKD network designed and implemented by Selex-SI and we give an overview of the obtained results.

  1. Majorization of quantum polarization distributions

    CERN Document Server

    Luis, Alfredo

    2016-01-01

    Majorization provides a rather powerful partial-order classification of probability distributions depending only on the spread of the statistics, and not on the actual numerical values of the variable being described. We propose to apply majorization as a meta-measure of quantum polarization fluctuations, this is to say of the degree of polarization. We compare the polarization fluctuations of the most relevant classes of quantum and classical-like states. In particular we test the Lieb's conjecture regarding classical-like states as the most polarized and a complementary conjecture that the most unpolarized pure states are the most nonclassical.

  2. Wigner distributions in quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Ercolessi, E; Marmo, G; Morandi, G; Mukunda, N [Physics Department, University of Bologna, INFN and CNISM. 46 v.Irnerio. I-40126, Bologna (Italy); Dip. di Scienze Fisiche. University di Napoli ' Federico II' and INFN. v.Cinzia. I-80100 Naples (Italy); Physics Department, University of Bologna, INFN and CNISM. 6/2 v.le Berti Pichat. I-40127, Bologna (Italy); Centre for High-Energy Physics. Indian Institute of Science. Bamgalore 560012 (India)

    2007-11-15

    The Weyl-Wigner description of quantum mechanical operators and states in classical phase-space language is well known for Cartesian systems. We describe a new approach based on ideas of Dirac which leads to the same results but with interesting additional insights. A way to set up Wigner distributions in an interesting non-Cartesian case, when the configuration space is a compact connected Lie group, is outlined. Both these methods are adapted to quantum systems with finite-dimensional Hilbert spaces, and the results are contrasted.

  3. A public-key cryptosystem for quantum message transmission

    Science.gov (United States)

    Yang, Li

    2005-01-01

    We present a quantum public-key cryptography protocol for quantum message transmission. The private key of this protocol includes three classical matrices: a generator matrix of a Goppa code, an invertible matrix and a permutation matrix. The public key is product of these three matrices. The encryption and decryption algorithms are merely quantum computations related with the transformations between bases of the quantum registers. The security of this protocol is based on the hypothesis that there is no effective algorithm of NP-complete problem.

  4. Reparable Key Distribution Protocols for Internet Environments

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    It has claimed that any practical way to achieve perfect reparability for key distribution protocol (KDP) could only be futile. Fortunately, this paper presents reparable KDPs for internet environments with the use of the concept of timestamps.

  5. Macro-micro entanglement in optical system and its application in quantum key distribution%光学体系宏观-微观纠缠及其在量子密钥分配中的应用

    Institute of Scientific and Technical Information of China (English)

    安雪碧; 银振强; 韩正甫

    2015-01-01

    amplification and de-amplification process. Inspired by this thought, two groups create and verify mac-micro entanglement between one photon and 108 photons. What they used to amplify the micro states is the displacement operation in phase space, which can be realized by combining a single photon state and a coherent state with a highly asymmetric beam splitter. Because the entanglement is a precondition for a secure quantum key distribution, and the macro-micro entanglement has more photons than the traditional micro entanglement, we will discuss the possibility whether the macro-micro entanglement can be used in quantum key distribution and improve the distance of the quantum key distribution. We point out that the mac-micro entanglement and the binary reverse reconciliation continuous variable quantum key distribution protocol are the same in physics essence. We will introduce a quantum key distribution scheme with two phase entangled coherent states. Although the security proof of the scheme is not complete, it still provides us with the possibility to use the macro-micro entanglement in quantum key distribution.

  6. Entanglement distribution in quantum networks

    Energy Technology Data Exchange (ETDEWEB)

    Perseguers, Sebastien

    2010-04-15

    This Thesis contributes to the theory of entanglement distribution in quantum networks, analyzing the generation of long-distance entanglement in particular. We consider that neighboring stations share one partially entangled pair of qubits, which emphasizes the difficulty of creating remote entanglement in realistic settings. The task is then to design local quantum operations at the stations, such that the entanglement present in the links of the whole network gets concentrated between few parties only, regardless of their spatial arrangement. First, we study quantum networks with a two-dimensional lattice structure, where quantum connections between the stations (nodes) are described by non-maximally entangled pure states (links). We show that the generation of a perfectly entangled pair of qubits over an arbitrarily long distance is possible if the initial entanglement of the links is larger than a threshold. This critical value highly depends on the geometry of the lattice, in particular on the connectivity of the nodes, and is related to a classical percolation problem. We then develop a genuine quantum strategy based on multipartite entanglement, improving both the threshold and the success probability of the generation of long-distance entanglement. Second, we consider a mixed-state definition of the connections of the quantum networks. This formalism is well-adapted for a more realistic description of systems in which noise (random errors) inevitably occurs. New techniques are required to create remote entanglement in this setting, and we show how to locally extract and globally process some error syndromes in order to create useful long-distance quantum correlations. Finally, we turn to networks that have a complex topology, which is the case for most real-world communication networks such as the Internet for instance. Besides many other characteristics, these systems have in common the small-world feature, stating that any two nodes are separated by a

  7. LDPC码在量子密钥分配多维协商算法中的应用%The Application of LDPC Codes in the Multidimensional Reconciliation of Quantum Key Distribution

    Institute of Scientific and Technical Information of China (English)

    林毅; 何广强; 曾贵华

    2013-01-01

    密钥协商是量子密钥分配(QKD)的重要环节,影响着QKD的密钥率和安全距离.作为一种低信噪比时较为高效的密钥协商方案,多维协商算法被很好地应用在高斯调制连续变量QKD中,延长了通信距离.本文研究了二进制LDPC码在多维协商算法中的应用方案,进而扩展到多进制LDPC码.仿真表明,相比二进制LDPC码,利用多进制LDPC码能够使多维协商性能获得明显增益.%Secret key reconciliation is an important phase in quantum key distribution (QKD),which influences both the secret key rate and the speed of QKD.As an efficient reconciliation scheme under low SNR regime,multidimensional reconciliation scheme has been well adapted to the Gaussian-modulated continuous-variable QKD protocol and has extended the communication distance.We first investigate the application of binary LDPC Codes in the multidimensional reconciliation,and then extend to non-binary LDPC Codes.In the numerical simulations,we observe an obvious performace gain with our settings by using non-binary LDPC Codes,compared to binary LDPC Codes.

