Secure Quantum Key Distribution over 421 km of Optical Fiber

Boaron, Alberto; Boso, Gianluca; Rusca, Davide; Vulliez, Cédric; Autebert, Claire; Caloz, Misael; Perrenoud, Matthieu; Gras, Gaétan Daniel Michel; Bussières, Félix; Li, Mingjun; Nolan, Daniel A.; Martin, Anthony; Zbinden, Hugo

doi:10.1103/physrevlett.121.190502

Cited by 588 publications

(393 citation statements)

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“…The fluctuations of the relative permittivity of the atmospheric air can be statistically modeled [24][25][26][27][28][29][30][31][32]. The probability distribution of the parameters in equation (2) can then be analytically estimated, as shown in [21,22]. A brief recap of the derivation and the main results is presented in appendix A.…”

Section: Free-space Optical Links and The Elliptic Beam Approximationmentioning

confidence: 99%

Satellite-based links for quantum key distribution: beam effects and weather dependence

2019

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The establishment of a world-wide quantum communication network relies on the synergistic integration of satellite-based links and fiber-based networks. The first are helpful for long-distance communication, as the photon losses introduced by the optical fibers are too detrimental for lengths greater than about 200 km. This work aims at giving, on the one hand, a comprehensive and fundamental model for the losses suffered by the quantum signals during the propagation along an atmospheric free-space link. On the other hand, a performance analysis of different quantum key distribution (QKD) implementations is performed, including finite-key effects, focusing on different interesting practical scenarios. The specific approach that we chose allows to precisely model the contribution due to different weather conditions, paving the way towards more accurate feasibility studies of satellite-based QKD missions. IntroductionQuantum key distribution (QKD) and quantum communication in general have the potential to revolutionise the way we communicate confidential information over the internet. The natural carriers for quantum information are photons, that are already widely used in classical networks of optical fibers to achieve high communication rates. Unfortunately, even though enormous improvements have been obtained in the last years [1, 2], scaling quantum communication protocols over long distances is very challenging, due to the losses experienced during the propagation inside the optical fibers. Several schemes for the realization of quantum repeaters have been proposed in recent years, that could allow to bridge long distances and naturally be implemented inside a quantum communication network [3][4][5][6][7]. Considering the important technological hurdles that quantum repeaters should overcome before becoming useful, satellite-based free-space links look like the most practical way to achieve long-distance QKD in the short term [8]. They can take advantage of the satellite technology and the optical communication methods developed in the last decades in the classical case. Various feasibility studies had addressed this topic in the last twenty years [8][9][10][11] and several experiments have definitely proved that the technology involved is ready for deployment [12][13][14][15][16].Optical satellite-based links have the important drawback of being strongly dependent on the weather conditions [17][18][19][20]. The presence of turbulent eddies and scattering particles like haze or fog generates random fluctuations of the relative permittivity of the air, on different length-and time-scales. This phenomenon affects the light propagation in a complicated way, inducing random deviations and deformations of any optical beam sent through the atmosphere. It results in reduced transmittance, because of geometrical losses due to the finite collection aperture, and random modifications of the phase front. A comprehensive model of these effects is then necessary, in order to precisely evaluate the performance of the link w...

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Section: Free-space Optical Links and The Elliptic Beam Approximationmentioning

confidence: 99%

Satellite-based links for quantum key distribution: beam effects and weather dependence

2019

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“…We also observe that the protocol seems to be quite robust against intensity fluctuations of the optical pulses prepared by the parties.The last few decades have witnessed major advancements in the field of quantum communication [1, 2], with quantum key distribution (QKD) [3-13] being its most developed application. Recent experiments over about 400 km of optical fibers [14,15] and over about 1000 km of satellite-to-ground links [16,17] demonstrated that QKD over long distances is possible. Despite such remarkable experimental achievements, the private capacity of point-to-point QKD is intrinsically limited by fundamental bounds [18,19].…”

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confidence: 99%

Practical decoy-state method for twin-field quantum key distribution

Grasselli

Curty

2019

New J. Phys.

