World Quantum Day: it really is time to think about PQC

Concept artwork generated by Google Gemini on World Quantum Day showing the interplay of quantum mechanics and computing. The design elements symbolise particle dynamics and the 0/1 states inherent to quantum technology.

World Quantum Day is celebrated on 14 April, a reference to 4.14, the rounded first digits of Planck’s constant: 4.1356677×10⁻¹⁵ eV⋅s, or 0.000 000 000 000 004 1356677 electron volt second. While Planck's constant is a fundamental constant governing quantum physics, developments in the world of quantum computing have been moving rapidly.

In a study published in Physical Review Letters, a team led by Professor Peng Xinhua and Associate Professor Li Zhaokai from the University of Science and Technology of China of the Chinese Academy of Sciences demonstrated that a quantum processor comprising nine interacting spins, considered a small quantum computer, outperformed classical networks with thousands of nodes in realistic weather forecasting. 

Another breakthrough has been with a study published on Physical Review X by authors from multiple academic institutions in Europe, including the Norwegian University of Science and Technology (NTNU), the Niels Bohr Institute, and Universiteit Leiden. 

“In quantum computers, information is transmitted and stored using so-called qubits (quantum bits). But quantum information can quickly be lost,” explained Jeroen Danon, a professor at the NTNU Department of Physics. 

Traditionally, it takes around 1 second to measure how long it takes before quantum information is lost. 

“We managed to do it in approximately 10 milliseconds, i.e. more than 100 times faster. And more or less in real time,” Danon said.

As a result, the loss of quantum information can be determined much more quickly and accurately, with the ability to observe small and rapid changes that were previously invisible.

“This will in turn make it easier to identify the underlying causes that make the information disappear," Danon said. 

This year, Ian Farquhar, Security CTO, Gigamon, said that Quantum Day should be a wakeup call for many organisations. "There is little time left to transition, and quantum could be here in as little as four years’ time in some parts of the world," he explained, referring to Q-Day.

"Even if there’s ongoing debate about how quickly quantum computing will scale, the risk is significant enough and the timelines short enough that organisations can no longer afford to wait. What’s often overlooked is that this isn’t just about ‘harvest now, decrypt later,’ but ‘harvest now, forge later.’ If private keys are compromised, the integrity of identities, transactions, and digital signatures comes into question, derailing longstanding trust and risk calculations that form the backbone of the modern era. This will impact organisations across every industry, impacting consumers and businesses alike." 

Robert Hann, Global VP of Technical Solutions & Centre of Excellence at Entrust, also said that universal migration should have already started. 

"On World Quantum Day 2026, adversaries are already using ‘harvest now, decrypt later’ tactics, and if Google’s latest predictions are correct, Q-Day could arrive as early as 2029. Migrating data and asset protection infrastructure to post-quantum cryptography (PQC) is a multi-year journey, spanning data in motion, data at rest, and data in use," he said. 

"A year on from NIST’s quantum-safe standards, we’re seeing organisations start to move from planning PQC to deployment. Large enterprises such as Mastercard are already advocating early adoption, particularly in the finance sector. In Singapore, the Cyber Security Agency (CSA) has already begun laying the groundwork for quantum-safe migration, launching a Quantum-Safe Handbook and Quantum Readiness Index in 2025. Yet, many organisations continue to underestimate the threat." 

According to Hann, the 2026 Global State of Post-Quantum and Cryptographic Security Trends report shows that only 33% of organisations in Singapore and 38% globally are currently transitioning to PQC. "In 2026, leaders need to take decisive action to protect how identities are issued, verified, and trusted in a post-quantum world," Hann continued. 

To prepare for the advent of quantum computing Farquhar recommended that organisations should create a dedicated team internally, much like a cryptographic centre of excellence. "From there, this team can inventory where cryptography exists across their environments, prioritising what matters most, and building the internal muscle, often through dedicated teams, to manage and execute these upgrades," he suggested. 

"Once done, we then need to monitor our environments to ensure that vulnerable non-PQC crypto has not been missed or sneaks back in. If that effort results in true cryptographic agility, where policies and algorithms can be swapped out quickly in response to future threats, then the investment will have been worth it regardless of how the quantum threat ultimately evolves.”

The concept of harvest now, decrypt later refers to cybercriminals stealing encrypted data to decrypt it when quantum technology is available. Harvest now, forge later is a bolder concept, pointing out that if cybercriminals can decrypt, they can also impersonate (forge) trusted vendors for their own purposes.

*PQC stands for post-quantum cryptography, while Q-Day, sometimes also called Quantum Day, is the day quantum computers become powerful enough to crack today's public-key cryptography standards. 

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