The Experts below are selected from a list of 14676 Experts worldwide ranked by ideXlab platform
Nicolas Gisin - One of the best experts on this subject based on the ideXlab platform.
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tight finite key analysis for Quantum Cryptography
Nature Communications, 2012Co-Authors: Marco Tomamichel, Nicolas Gisin, Renato RennerAbstract: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.
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upper bounds for the security of two distributed phase reference protocols of Quantum Cryptography
New Journal of Physics, 2008Co-Authors: Cyril Branciard, Nicolas Gisin, Valerio ScaraniAbstract:The differential-phase-shift (DPS) and the coherent-one-way (COW) are among the most practical protocols for Quantum Cryptography, and are therefore the object of fast-paced experimental developments. The assessment of their security is also a challenge for theorists: the existing tools, that allow to prove security against the most general attacks, do not apply to these two protocols in any straightforward way. We present new upper bounds for their security in the limit of large distances ( d & 50 km with typical values in optical fibers) by considering a large class of collective attacks, namely those in which the adversary attaches ancillary Quantum systems to each pulse or to each pair of pulses. We introduce also two modified versions of the COW protocol, which may prove more robust than the original one.
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upper bounds for the security of two distributed phase reference protocols of Quantum Cryptography coherent one way and differential phase shift
arXiv: Quantum Physics, 2007Co-Authors: Cyril Branciard, Nicolas Gisin, Valerio ScaraniAbstract:The Differential-Phase-Shift (DPS) and the Coherent-One-Way (COW) are among the most practical protocols for Quantum Cryptography, and are therefore the object of fast-paced experimental developments. The assessment of their security is also a challenge for theorists: the existing tools, that allow to prove security against the most general attacks, do not apply to these two protocols in any straightforward way. We present new upper bounds for their security in the limit of large distances ($d \gtrsim 50$km with typical values in optical fibers) by considering a large class of collective attacks, namely those in which the adversary attaches ancillary Quantum systems to each pulse or to each pair of pulses. We introduce also two modified versions of the COW protocol, which may prove more robust than the original one.
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zero error attacks and detection statistics in the coherent one way protocol for Quantum Cryptography
arXiv: Quantum Physics, 2006Co-Authors: Cyril Branciard, Nicolas Gisin, Norbert Lutkenhaus, Valerio ScaraniAbstract:This is a study of the security of the Coherent One-Way (COW) protocol for Quantum Cryptography, proposed recently as a simple and fast experimental scheme. In the zero-error regime, the eavesdropper Eve can only take advantage of the losses in the transmission. We consider new attacks, based on unambiguous state discrimination, which perform better than the basic beam-splitting attack, but which can be detected by a careful analysis of the detection statistics. These results stress the importance of testing several statistical parameters in order to achieve higher rates of secret bits.
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reduced randomness in Quantum Cryptography with sequences of qubits encoded in the same basis
Physical Review A, 2006Co-Authors: Louisphilippe Lamoureux, Helle Bechmannpasquinucci, Nicolas Cerf, Nicolas Gisin, Chiara MacchiavelloAbstract:We consider the cloning of sequences of qubits prepared in the states used in the BB84 or six-state Quantum Cryptography protocol, and show that the single-qubit fidelity is unaffected even if entire sequences of qubits are prepared in the same basis. This result is only valid provided that the sequences are much shorter than the total key. It is of great importance for practical Quantum cryptosystems because it reduces the need for high-speed random number generation without impairing on the security against finite-size cloning attacks.
Ulrik L Andersen - One of the best experts on this subject based on the ideXlab platform.
