The goal of this paper is to extend the framework finite size analysis recently developed for quantum key distribution continuous-variable protocols. We do not solve problem completely here, and we mainly consider effects on parameter estimation procedure. Despite fact that some questions are left open, able give an secret rate protocols which contain a postselection As expected, these results significantly more pessimistic than ones obtained in asymptotic regime. However, show recent...

We present a continuous-variable quantum key distribution protocol combining discrete modulation and reverse reconciliation. This is proven unconditionally secure allows the of secret keys over long distances, thanks to reconciliation scheme efficient at very low signal-to-noise ratio.

We give the first composable security proof for continuous-variable quantum key distribution with coherent states against collective attacks. Crucially, in limit of large blocks secret rate converges to usual value computed from Holevo bound. Combining our either de Finetti theorem or postselection technique then shows protocol general attacks, thereby confirming long-standing conjecture that Gaussian attacks are optimal asymptotically framework. expect parameter estimation procedure, which...

The ability to distribute secret keys between two parties with information-theoretic security, that is, regardless of the capacities a malevolent eavesdropper, is one most celebrated results in field quantum information processing and communication. Indeed, key distribution illustrates power encoding on properties light has far reaching implications high-security applications. Today, systems operate real-world conditions are commercially available. As protocols, was first designed for...

We provide a security analysis for continuous variable quantum key distribution protocols based on the transmission of two-mode squeezed vacuum states measured via homodyne detection. employ version entropic uncertainty relation smooth entropies to give lower bound number secret bits which can be extracted from finite runs protocol. This is valid under general coherent attacks, and gives rise keys are composably secure. For comparison, we also assumption collective attacks. both scenarios,...

We designed high-efficiency error correcting codes allowing to extract an errorless secret key in a continuous-variable quantum distribution protocol using Gaussian modulation of coherent states and homodyne detection. These are available for wide range signal-to-noise ratios on AWGN channel with binary can be combined multidimensional reconciliation method proven secure against arbitrary collective attacks. This improved procedure considerably extends the modulation, giving rate about...

We prove the security of Gaussian continuous-variable quantum key distribution with coherent states against arbitrary attacks in finite-size regime. In contrast to previously known proofs principle (based on de Finetti theorem), our result is applicable practically relevant This achieved using a novel proof approach, which exploits phase-space symmetries protocols as well postselection technique introduced by Christandl, Koenig, and Renner [Phys. Rev. Lett. 102, 020504 (2009)].

Establishing the security of continuous-variable quantum key distribution against general attacks in a realistic finite-size regime is an outstanding open problem field theoretical cryptography if we restrict our attention to protocols that rely on exchange coherent states. Indeed, techniques based uncertainty principle are not known work for such protocols, and usual tools de Finetti reductions only provide unrealistically large block lengths. We address this here by considering new type...

Abstract Establishing secure communication links at a global scale is major potential application of quantum information science but also extremely challenging for the underlying technology. Although milestone experiments using satellite-to-ground and exploiting singe-photon encoding implementing key distribution have shown recently that this goal achievable, it still necessary to further investigate practical solutions compatible with classical optical systems. Here, we examine feasibility...

Abstract The main obstacle to large scale quantum computing are the errors present in every physical qubit realization. Correcting these requires a number of additional qubits. Two avenues reduce this overhead (i) low-density parity check (LDPC) codes requiring very few qubits correct (ii) cat where bit-flip exponentially suppressed by design. In work, we combine both approaches obtain an extremely low architecture. Assuming phase-flip error probability ϵ ≈ 0.1% per and operation, one...

As quantum key distribution becomes a mature technology, it appears clearly that some assumptions made in the security proofs cannot be justified practical implementations. This might open door to possible side-channel attacks. We examine several discrepancies between theoretical models and experimental setups case of continuous-variable distribution. study particular impact an imperfect modulation on Gaussian protocols show approximating with discrete one is sufficient practice. also...

We propose a method for extracting an errorless secret key in continuous-variable quantum distribution protocol, which is based on Gaussian modulation of coherent states and homodyne detection. The crucial feature eight-dimensional reconciliation the algebraic properties octonions. Since protocol does not use any post-selection, it can be proven secure against arbitrary collective attacks by using well-established theorems optimality attacks. By this coding scheme with appropriate...

In this paper, we consider continuous-variable quantum-key-distribution (QKD) protocols which use non-Gaussian modulations. These specific modulation schemes are compatible with very efficient error-correction procedures, hence allowing the to outperform previous in terms of achievable range. their simplest implementation, these secure for any linear quantum channels (hence against Gaussian attacks). We also show how decoy states makes arbitrary collective attacks, implies unconditional...

Reconciliation is an essential part of any secret-key agreement protocol and hence a Quantum Key Distribution (QKD) protocol, where two legitimate parties are given correlated data want to agree on common string in the presence adversary, while revealing minimum amount information. In this paper, we show that for discrete-variable QKD protocols, problem can be advantageously solved with Low Density Parity Check (LDPC) codes optimized BSC. particular, demonstrate our method leads significant...

We establish a lower bound on the asymptotic secret key rate of continuous-variable quantum distribution with discrete modulation coherent states. The is valid against collective attacks and obtained by formulating problem as semidefinite program. illustrate our general approach quadrature phase-shift keying (QPSK) scheme show that distances over 100 km are achievable for realistic values noise. also discuss application to more complex amplitude modulations (QAM) schemes. This work major...

We show that the maximum transmission distance of continuous-variable quantum key distribution in presence a Gaussian noisy lossy channel can be arbitrarily increased using heralded noiseless linear amplifier. explicitly consider protocol amplitude- and phase-modulated coherent states with reverse reconciliation. Assuming secret rate drops to zero for line transmittance ${T}_{\mathrm{lim}}$, we find amplifier amplitude gain $g$ improve this value ${T}_{\mathrm{lim}}/{g}^{2}$, corresponding...

We report on the design and performance of a point-to-point classical symmetric encryption link with fast key renewal provided by Continuous Variable Quantum Key Distribution (CVQKD) system. Our system was operational able to encrypt communications during more than six months, from end July 2010 until beginning February 2011. This field test first demonstration reliability CVQKD over long period time in server room environment. strengthens potential for information technology security...

In this work we present a security analysis for quantum key distribution, establishing rigorous tradeoff between various protocol and parameters class of entanglement-based prepare-and-measure protocols. The goal paper is twofold: 1) to review clarify the state-of-the-art based on entropic uncertainty relations, 2) provide an accessible resource researchers interested in cryptographic protocols that takes into account finite effects. For purpose collect several arguments spread literature...

Quantum computers, that may become available one day, would impact many scientific fields, most notably cryptography since asymmetric primitives are insecure against an adversary with quantum capabilities. Cryptographers already anticipating this threat by proposing and studying a number of potentially quantum-safe alternatives for those primitives. On the other hand, symmetric seem less vulnerable computing: main known applicable result is Grover's algorithm gives quadratic speed-up...

Tanner codes are long error correcting obtained from short and a graph, with bits on the edges parity-check constraints enforced at vertices of graph. Combining good together spectral expander graph yields celebrated Sipser Spielman, which asymptotically classical LDPC codes. In this work we apply prescription to left-right Cayley complex that lies heart recent construction c <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> locally...

The recently proposed Universal Blind Quantum Computation (UBQC) protocol allows a client to perform an arbitrary quantum computation on remote server such that perfect privacy is guaranteed if the capable of producing random separable single qubit states. While from theoretical point view, this arguably constitutes lowest possible requirement, pragmatic generation qubits which can be sent along long distances without loss quite challenging and never achieved perfectly. In analogy concept...