Tagged: QKD: quantum key distribution Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 10:19 am on July 28, 2022 Permalink | Reply
    Tags: "A key role for quantum entanglement", QKD: quantum key distribution,   

    From The Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH): “A key role for quantum entanglement” 

    From The Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH)

    Andreas Trabesinger
    Tanya Petersen

    A method known as quantum key distribution has long held the promise of communication security not possible in conventional cryptography. For the first time, an international team of scientists, including researchers from EPFL, has demonstrated experimentally an approach to quantum key distribution based on high-quality quantum entanglement — offering much broader security guarantees than previous schemes.

    The art of cryptography is to skillfully transform messages so that they become meaningless to everyone but the intended recipients. Modern cryptographic schemes, such as those underpinning digital commerce, prevent adversaries from illegitimately deciphering messages — say, credit-card information — by requiring them to perform mathematical operations that consume a prohibitively large amount of computational power.

    However, for several decades now, ingenious theoretical concepts have been introduced in which security doesn’t depend on an eavesdropper’s finite number-crunching capabilities. Instead, the basic laws of quantum physics limit how much information, if any, an adversary can ultimately intercept.

    In one such concept, called quantum key distribution, security can be guaranteed with only a few general assumptions about the physical apparatus used yet practically, it has remained out of reach. Now, writing in Nature [below], an international team of researchers from EPFL’s School of Computer and Communication Sciences, ETH Zürich, the University of Geneva, the University of Oxford and the Université Paris-Saclay report the first demonstration of this sort of protocol — taking a decisive step towards practical devices offering such exquisite security.

    The key is a secret

    Secure communication is all about keeping information private. It might be surprising, therefore, that in real-world applications large parts of the transactions between legitimate users are played out in public. The key is that sender and receiver do not have to keep their entire communication hidden.

    In essence, they only have to share one “secret”; in practice, this secret is a string of bits, known as a cryptographic key, that enables everyone in its possession to turn coded messages into meaningful information. Once the legitimate parties have ensured that they, and only they, share such a key, pretty much all the other communication can happen in plain view. The question, then, is how to ensure that only the legitimate parties share a secret key. The process of accomplishing this is known as ‘key distribution’.

    The cryptographic algorithms underlying, for instance, RSA — one of the most widely used cryptographic systems —relies on the fact that for today’s computers it is hard to find the prime factors of a large number, whereas it is easy for them to multiply known prime factors to obtain that number. Secrecy is therefore ensured by mathematical difficulty. But what is impossibly difficult today might be easy tomorrow. Famously, quantum computers can find prime factors significantly more efficiently than classical computers. Once quantum computers with a sufficiently large number of qubits become available, RSA encoding is destined to become penetrable.

    But quantum theory provides the basis not only for cracking the cryptosystems at the heart of digital commerce, but also for a potential solution to the problem: a way entirely different from RSA for distributing cryptographic keys — one that has nothing to do with the hardness of performing mathematical operations, but with fundamental physical laws. Enter quantum key distribution, or QKD for short.

    “Over the years, it has been realized that QKD schemes can have a remarkable benefit: users have to make only very general assumptions regarding the devices employed in the process. The newest form of QKD is now generally known as ‘device-independent QKD’, and an experimental implementation of this became a major goal in the field. That’s why it is exciting that such a breakthrough experiment has now finally been achieved,” said Professor Rüdiger Ubanke, Dean of the IC School who, together with PhD student Kirill Ivanov, is one of the paper’s authors.

    Culmination of years of work

    The experiment involved two single ions — one for the sender and one of the receiver — confined in separate traps that were connected with an optical-fibre link. In this basic quantum network, entanglement between the ions was generated with record-high fidelity over millions of runs. Without such a sustained source of high-quality entanglement, the protocol could not have been run in a practically meaningful manner. Equally important was to certify that the entanglement was suitably exploited. For the analysis of the data, as well as for an efficient extraction of the cryptographic key and to ensure optimal operation during the experiment, significant advances in theory were needed.