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advances in Quantum Cryptography
Advances in Optics and Photonics, 2020Co-Authors: Stefano Pirandola, Ulrik L Andersen, Leonardo Banchi, Mario Berta, Darius Bunandar, Roger Colbeck, Dirk Englund, Tobias Gehring, Cosmo Lupo, Carlo OttavianiAbstract:Quantum Cryptography is arguably the fastest growing area in Quantum information science. Novel theoretical protocols are designed on a regular basis, security proofs are constantly improving, and experiments are gradually moving from proof-of-principle lab demonstrations to in-field implementations and technological prototypes. In this paper, we provide both a general introduction and a state-of-the-art description of the recent advances in the field, both theoretical and experimental. We start by reviewing protocols of Quantum key distribution based on discrete variable systems. Next we consider aspects of device independence, satellite challenges, and protocols based on continuous-variable systems. We will then discuss the ultimate limits of point-to-point private communications and how Quantum repeaters and networks may overcome these restrictions. Finally, we will discuss some aspects of Quantum Cryptography beyond standard Quantum key distribution, including Quantum random number generators and Quantum digital signatures.
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advances in Quantum Cryptography
arXiv: Quantum Physics, 2019Co-Authors: Stefano Pirandola, Ulrik L Andersen, Leonardo Banchi, Mario Berta, Darius Bunandar, Roger Colbeck, Dirk Englund, Tobias Gehring, Cosmo Lupo, Carlo OttavianiAbstract:Quantum Cryptography is arguably the fastest growing area in Quantum information science. Novel theoretical protocols are designed on a regular basis, security proofs are constantly improving, and experiments are gradually moving from proof-of-principle lab demonstrations to in-field implementations and technological prototypes. In this review, we provide both a general introduction and a state of the art description of the recent advances in the field, both theoretically and experimentally. We start by reviewing protocols of Quantum key distribution based on discrete variable systems. Next we consider aspects of device independence, satellite challenges, and high rate protocols based on continuous variable systems. We will then discuss the ultimate limits of point-to-point private communications and how Quantum repeaters and networks may overcome these restrictions. Finally, we will discuss some aspects of Quantum Cryptography beyond standard Quantum key distribution, including Quantum data locking and Quantum digital signatures.
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reply to discrete and continuous variables for measurement device independent Quantum Cryptography
Nature Photonics, 2015Co-Authors: Stefano Pirandola, Carlo Ottaviani, Christian Weedbrook, Tobias Gehring, Gaetana Spedalieri, Samuel L Braunstein, Seth Lloyd, Christian S Jacobsen, Ulrik L AndersenAbstract:Reply to 'Discrete and continuous variables for measurement-device-independent Quantum Cryptography'
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High-rate measurement-device-independent Quantum Cryptography
Nature Photonics, 2015Co-Authors: Stefano Pirandola, Carlo Ottaviani, Christian Weedbrook, Tobias Gehring, Gaetana Spedalieri, Samuel L Braunstein, Seth Lloyd, Christian S Jacobsen, Ulrik L AndersenAbstract:Quantum Cryptography achieves a formidable task—the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum Cryptography is now headed towards solving the practical problem of constructing scalable and secure Quantum networks. A significant step in this direction has been the introduction of measurement-device independence, where the secret key between two parties is established by the measurement of an untrusted relay. Unfortunately, although qubit-implemented protocols can reach long distances, their key rates are typically very low, unsuitable for the demands of a metropolitan network. Here we show, theoretically and experimentally, that a solution can come from the use of continuous-variable systems. We design a coherent-state network protocol able to achieve remarkably high key rates at metropolitan distances, in fact three orders of magnitude higher than those currently achieved. Our protocol could be employed to build high-rate Quantum networks where devices securely connect to nearby access points or proxy servers. An end-to-end continuous-variable Quantum key distribution system with an untrusted node is proposed. A proof-of-principle experiment shows that 10^−1 secret key bits per relay use are distributed at 4 dB loss, corresponding to 20 km in optical fibre.
Valerio Scarani - One of the best experts on this subject based on the ideXlab platform.