  8. Engineering trade studies for a quantum key distribution system over a 30  km free-space maritime channel.

    Science.gov (United States)

    Gariano, John; Neifeld, Mark; Djordjevic, Ivan

    2017-01-20

    Here, we present the engineering trade studies of a free-space optical communication system operating over a 30 km maritime channel for the months of January and July. The system under study follows the BB84 protocol with the following assumptions: a weak coherent source is used, Eve is performing the intercept resend attack and photon number splitting attack, prior knowledge of Eve's location is known, and Eve is allowed to know a small percentage of the final key. In this system, we examine the effect of changing several parameters in the following areas: the implementation of the BB84 protocol over the public channel, the technology in the receiver, and our assumptions about Eve. For each parameter, we examine how different values impact the secure key rate for a constant brightness. Additionally, we will optimize the brightness of the source for each parameter to study the improvement in the secure key rate.

  9. One-way quantum identity authentication based on public key

    Institute of Scientific and Technical Information of China (English)

    ZHANG XingLan

    2009-01-01

    Based on public key, a quantum identity authenticated (QIA) system is proposed without quantum entanglement. The public key acts as the authentication key of a user. Following the idea of the classical public key infrastructure (PKI), a trusted center of authentication (CA) is involved. The user selects a public key randomly and CA generates a private key for the user according to his public key. When it is necessary to perform QIA, the user sends a sequence of single photons encoded with its private key and a message to CA. According to the corresponding secret key kept by CA, CA performs the unitary operations on the single photon sequence. At last, the receiver can judge whether the user is an impersonator.

  10. Analysis of Information Leakage in Quantum Key Agreement

    Institute of Scientific and Technical Information of China (English)

    LIU Sheng-li; ZHENG Dong; CHENG Ke-fei

    2006-01-01

    Quantum key agreement is one of the approaches to unconditional security. Since 1980's, different protocols for quantum key agreement have been proposed and analyzed. A new quantum key agreement protocol was presented in 2004, and a detailed analysis to the protocol was given. The possible game played between legitimate users and the enemy was described:sitting in the middle, an adversary can play a "man-in-the-middle" attack to cheat the sender and receiver. The information leaked to the adversary is essential to the length of the final quantum secret key. It was shown how to determine the amount of information leaked to the enemy and the amount of uncertainty between the legitimate sender and receiver.

  11. Public-key cryptography based on bounded quantum reference frames

    OpenAIRE

    Ioannou, Lawrence M.; Mosca, Michele

    2009-01-01

    We demonstrate that the framework of bounded quantum reference frames has application to building quantum-public-key cryptographic protocols and proving their security. Thus, the framework we introduce can be seen as a public-key analogue of the framework of Bartlett et al. (Phys. Rev. A 70, 032307), where a private shared reference frame is shown to have cryptographic application. The protocol we present in this paper is an identification scheme, which, like a digital signature scheme, is a ...

  12. Efficient quantum secure communication with a publicly known key

    Institute of Scientific and Technical Information of China (English)

    Li Chun-Yan; Li Xi-Han; Deng Fu-Guo; Zhou Hong-Yu

    2008-01-01

    This paper presents a simple way for an eavesdropper to eavesdrop freely the secret message in the experimental realization of quantum communication protocol proposed by Beige et al (2002 Acta Phys. Pol. A 101 357). Moreover, it introduces an efficient quantum secure communication protocol based on a publicly known key with decoy photons and two biased bases by modifying the original protocol. The total efficiency of this new protocol is double that of the original one. With a low noise quantum channel, this protocol can be used for transmitting a secret message. At present, this protocol is good for generating a private key efficiently.

  13. Key Predistribution Schemes for Distributed Sensor Networks

    CERN Document Server

    Bose, Mausumi; Mukerjee, Rahul

    2011-01-01

    Key predistribution schemes for distributed sensor networks have received significant attention in the recent literature. In this paper we propose a new construction method for these schemes based on combinations of duals of standard block designs. Our method is a broad spectrum one which works for any intersection threshold. By varying the initial designs, we can generate various schemes and this makes the method quite flexible. We also obtain explicit algebraic expressions for the metrics for local connectivity and resiliency. These schemes are quite efficient with regard to connectivity and resiliency and at the same time they allow a straightforward shared-key discovery.

  14. Quantum sealed-bid auction using a modified scheme for multiparty circular quantum key agreement

    Science.gov (United States)

    Sharma, Rishi Dutt; Thapliyal, Kishore; Pathak, Anirban

    2017-07-01

    A feasible, secure and collusion attack-free quantum sealed-bid auction protocol is proposed using a modified scheme for multiparty circular quantum key agreement. In the proposed protocol, the set of all ( n) bidders is grouped into l subsets (sub-circles) in such a way that only the initiator (who prepares the quantum state to be distributed for a particular round of communication and acts as the receiver in that round) is a member of all the subsets (sub-circles) prepared for a particular round, while any other bidder is part of only a single subset. All n bidders and auctioneer initiate one round of communication, and each of them prepares l copies of a ( r-1) -partite entangled state (one for each sub-circle), where r=n/l+1. The efficiency and security of the proposed protocol are critically analyzed. It is shown that the proposed protocol is free from the collusion attacks that are possible on the existing schemes of quantum sealed-bid auction. Further, it is observed that the security against collusion attack increases with the increase in l, but that reduces the complexity (number of entangled qubits in each entangled state) of the entangled states to be used and that makes the scheme scalable and implementable with the available technologies. The additional security and scalability are shown to arise due to the use of a circular structure in place of a complete-graph or tree-type structure used earlier.

  15. Multi-Seed Key Distribution Scheme Test

    Institute of Scientific and Technical Information of China (English)

    XIE Yumin; SHI Feng; MING Yang; Muhammad Kamran; YANG Xiaoxu

    2006-01-01

    The key problem of securing multicast is to generate, distribute and update Session Encryption Key(SEK). Polynomial expansion with multi-seed(MPE) scheme is an approach which is based on Polynomial expansion(PE) scheme and overcomes PE's shortage. Its operation is demonstrated by using multi-seed, the group member is partitioned to many subgroups. While updating the SEK, computation is needed only in one of subgroups, the other of them will use the computation history to update their SEK. The key problems to design a MPE scheme application includes to find a feasible one way function as well as to generate a Strict Prime Number(SPN). Those technologies with multi-seed and computation history concepts make MPE as a good choice in practical applications. A prototype test system is designed and solutions of all above mentioned problems are included in this proposed paper.