    In the experiment, the ‘legitimate parties’ — the ions — were located in one and the same laboratory. But there is a clear route to extending the distance between them to kilometres and beyond. With that perspective, together with further recent progress made in related experiments in Germany and China, there is now a real prospect of turning theoretical into practical technology.

    Science paper:

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    EPFL bloc

    EPFL campus

    The Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH) is a research institute and university in Lausanne, Switzerland, that specializes in natural sciences and engineering. It is one of the two Swiss Federal Institutes of Technology, and it has three main missions: education, research and technology transfer.

    The QS World University Rankings ranks EPFL(CH) 14th in the world across all fields in their 2020/2021 ranking, whereas Times Higher Education World University Rankings ranks EPFL(CH) as the world’s 19th best school for Engineering and Technology in 2020.

    EPFL(CH) is located in the French-speaking part of Switzerland; the sister institution in the German-speaking part of Switzerland is The Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich] (CH). Associated with several specialized research institutes, the two universities form The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles Polytechniques Fédérales] (CH) which is directly dependent on the Federal Department of Economic Affairs, Education and Research. In connection with research and teaching activities, EPFL(CH) operates a nuclear reactor CROCUS; a Tokamak Fusion reactor; a Blue Gene/Q Supercomputer; and P3 bio-hazard facilities.

    ETH Zürich, EPFL (Swiss Federal Institute of Technology in Lausanne) [École Polytechnique Fédérale de Lausanne](CH), and four associated research institutes form The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) with the aim of collaborating on scientific projects.

    The roots of modern-day EPFL(CH) can be traced back to the foundation of a private school under the name École Spéciale de Lausanne in 1853 at the initiative of Lois Rivier, a graduate of the École Centrale Paris (FR) and John Gay the then professor and rector of the Académie de Lausanne. At its inception it had only 11 students and the offices were located at Rue du Valentin in Lausanne. In 1869, it became the technical department of the public Académie de Lausanne. When the Académie was reorganized and acquired the status of a university in 1890, the technical faculty changed its name to École d’Ingénieurs de l’Université de Lausanne. In 1946, it was renamed the École polytechnique de l’Université de Lausanne (EPUL). In 1969, the EPUL was separated from the rest of the University of Lausanne and became a federal institute under its current name. EPFL(CH), like ETH Zürich (CH), is thus directly controlled by the Swiss federal government. In contrast, all other universities in Switzerland are controlled by their respective cantonal governments. Following the nomination of Patrick Aebischer as president in 2000, EPFL(CH) has started to develop into the field of life sciences. It absorbed the Swiss Institute for Experimental Cancer Research (ISREC) in 2008.

    In 1946, there were 360 students. In 1969, EPFL(CH) had 1,400 students and 55 professors. In the past two decades the university has grown rapidly and as of 2012 roughly 14,000 people study or work on campus, about 9,300 of these being Bachelor, Master or PhD students. The environment at modern day EPFL(CH) is highly international with the school attracting students and researchers from all over the world. More than 125 countries are represented on the campus and the university has two official languages, French and English.


    EPFL is organized into eight schools, themselves formed of institutes that group research units (laboratories or chairs) around common themes:

    School of Basic Sciences
    Institute of Mathematics
    Institute of Chemical Sciences and Engineering
    Institute of Physics
    European Centre of Atomic and Molecular Computations
    Bernoulli Center
    Biomedical Imaging Research Center
    Interdisciplinary Center for Electron Microscopy
    MPG-EPFL Centre for Molecular Nanosciences and Technology
    Swiss Plasma Center
    Laboratory of Astrophysics

    School of Engineering

    Institute of Electrical Engineering
    Institute of Mechanical Engineering
    Institute of Materials
    Institute of Microengineering
    Institute of Bioengineering

    School of Architecture, Civil and Environmental Engineering

    Institute of Architecture
    Civil Engineering Institute
    Institute of Urban and Regional Sciences
    Environmental Engineering Institute