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upper bounds for the security of two distributed phase reference protocols of Quantum Cryptography
New Journal of Physics, 2008Co-Authors: Cyril Branciard, Nicolas Gisin, Valerio ScaraniAbstract:The differential-phase-shift (DPS) and the coherent-one-way (COW) are among the most practical protocols for Quantum Cryptography, and are therefore the object of fast-paced experimental developments. The assessment of their security is also a challenge for theorists: the existing tools, that allow to prove security against the most general attacks, do not apply to these two protocols in any straightforward way. We present new upper bounds for their security in the limit of large distances ( d & 50 km with typical values in optical fibers) by considering a large class of collective attacks, namely those in which the adversary attaches ancillary Quantum systems to each pulse or to each pair of pulses. We introduce also two modified versions of the COW protocol, which may prove more robust than the original one.
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upper bounds for the security of two distributed phase reference protocols of Quantum Cryptography coherent one way and differential phase shift
arXiv: Quantum Physics, 2007Co-Authors: Cyril Branciard, Nicolas Gisin, Valerio ScaraniAbstract:The Differential-Phase-Shift (DPS) and the Coherent-One-Way (COW) are among the most practical protocols for Quantum Cryptography, and are therefore the object of fast-paced experimental developments. The assessment of their security is also a challenge for theorists: the existing tools, that allow to prove security against the most general attacks, do not apply to these two protocols in any straightforward way. We present new upper bounds for their security in the limit of large distances ($d \gtrsim 50$km with typical values in optical fibers) by considering a large class of collective attacks, namely those in which the adversary attaches ancillary Quantum systems to each pulse or to each pair of pulses. We introduce also two modified versions of the COW protocol, which may prove more robust than the original one.
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zero error attacks and detection statistics in the coherent one way protocol for Quantum Cryptography
arXiv: Quantum Physics, 2006Co-Authors: Cyril Branciard, Nicolas Gisin, Norbert Lutkenhaus, Valerio ScaraniAbstract:This is a study of the security of the Coherent One-Way (COW) protocol for Quantum Cryptography, proposed recently as a simple and fast experimental scheme. In the zero-error regime, the eavesdropper Eve can only take advantage of the losses in the transmission. We consider new attacks, based on unambiguous state discrimination, which perform better than the basic beam-splitting attack, but which can be detected by a careful analysis of the detection statistics. These results stress the importance of testing several statistical parameters in order to achieve higher rates of secret bits.
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Coherent-pulse implementations of Quantum Cryptography protocols resistant to photon-number-splitting attacks
Physical Review A - Atomic Molecular and Optical Physics, 2004Co-Authors: Antonio Acín, Nicolas Gisin, Valerio ScaraniAbstract:We propose a class of Quantum Cryptography protocols that are robust against photon-number-splitting attacks (PNS) in a weak coherent-pulse implementation. We give a quite exhaustive analysis of several eavesdropping attacks on these schemes. The honest parties (Alice and Bob) use present-day technology, in particular an attenuated laser as an approximation of a single-photon source. The idea of the protocols is to exploit the nonorthogonality of Quantum states to decrease the information accessible to Eve due to the multiphoton pulses produced by the imperfect source. The distance at which the key distribution becomes insecure due to the PNS attack is significantly increased compared to the existing schemes. We also show that strong-pulse implementations, where a strong pulse is included as a reference, allow for key distribution robust against photon-number-splitting attacks.
Stefano Pirandola - One of the best experts on this subject based on the ideXlab platform.
