World Quantum Day is an international annual celebration, an act of global outreach, dedicated to promoting public awareness and understanding of quantum science and technology. It is observed every year on April 14. The date April 14 was chosen because the rounded first three digits of Planck's constant ($4.1356677 \times 10^{-15} \text{ eV}\cdot\text{s}$) are 4.14, a fundamental constant that governs quantum physics.
The initiative began in 2021 by an international group of scientists, engineers, and educators, with the first official celebration taking place on April 14, 2022. The day was created to highlight the profound impact of quantum mechanics, which is the most fundamental theory describing nature at the level of elementary particles, and to showcase its transformative applications. It is a decentralized, "bottom-up" initiative supported by a Coordination Team and representatives from over 65 countries.
The mechanism of the celebration involves a global network hosting various outreach activities, such as talks, symposiums, lab tours, and interviews, with over 440 events held in more than 120 countries in 2024. The day connects to the broader concept of quantum information science and engineering, which exploits properties like superposition and entanglement to create cutting-edge technologies. These advancements hold the potential to revolutionize sectors like quantum computing, secure communication, healthcare, and cybersecurity. The year 2025 is particularly significant as it marks a century since the formal establishment of quantum mechanics, leading to the designation of the International Year of Quantum Science and Technology (IYQ 2025). The celebration has grown, with the number of events surpassing 400 in 2023, and the US Senate passed a resolution on May 2, 2023, commemorating and supporting the day.