Implementation of continuous-variable quantum key distribution with composable and one-sided-device-independent security against coherent attacks

Gehring, Tobias; Händchen, Vitus; Duhme, Jörg; Furrer, Fabian; Franz, Titus; Pacher, Christoph; Werner, R. F.; Schnabel, R.

doi:10.1038/ncomms9795

Cited by 237 publications

(180 citation statements)

References 44 publications

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“…However, in practice we must modify these expressions, multiplying Alice and Bob's mutual information by a factor β < 1 to account for finite information reconciliation efficiency (see Supplement 1 for explicit calculations). Reconciliation efficiencies for CV-QKD have increased substantially in the past few years [55,56], with efficiencies of between 94% and 95.5% recently reported [42]. Here, we choose β 0.95.…”

Section: Resultsmentioning

confidence: 99%

“…Protocols motivated by these hardware advantages have begun to appear. A direct extension [28] to the infinite-dimensional Hilbert spaces relevant for CV-QKD [41] has been applied to propose a discretized 1sDI-CV-QKD protocol that also accounts for finite-size effects [15,16], and a scheme independent of Bob's devices only has recently been demonstrated [42].…”

Section: Introductionmentioning

confidence: 99%

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Experimental demonstration of Gaussian protocols for one-sided device-independent quantum key distribution

Walk¹,

Hosseini²,

Geng³

et al. 2016

Optica

180

104

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Nonlocal correlations, a longstanding foundational topic in quantum information, have recently found application as a resource for cryptographic tasks where not all devices are trusted, for example, in settings with a highly secure central hub, such as a bank or government department, and less secure satellite stations, which are inherently more vulnerable to hardware "hacking" attacks. The asymmetric phenomena of Einstein-Podolsky-Rosen (EPR) steering plays a key role in one-sided device-independent (1sDI) quantum key distribution (QKD) protocols. In the context of continuous-variable (CV) QKD schemes utilizing Gaussian states and measurements, we identify all protocols that can be 1sDI and their maximum loss tolerance. Surprisingly, this includes a protocol that uses only coherent states. We also establish a direct link between the relevant EPR steering inequality and the secret key rate, further strengthening the relationship between these asymmetric notions of nonlocality and device independence. We experimentally implement both entanglement-based and coherent-state protocols, and measure the correlations necessary for 1sDI key distribution up to an applied loss equivalent to 7.5 and 3.5 km of optical fiber transmission, respectively. We also engage in detailed modeling to understand the limits of our current experiment and the potential for further improvements. The new protocols we uncover apply the cheap and efficient hardware of CV-QKD systems in a significantly more secure setting.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental demonstration of Gaussian protocols for one-sided device-independent quantum key distribution

Walk¹,

Hosseini²,

Geng³

et al. 2016

Optica

180

104

View full text Add to dashboard Cite

show abstract

“…These protocols [9,10], which do not require single-photon detectors, are particularly appealing in terms of implementation [11] but their security is still far from being completely understood. Recently, a composable security proof for a CV protocol was obtained [12][13][14] from an entropic uncertainty principle [15] but the protocol requires the generation of squeezed states and is only moderately tolerant to losses. Other approaches to establish the security of a protocol typically consist of two independent steps: first a composable security proof valid against collective attacks, a restricted type of attacks where the quantum state shared by Alice and Bob protocol displays a tensor product structure, followed by an additional argument to obtain security against general attacks.…”

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confidence: 99%

Composable Security Proof for Continuous-Variable Quantum Key Distribution with Coherent States