  16. On the complexity of search for keys in quantum cryptography

    Science.gov (United States)

    Molotkov, S. N.

    2016-03-01

    The trace distance is used as a security criterion in proofs of security of keys in quantum cryptography. Some authors doubted that this criterion can be reduced to criteria used in classical cryptography. The following question has been answered in this work. Let a quantum cryptography system provide an ɛ-secure key such that ½‖ρ XE - ρ U ⊗ ρ E ‖1 cryptography. Bounds for the minimum and maximum numbers of search steps for the determination of the actual key have been presented.

  17. Quantum Encryption Minimising Key Leakage under Known Plaintext Attacks

    DEFF Research Database (Denmark)

    Pedersen, Thomas Brochmann

    2006-01-01

    In this dissertation we show how, by using a quantum channel, we can get more unconditionally secret communication with a symmetric key under known plaintext attacks. In unconditionally secret encryption schemes the key is necessarily an expensive resource since it cannot safely be reused for more...... than one encryption. In classical cryptography an amount of key comparable to the amount of message is leaked at each encryption. Many assumptions and models have been proposed which allows to safely encrypt more message with the same amount of key. Most of the proposed models are, however, either...... unrealistic, or rely on unproven assumptions. In this dissertation we encrypt messages by using properties of quantum mechanics. This model is based on our current understanding of nature, and is therefore a realistic model for encryption. It has previously been shown that the quantum mechanical model allows...

  18. Arbitrated quantum signature scheme based on reusable key

    Science.gov (United States)

    Yu, ChaoHua; Guo, GongDe; Lin, Song

    2014-11-01

    An arbitrated quantum signature scheme without using entangled states is proposed. In the scheme, by employing a classical hash function and random numbers, the secret keys of signer and receiver can be reused. It is shown that the proposed scheme is secure against several well-known attacks. Specifically, it can stand against the receiver's disavowal attack. Moreover, compared with previous relevant arbitrated quantum signature schemes, the scheme proposed has the advantage of less transmission complexity.

  19. Arbitrated quantum signature scheme based on reusable key

    Institute of Scientific and Technical Information of China (English)

    YU ChaoHua; GUO GongDe; LIN Song

    2014-01-01

    An arbitrated quantum signature scheme without using entangled states is proposed.In the scheme,by employing a classical hash function and random numbers,the secret keys of signer and receiver can be reused.It is shown that the proposed scheme is secure against several well-known attacks.Specifically,it can stand against the receiver's disavowal attack.Moreover,compared with previous relevant arbitrated quantum signature schemes,the scheme proposed has the advantage of less transmission complexity.

  20. Secret key rates for an encoded quantum repeater

    Science.gov (United States)

    Bratzik, Sylvia; Kampermann, Hermann; Bruß, Dagmar

    2014-03-01

    We investigate secret key rates for the quantum repeater using encoding [L. Jiang et al., Phys. Rev. A 79, 032325 (2009), 10.1103/PhysRevA.79.032325] and compare them to the standard repeater scheme by Briegel, Dür, Cirac, and Zoller. The former scheme has the advantage of a minimal consumption of classical communication. We analyze the trade-off in the secret key rate between the communication time and the required resources. For this purpose we introduce an error model for the repeater using encoding which allows for input Bell states with a fidelity smaller than one, in contrast to the model given by L. Jiang et al. [Phys. Rev. A 79, 032325 (2009), 10.1103/PhysRevA.79.032325]. We show that one can correct additional errors in the encoded connection procedure of this repeater and develop a suitable decoding algorithm. Furthermore, we derive the rate of producing entangled pairs for the quantum repeater using encoding and give the minimal parameter values (gate quality and initial fidelity) for establishing a nonzero secret key. We find that the generic quantum repeater is optimal regarding the secret key rate per memory per second and show that the encoded quantum repeater using the simple three-qubit repetition code can even have an advantage with respect to the resources compared to other recent quantum repeater schemes with encoding.

  1. Bit-oriented quantum public-key encryption based on quantum perfect encryption

    Science.gov (United States)

    Wu, Chenmiao; Yang, Li

    2016-08-01

    A bit-oriented quantum public-key encryption scheme is presented. We use Boolean functions as private-key and randomly changed pairs of quantum state and classical string as public-keys. Following the concept of quantum perfect encryption, we prepare the public-key with Hadamard transformation and Pauli transformation. The quantum part of public-keys is various with different classical strings. In contrast to the typical classical public-key scheme, one private-key in our scheme corresponds to an exponential number of public-keys. We investigate attack to the private-key and prove that the public-key is a totally mixed state. So the adversary cannot acquire any information about private-key from measurement of the public-key. Then, the attack to encryption is analyzed. Since the trace distance between two different ciphertexts is zero, the adversary cannot distinguish between the two ciphertext states and also obtains nothing about plaintext and private-key. Thus, we have the conclusion that the proposed scheme is information-theoretically secure under an attack of the private-key and encryption.

  2. Post-Quantum Key Exchange -- A New Hope

    NARCIS (Netherlands)

    Alkin, E.; Ducas, L.; Pöppelmann, T.; Schwabe, P.

