The theorem founded by Irish physicist John Bell in 1964 and named after him is one of the most profound discoveries in physics. In short, it says that no local realistic explanation of quantum physics is possible. The philosophical implications of the Bell theorem are startling: either one must abandon the realistic view that external reality exists prior to and independent of observations, or dramatically revise our concepts of space and time.
Needless to say either of the choices requires radical revision of the ruling philosophical view of most scientists and is in sharp contrast to our everyday experience. The present-day impact of the Bell theorem is immense. Nobody, including John Bell himself, could ever dream that his answering of such a very deep philosophical question would become the cornerstone of today’s newly evolving technology of quantum information.
This includes quantum cryptography and quantum computation which are thought to be more efficient than their classical counterparts can ever be. The theorem of John Bell has not only fundamentally changed our understanding of physical reality but might also have one of the decisive impacts on our future social and economic development.
Časlav Brukner is associate professor of theoretical physics at the University of Vienna and chair professor of physics at Tsinghua University in Beijing.