2015

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We give the first composable security proof for continuous-variable quantum key distribution with coherent states against collective attacks. Crucially, in the limit of large blocks the secret key rate converges to the usual value computed from the Holevo bound. Combining our proof with either the de Finetti theorem or the Postselection technique then shows the security of the protocol against general attacks, thereby confirming the long-standing conjecture that Gaussian attacks are optimal asymptotically in the composable security framework.We expect that our parameter estimation procedure, which does not rely on any assumption about the quantum state being measured, will find applications elsewhere, for instance for the reliable quantification of continuous-variable entanglement in finite-size settings.Quantum key distribution (QKD) is a cryptographic primitive that allows two distant parties, Alice and Bob, who have access to an insecure quantum channel and an authenticated classical channel, to distill a secret key. QKD has spurred a lot of interest in the past decades because it is arguably the first application of the field of quantum information to reach commercial maturity [1]. Despite a lot of effort invested in the theoretical analysis of QKD protocols, composable security [2,3] has only been established for a handful of protocols, for instance BB84 [4]. This major achievement is the latest step in a series of more and more refined security proofs and improved bounds for the secret key rates. More precisely, composable security proofs have successively used an exponential version of the de Finetti theorem [5], the Postselection technique [6] and an entropic uncertainty principle [7].The situation for continuous-variable (CV) protocols is much less advanced [8]. These protocols [9, 10], which do not require single-photon detectors, are particularly appealing in terms of implementation [11] but their security is still far from being completely understood. Recently, a composable security proof for a CV protocol was obtained [12][13][14] from an entropic uncertainty principle [15] but the protocol requires the generation of squeezed states and is only moderately tolerant to losses. Other approaches to establish the security of a protocol typically consist of two independent steps: first a composable security proof valid against collective attacks, a restricted type of attacks where the quantum state shared by Alice and Bob protocol displays a tensor product structure, followed by an additional argument to obtain security against general attacks. These two steps have been partially completed in the case of CV protocols: a reduction from general to collective attacks is obtained via two possible techniques, namely a de Finetti theorem [16], and the Postselection technique [17], the latter technique being more efficient but at the price of adding an unpracti- * Electronic address: anthony.leverrier@inria.fr cal symmetrization step to the protocol (The Postselection technique should not be mistaken with the po...

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“…In order to study solely the influence of a fading channel (for η 1,2 = 1) on the security of the CV QKD protocols, we look at the case of collective attacks conducted in case of noiseless channel ( atm = 0) and perfect post-processing accessible to trusted parties (β = 1, which is a theoretical limit, but recent protocols [27,37,43,44] are very close to it). Figure 1(b) depicts a positive key rate and it is dependency on the squeezing V s and modulation variance V m for various values of transmittance fluctuations Var( √ η) for η = 1/2.…”

Section: General Fading Channel Influencementioning

confidence: 99%

Squeezing-enhanced quantum key distribution over atmospheric channels

2020

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We propose the Gaussian continuous-variable quantum key distribution using squeezed states in the composite channels including atmospheric propagation with transmittance fluctuations. We show that adjustments of signal modulation and use of optimal feasible squeezing can be sufficient to significantly overcome the coherent-state protocol and drastically improve the performance of quantum key distribution in atmospheric channels, also in the presence of additional attenuating and noisy channels. Furthermore, we consider examples of atmospheric links of different lengths, and show that optimization of both squeezing and modulation is crucial for reduction of protocol downtime and increase of secure atmospheric channel distance. Our results demonstrate unexpected advantage of fragile squeezed states of light in the free-space quantum key distribution applicable in daylight and stable against atmospheric turbulence.Quantum key distribution (QKD) [1-5] is one of the major practical applications of quantum information theory, which provides trusted parties (Alice and Bob) with the methods (protocols) for provably secure distribution of secret cryptographic keys so that security of the key can be verified using fundamental principles of quantum physics. One of the main requirements of QKD is the availability of a dedicated quantum channel capable of transmitting coherent quantum signals between the sending and receiving stations. In the case of fiber-optical channels, being the typical media for QKD implementations, this means a dedicated optical fiber, possibly with co-existing classical or quantum signals. However, the dedicated fiber-optical infrastructure can be unavailable, e.g., in the case of movable stations, necessity of quick channel deployment or in hostile environments. Moreover, the extra-long-distance inter-continental quantum communication over satellites relies on the free-space channels [6]. Therefore, the free-space channels are an important physical medium for QKD implementations.The main issue faced by the discrete-variable (DV) QKD protocols, based on single-photon states or weak coherent pulses and the direct photon counting, is the sensitivity of the detectors to the background light, which adds noise to the measured data. This renders standard DV QKD protocols practically unusable in the daylight conditions unless spectral filtering is applied, which adds unwanted additional loss and complexity to the set-up. At the same time, applicability and efficiency are crucial for QKD as they directly affect the secret communication, based on the quantum-secure keys. Alternatively, continuous-variable (CV) QKD protocols [7-10], based on the multiphoton coherent [11][12][13][14][15] or squeezed states [16] and homodyne quadrature detection using off-the-shelf equipment, can overcome this limitation. Indeed, a homodyne detector, which matches a signal to a narrow-band local oscillator (LO) beam, being the phase reference for the measurement, can intrinsically filter out the background radiation and make CV Q...

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Implementation of continuous-variable quantum key distribution with composable and one-sided-device-independent security against coherent attacks

Cited by 237 publications

References 44 publications

Experimental demonstration of Gaussian protocols for one-sided device-independent quantum key distribution

Experimental demonstration of Gaussian protocols for one-sided device-independent quantum key distribution

Composable Security Proof for Continuous-Variable Quantum Key Distribution with Coherent States

Squeezing-enhanced quantum key distribution over atmospheric channels

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