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Twin-field (TF) quantum key distribution (QKD) represents a novel QKD approach whose principal merit is to beat the point-to-point private capacity of a lossy quantum channel, thanks to performing single-photon interference in an untrusted node. Indeed, recent security proofs of various TF-QKD type protocols have confirmed that the secret key rate of these schemes scales essentially as the square root of the transmittance of the channel. Here, we focus on the TF-QKD protocol introduced by Curty et al, whose secret key rate is nearly an order of magnitude higher than previous solutions. Its security relies on the estimation of the detection probabilities associated to various photon-number states through the decoy-state method. We derive analytical bounds on these quantities assuming that each party uses either two, three or four decoy intensity settings, and we investigate the protocol's performance in this scenario. Our simulations show that two decoy intensity settings are enough to beat the point-to-point private capacity of the channel, and that the use of four decoys is already basically optimal, in the sense that it almost reproduces the ideal scenario of infinite decoys. We also observe that the protocol seems to be quite robust against intensity fluctuations of the optical pulses prepared by the parties.The last few decades have witnessed major advancements in the field of quantum communication [1, 2], with quantum key distribution (QKD) [3-13] being its most developed application. Recent experiments over about 400 km of optical fibers [14,15] and over about 1000 km of satellite-to-ground links [16,17] demonstrated that QKD over long distances is possible. Despite such remarkable experimental achievements, the private capacity of point-to-point QKD is intrinsically limited by fundamental bounds [18,19]. These bounds state that in the high-loss regime the key rate scales basically linearly with the transmittance of the channel connecting the endusers Alice and Bob, i.e. it decreases exponentially with the total channel length. This imposes strict practical constraints on the possibility of achieving point-to-point QKD over arbitrary long distances.A way to overcome this limitation is to employ one or more intermediate nodes in the quantum channel connecting the parties. For instance, the use of quantum repeaters [20] yields a polynomial scaling of the communication efficiency with the distance [21]. Moreover, a quantum repeater scheme can be arbitrarily iterated along the quantum channel, thus increasing in principle the total communication distance between Alice and Bob as much as desired. Unfortunately, however, quantum repeaters are very challenging to build in practice with current technology: they either require quantum memories [20][21][22] or quantum error correction [23,24]. Of course, technology is improving, and quantum repeaters may become viable in the future.Other solutions, which attain a square-root improvement in the scaling of the key rate with respect to the transmittance of the channel, ...

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“…We also note that, although the results are calculated in the absence of device imperfections, the calculations of error rate for the X-basis for the weak coherent state are close to ones obtained experimentally in [26] with real device imperfections. With currently available state-of-the-art device performance (see [27]), the results would be even more representative of the actual error rates. Therefore, we expect that the results for the amplitude-squeezed coherent state obtained here represent a potential improvement over the weak coherent state.…”

Section: Resultsmentioning

confidence: 99%

“…In practice however, weak coherent source (attenuated laser) is often used instead, due to limitations of single photon source for QKD applications. Indeed, recently a record maximum distance of 421 km for fiber-based QKD with state-of-the-art device performance employing laser source has been reported [27]. Therefore, the analysis of multi-photon interference is important in a MDI-QKD setup for calibration purpose, and for predicting coincidence probability using other states, such as the squeezed coherent state.…”

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confidence: 99%

Quantum interference of multi-photon at beam splitter with application in measurement-device-independent quantum key distribution

Pradana

Chew

2019

New J. Phys.

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Keywords: quantum interference, multi-photon interference, Hong-Ou-Mandel effect, squeezed coherent state, quantum cryptography, measurement-device-independent quantum key distribution, quantum bit error rate AbstractDespite the relative simplicity of the traditional Hong-Ou-Mandel (HOM) interferometer setup, it is of fundamental interest in various quantum optics applications and quantum information technologies. In this article, multi-photon interference using the original HOM interferometer setup is analyzed. More specifically, for any photon number state with Gaussian spectral distribution entering the beam splitter, the general analytical solution is calculated. The result is then used to study the coincident probability for coherent sources (laser) and squeezed coherent state. We also look into the potential benefits of implementing the squeezed coherent state in discrete-variable Measurement-Device-Independent Quantum Key Distribution and find that by optimizing the squeezing parameter, the error rate can be significantly reduced. This in turn also enhances the secret key rate performance over the coherent state.When two identical single photons enter a 50:50 beam splitter, quantum interference of the photons causes both photons to exit at the same (but random) side of the beam splitter. This is known as the Hong-Ou-Mandel (HOM) effect. Experimentally, this is characterized by a dip in the coincidence rate [1], also referred to as the HOM dip. Coincidence here refers to mutual detection of photons at both sides or output modes of the beam splitter.The original purpose of HOM experiment is to characterize the temporal distinguishability of single photons, by accurate measurement of time interval and bandwidth of the photons, allowed by the HOM interferometer setup. An account of HOM effect for single photons with various choices of spectra, and also taking into account photon distinguishability, can be seen in [2]. To accomplish the same task of characterizing the temporal distinguishability for multi photons, however, the experimental setup is generally modified to include multiple beam splitters and photon detectors [3]. A number of multi-photon interference experiments with various setups can be found, for example, in [4][5][6][7][8][9][10][11]. A summary for some of these experiments with discussion of temporal distinguishability is given in [12]. The general results for multi-photon quantum interference using traditional HOM interferometer, specifically, for any photon number state with Gaussian spectral distribution, have not been discussed in the literature.Despite that, however, and despite the relative simplicity of the original HOM interferometer setup, it has proven to be useful and important in various applications, for example, in quantum interference of successive single photons from the same emitter [13][14][15][16], to determine the purity of photons emitted by quantum dot [13], in quantum interference between single photons emitted by independent atoms [17], to measure biphoton temporal wav...

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Secure Quantum Key Distribution over 421 km of Optical Fiber

Cited by 588 publications

References 24 publications

Satellite-based links for quantum key distribution: beam effects and weather dependence

Satellite-based links for quantum key distribution: beam effects and weather dependence

Practical decoy-state method for twin-field quantum key distribution

Quantum interference of multi-photon at beam splitter with application in measurement-device-independent quantum key distribution

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