    2016-01-01

    At IEEE Security & Privacy 2015, Bos, Costello, Naehrig, and Stebila proposed an instantiation of Peikert's ring-learning-with-errors--based (Ring-LWE) key-exchange protocol (PQCrypto 2014), together with an implementation integrated into OpenSSL, with the affirmed goal of providing post-quantum sec

  3. Quantum cryptography using coherent states: Randomized encryption and key generation

    Science.gov (United States)

    Corndorf, Eric

    With the advent of the global optical-telecommunications infrastructure, an increasing number of individuals, companies, and agencies communicate information with one another over public networks or physically-insecure private networks. While the majority of the traffic flowing through these networks requires little or no assurance of secrecy, the same cannot be said for certain communications between banks, between government agencies, within the military, and between corporations. In these arenas, the need to specify some level of secrecy in communications is a high priority. While the current approaches to securing sensitive information (namely the public-key-cryptography infrastructure and deterministic private-key ciphers like AES and 3DES) seem to be cryptographically strong based on empirical evidence, there exist no mathematical proofs of secrecy for any widely deployed cryptosystem. As an example, the ubiquitous public-key cryptosystems infer all of their secrecy from the assumption that factoring of the product of two large primes is necessarily time consuming---something which has not, and perhaps cannot, be proven. Since the 1980s, the possibility of using quantum-mechanical features of light as a physical mechanism for satisfying particular cryptographic objectives has been explored. This research has been fueled by the hopes that cryptosystems based on quantum systems may provide provable levels of secrecy which are at least as valid as quantum mechanics itself. Unfortunately, the most widely considered quantum-cryptographic protocols (BB84 and the Ekert protocol) have serious implementation problems. Specifically, they require quantum-mechanical states which are not readily available, and they rely on unproven relations between intrusion-level detection and the information available to an attacker. As a result, the secrecy level provided by these experimental implementations is entirely unspecified. In an effort to provably satisfy the cryptographic

  4. Integrated Quantum and Classical Key Scheme for Two Servers Password Authentication

    Directory of Open Access Journals (Sweden)

    A. Krishnan

    2010-01-01

    Full Text Available Problem statement: Traditional user authentication system uses passwords for their secured accessibility in a central server, which is prone to attack by adversaries. The adversaries gain access to the contents of the user in attack prone servers. To overcome this problem, the multi-server systems were being proposed in which the user communicate in parallel with several or all of the servers for the purpose of authentication. Such system requires a large communication bandwidth and needs for synchronization at the user. Approach: Present an efficient two server user password authentication and reduce the usage of communication traffic and bandwidth consumption between the servers. Integration of quantum and classical key exchange model is deployed to safeguard user access security in large networks. The proposed work presented, a two server system, front end service server interacts directly to the user and the back end control server visible to the service server. The performance measure of the user password made for the transformed two long secrets held by both service and control server. Further the proposal applied quantum key distribution model along with classical key exchange in the two server authentication. Three-party Quantum key distribution used in this model, one with implicit user authentication and other with explicit mutual authentication, deployed for ecommerce buyer authentication in internet peer servers. Results: Effect of online and offline dictionary attacks prevailing in the single and multi-server systems are analyzed. The performance efficiency test carried out in terms success rate of authenticity for two server shows 35% better than single server. The performance of integrated Quantum Key Distribution (QKD systems and classical public key model have shown experimentally better performance in terms of computational efficiency and security rounds (11% improvement than traditional cryptic security

  5. Quantum Encryption Minimising Key Leakage under Known Plaintext Attacks

    DEFF Research Database (Denmark)

    Pedersen, Thomas Brochmann

    2006-01-01

    In this dissertation we show how, by using a quantum channel, we can get more unconditionally secret communication with a symmetric key under known plaintext attacks. In unconditionally secret encryption schemes the key is necessarily an expensive resource since it cannot safely be reused for more......, or interactive encryption schemes, where the interaction does not need to occur online. In our model we show that the amount of key leaked under a known plaintext attack can be made arbitrarily small even in non-interactive encryption schemes. We also give an encryption scheme where eavesdropping can be detected...

  6. Randomized dynamical decoupling strategies and improved one-way key rates for quantum cryptography

    Energy Technology Data Exchange (ETDEWEB)

    Kern, Oliver

    2009-05-25

    The present thesis deals with various methods of quantum error correction. It is divided into two parts. In the first part, dynamical decoupling methods are considered which have the task of suppressing the influence of residual imperfections in a quantum memory. Such imperfections might be given by couplings between the finite dimensional quantum systems (qudits) constituting the quantum memory, for instance. The suppression is achieved by altering the dynamics of an imperfect quantum memory with the help of a sequence of local unitary operations applied to the qudits. Whereas up to now the operations of such decoupling sequences have been constructed in a deterministic fashion, strategies are developed in this thesis which construct the operations by random selection from a suitable set. Formulas are derived which estimate the average performance of such strategies. As it turns out, randomized decoupling strategies offer advantages and disadvantages over deterministic ones. It is possible to benefit from the advantages of both kind of strategies by designing combined strategies. Furthermore, it is investigated if and how the discussed decoupling strategies can be employed to protect a quantum computation running on the quantum memory. It is shown that a purely randomized decoupling strategy may be used by applying the decoupling operations and adjusted gates of the quantum algorithm in an alternating fashion. Again this method can be enhanced by the means of deterministic methods in order to obtain a combined decoupling method for quantum computations analogously to the combining strategies for quantum memories. The second part of the thesis deals with quantum error-correcting codes and protocols for quantum key distribution. The focus is on the BB84 and the 6-state protocol making use of only one-way communication during the error correction and privacy amplification steps. It is shown that by adding additional errors to the preliminary key (a process called

  7. Distributed measurement-based quantum computation

    CERN Document Server

    Danos, V; Kashefi, E; Panangaden, P; Danos, Vincent; Hondt, Ellie D'; Kashefi, Elham; Panangaden, Prakash

    2005-01-01

    We develop a formal model for distributed measurement-based quantum computations, adopting an agent-based view, such that computations are described locally where possible. Because the network quantum state is in general entangled, we need to model it as a global structure, reminiscent of global memory in classical agent systems. Local quantum computations are described as measurement patterns. Since measurement-based quantum computation is inherently distributed, this allows us to extend naturally several concepts of the measurement calculus, a formal model for such computations. Our goal is to define an assembly language, i.e. we assume that computations are well-defined and we do not concern ourselves with verification techniques. The operational semantics for systems of agents is given by a probabilistic transition system, and we define operational equivalence in a way that it corresponds to the notion of bisimilarity. With this in place, we prove that teleportation is bisimilar to a direct quantum channe...

