Quantum key distribution: defeating collective noise without reducing efficiency

2014 ◽  
Vol 14 (9&10) ◽  
pp. 845-856
Author(s):  
Song Lin ◽  
Gong-De Guo ◽  
Fei Gao ◽  
Xiao-Fen Liu
Keyword(s):  
Quantum Key Distribution ◽  
Quantum Communication ◽  
Transmission Rate ◽  
Key Distribution ◽  
Collective Noise ◽  
Bb84 Protocol ◽  
Communication Efficiency ◽  
Valid Solution ◽  
The Cost ◽  
Decoherence Free Subspace

Decoherence-free subspace (DFS) is a valid solution to realize quantum communication over a collective noise channel, and has been widely studied. Generally speaking, replacing a qubit with a DFS state will cause the reduction of communication efficiency. However, in this letter, it is shown that some kinds of noises may not lower the transmission rate of quantum key distribution. To illustrate it, we propose two quantum key distribution protocols based on Bell states. Here, two nonorthogonal and unbiased sets in a DFS are constructed by linear combination of particles at different positions. Since $n-1$ classical bits are distributed by using $2n$ qubits in our protocols, the transmission rate is close to that of noiseless BB84 protocol. Furthermore, when considering the cost of transmitting classical bits, the efficiencies of these protocols are even higher than that of BB84 protocol.

scholarly journals Efficient quantum communication under collective noise

2013 ◽  
Vol 13 (3&4) ◽  
pp. 290-323
Author(s):  
Michael Skotiniotis ◽  
Wolfgang Dur ◽  
Barbara Kraus
Keyword(s):  
Quantum Information ◽  
Discrete Group ◽  
Quantum Communication ◽  
Communication Protocol ◽  
Transmission Rate ◽  
Collective Noise ◽  
Cyclic Groups ◽  
Time Encoding ◽  
Decoherence Free Subspace ◽  
Quantum Communication Protocol

We introduce a new quantum communication protocol for the transmission of quantum information under collective noise. Our protocol utilizes a decoherence-free subspace in such a way that an optimal asymptotic transmission rate is achieved, while at the same time encoding and decoding operations can be efficiently implemented. The encoding and decoding circuit requires a number of elementary gates that scale linearly with the number of transmitted qudits, $m$. The logical depth of our encoding and decoding operations is constant and depends only on the channel in question. For channels described by an arbitrary discrete group $G$, i.e.~with a discrete number, $\lvert G\rvert$, of possible noise operators, perfect transmission at a rate $m/(m+r)$ is achieved with an overhead that scales at most as $\mathcal{O}(d^r)$ where the number of auxiliary qudits, $r$, depends solely on the group in question. Moreover, this overhead is independent of the number of transmitted qudits, $m$. For certain groups, e.g.~cyclic groups, we find that the overhead scales only linearly with the number of group elements $|G|$.

FAULT-TOLERATE QUANTUM KEY DISTRIBUTION OVER A COLLECTIVE-NOISE CHANNEL

2010 ◽  
Vol 08 (07) ◽  
pp. 1101-1109 ◽  
Author(s):  
CHUN-YAN LI ◽  
YAN-SONG LI
Keyword(s):  
Quantum Key Distribution ◽  
Single Photon ◽  
Bell State ◽  
Key Distribution ◽  
Quantum Systems ◽  
Collective Noise ◽  
Two Photon ◽  
Intrinsic Efficiency ◽  
Decoherence Free Subspace ◽  
Bell State Measurements

We present two quantum key distribution (QKD) schemes over a collective-noise channel. Each logical qubit, composed of two physical qubits with a decoherence-free subspace, is immune to a collective noise and can carry one bit of information in theory. Although the receiver should prepare entangled two-photon quantum systems, he can read out the information encoded by the sender with two unitary operations on two photons, resorting to only two single-photon measurements, not Bell-state measurements, which makes these protocols simpler than others in experiment. These two QKD protocols are deterministic, not random, which makes the classical information exchanged be reduced largely. Also, they have a high intrinsic efficiency.

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.

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 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", .

Quantum communication scheme with freely selectable users

2021 ◽  
pp. 2150156
Author(s):  
Tianqi Dou ◽  
Hongwei Liu ◽  
Jipeng Wang ◽  
Zhenhua Li ◽  
Wenxiu Qu ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
Quantum Communication ◽  
Information Science ◽  
Quantum Secret Sharing ◽  
Key Distribution ◽  
Communication Process ◽  
Secret Key ◽  
Quantum Information Science ◽  
Transmission Distance ◽  
Communication Scheme

Quantum communication plays an important role in quantum information science due to its unconditional security. In practical implementations, the users of each communication vary with the transmitted information, and hence not all users are required to participate in each communication round. Therefore, improving the flexibility and efficiency of the actual communication process is highly demanded. Here, we propose a theoretical quantum communication scheme that realizes secret key distribution for both the two-party quantum key distribution (QKD) and multi-party quantum secret sharing (QSS) modes. The sender, Alice, can freely select one or more users to share keys among all users, and nonactive users will not participate in the process of secret key sharing. Numerical simulations show the superiority of the proposed scheme in transmission distance and secure key rate. Consequently, the proposed scheme is valuable for secure quantum communication network scenarios.

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