scholarly journals Getting something out of nothing

2005 ◽  
Vol 5 (4&5) ◽  
pp. 413-418
Author(s):  
H-K Lo
Keyword(s):  
Quantum Key Distribution ◽  
Coherent States ◽  
Communication Complexity ◽  
Key Distribution ◽  
Vacuum State ◽  
Quantum Memory ◽  
Generation Rate ◽  
Key Generation

We study quantum key distribution with standard weak coherent states and show, rather counter-intuitively, that the detection events originated from vacua can contribute to secure key generation rate, over and above the best previous result. Our proof is based on a communication complexity/quantum memory argument. The key observation is that Eve does not have to store anything, if Alice sends out a vacuum state.

Security of quantum key distribution with imperfect devices

2004 ◽  
Vol 4 (5) ◽  
pp. 325-360
Author(s):  
D. Gottesman ◽  
H.-K. Lo ◽  
N. L\"utkenhaus ◽  
J. Preskill
Keyword(s):  
Lower Bound ◽  
Quantum Key Distribution ◽  
Coherent States ◽  
Key Distribution ◽  
Generation Rate ◽  
Key Generation ◽  
Special Cases ◽  
Quantum Key Distribution Protocol

We prove the security of the Bennett-Brassard (BB84) quantum key distribution protocol in the case where the source and detector are under the limited control of an adversary. Our proof applies when both the source and the detector have small basis-dependent flaws, as is typical in practical implementations of the protocol. We derive a general lower bound on the asymptotic key generation rate for weakly basis-dependent eavesdropping attacks, and also estimate the rate in some special cases: sources that emit weak coherent states with random phases, detectors with basis-dependent efficiency, and misaligned sources and detectors.

scholarly journals DECOY STATE QUANTUM KEY DISTRIBUTION

2005 ◽  
Vol 03 (supp01) ◽  
pp. 143-143 ◽  
Author(s):  
HOI-KWONG LO
Keyword(s):  
Quantum Key Distribution ◽  
Secure Communication ◽  
Key Distribution ◽  
Generation Rate ◽  
Key Generation ◽  
Long Distance ◽  
Decoy State ◽  
Bb84 Protocol ◽  
High Loss ◽  
Statistical Fluctuations

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", . We also have done the first experimental demonstration of decoy state quantum key distribution, over 15km of Telecom fibers. This part of work is published in "Experimental Decoy State Quantum Key Distribution Over 15km", .

The enhanced measurement-device-independent quantum key distribution with heralded pair coherent state

2019 ◽  
Vol 34 (04) ◽  
pp. 2050063
Author(s):  
Yefeng He ◽  
Wenping Ma
Keyword(s):  
Light Source ◽  
Error Rate ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Generation Rate ◽  
Key Generation ◽  
Measurement Device ◽  
Decoy State ◽  
Communication Distance ◽  
Measurement Device Independent

With heralded pair coherent states (HPCS), orbital angular momentum (OAM) states and pulse position modulation (PPM) technology, a decoy-state measurement-device-independent quantum key distribution (MDI-QKD) protocol is proposed. OAM states and PPM technology are used to realize the coding of the signal states in the HPCS light source. The use of HPCS light source, OAM coding and PPM coding cannot only reduce the error rate but also improve the key generation rate and communication distance. The new MDI-QKD protocol also employs three-intensity decoy states to avoid the attacks against the light source. By calculating the error rate and key generation rate, the performance of the MDI-QKD protocol is analyzed. Numerical simulation shows that the protocol has very low error rate and very high key generation rate. Moreover, the maximum communication distance can reach 455 km.

Security proof of quantum key distribution with detection efficiency mismatch

2009 ◽  
Vol 9 (1&2) ◽  
pp. 131-165
Author(s):  
C.-H. F. Fung ◽  
K. Tamaki ◽  
B. Qi ◽  
H.-K. Lo ◽  
X. Ma
Keyword(s):  
Quantum Key Distribution ◽  
Detection Efficiency ◽  
Key Distribution ◽  
Unconditional Security ◽  
Generation Rate ◽  
Key Generation ◽  
Efficiency Ratio ◽  
Physical Origin ◽  
Security Proof ◽  
Time Domains

In theory, quantum key distribution (QKD) offers unconditional security based on the laws of physics. However, as demonstrated in recent quantum hacking theory and experimental papers, detection efficiency loophole can be fatal to the security of practical QKD systems. Here, we describe the physical origin of detection efficiency mismatch in various domains including spatial, spectral, and time domains and in various experimental set-ups. More importantly, we prove the unconditional security of QKD even with detection efficiency mismatch. We explicitly show how the key generation rate is characterized by the maximal detection efficiency ratio between the two detectors. Furthermore, we prove that by randomly switching the bit assignments of the detectors, the effect of detection efficiency mismatch can be completely eliminated.

scholarly journals DECOY STATE QUANTUM KEY DISTRIBUTION

2010 ◽  
Vol 10 (2) ◽  
pp. 81-86
Author(s):  
Sellami Ali
Keyword(s):  
Distribution System ◽  
Quantum Key Distribution ◽  
Fiber Length ◽  
Key Distribution ◽  
Generation Rate ◽  
Key Generation ◽  
Decoy State ◽  
Set Up

Experimental weak + vacuum protocol has been demonstrated using commercial QKD system based on a standard bi-directional ‘Plug & Play’ set-up. By making simple modifications to a commercial quantum key distribution system, decoy state QKD allows us to achieve much better performance than QKD system without decoy state in terms of key generation rate and distance. We demonstrate an unconditionally secure key rate of 6.2931 x 10-4per pulse for a 25 km fiber length.

scholarly journals Security of high speed quantum key distribution with finite detector dead time

2014 ◽  
Vol 14 (3&4) ◽  
pp. 217-235
Author(s):  
Viacheslav Burenkov ◽  
Bing Qi ◽  
Ben Fortescue ◽  
Hoi-Kwong Lo
Keyword(s):  
Distribution System ◽  
Quantum Key Distribution ◽  
High Speed ◽  
Dead Time ◽  
Detection Efficiency ◽  
Transmission Rate ◽  
Key Distribution ◽  
Generation Rate ◽  
Key Generation ◽  
Bb84 Protocol

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 scheme for sifting bits. Analytical calculations and numerical simulations of the Bennett-Brassard BB84 protocol are performed. We study Rogers et al.'s scheme (further information is available in [D. J. Rogers, J. C. Bienfang, A. Nakassis, H. Xu, and C. W. Clark, New J. Phys.~{\bf 9}, 319 (2007)]) 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 scheme is no longer guaranteed to be secure. More specifically, Eve can induce a basis-dependent detection efficiency at the receiver's end. Modified key sifting schemes that are basis-independent and thus 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 simulate their key generation rate. It is shown that the maximum key generation rate is $1/(2\tau)$ for passive basis selection, and $1/\tau$ for active basis selection. The security analysis for finite detector dead time is also extended to the decoy state BB84 protocol for one particular secure sifting scheme.

scholarly journals Quantum key distribution in terms of the Greenberger-Horne-Zeilinger state: Multi-key generation

Laser Physics ◽  
2010 ◽  
Vol 20 (5) ◽  
pp. 1210-1214 ◽  
Author(s):  
F. A. A. El-Orany ◽  
M. R. B. Wahiddin ◽  
M. -A. Mat-Nor ◽  
N. Jamil ◽  
I. Bahari
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Key Generation
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