    School of Computer and Communication Sciences

    Algorithms & Theoretical Computer Science
    Artificial Intelligence & Machine Learning
    Computational Biology
    Computer Architecture & Integrated Systems
    Data Management & Information Retrieval
    Graphics & Vision
    Human-Computer Interaction
    Information & Communication Theory
    Programming Languages & Formal Methods
    Security & Cryptography
    Signal & Image Processing

    School of Life Sciences

    Bachelor-Master Teaching Section in Life Sciences and Technologies
    Brain Mind Institute
    Institute of Bioengineering
    Swiss Institute for Experimental Cancer Research
    Global Health Institute
    Ten Technology Platforms & Core Facilities (PTECH)
    Center for Phenogenomics
    NCCR Synaptic Bases of Mental Diseases

    College of Management of Technology

    Swiss Finance Institute at EPFL
    Section of Management of Technology and Entrepreneurship
    Institute of Technology and Public Policy
    Institute of Management of Technology and Entrepreneurship
    Section of Financial Engineering

    College of Humanities

    Human and social sciences teaching program

    EPFL Middle East

    Section of Energy Management and Sustainability

    In addition to the eight schools there are seven closely related institutions

    Swiss Cancer Centre
    Center for Biomedical Imaging (CIBM)
    Centre for Advanced Modelling Science (CADMOS)
    École Cantonale d’art de Lausanne (ECAL)
    Campus Biotech
    Wyss Center for Bio- and Neuro-engineering
    Swiss National Supercomputing Centre

  • richardmitnick 9:57 am on July 28, 2022 Permalink | Reply
    Tags: "Quantum entanglement makes quantum communication even more secure", "Quantum entanglement": a mysterious relationship between particles that links their properties even when separated over long distances., , QKD: quantum key distribution, ,   

    From “Science News”: “Quantum entanglement makes quantum communication even more secure” 

    From “Science News”

    Emily Conover

    Three studies show quantum devices don’t have to be perfectly understood to be snoop-proof.

    Quantum entanglement, a type of ethereal link between particles, improves the security of quantum communication, as demonstrated in three experiments (the one pictured, by researchers in France, Switzerland and England, used strontium ions in its test). Credit: David Nadlinger/University of Oxford.

    Stealthy communication just got more secure, thanks to quantum entanglement.

    Quantum physics provides a way to share secret information that’s mathematically proven to be safe from the prying eyes of spies. But until now, demonstrations of the technique, called quantum key distribution, rested on an assumption: The devices used to create and measure quantum particles have to be known to be flawless. Hidden defects could allow a stealthy snoop to penetrate the security unnoticed.

    Now, three teams of researchers have demonstrated the ability to perform secure quantum communication without prior confirmation that the devices are foolproof. Called device-independent quantum key distribution, the method is based on quantum entanglement, a mysterious relationship between particles that links their properties even when separated over long distances.

    In everyday communication, such as the transmission of credit card numbers over the internet, a secret code, or key, is used to garble the information, so that it can be read only by someone else with the key. But there’s a quandary: How can a distant sender and receiver share that key with one another while ensuring that no one else has intercepted it along the way?

    Quantum physics provides a way to share keys by transmitting a series of quantum particles, such as particles of light called photons, and performing measurements on them. By comparing notes, the users can be sure that no one else has intercepted the key. Those secret keys, once established, can then be used to encrypt the sensitive intel (SN: 12/13/17). By comparison, standard internet security rests on a relatively shaky foundation of math problems that are difficult for today’s computers to solve, which could be vulnerable to new technology, namely quantum computers (SN: 6/29/17).

    But quantum communication typically has a catch. “There cannot be any glitch that is unforeseen,” says quantum physicist Valerio Scarani of the National University of Singapore. For example, he says, imagine that your device is supposed to emit one photon but unknown to you, it emits two photons. Any such flaws would mean that the mathematical proof of security no longer holds up. A hacker could sniff out your secret key, even though the transmission seems secure.

