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CERN joins in the celebrations on 14 April involving scientists from more than 65 countries

Today, on 14 April, we celebrate World Quantum Day an international initiative launched by scientists from more than 65 countries to promote public understanding of quantum science and technology worldwide. The date 4.14 -- marks the rounded first 3 digits of Plancks constant, a crucial value in quantum mechanics that is used to describe the behaviour of particles at the subatomic level.

Officially launched in 2022, World Quantum Day already comprises more than 300 events held in 193 cities in 44 countries on 5 continents in 17 different languages. Scientists, engineers, educators, communicators, entrepreneurs, technologists, historians and artists all over the globe organise their own activities, such as outreach talks, exhibitions, workshops and panel discussions, to engage the general public with quantum science and explain how quantum technologies work and how they can impact our everyday life.

From quantum mechanics, quantum gravity, optics and information science to quantum computing, metrology and engineering, all domains of quantum science are celebrated, alongside their history, mathematical foundations and practical applications.

But what is quantum and why do we mark the date?

Quantum comes from the Latin word quantus, meaning how much/of what size. It is the smallest amount or unit of electromagnetic energy that can be measured. In short, quantum physics is the study of the smallest building blocks that make up our Universe. It seeks to describe the properties and behaviour of matter and energy at the most fundamental level. If you want to understand how atoms hold together, how electrons move through a computer chip or how magnets work, you will need to use quantum physics. A quantum-based theory can also help explore the origin of the matter-antimatter asymmetry or the nature of dark matter and dark energy phenomena that cannot be explained within the Standard Model.

Despite being recognised as the theoretical basis of modern physics, quantum science traces its origins back to the early 20th century when the German physicist Max Planck made a seemingly contradictory assumption that energy exists in individual units, which led to the first notion of quantum theory. Further investigations by Niels Bohr, Albert Einstein, Erwin Schrdinger and Richard Feynman made major contributions to the development of quantum mechanics, bringing a new dimension to the world of science.

As well as expanding our knowledge beyond the classical concepts, quantum physics lies at the core of some of the most profound technological advances. To give just a few examples, transistors, LEDs, lasers, GPS and medical imaging all rely on concepts of quantum physics. Quantum technologies also offer the potential to impact many other areas in the future: they hold great promise for improving how we secure communication and process information, for advancing the sensitivity of detectors and sensors and for changing the way we approach computing.

For the high-energy physics community, applications of quantum technologies could mean new advantages and possibilities for track reconstruction, simulation and event classification and the computing needs of CERNs world-leading research infrastructure the Large Hadron Collider (LHC) and its successors, the HL-LHC (High Luminosity Large Hadron Collider) and possibly the FCC (Future Circular Collider).

Quantum science evolved from a hypothesis, a revolutionary idea, to become one of the foundations of modern physics that has changed the way we think about the world forever, -- says Alberto Di Meglio, coordinator of the CERN Quantum Technology Initiative (QTI). Looking into the future, we can most certainly say that quantum science and technology will be a central cross-disciplinary field with a major impact on key societal and technological challenges. It is therefore important that we explore the potential of this breakthrough field and raise awareness about it today, pushing the boundaries of knowledge and technology. World Quantum Day is a great occasion to do this.

In 2022, CERN QTI already took part in the World Quantum Day celebrations by developing and hosting the event management website and organising a special scientific symposium at CERN. During the event, talks outlined the early days of quantum science at CERN and what those pioneering efforts mean for modern research.

To mark this years celebrations, the first-of-a-kind quantum workshop for high-school students will be held at CERN to introduce the young generation to the fascinating field of quantum science and promote early quantum physics education. Split into two parts, an introductory lecture and a hands-on session, the workshop will give a first insight into the concepts of quantum mechanics and explain how quantum science underpins the physical world around us and facilitates technological innovation. The event will be organised in close collaboration with Finlands QPlayLearn initiative, which uses innovative interactive tools to communicate the main aspects of quantum physics in a clear and accessible way to people of various ages and backgrounds.

To discover more about World Quantum Day, learn how to engage and find events taking place near you, visit: https://worldquantumday.org

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CERN marks the second World Quantum Day - CERN

April 14, 2023 Some classical computers have error correction built into their memories based on bits; quantum computers, to be workable in the future, will need error correction mechanisms, too, based on the vastly more sensitive qubits.

