In 1981, Mermin published a paper in which he explained quantum entanglement for the layperson using a “simple device.” It was the “Mermin device” that first showed me (Stuckey) the conundrum of entanglement in 1994. Now, 24 years later, I’ve answered Mermin’s challenge to explain how his device works. In this paper users.etown.edu/s/stuckeym/AJP2018.pdf I explain the Mermin device, how Unnikrishnan’s version of conservation of angular momentum resolves its conundrum, and how RBW justifies Unnikrishnan’s solution.
To answer John Wheeler's ``Really Big Question,'' ``Why the quantum?'' via quantum information theory according to Bub, one must explain both why the world is quantum rather than classical and why the world is quantum rather than superquantum, i.e., ``Why the Tsirelson bound?'' We show that the quantum correlations resulting from two Bell basis states, which uniquely produce the Tsirelson bound for the Clauser-Horne-Shimony-Holt (CHSH) quantity, can be derived from the conservation of angular momentum (on average) for the quantum exchange of momentum. This explanation of the Tsirelson bound does not require hidden variables or `causal influences'. Neither is this result surprising, since we already know that entangled states result from conservation principles and quantum states produce classical results on average. Accordingly, expecting the Bell inequality to be satisfied for quantum outcomes per classical probability theory means selectively abandoning the conservation of angular momentum. Since superquantum correlations exceed quantum correlations, we know that they would also violate conservation of angular momentum and we show how this happens using the Popescu-Rohrlich (PR) correlations. Thus, quantum correlations responsible for the Tsirelson bound satisfy conservation of angular momentum for the quantum exchange of momentum while both classical and superquantum correlations can fail to satisfy this constraint. We generalize the result to conservation per any measurement associated with a Bell basis state. While this constraint is not surprising per se, the details on how it obtains evidence a deeper principle at work in Nature, i.e., no preferred reference frame.
This is a link to our OUP Blog post, "Ascending to the god's-eye view of reality."
A recurring theme in natural philosophy is the tension between the God's-eye view of reality comprehended as a whole and the ant's-eye view of human consciousness, which senses a succession of events in time. Since the days of Isaac Newton, the ant's-eye view has dominated fundamental physics. We divide our description of the world into dynamical laws that, paradoxically, exist outside of time according to some, and initial conditions on which those laws act. The dynamical laws do not determine which initial conditions describe reality. That division has been enormously useful and successful pragmatically, but it leaves us far short of a full scientific account of the world as we know it. The account it gives – things are what they are because they were what they were – raises the question, Why were things that way and not any other? The God’s-eye view seems, in the light of relativity theory, to be far more natural. Relativity teaches us to consider spacetime as an organic whole whose different aspects are related by symmetries that are awkward to express if we insist on carving experience into time slices. Hermann Weyl expressed the organic view memorably in his 1949 book Philosophy of Mathematics and Natural Science (Princeton University Press, page 116):
"The objective world simply is, it does not happen. Only to the gaze of my consciousness, crawling upward along the life line of my body, does a section of this world come to life as a fleeting image in space which continuously changes in time."
To me, ascending from the ant’s-eye view to the God’s-eye view of physical reality is the most profound challenge for fundamental physics in the next 100 years.
Frank Wilczek: Physics in 100 Years. Physics Today 69(4), 32-39 (2016).
Theoretical physics and foundations of physics have not made much progress in the last few decades. Whether we are talking about unifying general relativity and quantum field theory (quantum gravity), explaining so-called dark energy and dark matter (cosmology), or the interpretation and implications of quantum mechanics and relativity, there is no consensus in sight. In addition, both enterprises are deeply puzzled about various facets of time including above all, time as experienced. The authors argue that, across the board, this impasse is the result of the “dynamical universe paradigm,” the idea that reality is fundamentally made up of physical entities that evolve in time from some initial state according to dynamical laws. Thus, in the dynamical universe, the initial conditions plus the dynamical laws explain everything else going exclusively forward in time. In cosmology, for example, the initial conditions reside in the Big Bang and the dynamical law is supplied by general relativity. Accordingly, the present state of the universe is explained exclusively by its past. This book offers a completely new paradigm (called Relational Blockworld), whereby the past, present and future co-determine each other via “adynamical global constraints,” such as the least action principle. Accordingly, the future is just as important for explaining the present as is the past. Most of the book is devoted to showing how Relational Blockworld resolves many of the current conundrums of both theoretical physics and foundations of physics, including the mystery of time as experienced and how that experience relates to the block universe.