  8. A quantum symmetric key cipher(Y-00) and key generation (Quantum stream cipher-Part II)

    CERN Document Server

    Hirota, O; Sohma, M; Fuse, M; Hirota, Osamu; Kato, Kentaro; Sohma, Masaki; Fuse, Masaru

    2004-01-01

    What obstructs the realization of useful quantum cryptography is single photon scheme, or entanglement which is not applicable to the current infrastructure of optical communication network. We are concerned with the following question: Can we realize the information theoretically secure symmetric key cipher under "the finite secret key" based on quantum-optical communications? A role of quantum information theory is to give an answer for such a question. As an answer for the question, a new quantum cryptography was proposed by H.P.Yuen, which can realize a secure symmetric key cipher with high speeds(Gbps) and for long distance(1000 Km). Although some researchers claim that Yuen protocol(Y-00) is equivalent to the classical cryptography, they are all mistaken. Indeed it has no classical analogue, and also provides a generalization even in the conventional cryptography. At present, it is proved that a basic model of Y-00 has at least the security such as $H(X|Y_E)=H(K|Y_E)=H(K)$, $H(K|Y_E,X)\\sim 0$ under the ...

  9. A new spin on quantum cryptography: Avoiding trapdoors and embracing public keys

    CERN Document Server

    Ioannou, Lawrence M

    2011-01-01

    We give new arguments in support of \\emph{signed quantum key establishment}, where quantum cryptography is used in a public-key infrastructure that provides the required authentication. We also analyze more thoroughly than previous works the benefits that quantum key establishment protocols have over certain classical protocols, motivated in part by the various objections to quantum key establishment that are sometimes raised. Previous knowledge of quantum cryptography on the reader's part is not required for this article, as the definition of "quantum key establishment" that we use is an entirely classical and black-box characterization (one need only trust that protocols satisfying the definition exist).

  10. Quantum algorithms for testing properties of distributions

    CERN Document Server

    Bravyi, Sergey; Hassidim, Avinatan

    2009-01-01

    Suppose one has access to oracles generating samples from two unknown probability distributions P and Q on some N-element set. How many samples does one need to test whether the two distributions are close or far from each other in the L_1-norm ? This and related questions have been extensively studied during the last years in the field of property testing. In the present paper we study quantum algorithms for testing properties of distributions. It is shown that the L_1-distance between P and Q can be estimated with a constant precision using approximately N^{1/2} queries in the quantum settings, whereas classical computers need \\Omega(N) queries. We also describe quantum algorithms for testing Uniformity and Orthogonality with query complexity O(N^{1/3}). The classical query complexity of these problems is known to be \\Omega(N^{1/2}).

  11. Encryption key distribution via chaos synchronization.

    Science.gov (United States)

    Keuninckx, Lars; Soriano, Miguel C; Fischer, Ingo; Mirasso, Claudio R; Nguimdo, Romain M; Van der Sande, Guy

    2017-02-24

    We present a novel encryption scheme, wherein an encryption key is generated by two distant complex nonlinear units, forced into synchronization by a chaotic driver. The concept is sufficiently generic to be implemented on either photonic, optoelectronic or electronic platforms. The method for generating the key bitstream from the chaotic signals is reconfigurable. Although derived from a deterministic process, the obtained bit series fulfill the randomness conditions as defined by the National Institute of Standards test suite. We demonstrate the feasibility of our concept on an electronic delay oscillator circuit and test the robustness against attacks using a state-of-the-art system identification method.

  12. Encryption key distribution via chaos synchronization

    Science.gov (United States)

    Keuninckx, Lars; Soriano, Miguel C.; Fischer, Ingo; Mirasso, Claudio R.; Nguimdo, Romain M.; Van der Sande, Guy

    2017-01-01

    We present a novel encryption scheme, wherein an encryption key is generated by two distant complex nonlinear units, forced into synchronization by a chaotic driver. The concept is sufficiently generic to be implemented on either photonic, optoelectronic or electronic platforms. The method for generating the key bitstream from the chaotic signals is reconfigurable. Although derived from a deterministic process, the obtained bit series fulfill the randomness conditions as defined by the National Institute of Standards test suite. We demonstrate the feasibility of our concept on an electronic delay oscillator circuit and test the robustness against attacks using a state-of-the-art system identification method. PMID:28233876

  13. Attractor black holes and quantum distribution functions

    Energy Technology Data Exchange (ETDEWEB)

    Montanez, S. [Instituto de Fisica Teorica CSIC-UAM, Modulo C-XVI, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Gomez, C. [Instituto de Fisica Teorica CSIC-UAM, Modulo C-XVI, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Theory Group, Physics Department, CERN, 1211 Geneva 23 (Switzerland)

    2007-05-15

    Using the attractor mechanism and the wavefunction interpretation of the topological string partition function on a Calabi Yau threefold M we study the relation between the Bekenstein-Hawking-Wald entropy of BPS Calabi-Yau black holes and quantum distribution functions defined on H{sup 3}(M). We discuss the OSV conjecture in this context. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  14. Quantum associative memory with improved distributed queries

    CERN Document Server

    Njafa, J -P Tchapet; Woafo, Paul

    2012-01-01

    The paper proposes an improved quantum associative algorithm with distributed query based on model proposed by Ezhov et al. We introduce two modifications of the query that optimized data retrieval of correct multi-patterns simultaneously for any rate of the number of the recognition pattern on the total patterns. Simulation results are given.

  15. Iterative quantum algorithm for distributed clock synchronization

    Institute of Scientific and Technical Information of China (English)

    Wang Hong-Fu; Zhang Shou

    2012-01-01

    Clock synchronization is a well-studied problem with many practical and scientific applications.We propose an arbitrary accuracy iterative quantum algorithm for distributed clock synchronization using only three qubits.The n bits of the time difference △ between two spatially separated clocks can be deterministically extracted by communicating only O(n) messages and executing the quantum iteration process n times based on the classical feedback and measurement operations.Finally,we also give the algorithm using only two qubits and discuss the success probability of the algorithm.

  16. MULTI-LEVEL KEY DISTRIBUTION ALGORITHM FOR SECRET KEY RECOVERY SYSTEM

    Directory of Open Access Journals (Sweden)

    TANAPAT MAHAVEERAWAT

    2015-02-01

    Full Text Available Most of Multi Agent Key Recovery Systems are proposed from the assumption that Key Recovery Agents in the system have same availability of security service levelagreement and trust. Which mean, secret key will be shared to each Key Recovery Agent in equal secret’s portion. Practically, each Key Recovery Agent may have their own limitation in terms of securityservice level agreement according to economic cost, complexity and risks. This paper proposedMulti Level Key Distribution Algorithm,which the secret key can be managed into portionsharing and assignto each Key Recovery Agent (KRA according to user’s trust. Withproposed algorithm, the experimental result had shown the advantage in secret sharing size and the system had improved initssecurity from the advantage of multilevel secret key distribution capability.

