World Quantum Day Celebrates Advances in Quantum Physics

Every year on April 14, the world celebrates World Quantum Day, a day dedicated to raising awareness about the significance of quantum physics. This initiative, which began in 2021, was driven by scientists, educators, and communicators from various countries and has since gained support from numerous scientific and academic organizations worldwide. Unlike official international days, it is not tied to any specific entity.

The date was chosen for its symbolic connection to quantum physics. In the Anglo-Saxon world, the date format of 4/14 reflects the first three digits of Planck's constant (4.14). Max Planck was the first to propose the quantization of physical quantities, marking the boundary between the classical and quantum worlds.

More than a century after the initial breakthroughs in quantum mechanics led to technologies like transistors, lasers, and magnetic resonance imaging, we find ourselves at a new frontier: quantum computing. This cutting-edge technology promises to tackle problems that classical computing cannot efficiently resolve. In a world often dominated by hype and fear of missing out (FOMO), claims about its immediate impact on drug development, new materials, and climate change are common. But where do we actually stand?

The term quantum advantage refers to the ability of quantum systems to solve problems more efficiently than classical methods. This doesn’t mean that a quantum processor is faster in terms of operations per second; rather, it can require significantly fewer operations to solve specific problems. Currently, a classical supercomputer can achieve around one trillion operations per second, whereas existing quantum devices operate at about one million operations per second.

So far, quantum advantage has been experimentally demonstrated in problems without direct practical applications. This shift has led to a new question: Can we achieve a useful quantum advantage? One of the most promising fields is the simulation of quantum physical systems. This was the original motivation behind quantum computing: if nature is quantum, let’s build machines that follow its rules. The simulation of the evolution of many-body quantum systems using techniques like Trotter decomposition has shown theoretical advantages and implications for studying magnetic materials, condensed matter, and particle physics.

In quantum chemistry, the potential is especially relevant. Algorithms like phase estimation or Krylov quantum diagonalization could allow us to study complex systems such as FeMoCo, which is responsible for nitrogen fixation in nature. Gaining a comprehensive grasp of this process could enable efficient replication of ammonia production, which is key for fertilizers and energy, compared to current industrial methods that are far more energy-intensive.

Beyond simulation, there are quantum algorithms with implications for computing. The most well-known is Peter Shor’s algorithm, which can efficiently factor large numbers, posing a threat to current cryptography. In machine learning and artificial intelligence, variational algorithms have been proposed, but it remains unclear whether they offer real advantages. Recent proposals like Decoded Quantum Interferometry (DQI) suggest potential benefits in optimization problems relevant to industry, but practical applications are still a long way off.

Why don’t we already have useful quantum advantages? Current devices, which operate around 100 qubits (the quantum equivalent of classical bits), exhibit frequent errors—approximately one error per thousand operations. This limitation restricts the length of algorithms that can run reliably. Many quantum demonstrations have been quickly replicated using advanced classical techniques, such as tensor networks or operator propagation methods, which continue to improve and exert pressure on the quantum field.

Several studies have raised doubts about certain proposed quantum advantages in machine learning. In some cases, if algorithms can be trained efficiently, they can also be simulated classically. In others, the problems they attempt to solve are too simple to warrant a quantum advantage. Other proposals, like DQI, currently lack direct practical applications, as they tackle problems that require specific structures to be efficient.

Long-term solutions involve quantum error correction. This technique constructs reliable logical qubits from many noisy physical qubits, theoretically allowing for arbitrary error reduction, albeit at the cost of significantly increased resource requirements. The most accepted estimates for breaking a real-world cryptographic key (RSA-2048) suggest that around 20 million noisy qubits and an execution time of eight hours would be required to reduce the failure rate to one error per trillion operations. Recent proposals suggest reducing these requirements to tens or hundreds of thousands of qubits, but they assume technological advancements that have yet to be achieved and are not trivial.

Progress has been rapid, but time is needed to advance, especially when we have processors with only 100 qubits and need tens or hundreds of thousands. The message, though, should not be one of pessimism but of caution. In a hype-driven environment, it is the scientific community's responsibility to be rigorous and honest about the real state of technology. Quantum computing has enormous potential, but its transformational impact still requires fundamental advances and basic science.

On April 14, alongside World Quantum Day, Fundación Telefónica announced the Revolution Quantum exhibition, set to open on May 7 at the Espacio Fundación Telefónica. This exhibition invites visitors to discover one of the most substantial scientific and technological transformations of our time. It showcases how quantum physics has already changed our way of living through technologies like semiconductors, lasers, and modern electronics—the pillars of today’s digital world.

The exhibition is structured into five thematic blocks, tracing the history and impact of quantum physics. It culminates in the second quantum revolution, where we no longer just describe nature but manipulate individual quantum systems, paving the way for technologies like quantum computing and ultra-secure communications.

Accompanying the exhibition is the launch of TELOS 129: Quantum Inspiration, a special issue of Fundación Telefónica's contemporary thought magazine. This issue, commissioned by physicist Juan Ignacio Cirac, features prominent voices in scientific thought, exploring how quantum science is redefining our comprehension of knowledge, technology, and reality.

World Quantum Day serves as a celebration of the first quantum revolution in the 20th century and as a moment to approach the new era we are entering: the second quantum revolution. As we stand on the brink of this new technological frontier, the potential for quantum computing remains vast, yet the path ahead is filled with challenges that require our attention and dedication.