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Quantum cryptography
 Rev. Mod. Phys
, 2002
"... Quantum cryptography could well be the first application of quantum mechanics at the individual quanta level. The very fast progress in both theory and experiments over the recent years are reviewed, with emphasis on open questions and technological issues. Contents I ..."
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Cited by 182 (6 self)
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Quantum cryptography could well be the first application of quantum mechanics at the individual quanta level. The very fast progress in both theory and experiments over the recent years are reviewed, with emphasis on open questions and technological issues. Contents I
Information and Computation: Classical and Quantum Aspects
 REVIEWS OF MODERN PHYSICS
, 2001
"... Quantum theory has found a new field of applications in the realm of information and computation during the recent years. This paper reviews how quantum physics allows information coding in classically unexpected and subtle nonlocal ways, as well as information processing with an efficiency largely ..."
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Cited by 36 (3 self)
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Quantum theory has found a new field of applications in the realm of information and computation during the recent years. This paper reviews how quantum physics allows information coding in classically unexpected and subtle nonlocal ways, as well as information processing with an efficiency largely surpassing that of the present and foreseeable classical computers. Some outstanding aspects of classical and quantum information theory will be addressed here. Quantum teleportation, dense coding, and quantum cryptography are discussed as a few samples of the impact of quanta in the transmission of information. Quantum logic gates and quantum algorithms are also discussed as instances of the improvement in information processing by a quantum computer. We provide finally some examples of current experimental
The structure of bipartite quantum states. Insights from group theory and cryptography
, 2006
"... dissertation is the result of my own work and includes nothing which is the outcome Currently, a rethinking of the fundamental properties of quantum mechanical systems in the light of quantum computation and quantum cryptography is taking place. In this PhD thesis, I wish to contribute to this effor ..."
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Cited by 22 (1 self)
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dissertation is the result of my own work and includes nothing which is the outcome Currently, a rethinking of the fundamental properties of quantum mechanical systems in the light of quantum computation and quantum cryptography is taking place. In this PhD thesis, I wish to contribute to this effort with a study of the bipartite quantum state. Bipartite quantummechanical systems are made up of just two subsystems, A and B, yet, the quantum states that describe these systems have a rich structure. The focus is twofold: Part I studies the relations between the spectra of the joint and the reduced states, and in part II, I will analyse the amount of entanglement, or quantum correlations, present in a given state. In part I, the mathematical tools from group theory play an important role, mainly drawing on the representation theory of finite and Lie groups and the SchurWeyl duality. This duality will be used to derive a onetoone relation between the spectra of a joint quantum system AB and its parts A and B, and the Kronecker coefficients of the symmetric group. In this way the two problems are connected for the first time, which
Defeating Classical Bit Commitments With a Quantum Computer
, 1998
"... It has been recently shown by Mayers that no bit commitment is secure if the participants have unlimited computational power and technology. However it was noticed that a secure protocol could be obtained by forcing the cheater to execute a measurement. Similar situations had been encountered previo ..."
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Cited by 15 (2 self)
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It has been recently shown by Mayers that no bit commitment is secure if the participants have unlimited computational power and technology. However it was noticed that a secure protocol could be obtained by forcing the cheater to execute a measurement. Similar situations had been encountered previously in the design of Quantum Oblivious Transfer. The question is whether a classical bit commitment could be used for this specific purpose. We demonstrate that, surprisingly, classical unconditionally concealing bit commitments do not help.
Quantum Bit Commitment From a Physical Assumption
 In Advances in Cryptology — CRYPTO
, 1998
"... Abstract. Mayers and independently Lo and Chau have shown that unconditionally secure quantum bit commitment is impossible. In this paper we show that under the assumption that the sender is not able to perform generalized measurements involving more than n qubits coherently (ncoherent measurements ..."
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Cited by 14 (4 self)
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Abstract. Mayers and independently Lo and Chau have shown that unconditionally secure quantum bit commitment is impossible. In this paper we show that under the assumption that the sender is not able to perform generalized measurements involving more than n qubits coherently (ncoherent measurements) then quantum bit commitment is possible. A commitment scheme is δbinding if for each execution there is an ˜x ∈{0,1}that cannot be unveiled with probability of success better than δ. Our bit commitment scheme requires the transmission of N qubits and is δbinding, for any δ>0, if the committer can only carry out ncoherent measurements for some n ∈ Ω(N). For some α> 0, the scheme is 2 −αNbinding against ncoherent measurements for some n ∈ Ω ( √ N). The security against malicious receivers is unconditional. 1
The quantum bit commitment theorem
 Foundations of Physics 31: 735–756
, 2001
"... Unconditionally secure twoparty bit commitment based solely on the principles of quantum mechanics (without exploiting special relativistic signalling constraints, or principles of general relativity or thermodynamics) has been shown to be impossible, but the claim is repeatedly challenged. The qua ..."