Cornell researchers have recently taken a step toward fault-tolerant quantum computing: they constructed a simple model containing exotic particles called non-Abelian anyons, compact and practical enough to run on modern quantum hardware. Realizing these particles, which can only exist in two dimensions, is a move towards implementing it in the real world.

Thanks to some creative thinking, Yuri Lensky, a former Bethe/Wilkins/Kavli Institute at Cornell (KIC) postdoctoral fellow in physics in the College of Arts and Sciences (A&S), collaborating withEun-Ah Kim, professor of physics (A&S), came up with a simple recipe that could be used for robustly computing with non-Abelian anyons, including specific instructions for executing the effect experimentally on devices available today.

Their paper, Graph Gauge Theory of Mobile Non-Abelian Anyons in a Qubit Stabilizer Code, written in collaboration with theorists at Google Quantum AI, published March 24 in Annals of Physics. Google Quantum AI researchers, together with Lensky and Kim, have proved the theory with a successful experiment as reported in a preprint publication, Observation of Non-Abelian Exchange Statistics on a Superconducting Processor, on the research-sharing platform arXiv.

This two-dimensional state is interesting both from a quantum condensed matter physics perspective it has some novel properties that are very special to 2D physics and from a quantum information perspective, Lensky said. Its something truly quantum, but its also potentially useful for quantum computation. It protects bits of quantum information by storing them non-locally, and our protocol allows us to compute with these bits.

Kim explained the principle that animates non-Abelian anyons by holding out two identical one-pound barbells. When she crosses her arms, the identical barbells change positions, but as objects defined by classical physics, their state remains the same. They are interchangeable.

If those barbells represent two identical quantum particles, remarkably in certain 2D systems their trails through space-time can produce a measurable record of the change (picture the crossed arms.) This process of exchange is called a braid, after the shapes of the particle trails.

Quantum mechanically, when you move one particle around the other, Kim said, holding one weight still and moving the other in a circle around it, the wave function, which is a solution to the Schrdinger equation describing quantum mechanical motion, can be multiplied by a phase factor or it can become something thats very different.

When the wave function gains a global sign that can only be observed through interferometry, a measurement of the interference of waves, thats called an Abelian anyon. When the wave function becomes measurably different, its a non-Abelian anyon, she said.

Non-Abelian anyons could be harnessed to create qubits defined not on a single particle, but on a pair of identical quantum particles: nonlocally encoded.

If I put the qubit shared between these particles in a zero state and move them apart, then whatever happens locally to one of these anyons, the zero state will remain. The qubit set to zero is safe from corruption, Kim said. Non-Abelian anyons could be used in a platform for protected qubits.

But while physicists have theorized about these exotic particles for years Alexei Kitaev proposed operating on protected bits of quantum memory by braiding non-Abelian anyons back around 2001, Lensky said they have never been observed in a physical system before now.

When Google Quantum AI developed the quantum processor platform capabilities to realize the surface code and braiding of Abelian anyons in a physical system, Lensky said, This was [our] inspiration to look for a way to realize the physics of non-Abelian anyons as soon as possible.

We knew they had the working ingredients, but they didnt have a recipe, Kim said. We figured out how to move these non-Abelian anyons, then we told the experimentalists what to do. It was possible because Yuri and I were thinking in a flexible, creative and open-minded way.

Past theoretical research identified non-Abelian properties, but came up short on how to move them, a necessary step. A key insight from Lensky and Kim was to give up the regularity of a grid and arrange qubits in an almost hand-drawn manner but backed up by robust mathematics.

After this simple geometric insight, using gauge theory, we were able to come up with the protocol of taking this picture and implementing it on a chip in a robust and efficient way, Kim said. With this 10-qubit system, we were able to encode multiple non-Abelian anyons, and therefore multiple logical information-carrying qubits, and a precise recipe for what the experimentalists need to do every step of the way.

Although the focus of the theory and experiment is simply to realize non-Abelian anyons in the real world, this can also be viewed as a first small step towards implementing computation by braiding, Lensky said.

This research was supported by an A&S New Frontier Grant; an Ewha Frontier 10-10 Research Grant; the Simons Fellowship in Theoretical Physics; and the National Science Foundation.

Source: Kate Blackwood, Cornell

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Cornell Researchers Bring Quantum Error Correction Closer to Reality with Non-Abelian Anyons - HPCwire