scholarly journals Clocks without “Time” in Entangled-State Experiments

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 434
Author(s):  
F. Hadi Madjid ◽  
John M. Myers
Keyword(s):  
General Relativity ◽  
Special Relativity ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Entangled States ◽  
Entangled State ◽  
Definition Of ◽  
Do So

Entangled states of light exhibit measurable correlations between light detections at separated locations. These correlations are exploited in entangled-state quantum key distribution. To do so involves setting up and maintaining a rhythm of communication among clocks at separated locations. Here, we try to disentangle our thinking about clocks as used in actual experiments from theories of time, such as special relativity or general relativity, which already differ between each other. Special relativity intertwines the concept of time with a particular definition of the synchronization of clocks, which precludes synchronizing every clock to every other clock. General relativity imposes additional barriers to synchronization, barriers that invite seeking an alternative depending on any global concept of time. To this end, we focus on how clocks are actually used in some experimental situations. We show how working with clocks without worrying about time makes it possible to generalize some designs for quantum key distribution and also clarifies the need for alternatives to the special-relativistic definition of synchronization.

scholarly journals TIGHTENING THE EAVESDROPPING ACCESSIBLE INFORMATION FOR CONTINUOUS VARIABLE QUANTUM KEY DISTRIBUTION PROTOCOLS THAT INVOLVE NONMAXIMALLY ENTANGLEMENT

2012 ◽  
Vol 26 (16) ◽  
pp. 1250109 ◽  
Author(s):  
A. BECIR ◽  
M. R. B. WAHIDDIN
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Upper Bounds ◽  
Entangled States ◽  
Entangled State ◽  
Protocol Implementation ◽  
Accessible Information ◽  
Heisenberg Uncertainty

In this paper, we derive tight bounds for the eavesdropping attacks on continuous variable quantum key distribution (CV-QKD) protocol that involves nonmaximally entangled states. We show that deriving bounds on the eavesdropper's accessible information based on the Heisenberg uncertainty yields upper bounds, but those bounds are not tight. For this reason, we follow different techniques to derive the desired tight bounds. The new bounds are tight for all CV-QKD protocols that involve two-mode entangled state. Our derivations are applied to direct and reverse reconciliation schemes of protocol implementation, respectively.

ERROR-REJECTING BENNETT–BRASSARD–MERMIN QUANTUM KEY DISTRIBUTION PROTOCOL BASED ON LINEAR OPTICS OVER A COLLECTIVE-NOISE CHANNEL

2010 ◽  
Vol 08 (07) ◽  
pp. 1141-1151 ◽  
Author(s):  
XI-HAN LI ◽  
XIAO-JIAO DUAN ◽  
FU-GUO DENG ◽  
HONG-YU ZHOU
Keyword(s):  
Quantum Entanglement ◽  
Quantum Key Distribution ◽  
Quantum Information Processing ◽  
Key Distribution ◽  
Entangled State ◽  
Collective Noise ◽  
Linear Optics ◽  
Entanglement Purification ◽  
Measurement Results ◽  
Entangled Quantum States

Quantum entanglement is an important element of quantum information processing. Sharing entangled quantum states between two remote parties is a precondition of most quantum communication schemes. We will show that the protocol proposed by Yamamoto et al. (Phys. Rev. Lett.95 (2005) 040503) for transmitting single quantum qubit against collective noise with linear optics is also suitable for distributing the components of entanglements with some modifications. An additional qubit is introduced to reduce the effect of collective noise, and the receiver can take advantage of the time discrimination and the measurement results of the assistant qubit to reconstruct a pure entanglement with the sender. Although the scheme succeeds probabilistically, the fidelity of the entangled state is almost unity in principle. The resource used in our protocol to get a pure entangled state is finite, which establishes entanglement more easily in practice than quantum entanglement purification. Also, we discuss its application in quantum key distribution over a collective channel in detail.

scholarly journals An improved coding method of quantum key distribution protocols based on Fibonacci-valued OAM entangled states

2017 ◽  
Vol 381 (35) ◽  
pp. 2922-2926 ◽  
Author(s):  
Hong Lai ◽  
Ming-Xing Luo ◽  
Cheng Zhan ◽  
Josef Pieprzyk ◽  
Mehmet A. Orgun
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Entangled States ◽  
Coding Method

scholarly journals A largely self-contained and complete security proof for quantum key distribution