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Cited by 11 (4 self)
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Unconditionally secure twoparty bit commitment based solely on the principles of quantum mechanics (without exploiting special relativistic signalling constraints, or principles of general relativity or thermodynamics) has been shown to be impossible, but the claim is repeatedly challenged. The quantum bit commitment theorem is reviewed here and the central conceptual point, that an ``Einstein Podolsky Rosen' ' attack or cheating strategy can always be applied, is clarified. The question of whether following such a cheating strategy can ever be disadvantageous to the cheater is considered and answered in the negative. There is, indeed, no loophole in the theorem. 1.
Remote preparation of arbitrary ensembles and quantum bit commitment
, 2008
"... The HughstonJozsaWootters theorem shows that any finite ensemble of quantum states can be prepared “at a distance”, and it has been used to demonstrate the insecurity of all bit commitment protocols based on finite quantum systems without superselection rules. In this paper, we prove a generalized ..."
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Cited by 7 (0 self)
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The HughstonJozsaWootters theorem shows that any finite ensemble of quantum states can be prepared “at a distance”, and it has been used to demonstrate the insecurity of all bit commitment protocols based on finite quantum systems without superselection rules. In this paper, we prove a generalized HJW theorem for arbitrary ensembles of states on a C∗algebra. We then use this result to demonstrate the insecurity of bit commitment protocols based on infinite quantum systems, and quantum systems with Abelian superselection rules.
On Deniability in Quantum Key Exchange
"... Abstract. We show that claims of “perfect security ” for keys produced by quantum key exchange (QKE) are limited to “privacy ” and “integrity.” Unlike a onetime pad, QKE does not necessarily enable Sender and Receiver to pretend later to have established a different key. This result is puzzling in ..."
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Cited by 2 (0 self)
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Abstract. We show that claims of “perfect security ” for keys produced by quantum key exchange (QKE) are limited to “privacy ” and “integrity.” Unlike a onetime pad, QKE does not necessarily enable Sender and Receiver to pretend later to have established a different key. This result is puzzling in light of Mayers ’ “NoGo ” theorem showing the impossibility of quantum bit commitment. But even though a simple and intuitive application of Mayers ’ protocol transformation appears sufficient to provide deniability (else QBC would be possible), we show several reasons why such conclusions are illfounded. Mayers ’ transformation arguments, while sound for QBC, are insufficient to establish deniability in QKE. Having shed light on several unadvertised pitfalls, we then provide a candidate deniable QKE protocol. This itself indicates further shortfalls in current proof techniques, including reductions that preserve privacy but fail to preserve deniability. In sum, purchasing undeniability with an offtheshelf QKE protocol is significantly more expensive and dangerous than the mere optic fiber for which “perfect security ” is advertised. 1
On the (Im)Possibility of Quantum String . . .
, 2005
"... Unconditionally secure nonrelativistic bit commitment is known to be impossible in both the classical and quantum worlds. However, when committing to a string of n bits at once, how far can we stretch the quantum limits? We consider quantum schemes where Alice commits a string of n bits to Bob, in ..."
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Unconditionally secure nonrelativistic bit commitment is known to be impossible in both the classical and quantum worlds. However, when committing to a string of n bits at once, how far can we stretch the quantum limits? We consider quantum schemes where Alice commits a string of n bits to Bob, in such a way that she can only cheat on a bits and Bob can learn at most b bits of ”information ” before the reveal phase. We show a negative and a positive result, depending on how we measure Bob’s information. If we use the Holevo quantity, no good schemes exist: a + b is at least n. If, however, we use accessible information, there exists a scheme where a = 4 log n + O(1) and b = 4. This is classically impossible. Our protocol is not efficient, however, we also exhibit an efficient scheme when Bob’s measurement circuit is restricted to polynomial size. Our scheme also implies a protocol for n simultaneous coin flips which achieves higher entropy of the resulting string than any previously known protocol.
Unconditionally Secure Quantum Bit Commitment Really Is Impossible
, 2000
"... Unconditionally secure quantum bit commitment has been shown to be impossible by Mayers [22] and Lo and Chau [18, 19], but the claim is repeatedly challenged. The bit commitment theorem is reviewed here and the central conceptual point, that an ”EinsteinPodolskyRosen ’ attack or cheating strategy ..."
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Unconditionally secure quantum bit commitment has been shown to be impossible by Mayers [22] and Lo and Chau [18, 19], but the claim is repeatedly challenged. The bit commitment theorem is reviewed here and the central conceptual point, that an ”EinsteinPodolskyRosen ’ attack or cheating strategy can always be applied, is clarified. The question of whether following such a cheating strategy can ever be disadvantageous to the cheater is considered and answered in the negative. PACS numbers: 03.67.a, 03.67.Dd, 89.70.+c 1