A5076065879- Quantum Information and Cryptography
- Quantum Computing Algorithms and Architecture
- Quantum Mechanics and Applications
- Quantum optics and atomic interactions
- Laser-Matter Interactions and Applications
- Neural Networks and Reservoir Computing
- Orbital Angular Momentum in Optics
- Photonic and Optical Devices
- Chaos-based Image/Signal Encryption
- Quantum-Dot Cellular Automata
- Biofield Effects and Biophysics
- Quantum and electron transport phenomena
- Optical Network Technologies
- Cryptographic Implementations and Security
- Cryptography and Data Security
- Spectroscopy and Quantum Chemical Studies
- Mechanical and Optical Resonators
- Semiconductor Quantum Structures and Devices
- Physical Unclonable Functions (PUFs) and Hardware Security
- Blind Source Separation Techniques
- Molecular Communication and Nanonetworks
- Hyperglycemia and glycemic control in critically ill and hospitalized patients
- Advanced Breast Cancer Therapies
- Ship Hydrodynamics and Maneuverability
- Advancements in PLL and VCO Technologies
University of Waterloo
2016-2025
Perimeter Institute
2018-2020
Max Planck Institute for the Science of Light
2004-2011
Friedrich-Alexander-Universität Erlangen-Nürnberg
1995-2010
Universität Innsbruck
1998-2009
Technical University of Darmstadt
2009
The University of Queensland
2009
Institute of Theoretical Physics
2009
Helsinki Institute of Physics
1999-2007
University of Helsinki
1999-2005
Quantum key distribution (QKD) is the first quantum information task to reach level of mature technology, already fit for commercialization. It aims at creation a secret between authorized partners connected by channel and classical authenticated channel. The security can in principle be guaranteed without putting any restriction on eavesdropper's power. two sections provide concise up-to-date review QKD, biased toward practical side. rest paper presents essential theoretical tools that have...
We provide limits to practical quantum key distribution, taking into account channel losses, a realistic detection process, and imperfections in the "qubits" sent from sender receiver. As we show, even distribution with perfect qubits might not be achievable over long distances when other are taken account. Furthermore, existing experimental schemes (based on weak pulses) currently do offer unconditional security for reported signal strength. Finally show that parametric down-conversion...
In this paper, we present the quantum key distribution (QKD) network designed and implemented by European project SEcure COmmunication based on Quantum Cryptography (SECOQC) (2004–2008), unifying efforts of 41 research industrial organizations. The paper summarizes SECOQC approach to QKD networks with a focus trusted repeater paradigm. It discusses architecture functionality prototype, which has been put into operation in Vienna 2008 publicly demonstrated framework conference held from...
I prove the security of quantum key distribution against individual attacks for realistic signals sources, including weak coherent pulses and down-conversion sources. The proof applies to Bennett-Brassard 1984 protocol with standard detection scheme (no strong reference pulse). obtain a formula secure bit rate per time slot an experimental setup, which can be used optimize performance existing schemes considered scenario.
We prove the security of Bennett-Brassard (BB84) quantum key distribution protocol in case where source and detector are under limited control an adversary. Our proof applies when both have small basis-dependent flaws, as is typical practical implementations protocol. derive a general lower bound on asymptotic generation rate for weakly eavesdropping attacks, also estimate some special cases: sources that emit weak coherent states with random phases, detectors efficiency, misaligned detectors.
In this paper we investigate the possibility to make complete Bell measurements on a product Hilbert space of two two-level bosonic systems. We restrict our tools linear elements, like beam splitters and phase shifters, delay lines electronically switched photo-detectors, auxiliary bosons. As result show that with these never failing measurement is impossible.
Abstract Despite the tremendous progress of quantum cryptography, efficient communication over long distances (≥1000 km) remains an outstanding challenge due to fiber attenuation and operation errors accumulated entire distance. Quantum repeaters (QRs), as a promising approach, can overcome both photon loss hence significantly speedup rate. Depending on methods used correct errors, all proposed QR schemes be classified into three categories (generations). Here we present first systematic...
We present an experimental study of higher-dimensional quantum key distribution protocols based on mutually unbiased bases, implemented by means photons carrying orbital angular momentum. perform ($d+1$) measurements in a classically simulated prepare-and-measure scheme and pair entangled for dimensions ranging from $d=2$ to 5. In our analysis, we pay attention the detection efficiency photon creation probability. As security measures, determine data average error rate, mutual information...