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advances in Quantum Cryptography
Advances in Optics and Photonics, 2020Co-Authors: Stefano Pirandola, Ulrik L Andersen, Leonardo Banchi, Mario Berta, Darius Bunandar, Roger Colbeck, Dirk Englund, Tobias Gehring, Cosmo Lupo, Carlo OttavianiAbstract:Quantum Cryptography is arguably the fastest growing area in Quantum information science. Novel theoretical protocols are designed on a regular basis, security proofs are constantly improving, and experiments are gradually moving from proof-of-principle lab demonstrations to in-field implementations and technological prototypes. In this paper, we provide both a general introduction and a state-of-the-art description of the recent advances in the field, both theoretical and experimental. We start by reviewing protocols of Quantum key distribution based on discrete variable systems. Next we consider aspects of device independence, satellite challenges, and protocols based on continuous-variable systems. We will then discuss the ultimate limits of point-to-point private communications and how Quantum repeaters and networks may overcome these restrictions. Finally, we will discuss some aspects of Quantum Cryptography beyond standard Quantum key distribution, including Quantum random number generators and Quantum digital signatures.
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Terahertz Quantum Cryptography
IEEE Journal on Selected Areas in Communications, 2020Co-Authors: Carlo Ottaviani, Matthew J. Woolley, Misha Erementchouk, Pinaki Mazumder, Stefano Pirandola, John F. Federici, Christian WeedbrookAbstract:A well-known empirical rule for the demand of wireless communication systems is that of Edholm's law of bandwidth. It states that the demand for bandwidth in wireless short-range communications doubles every 18 months. With the growing demand for bandwidth and the decreasing cell size of wireless systems, terahertz (THz) communication systems are expected to become increasingly important in modern day applications. With this expectation comes the need for protecting users' privacy and security in the best way possible. With that in mind, we show that Quantum key distribution can operate in the THz regime and we derive the relevant secret key rates against realistic collective attacks. In the extended THz range (from 0.1 to 50 THz), we find that below 1 THz, the main detrimental factor is thermal noise, while at higher frequencies it is atmospheric absorption. Our results show that high-rate THz Quantum Cryptography is possible over distances varying from a few meters using direct reconciliation, to about 220m via reverse reconciliation. We also give a specific example of the physical hardware and architecture that could be used to realize our THz Quantum key distribution scheme.
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advances in Quantum Cryptography
arXiv: Quantum Physics, 2019Co-Authors: Stefano Pirandola, Ulrik L Andersen, Leonardo Banchi, Mario Berta, Darius Bunandar, Roger Colbeck, Dirk Englund, Tobias Gehring, Cosmo Lupo, Carlo OttavianiAbstract:Quantum Cryptography is arguably the fastest growing area in Quantum information science. Novel theoretical protocols are designed on a regular basis, security proofs are constantly improving, and experiments are gradually moving from proof-of-principle lab demonstrations to in-field implementations and technological prototypes. In this review, we provide both a general introduction and a state of the art description of the recent advances in the field, both theoretically and experimentally. We start by reviewing protocols of Quantum key distribution based on discrete variable systems. Next we consider aspects of device independence, satellite challenges, and high rate protocols based on continuous variable systems. We will then discuss the ultimate limits of point-to-point private communications and how Quantum repeaters and networks may overcome these restrictions. Finally, we will discuss some aspects of Quantum Cryptography beyond standard Quantum key distribution, including Quantum data locking and Quantum digital signatures.
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reply to discrete and continuous variables for measurement device independent Quantum Cryptography
Nature Photonics, 2015Co-Authors: Stefano Pirandola, Carlo Ottaviani, Christian Weedbrook, Tobias Gehring, Gaetana Spedalieri, Samuel L Braunstein, Seth Lloyd, Christian S Jacobsen, Ulrik L AndersenAbstract:Reply to 'Discrete and continuous variables for measurement-device-independent Quantum Cryptography'
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High-rate measurement-device-independent Quantum Cryptography
Nature Photonics, 2015Co-Authors: Stefano Pirandola, Carlo Ottaviani, Christian Weedbrook, Tobias Gehring, Gaetana Spedalieri, Samuel L Braunstein, Seth Lloyd, Christian S Jacobsen, Ulrik L AndersenAbstract:Quantum Cryptography achieves a formidable task—the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum Cryptography is now headed towards solving the practical problem of constructing scalable and secure Quantum networks. A significant step in this direction has been the introduction of measurement-device independence, where the secret key between two parties is established by the measurement of an untrusted relay. Unfortunately, although qubit-implemented protocols can reach long distances, their key rates are typically very low, unsuitable for the demands of a metropolitan network. Here we show, theoretically and experimentally, that a solution can come from the use of continuous-variable systems. We design a coherent-state network protocol able to achieve remarkably high key rates at metropolitan distances, in fact three orders of magnitude higher than those currently achieved. Our protocol could be employed to build high-rate Quantum networks where devices securely connect to nearby access points or proxy servers. An end-to-end continuous-variable Quantum key distribution system with an untrusted node is proposed. A proof-of-principle experiment shows that 10^−1 secret key bits per relay use are distributed at 4 dB loss, corresponding to 20 km in optical fibre.