    Device-independent quantum key distribution can rule out such flaws. The method builds off of a quantum technique known as a Bell test, which involves measurements of entangled particles. Such tests can prove that quantum mechanics really does have “spooky” properties, namely nonlocality, the idea that measurements of one particle can be correlated with those of a distant particle. In 2015, researchers performed the first “loophole-free” Bell tests, which certified beyond a doubt that quantum physics’ counterintuitive nature is real (SN: 12/15/15).

    “The Bell test basically acts as a guarantee,” says Jean-Daniel Bancal of CEA Saclay in France. A faulty device would fail the test, so “we can infer that the device is working properly.”

    In their study, Bancal and colleagues used entangled, electrically charged strontium atoms separated by about two meters. Measurements of those ions certified that their devices were behaving properly, and the researchers generated a secret key, the team reports in the July 28 Nature [below].

    Typically, quantum communication is meant for long-distance dispatches. (To share a secret with someone two meters away, it would be easier to simply walk across the room.) So Scarani and colleagues studied entangled rubidium atoms 400 meters apart. The setup had what it took to produce a secret key, the researchers report in the same issue of Nature below]. But the team didn’t follow the process all the way through: The extra distance meant that producing a key would have taken months.

    In the third study, published in the July 29 Physical Review Letters [below], researchers wrangled entangled photons rather than atoms or ions. Physicist Wen-Zhao Liu of the University of Science and Technology of China in Hefei and colleagues also demonstrated the capability to generate keys, at distances up to 220 meters. This is particularly challenging to do with photons, Liu says, because photons are often lost in the process of transmission and detection.

    Loophole-free Bell tests are already no easy feat, and these techniques are even more challenging, says physicist Krister Shalm of the National Institute of Standards and Technology in Boulder, Colo. “The requirements for this experiment are so absurdly high that it’s just an impressive achievement to be able to demonstrate some of these capabilities,” says Shalm, who wrote a perspective in the same issue of Nature [below].

    That means that the technique won’t see practical use anytime soon, says physicist Nicolas Gisin of the University of Geneva, who was not involved with the research.

    Still, device-independent quantum key distribution is “a totally fascinating idea,” Gisin says. Bell tests were designed to answer a philosophical question about the nature of reality — whether quantum physics really is as weird as it seems. “To see that this now becomes a tool that enables something else,” he says, “this is the beauty.”

    Science papers:


    Physical Review Letters


    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

  • richardmitnick 9:07 am on March 24, 2022 Permalink | Reply
    Tags: "Single-Photon Source Paves the Way for Practical Quantum Encryption", , QKD offers impenetrable encryption for data communication by using the quantum properties of light to generate secure random keys for encrypting and decrypting data., QKD: quantum key distribution   

    FromOptica: “Single-Photon Source Paves the Way for Practical Quantum Encryption” 


    23 March 2022

    A new high-purity single photon source that can operate at room temperature is an important step toward practical applications of quantum technology, such as highly secure communication based on quantum key distribution. Helen Zeng is pictured.Credit: Helen Zeng, University of Technology Sydney(AU).

    Researchers have developed a new high-purity single-photon source that can operate at room temperature. The source is an important step toward practical applications of quantum technology, such as highly secure communication based on quantum key distribution (QKD).

    “We developed an on-demand way to generate photons with high purity in a scalable and portable system that operates at room temperature,” said Helen Zeng, a member of the research team from the University of Technology Sydney in Australia. “Our single-photon source could advance the development of practical QKD systems and can be integrated into a variety of real-world quantum photonic applications.”

    In the Optica Publishing Group journal Optics Letters, Zeng and colleagues from The University of New South Wales Sydney (AU) and Macquarie University(AU) describe their new single-photon source and show that it can produce over ten million single photons per second at room temperature. They also incorporated the single-photon source into a fully portable device that can perform QKD.

