On 24 March 2026, the Quantum Security Defence (QSECDEF) World Symposium will debut at the Palais des Congrès de Paris, bringing together senior leaders from industry, government, and academia to address a central challenge of the coming decade - securing communications and critical infrastructure in the Quantum-AI era. As quantum technologies threaten conventional cryptography and reshape global security, this half-day programme will highlight deployable quantum-secure solutions, certification pathways, and transition strategies for practical adoption across telecoms, defence, and enterprise networks. Participants will gain technically grounded guidance on assessing quantum risk, designing resilient and interoperable systems, and advancing international collaboration around quantum-safe technologies - hosted alongside the third annual Quantum Networks Summit in Paris. Whether your focus is post-quantum cryptography, secure quantum communications, or policymaking for quantum resilience, the symposium offers a focused forum to engage with thought leaders, contribute to high-level discussions, and help shape the future of secure quantum ecosystems.\