  17. Superfluid (quantum) turbulence and distributed chaos

    CERN Document Server

    Bershadskii, A

    2016-01-01

    Properties of distributed chaos in superfluid (quantum) turbulence have been studied using the data of recent direct numerical simulations (HVBK two-fluid model for He II, and a moving grid in the frames of Gross-Pitaevskii model of the Bose-Einstein condensates at low temperatures). It is found that for the viscous (normal) component of the velocity field in He II the viscosity dominates the distributed chaos with the stretched exponential spectrum $\\exp(-k/k_{\\beta})^{\\beta}$ and $\\beta = 2/3$. For the superfluid component the distributed chaos is dominated by the vorticity correlation integral with $\\beta =1/2$ (the soft spontaneous breaking of the space translational symmetry - homogeneity). For very low temperature the distributed chaos is tuned to the large-scale coherent motions: the viscous (normal) component is tuned to the fundamental mode, whereas the superfluid component is subharmonically tuned. For the Gross-Pitaevskii superfluid turbulence incompressible part of the energy spectrum (containing ...

  18. Distributed public key schemes secure against continual leakage

    DEFF Research Database (Denmark)

    Akavia, Adi; Goldwasser, Shafi; Hazay, Carmit

    2012-01-01

    In this work we study distributed public key schemes secure against continual memory leakage. The secret key will be shared among two computing devices communicating over a public channel, and the decryption operation will be computed by a simple 2-party protocol between the devices. Similarly...... the value of the respective function on the internal state of the respective device (namely, on its secret share, internal randomness, and results of intermediate computations). We present distributed public key encryption (DPKE) and distributed identity based encryption (DIBE) schemes that are secure...

  19. Applications of single-qubit rotations in quantum public-key cryptography

    OpenAIRE

    Nikolopoulos, Georgios M.

    2008-01-01

    We discuss cryptographic applications of single-qubit rotations from the perspective of trapdoor one-way functions and public-key encryption. In particular, we present an asymmetric cryptosystem whose security relies on fundamental principles of quantum physics. A quantum public key is used for the encryption of messages while decryption is possible by means of a classical private key only. The trapdoor one-way function underlying the proposed cryptosystem maps integer numbers to quantum stat...

  20. Distributivity breaking and macroscopic quantum games

    CERN Document Server

    Grib, A A; Parfionov, G N; Starkov, K A

    2005-01-01

    Examples of games between two partners with mixed strategies, calculated by the use of the probability amplitude as some vector in Hilbert space are given. The games are macroscopic, no microscopic quantum agent is supposed. The reason for the use of the quantum formalism is in breaking of the distributivity property for the lattice of yes-no questions arising due to the special rules of games. The rules of the games suppose two parts: the preparation and measurement. In the first part due to use of the quantum logical orthocomplemented non-distributive lattice the partners freely choose the wave functions as descriptions of their strategies. The second part consists of classical games described by Boolean sublattices of the initial non-Boolean lattice with same strategies which were chosen in the first part. Examples of games for spin one half are given. New Nash equilibria are found for some cases. Heisenberg uncertainty relations without the Planck constant are written for the "spin one half game".

  1. Two-Dimensional Key Table-Based Group Key Distribution in Advanced Metering Infrastructure

    Directory of Open Access Journals (Sweden)

    Woong Go

    2014-01-01

    Full Text Available A smart grid provides two-way communication by using the information and communication technology. In order to establish two-way communication, the advanced metering infrastructure (AMI is used in the smart grid as the core infrastructure. This infrastructure consists of smart meters, data collection units, maintenance data management systems, and so on. However, potential security problems of the AMI increase owing to the application of the public network. This is because the transmitted information is electricity consumption data for charging. Thus, in order to establish a secure connection to transmit electricity consumption data, encryption is necessary, for which key distribution is required. Further, a group key is more efficient than a pairwise key in the hierarchical structure of the AMI. Therefore, we propose a group key distribution scheme using a two-dimensional key table through the analysis result of the sensor network group key distribution scheme. The proposed scheme has three phases: group key predistribution, selection of group key generation element, and generation of group key.

  2. Quantum-to-the-Home: Achieving Gbits/s Secure Key Rates via Commercial Off-the-Shelf Telecommunication Equipment

    Directory of Open Access Journals (Sweden)

    Rameez Asif

    2017-01-01

    Full Text Available There is current significant interest in Fiber-to-the-Home (FTTH networks, that is, end-to-end optical connectivity. Currently, it may be limited due to the presence of last-mile copper wire connections. However, in near future, it is envisaged that FTTH connections will exist, and a key offering would be the possibility of optical encryption that can best be implemented using Quantum Key Distribution (QKD. However, it is very important that the QKD infrastructure is compatible with the already existing networks for a smooth transition and integration with the classical data traffic. In this paper, we report the feasibility of using off-the-shelf telecommunication components to enable high performance Continuous Variable-Quantum Key Distribution (CV-QKD systems that can yield secure key rates in the range of 100 Mbits/s under practical operating conditions. Multilevel phase modulated signals (m-PSK are evaluated in terms of secure key rates and transmission distances. The traditional receiver is discussed, aided by the phase noise cancellation based digital signal processing module for detecting the complex quantum signals. Furthermore, we have discussed the compatibility of multiplexers and demultiplexers for wavelength division multiplexed Quantum-to-the-Home (QTTH network and the impact of splitting ratio is analyzed. The results are thoroughly compared with the commercially available high-cost encryption modules.

  3. Quantum arrival-time distributions from intensity functions

    DEFF Research Database (Denmark)

    Wlodarz, Joachim

    2002-01-01

    The quantum time-of-arrival problem is discussed within the standard formulation of nonrelativistic quantum mechanics with parametric time. It is shown that a general class of arrival-time probability distributions results from the assumption that the arrival process of a quantum particle...

  4. Efficient, Robust and Constant-Round Distributed RSA Key Generation

    DEFF Research Database (Denmark)

    Damgård, Ivan Bjerre; Mikkelsen, Gert Læssøe

    2010-01-01

    We present the first protocol for distributed RSA key generation which is constant round, secure against malicious adversaries and has a negligibly small bound on the error probability, even using only one iteration of the underlying primality test on each candidate number.......We present the first protocol for distributed RSA key generation which is constant round, secure against malicious adversaries and has a negligibly small bound on the error probability, even using only one iteration of the underlying primality test on each candidate number....

