Within the captivating domain of quantum physics, a recent study has introduced a groundbreaking improvement in Hardy’s paradox, significantly enhancing our ability to test the fundamental principles of quantum mechanics against local realism. This advancement, spearheaded by researchers Professor Jing-Ling Chen from the Nankai University, together with Professor Kai Chen from the University of Science and Technology of China, and their team, was recently published in the esteemed journal, Results in Physics.

Hardy’s paradox, a pivotal concept in quantum mechanics, has traditionally provided a stark contrast between predictions of quantum mechanics and local realistic theories, where the latter assumes that properties of particles exist independently of observation. The original paradox suggests that under certain conditions, outcomes predicted by quantum mechanics cannot be explained by any local hidden variable theories—essentially challenging the classical understanding of reality.

The team has developed what they term a “realigned Hardy’s paradox,” which not only strengthens the original paradox’s assertions but does so with a simpler set of requirements and increased robustness against experimental imperfections. The enhancement comes from extending the paradox to include multiple measurements, thereby significantly increasing the violation values observed during quantum entanglement experiments.

The realigned Hardy’s paradox demonstrates that when quantum entanglement is considered, the expected outcomes substantially deviate from those predicted by any local realistic theories. The improvements seen in the experiments show a notable increase from the minor value in the original setup to higher levels of observed values in the scenarios involving two, four, and six measurements respectively.

One of the major advantages of the realigned version is its tolerance for experimental errors, making it a robust tool for testing quantum nonlocality. This property is particularly valuable because it helps close loopholes such as the detection loophole, where the validity of quantum experiments can be questioned due to unobserved or lost particles.

Professor Jing-Ling Chen commented, “This enhanced version of Hardy’s paradox could lead to more secure quantum communication protocols and has potential applications in quantum computing where quantum bits are manipulated at fundamental levels.”

Professor Kai Chen added, “The broader impact of this research stretches beyond theoretical physics, touching on the practical realms of quantum computing and cryptography. By providing a more stringent test of quantum nonlocality, the realigned Hardy’s paradox could help in developing new technologies that are fundamentally secure from hacking attempts that exploit the classical assumptions of locality and realism.”

The research findings not only offer a new lens to view the quantum world but also pave the way for practical applications that harness the strange, counterintuitive properties of quantum phenomena. As quantum technologies continue to evolve, the insights from this study will be critical in shaping future innovations in the field.

Journal Reference

Shuai Zhao, Qing Zhou, et al., “Realigned Hardy’s Paradox,” Results in Physics, 2024. DOI: https://doi.org/10.1016/j.rinp.2023.107210

About The Author

Jing-Ling Chen is a professor of physics at Nankai University. He got his bachelor’s degree (1994), master’s degree (1997) and doctor’s degree (2000) in Nankai University, P. R. China. He has been a post-doc at Beijing institute of apply physics (2000-2002) and a research fellow at National University of Singapore (2002-2005), respectively. His research interest is quantum physics and quantum information, especially in quantum fundamental problems, such as EPR paradox, quantum entanglement, EPR steering, Bell’s nonlocality and quantum contextuality. Due to his contribution in quantum foundations, he has won the Paul Ehrenfest Best Paper Award for Quantum Foundations (2021). Recently, he has made some original explorations on spin, such as proposing the spin vector potential, presenting the spin-type Aharonov-Bohm effect, and predicting the spin angular-momentum wave.