Quantum repeaters (QRs) provide a way of enabling long distance quantum communication by establishing entangled qubits between remote locations. We investigate new approach to QRs in which information can be faithfully transmitted via noisy channel without the use teleportation, thus eliminating need establish links. Our makes small encoding blocks fault-tolerantly correct both operational and photon loss errors. describe optimize resource requirement for these with aim generation secure...
We demonstrate that secure quantum key distribution systems based on continuous variable implementations can operate beyond the apparent 3 dB loss limit is implied by beam splitting attack. The was established for standard minimum uncertainty states such as coherent states. show that, an appropriate postselection mechanism, we enter a region where Eve's knowledge Alice's falls behind information shared between Alice and Bob, even in presence of substantial losses.
We demonstrate that a necessary precondition for an unconditionally secure quantum key distribution is both sender and receiver can use the available measurement results to prove presence of entanglement in state effectively distributed between them. One thus systematically search using class witness operators be constructed from observed data. apply such analysis two well-known protocols, namely, 4-state protocol 6-state protocol. As special case, we show that, some asymmetric error...
This paper prove the security of Bennett-Brassard (BB84) quantum key distribution protocol in case where source and detector are under limited control an adversary. proof applies when both have small basis-dependent flaws, as is typical practical implementations protocol. The estimation generation rate some special cases: sources that emit weak coherent states, detectors with efficiency, misaligned detectors.
In this article I present a protocol for quantum cryptography which is secure against attacks on individual signals. It based the Bennett-Brassard of 1984 (BB84). The security proof complete as far use single photons signal states concerned. Emphasis given to practicability resulting protocol. For each run key distribution statement gives probability successful generation and an eavesdropper's knowledge, measured change in Shannon entropy, be below specified maximal value.
We introduce a quantitative measure of nonclassical behavior based on negative regions quasiprobability distributions. Zeros the antinormal ordered phase-space representation characterize state to be maximally with respect this measure. All pure states particle or single field mode, except those Gaussian distributions, have one more zeros in representation.
We introduce a new continuous-variable quantum key distribution (CV-QKD) protocol, self-referenced CV-QKD, that eliminates the need for transmission of high-power local oscillator between communicating parties. In this each signal pulse is accompanied by reference (or pair twin pulses), used to align Alice's and Bob's measurement bases. The method phase estimation compensation based on can be viewed as analog intradyne detection in classical coherent communication, which extracts information...
Variations of phase-matching measurement-device-independent quantum key distribution (PM-MDI QKD) protocols have been investigated before, but it was recently discovered that this type protocol (under the name twin-field can beat linear scaling repeaterless bound on secret capacity. We propose a variation PM-MDI QKD protocol, which reduces sifting cost and uses non-phase-randomized coherent states as test states. provide security proof in infinite limit. Our is conceptually simple gives...
Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret rate a given protocol. Analytical formulas are known protocols symmetries, since symmetry simplifies analysis. However, experimental imperfections break hence effect of on rates difficult estimate. Furthermore, it an interesting question whether (intentionally) asymmetric could outperform symmetric ones. Here, we develop robust...
Quantum key distribution can be performed with practical signal sources such as weak coherent pulses. One example of a scheme is the Bennett-Brassard protocol that implemented via polarization signals, or equivalent signals. It turns out most powerful tool at disposition an eavesdropper photon-number splitting attack. We show this attack extended in relevant parameter regime so to preserve Poissonian photon number combination source and lossy channel.
The use of linearly independent signal states in realistic implementations quantum key distribution (QKD) enables an eavesdropper to perform unambiguous state discrimination. We explore quantitatively the limits for secure QKD imposed by this fact taking into account that receiver can monitor some extend photon number statistics signals even with todays standard detection schemes. compare our attack beamsplitting and show security against does not necessarily imply considered here.
Measurements with photodetectors are naturally described in the infinite dimensional Fock space of one or several modes. For some measurements, a model has been postulated which describes full measurement as composition mapping (squashing) signal into small Hilbert followed by specified target measurement. We present formalism to investigate whether given pair and measurements can be connected squashing model. show that used Bennett-Brassard 1984 (BB84) protocol does allow description,...
Entanglement detection typically relies on linear inequalities for mean values of certain observables (entanglement witnesses), where violation indicates entanglement. We provide a general method to improve any these bipartite systems via nonlinear expressions. The nonlinearities are different orders and can be directly measured in experiments, often without extra effort.