  5. SeaQuaKE: Sea-optimized Quantum Key Exchange

    Science.gov (United States)

    2015-01-01

    approach can simplify the need for high-speed random number generation . The two degrees of freedom we will focus on in our study include polarization...channel, and quantum receiver elements are included in our end-to-end systems model. The system performance at a number of infrared transmission...to-noise ratio in classical signals. By increasing CAR, a quantum communications system will generate relatively fewer erroneous correlated

  6. METADATA DRIVEN EFFICIENT KEY GENERATION AND DISTRIBUTION IN CLOUD SECURITY

    Directory of Open Access Journals (Sweden)

    R. Anitha

    2014-01-01

    Full Text Available With rapid development of cloud computing to a greater extent IT industries outsource their sensitive data at cloud data storage location. To keep the stored data confidential against untrusted cloud service providers, a natural way is to store only encrypted data in the cloud severs and providing an efficient access control mechanism using a competent cipher key-Cmxn, which is becoming a promising cryptographic solution. In this proposed model the cipher key is generated based on attributes of metadata. The key problems of this approach includes, the generation of cipher key-Cmxn and establishing an access control mechanism for the encrypted data using cipher key, where keys cannot be revoked without the involvement of data owner and the Metadata Data Server (MDS, hence makes data owner feels comfortable about the data stored. From this study, we propose a novel Metadata driven efficient key generation and distribution policies for cloud data security system by exploiting the characteristic of the metadata stored. Our design enforces security by providing two novel features. 1. Generation of Cipher key-Cmxn using modified feistel network, which holds good for the avalanche effect as each round of the feistel function, depends on the previous round. 2. A novel key distribution policy is designed where the encryption and decryption keys cannot be compromised without the involvement of data owner and the Metadata Data Server (MDS, hence makes data owner comfortable about the data stored. We have implemented a security model that incorporates our ideas and evaluated the performance and scalability of the secured model.

  7. Key issues and technical route of cyber physical distribution system

    Science.gov (United States)

    Zheng, P. X.; Chen, B.; Zheng, L. J.; Zhang, G. L.; Fan, Y. L.; Pei, T.

    2017-01-01

    Relying on the National High Technology Research and Development Program, this paper introduced the key issues in Cyber Physical Distribution System (CPDS), mainly includes: composite modelling method and interaction mechanism, system planning method, security defence technology, distributed control theory. Then on this basis, the corresponding technical route is proposed, and a more detailed research framework along with main schemes to be adopted is also presented.

  8. Quantum error-correction failure distributions: Comparison of coherent and stochastic error models

    Science.gov (United States)

    Barnes, Jeff P.; Trout, Colin J.; Lucarelli, Dennis; Clader, B. D.

    2017-06-01

    We compare failure distributions of quantum error correction circuits for stochastic errors and coherent errors. We utilize a fully coherent simulation of a fault-tolerant quantum error correcting circuit for a d =3 Steane and surface code. We find that the output distributions are markedly different for the two error models, showing that no simple mapping between the two error models exists. Coherent errors create very broad and heavy-tailed failure distributions. This suggests that they are susceptible to outlier events and that mean statistics, such as pseudothreshold estimates, may not provide the key figure of merit. This provides further statistical insight into why coherent errors can be so harmful for quantum error correction. These output probability distributions may also provide a useful metric that can be utilized when optimizing quantum error correcting codes and decoding procedures for purely coherent errors.

  9. A Council-based Distributed Key Management Scheme for MANETs

    Directory of Open Access Journals (Sweden)

    Mohammed ELKOUTBI

    2010-09-01

    Full Text Available Abstract—Mobile ad hoc networks (MAETs have beenproposed as an extremely flexible technology for establishingwireless communications. In comparison with fixed networks,some new security issues have arisen with the introduction ofMAETs. Secure routing, in particular, is an important andcomplicated issue. Clustering is commonly used in order to limitthe amount of secure routing information. In this work, wepropose an enhanced solution for ad hoc key management basedon a cauterized architecture. This solution uses clusters as aframework to manage cryptographic keys in a distributed way.This paper sheds light on the key management algorithm for theOLSR protocol standard. Our algorithm takes into account thenode mobility and engenders major improvements regarding thenumber of elected cluster heads to create a PKI council. Ourobjective is to distribute the certification authority functions for areduced and less mobile cluster heads that will serve for keysexchange.

  10. Applications of single-qubit rotations in quantum public-key cryptography

    Science.gov (United States)

    Nikolopoulos, Georgios M.

    2008-03-01

    We discuss cryptographic applications of single-qubit rotations from the perspective of trapdoor one-way functions and public-key encryption. In particular, we present an asymmetric cryptosystem whose security relies on fundamental principles of quantum physics. A quantum public key is used for the encryption of messages while decryption is possible by means of a classical private key only. The trapdoor one-way function underlying the proposed cryptosystem maps integer numbers to quantum states of a qubit and its inversion can be infeasible by virtue of the Holevo’s theorem.

  11. Quasi-quantum phenomena: the key to understanding homeopathy.

    Science.gov (United States)

    Molski, Marcin

    2010-04-01

    On the basis of the first- and second-order Gompertzian kinetics it has been proved that the crystallization and its reciprocal process of dissolution belong to the class of quasi-quantum non-local coherent phenomena. Hence, there exists a direct link to homeopathy: molecules of the remedy prepared in the process of dilution of the active substance are non-locally interconnected at-a-distance. The results obtained provide strong arguments justifying formulated ad hoc macroscopic versions of quantum non-locality, entanglement and coherence employed in interpretation of the homeopathic remedies activity and effectiveness. In particular they are consistent with the predictions of the weak quantum theory developed by Atmanspacher and coworkers.

