New Experiments Focus on the Nature of Quantum Reality
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The "quantum three-box paradox" implemented by Prof. Andrew Briggs' laboratory. |
What is the relationship between the weird microscopic world described by quantum physics and the everyday macroscopic world of human experience? As yet, it is not possible to reconcile the two perspectives. How the macroscopic emerges from the microscopic, and what concepts are needed to understand this transition, remains one of the most basic and pressing issues in modern physics.
In 2010, a conference was held in Oxford to mark the 80th birthday of John Polkinghorne, the physicist and theologian whose wide-ranging inquiries have been influential in the study of science and religion. The conference, sponsored by the John Templeton Foundation, focused on a series of papers from scientists and philosophers who explored the theme of the conference title, Quantum Physics and the Nature of Reality.
"The conference was carefully planned to produce a set of questions, which came to be known as The Oxford Questions," explains Professor Andrew Briggs of Oxford University. "They focus the collected wisdom of the conference on the deeper significance of quantum physics and the fundamental challenges that quantum physics throws up which have yet to be resolved."
The conversations have continued since 2010, in particular around one of the Oxford questions that is concerned with the relationship between the world of the very, very small and the macroscopic. It is brought into focus by a celebrated thought experiment known as Schrödinger's cat. The experiment imagines a cat in a box that lives if a quantum event such as the release of a fundamental particle doesn't happen, and dies if one does. A paradox arises because according to quantum theory, and so presumably at the microscopic level of the reality it describes, the quantum event can both happen and not happen—a so-called superposition of states. This implies that the cat should be both alive and dead, in conflict with our everyday intuition and experience.
To put it another way, the quantum level appears to be one of fundamental indeterminacy. According to Heisenberg's Uncertainty Principle, it is not possible to know everything about a quantum particle in the way that classical physics would expect.
Physicists are working on a range of possible answers to such challenges. In recent years, a series of brilliant experiments have started to narrow that range. In essence, these experiments have brought the quantum world closer to the everyday world. They are testing the limits of when "quantumness" might give way to life as we experience it.
For example, some researchers have been able to examine systems of atoms and particles that are considered large by quantum standards. One study has tested molecules of up to 430 atoms—approximately 350% more than in all previous comparable experiments. Another, recently reported in Nature, studied the phenomenon of quantum teleportation, the apparently instantaneous transmission of states from one entangled particle to another, which has now been demonstrated on distances reaching over 100 kilometers or approximately 62 miles. A third experiment, by members of Professor Briggs' laboratory with collaborators from Delft in the Netherlands and supported by the John Templeton Foundation, has implemented a "quantum three-box paradox," which was first proposed over a quarter of a century ago. They have shown how this can be recast as a test of the reality of the quantum state.
"These experiments are nudging some of the candidate interpretations in certain directions," says Briggs—though he also stresses that physicists are far from arriving at any settled opinion. "My colleagues talk of being 'halfway through the woods,'" he continues. "And it may be that one day a new theory will be discovered that will be as different from quantum mechanics as quantum theory is from what went before."
What is striking, though, is that new experimentation is shedding light on the possible answers to these profound questions, and that is helping physicists and philosophers to ask better questions, too. "Even though quantum phenomena provide a basis for many applications today and probably even more in the near future," says Vladimir Bužek, vice president of mathematical and physical sciences at the John Templeton Foundation, "we still do not understand the 'true nature' of the quantum world." There are still many exciting advances to be made and this quest to understand the "quantum" is a big challenge, reflecting the spirit of Sir John and his philosophy, "How little we know, how eager to learn."
Complexity Course for All at Santa Fe Institute
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VIDEO: Introduction to Complexity |
A new introductory online course studying complexity, requiring no background in science or math, is currently being offered by the Santa Fe Institute. All that is required to enroll is a lively interest and willingness to take part. The course is free and already underway, though individuals can still sign up.
Participants will learn about how complexity arises in nature on scales that range from genes to cells to natural and social systems. The tools scientists use to grapple with various elements of complex systems will also be explored—tools including fractals, information theory, self-organization, and networks. Students will receive a certificate of completion after a final exam.
The course is the first in a series of Massive Open Online Courses (MOOCs) being offered by the Santa Fe Institute and supported by a $5 million grant from the John Templeton Foundation. The instructor is Dr. Melanie Mitchell, professor of computer science at Portland State University, external professor at the Santa Fe Institute, and author of Complexity: A Guided Tour, which won the Phi Beta Kappa Science Book Award in 2010. Full details about the course are online.
How Do the Greatest Scientific Innovations Happen?
What was the final, crucial stage that allowed Albert Einstein to arrive at his breakthrough theory of relativity? Thomas Kuhn, author of the influential study The Structure of Scientific Revolutions, described that moment of exceptional creativity as "inscrutable." Half a century later, many would still feel the same way.
A new book from Templeton Press, Exceptional Creativity in Science and Technology, explores the latest thinking about scientific innovation. It stems from a Humble Approach Initiative symposium that brought together a range of scholars to think about the generation of new discoveries and insights.
Edited by Andrew Robinson, the essays in the collection are written by scholars and scientists, including two Nobel laureates, the late Baruch Blumberg and Philip W. Anderson, and represent contributions from many academic disciplines. A lively afterward is provided by Freeman Dyson.
"[This is] a fascinating work," said Sir David Weatherall, Regius Professor of Medicine Emeritus at the University of Oxford. "[It] explores the origins of some of the greatest scientific institutions in the world and their innovations which have changed all our lives."