Christian Weedbrook - One of the best experts on this subject based on the ideXlab platform.
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Terahertz Quantum Cryptography
IEEE Journal on Selected Areas in Communications, 2020Co-Authors: Carlo Ottaviani, Matthew J. Woolley, Misha Erementchouk, Pinaki Mazumder, Stefano Pirandola, John F. Federici, Christian WeedbrookAbstract:A well-known empirical rule for the demand of wireless communication systems is that of Edholm's law of bandwidth. It states that the demand for bandwidth in wireless short-range communications doubles every 18 months. With the growing demand for bandwidth and the decreasing cell size of wireless systems, terahertz (THz) communication systems are expected to become increasingly important in modern day applications. With this expectation comes the need for protecting users' privacy and security in the best way possible. With that in mind, we show that Quantum key distribution can operate in the THz regime and we derive the relevant secret key rates against realistic collective attacks. In the extended THz range (from 0.1 to 50 THz), we find that below 1 THz, the main detrimental factor is thermal noise, while at higher frequencies it is atmospheric absorption. Our results show that high-rate THz Quantum Cryptography is possible over distances varying from a few meters using direct reconciliation, to about 220m via reverse reconciliation. We also give a specific example of the physical hardware and architecture that could be used to realize our THz Quantum key distribution scheme.
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reply to discrete and continuous variables for measurement device independent Quantum Cryptography
Nature Photonics, 2015Co-Authors: Stefano Pirandola, Carlo Ottaviani, Christian Weedbrook, Tobias Gehring, Gaetana Spedalieri, Samuel L Braunstein, Seth Lloyd, Christian S Jacobsen, Ulrik L AndersenAbstract:Reply to 'Discrete and continuous variables for measurement-device-independent Quantum Cryptography'
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High-rate measurement-device-independent Quantum Cryptography
Nature Photonics, 2015Co-Authors: Stefano Pirandola, Carlo Ottaviani, Christian Weedbrook, Tobias Gehring, Gaetana Spedalieri, Samuel L Braunstein, Seth Lloyd, Christian S Jacobsen, Ulrik L AndersenAbstract:Quantum Cryptography achieves a formidable task—the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum Cryptography is now headed towards solving the practical problem of constructing scalable and secure Quantum networks. A significant step in this direction has been the introduction of measurement-device independence, where the secret key between two parties is established by the measurement of an untrusted relay. Unfortunately, although qubit-implemented protocols can reach long distances, their key rates are typically very low, unsuitable for the demands of a metropolitan network. Here we show, theoretically and experimentally, that a solution can come from the use of continuous-variable systems. We design a coherent-state network protocol able to achieve remarkably high key rates at metropolitan distances, in fact three orders of magnitude higher than those currently achieved. Our protocol could be employed to build high-rate Quantum networks where devices securely connect to nearby access points or proxy servers. An end-to-end continuous-variable Quantum key distribution system with an untrusted node is proposed. A proof-of-principle experiment shows that 10^−1 secret key bits per relay use are distributed at 4 dB loss, corresponding to 20 km in optical fibre.