  12. Design of an Efficient Neural Key Distribution Centre

    CERN Document Server

    Bisalapur, Sahana S

    2011-01-01

    The goal of any cryptographic system is the exchange of information among the intended users without any leakage of information to others who may have unauthorized access to it. A common secret key could be created over a public channel accessible to any opponent. Neural networks can be used to generate common secret key. In case of neural cryptography, both the communicating networks receive an identical input vector, generate an output bit and are trained based on the output bit. The two networks and their weight vectors exhibit a novel phenomenon, where the networks synchronize to a state with identical time-dependent weights. The generated secret key over a public channel is used for encrypting and decrypting the information being sent on the channel. This secret key is distributed to the other vendor efficiently by using an agent based approach.

  13. Two-party quantum key agreement based on four-particle GHZ states

    Science.gov (United States)

    He, Ye-Feng; Ma, Wen-Ping

    2016-04-01

    Based on four-particle GHZ states, the double CNOT operation and the delayed measurement technique, a two-party quantum key agreement (QKA) protocols is proposed. The double CNOT operation makes each four-particle GHZ state collapse into two independent quantum states without any entanglement. Furthermore, one party can directly know the two quantum states and the other party can be aware of the two quantum states by using the corresponding measurement. According to the initial states of the two quantum states, two parties can extract the secret keys of each other by using the publicly announced value or by performing the delayed measurement, respectively. Then the protocol achieves the fair establishment of a shared key. The security analysis shows that the new protocol can resist against participant attacks, the Trojan horse attacks and other outsider attacks. Furthermore, the new protocol also has no information leakage problem and has high qubit efficiency.

  14. SeaQuaKE: Sea-Optimized Quantum Key Exchange

    Science.gov (United States)

    2014-08-01

    and Bell Labs heritage , Applied Communication Sciences excels at creating innovative technologies and services to solve the most difficult and...001). In this technical report, we describe details of the hyperentanglement source architecture we propose for use in a maritime quantum...3 3.1 Source Architecture and Modeling

  15. Quantum displacement receiver for M-ary phase-shift-keyed coherent states

    Energy Technology Data Exchange (ETDEWEB)

    Izumi, Shuro [National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795, Japan and Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Takeoka, Masahiro; Fujiwara, Mikio; Sasaki, Masahide [National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795 (Japan); Pozza, Nicola Dalla; Assalini, Antonio [Department of Information Engineering, University of Padua, Via Gradenigo 6/B, 35131, Padova (Italy); Ema, Kazuhiro [Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2014-12-04

    We propose quantum receivers for 3- and 4-ary phase-shift-keyed (PSK) coherent state signals to overcome the standard quantum limit (SQL). Our receiver, consisting of a displacement operation and on-off detectors with or without feedforward, provides an error probability performance beyond the SQL. We show feedforward operations can tolerate the requirement for the detector specifications.

  16. Distributed Generation in Power Systems: An Overview and Key Issues

    DEFF Research Database (Denmark)

    Singh, Sri Niwas

    2009-01-01

    The necessity for smart electrical systems having minimum technical loss and environmental impact is providing impetus to go for Distributed Generations (DGs) which may offer several other advantages such as reduced transmission and distribution system resources, increased reliability, better power...... quality, etc. However, depending on the system configuration and management, these advantages may not be true. Moreover, due to structural and managerial changes in the electricity supply industry motivated with introduction of completion, the role of small generations distributed in the low....../medium voltage network has gained importance. This paper adopts a systematic approach by focusing on the most important research areas related to the distributed generations. Various DG technologies are described and penetration of DGs in the Indian system has been discussed. This paper also highlights the key...

  17. Implementation of Physical Layer Key Distribution using Software Defined Radios

    Directory of Open Access Journals (Sweden)

    S. Kambala

    2013-01-01

    Full Text Available It was well known from Shannon’s days that characteristics of the physical channel like attenuation, fading and noise can impair reliable communication. But it was more recently that the beneficial side effects of channel characteristics in ensuring secret communication started getting attention. Studies have been made to quantify the amount of secrecy that can be reaped by combining channel coding with security protocols. The Wiretap channel proposed by Wyner is arguably one of the oldest models of physical layer security protocols. In this paper, we present a brief tutorial introduction to the Wiretap channel, followed by an application of the physical layer model to a class of Key Distribution protocols. We present results from an implementation of key distribution protocols using Software Defined Radio tools along with physical RF hardware peripherals. We believe this approach is much more tangible and informative than computer based simulation studies.

  18. Quantum-secure authentication of a physical unclonable key

    NARCIS (Netherlands)

    Goorden, S.A.; Horstmann, M.; Mosk, A.P.; Skoric, B.; Pinkse, P.W.H.

    2014-01-01

    Authentication of persons and objects is a crucial aspect of security. We experimentally demonstrate quantumsecure authentication (QSA) of a classical multiplescattering key. The key is authenticated by illuminating it with a light pulse containing fewer photons than spatial degrees of freedom and v

  19. Performance study on Gossip-based group key distribution protocal

    Institute of Scientific and Technical Information of China (English)

    Yao Yan; Ma Jiaqing; Zhong Yiping; Zhang Shiyong

    2006-01-01

    Group key distribution is faced with two important problems, i.e. reliability and scalability, to support security multicast for large and dynamic groups. With group member increasing, traditional reliable multicast protocol can not deal with them fully. Gossip-based group key distribution idea for wide-area dissemination was provided. It is based on an gossip-based loss recovery control mechanism. It can provide a probabilistic reliable guarantee for a information dissemination to reach every group member, which can achieve scalability and reliability. To achieve full reliability, three layers protocol model in group key distribution was provided. One is best effect layer, which provides unreliable dissemination. Other is gossip-based loss recovery layer, which provides probabilistic reliable guarantee. Last is vsync-based layer, which provide deterministic loss recovery. We integrate probabilistic loss recovery method with deterministic one. The model possess scalability that probabilistic method has and full reliability prosthesis by vsync-based. To evaluate the effectiveness of gossip technique in scalable and reliable multicast protocols. We have compared gossip protocol with other reliable multicast protocols. Experimental result shows that gossip protocol has better scalability than other.

  20. Optically Controlled Distributed Quantum Computing Using Atomic Ensembles As Qubits

    Science.gov (United States)

    2016-02-23

    Distribution approved for public release. 8 Figure 7: Schematic Illustration of a network of small-scale quantum...quantum bits in different systems, for example, Rb atoms and NV diamond, preferably using telecom fibres. In this paper, we describe a quantum frequency...converter (QFC) that will perform this telecom band qubit conversion. The QFC is based on periodically poled lithium niobate waveguides. For