Quantum ◽  
2017 ◽  
Vol 1 ◽  
pp. 14 ◽  
Author(s):  
Marco Tomamichel ◽  
Anthony Leverrier
Keyword(s):  
Quantum Key Distribution ◽  
Estimation Error ◽  
Security Analysis ◽  
Key Distribution ◽  
Operational Definition ◽  
Uncertainty Relations ◽  
Secret Key ◽  
Security Proof ◽  
Key Length ◽  
Definition Of

In this work we present a security analysis for quantum key distribution, establishing a rigorous tradeoff between various protocol and security parameters for a class of entanglement-based and prepare-and-measure protocols. The goal of this paper is twofold: 1) to review and clarify the stateof-the-art security analysis based on entropic uncertainty relations, and 2) to provide an accessible resource for researchers interested in a security analysis of quantum cryptographic protocols that takes into account finite resource effects. For this purpose we collect and clarify several arguments spread in the literature on the subject with the goal of making this treatment largely self-contained. More precisely, we focus on a class of prepare-and-measure protocols based on the Bennett-Brassard (BB84) protocol as well as a class of entanglement-based protocols similar to the Bennett-Brassard-Mermin (BBM92) protocol. We carefully formalize the different steps in these protocols, including randomization, measurement, parameter estimation, error correction and privacy amplification, allowing us to be mathematically precise throughout the security analysis. We start from an operational definition of what it means for a quantum key distribution protocol to be secure and derive simple conditions that serve as sufficient condition for secrecy and correctness. We then derive and eventually discuss tradeoff relations between the block length of the classical computation, the noise tolerance, the secret key length and the security parameters for our protocols. Our results significantly improve upon previously reported tradeoffs.

scholarly journals Foundations of Finsler Spacetimes from the Observers’ Viewpoint

Universe ◽  
2020 ◽  
Vol 6 (4) ◽  
pp. 55 ◽  
Author(s):  
Antonio N. Bernal ◽  
Miguel A. Javaloyes ◽  
Miguel Sánchez
Keyword(s):  
General Relativity ◽  
Special Relativity ◽  
Linear Approximation ◽  
Classical Mechanics ◽  
Finsler Metric ◽  
Speed Of Light ◽  
Cone Structure ◽  
Mathematical Definition ◽  
Finsler Spacetime ◽  
Definition Of

Physical foundations for relativistic spacetimes are revisited in order to check at what extent Finsler spacetimes lie in their framework. Arguments based on inertial observers (as in the foundations of special relativity and classical mechanics) are shown to correspond with a double linear approximation in the measurement of space and time. While general relativity appears by dropping the first linearization, Finsler spacetimes appear by dropping the second one. The classical Ehlers–Pirani–Schild approach is carefully discussed and shown to be compatible with the Lorentz–Finsler case. The precise mathematical definition of Finsler spacetime is discussed by using the space of observers. Special care is taken in some issues such as the fact that a Lorentz–Finsler metric would be physically measurable only on the causal directions for a cone structure, the implications for models of spacetimes of some apparently innocuous hypotheses on differentiability, or the possibilities of measurement of a varying speed of light.

A TWO-STEP CHANNEL-ENCRYPTING QUANTUM KEY DISTRIBUTION PROTOCOL

2010 ◽  
Vol 08 (06) ◽  
pp. 1013-1022 ◽  
Author(s):  
FEN-ZHUO GUO ◽  
FEI GAO ◽  
QIAO-YAN WEN ◽  
FU-CHEN ZHU
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Entangled States ◽  
Ideal Condition ◽  
Practical Situation ◽  
Information Carrier ◽  
General Individual Attack ◽  
Epr State ◽  
Quantum Key Distribution Protocol ◽  
Individual Attack

A two-step channel-encrypting quantum key distribution protocol is proposed. Using the previously shared EPR pairs as the quantum key, two bits of classical key can be established via one information carrier EPR state on average. In theory, the efficiency of this protocol reaches 100%, and there is no need to consume any entangled states including both the quantum key and the information carriers in ideal condition. The protocol can resist the particular attack that is fatal to other some channel-encrypting schemes. Principally, we prove the security against the most general individual attack of this protocol. Entanglement collapse in practical situation, as well as the realistic implementation of this protocol is also discussed.

Entangled state quantum key distribution

2005 ◽  
Author(s):  
H. Hubel ◽  
A. Fedrizzi ◽  
A. Poppe ◽  
T. Lorunser ◽  
A. Zeilinger
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Entangled State
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