    The new single-photon source uniquely combines a 2D material called hexagonal boron nitride with an optical component known as a hemispherical solid immersion lens, which increases the source’s efficiency by a factor of six.

    Single photons at room temperature

    QKD offers impenetrable encryption for data communication by using the quantum properties of light to generate secure random keys for encrypting and decrypting data. QKD systems require robust and bright sources that emit light as a string of single photons. However, most of today’s single-photon sources don’t perform well unless operated at cryogenic temperatures hundreds of degrees below zero, which limits their practicality.

    Although hexagonal boron nitride has previously been used to create a single-photon source that operates at room temperature, until now researchers had not been able to achieve the efficiency needed for real-world application. “Most approaches used to improve hexagonal boron nitride single-photon sources rely on precisely positioning the emitter or using nano-fabrication,” said Zeng. “This makes the devices complex, difficult to scale and not easy to mass produce.”

    Zeng and colleagues set out to create a better solution by using a solid immersion lens to focus the photons coming from the single-photon emitter, allowing more photons to be detected. These lenses are commercially available and easy to fabricate.

    The researchers combined their new single-photon source with a custom-built portable confocal microscope that can measure the single photons at room temperature, creating a system that can perform QKD. The single-photon source and confocal microscope are housed inside a robust package that measures just 500 x 500 millimeters and weighs around 10 kilograms. The package is also engineered to deal with vibration and stray light.

    The single-photon source and confocal microscope are housed inside a robust package that measures just 500 x 500 millimeters and weighs around 10 kilograms. Credit: Helen Zeng, University of Technology Sydney.

    “Our streamlined device is easier to use and much smaller than traditional optical table setups, which often take up entire labs,” said Zeng. “This allows the system to be used with a range of quantum computing schemes. It could also be adapted to work with existing telecommunications infrastructure.”

    Demonstrating quantum cryptography

    Tests of the new single-photon source showed that it could achieve a single-photon collection rate of 107 Hz while maintaining excellent purity – meaning each pulse had a low probability of containing more than one photon. It also showed exceptional stability over many hours of continuous operation. The researchers also demonstrated the system’s ability to perform QKD under realistic conditions, showing that secured QKD with 20 MHz repetition rates would be feasible over several kilometers.

    Now that the researchers have established proof that their portable device can perform complex quantum cryptography, they plan to perform further testing of its robustness, stability, and efficiency during encryption. They also plan to use the new source to perform QKD in real-world conditions, rather than inside the lab. “We are now ready to transform these scientific advances in quantum 2D materials into technology ready products,” said Igor Aharonovich, who led the project.

    See the full article here.


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Optica Publishing Group publishes high-quality, peer-reviewed articles in its portfolio of journals, which serve the full breadth of the optics and photonics community.

    Optica is an open-access, online-only journal dedicated to the rapid dissemination of high-impact peer-reviewed research across the entire spectrum of optics and photonics. Published monthly by Optica Publishing Group, Optica provides a forum for pioneering research to be swiftly accessed by the international community, whether that research is theoretical or experimental, fundamental or applied.

    The Journal seeks articles that will be of significant interest to the optics and broader scientific community. As a result, the process for paper acceptance is inherently highly selective.

    The acceptance criteria for Optica include:

    Significance, potential impact, originality,
    High technical quality, integrity and scientific rigor,
    Readability, interest to the broader optics and scientific communities.

    Optica publishes original research letters (4 pages), research articles (6-8 pages), and mini-reviews (8-12 pages). The Journal has recently introduced memoranda (2 pages); short announcements of particularly exciting breakthroughs and innovations. Comments and Replies will also be published. Incremental work that does not convincingly add new and important results of broad interest to the optics and photonics communities will be declined by Optica.

Compose new post
Next post/Next comment
Previous post/Previous comment
Show/Hide comments
Go to top
Go to login
Show/Hide help
shift + esc
%d bloggers like this: