14 Two Enigmatic “Thought Experiments”
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Study of Quantum Spin Correlations of Relativistic Electron Pairs
Study of quantum spin correlations of relativistic electron pairs Project status Nov. 2015 Jacek Ciborowski Marta Włodarczyk, Michał Drągowski, Artem Poliszczuk (UW) Joachim Enders, Yuliya Fritsche (TU Darmstadt) Warszawa 20.XI.2015 Quantum spin correlations In this exp: e1,e2 – electrons under study a, b - directions of spin projections (+- ½) 4 combinations for e1 and e2: ++, --, +-, -+ Probabilities: P++ , P+- , P-+ , P- - (ΣP=1) Correlation function : C = P++ + P-- - P-+ - P-+ Historical perspective • Einstein Podolsky Rosen (EPR) paradox (1935): QM is not a complete local realistic theory • Bohm & Aharonov formulation involving spin correlations (1957) • Bell inequalities (1964) a local realistic theory must obey a class of inequalities • practical approach to Bell’s inequalities: counting aacoincidences to measure correlations The EPR paradox Boris Podolsky Nathan Rosen Albert Einstein (1896-1966) (1909-1995) (1979-1955) A. Afriat and F. Selleri, The Einstein, Podolsky and Rosen Paradox (Plenum Press, New York and London, 1999) Bohm’s version with the spin Two spin-1/2 fermions in a singlet state: E.g. if spin projection of 1 on Z axis is measured 1/2 spin projection of 2 must be -1/2 All projections should be elements of reality (QM predicts that only S2 and David Bohm (1917-1992) Sz can be determined) Hidden variables? ”Quantum Theory” (1951) Phys. Rev. 85(1952)166,180 The Bell inequalities J.S.Bell: Impossible to reconcile the concept of hidden variables with statistical predictions of QM If local realism quantum correlations -
Quantum Eraser
Quantum Eraser March 18, 2015 It was in 1935 that Albert Einstein, with his collaborators Boris Podolsky and Nathan Rosen, exploiting the bizarre property of quantum entanglement (not yet known under that name which was coined in Schrödinger (1935)), noted that QM demands that systems maintain a variety of ‘correlational properties’ amongst their parts no matter how far the parts might be sepa- rated from each other (see 1935, the source of what has become known as the EPR paradox). In itself there appears to be nothing strange in this; such cor- relational properties are common in classical physics no less than in ordinary experience. Consider two qualitatively identical billiard balls approaching each other with equal but opposite velocities. The total momentum is zero. After they collide and rebound, measurement of the velocity of one ball will naturally reveal the velocity of the other. But the EPR argument coupled this observation with the orthodox Copen- hagen interpretation of QM, which states that until a measurement of a par- ticular property is made on a system, that system cannot, in general, be said to possess any definite value of that property. It is easy to see that if dis- tant correlations are preserved through measurement processes that ‘bring into being’ the measured values there is a prima facie conflict between the Copenhagen interpretation and the relativistic stricture that no information can be transmitted faster than the speed of light. Suppose, for example, we have a system with some property which is anti-correlated (in real cases, this property could be spin). -
Required Readings
HPS/PHIL 93872 Spring 2006 Historical Foundations of the Quantum Theory Don Howard, Instructor Required Readings: Topic: Readings: Planck and black-body radiation. Martin Klein. “Planck, Entropy, and Quanta, 19011906.” The Natural Philosopher 1 (1963), 83-108. Martin Klein. “Einstein’s First Paper on Quanta.” The Natural Einstein and the photo-electric effect. Philosopher 2 (1963), 59-86. Max Jammer. “Regularities in Line Spectra”; “Bohr’s Theory The Bohr model of the atom and spectral of the Hydrogen Atom.” In The Conceptual Development of series. Quantum Mechanics. New York: McGraw-Hill, 1966, pp. 62- 88. The Bohr-Sommerfeld “old” quantum Max Jammer. “The Older Quantum Theory.” In The Conceptual theory; Einstein on transition Development of Quantum Mechanics. New York: McGraw-Hill, probabilities. 1966, pp. 89-156. The Bohr-Kramers-Slater theory. Max Jammer. “The Transition to Quantum Mechanics.” In The Conceptual Development of Quantum Mechanics. New York: McGraw-Hill, 1966, pp. 157-195. Bose-Einstein statistics. Don Howard. “‘Nicht sein kann was nicht sein darf,’ or the Prehistory of EPR, 1909-1935: Einstein’s Early Worries about the Quantum Mechanics of Composite Systems.” In Sixty-Two Years of Uncertainty: Historical, Philosophical, and Physical Inquiries into the Foundations of Quantum Mechanics. Arthur Miller, ed. New York: Plenum, 1990, pp. 61-111. Max Jammer. “The Formation of Quantum Mechanics.” In The Schrödinger and wave mechanics; Conceptual Development of Quantum Mechanics. New York: Heisenberg and matrix mechanics. McGraw-Hill, 1966, pp. 196-280. James T. Cushing. “Early Attempts at Causal Theories: A De Broglie and the origins of pilot-wave Stillborn Program.” In Quantum Mechanics: Historical theory. -
Nonlocal Single Particle Steering Generated Through Single Particle Entanglement L
www.nature.com/scientificreports OPEN Nonlocal single particle steering generated through single particle entanglement L. M. Arévalo Aguilar In 1927, at the Solvay conference, Einstein posed a thought experiment with the primary intention of showing the incompleteness of quantum mechanics; to prove it, he employed the instantaneous nonlocal efects caused by the collapse of the wavefunction of a single particle—the spooky action at a distance–, when a measurement is done. This historical event preceded the well-know Einstein– Podolsk–Rosen criticism over the incompleteness of quantum mechanics. Here, by using the Stern– Gerlach experiment, we demonstrate how the instantaneous nonlocal feature of the collapse of the wavefunction together with the single-particle entanglement can be used to produce the nonlocal efect of steering, i.e. the single-particle steering. In the steering process Bob gets a quantum state depending on which observable Alice decides to measure. To accomplish this, we fully exploit the spreading (over large distances) of the entangled wavefunction of the single-particle. In particular, we demonstrate that the nonlocality of the single-particle entangled state allows the particle to “know” about the kind of detector Alice is using to steer Bob’s state. Therefore, notwithstanding strong counterarguments, we prove that the single-particle entanglement gives rise to truly nonlocal efects at two faraway places. This opens the possibility of using the single-particle entanglement for implementing truly nonlocal task. Einstein eforts to cope with the challenge of the conceptual understanding of quantum mechanics has been a source of inspiration for its development; in particular, the fact that the quantum description of physical reality is not compatible with causal locality was critically analized by him. -
Style Plain.Bst
Style plain.bst [1] Albert Einstein. Die Grundlage der allgemeinen Relativitätstheorie. An- nalen der Physik, 354(7) :769–822, 1916. [2] Albert Einstein. The Meaning of Relativity – Including the Relativistic Theory of the Non–Symmetric Field. Princeton University Press, 5 rev e. edition, 2004. [3] Albert Einstein, B. Podolsky, and N. Rosen. Can Quantum-Mechanical Description of Physical Reality Be Considered Complete ? Physical Review, 47(10) :777–780, 1935. [4] Albert Einstein and Nathan Rosen. The particle problem in the general theory of relativity. Physical Review, 48(1) :73, 1935. [5] Albert Einstein and Nathan Rosen. Two-body problem in general relativity theory. Physical Review, 49(5) :404, 1936. [6] Philip M. Morse, Herman Feshbach, and E. L. Hill. Methods of Theoretical Physics. American journal of physics, 22(6) :410–413, September 1954. Style abbrv.bst [1] A. Einstein. Die Grundlage der allgemeinen Relativitätstheorie. Annalen der Physik, 354(7) :769–822, 1916. [2] A. Einstein. The Meaning of Relativity – Including the Relativistic Theory of the Non–Symmetric Field. Princeton University Press, 5 rev e. edition, 2004. [3] A. Einstein, B. Podolsky, and N. Rosen. Can Quantum-Mechanical Des- cription of Physical Reality Be Considered Complete ? Physical Review, 47(10) :777–780, 1935. [4] A. Einstein and N. Rosen. The particle problem in the general theory of relativity. Physical Review, 48(1) :73, 1935. [5] A. Einstein and N. Rosen. Two-body problem in general relativity theory. Physical Review, 49(5) :404, 1936. [6] P. M. Morse, H. Feshbach, and E. L. Hill. Methods of Theoretical Physics. American journal of physics, 22(6) :410–413, Sept. -
Letters to the Editor
Letters to the Editor Nathan Rosen and Black Judaism. Merzbacher has informed There is another advantage of tablet Mountain me that Professor Rosen used to apps which, being unfamiliar with Thank you for your excellent article return to Chapel Hill during the sum- them, the author doesn’t anticipate: in the February 2013 Notices on von mers where he collaborated with Merz- no matter how many blackboards Neumann and the book review of bacher on various research projects. are available, total space is limited, Transcending Tradition. Having been but the apps can store an unlimited educated in North Carolina, I was —Paul F. Zweifel number of handwritten screens. If an especially interested in the discus- Virginia Tech (emeritus) audience member wants a copy of the sion of Black Mountain College in [email protected] notes after a talk, I can either print a the latter. One prominent faculty copy or email the stored document. member there not mentioned in the (Received January 22, 2013) The apps can even record audio from review was the Jewish physicist (and In Defense of Technology for the presentation. disciple of Einstein) Nathan Rosen. Mathematical Talks I think what the author observes about use of computer-based slides Although I earned my Ph.D. in phys- In response to V. V. Peller’s com- today represents not a failure of the ics at Duke University, I was allowed mentary, “Utilization of technology computer as a platform for the pre- to take courses at the University of for mathematical talks: An alarming sentation, but rather inadequately North Carolina in Chapel Hill. -
Can Quantum-Mechanical Description of Physical Reality Be Considered
Can quantum-mechanical description of physical reality be considered incomplete? Gilles Brassard Andr´eAllan M´ethot D´epartement d’informatique et de recherche op´erationnelle Universit´ede Montr´eal, C.P. 6128, Succ. Centre-Ville Montr´eal (QC), H3C 3J7 Canada {brassard, methotan}@iro.umontreal.ca 13 June 2005 Abstract In loving memory of Asher Peres, we discuss a most important and influential paper written in 1935 by his thesis supervisor and men- tor Nathan Rosen, together with Albert Einstein and Boris Podolsky. In that paper, the trio known as EPR questioned the completeness of quantum mechanics. The authors argued that the then-new theory should not be considered final because they believed it incapable of describing physical reality. The epic battle between Einstein and Bohr arXiv:quant-ph/0701001v1 30 Dec 2006 intensified following the latter’s response later the same year. Three decades elapsed before John S. Bell gave a devastating proof that the EPR argument was fatally flawed. The modest purpose of our paper is to give a critical analysis of the original EPR paper and point out its logical shortcomings in a way that could have been done 70 years ago, with no need to wait for Bell’s theorem. We also present an overview of Bohr’s response in the interest of showing how it failed to address the gist of the EPR argument. Dedicated to the memory of Asher Peres 1 Introduction In 1935, Albert Einstein, Boris Podolsky and Nathan Rosen published a paper that sent shock waves in the physics community [5], especially in Copenhagen. -
Introduction to Regge and Wheeler “Stability of a Schwarzschild Singularity”
September 24, 2019 12:14 World Scientific Reprint - 10in x 7in 11643-main page 3 3 Introduction to Regge and Wheeler “Stability of a Schwarzschild Singularity” Kip S. Thorne Theoretical Astrophysics, California Institute of Technology, Pasadena, CA 91125 USA 1. Introduction The paper “Stability of a Schwarzschild Singularity” by Tullio Regge and John Archibald Wheeler1 was the pioneering formulation of the theory of weak (linearized) gravitational perturbations of black holes. This paper is remarkable because black holes were extremely poorly understood in 1957, when it was published, and the very name black hole would not be introduced into physics (by Wheeler) until eleven years later. Over the sixty years since the paper’s publication, it has been a foundation for an enormous edifice of ideas, insights, and quantitative results, including, for example: Proofs that black holes are stable against linear perturbations — both non-spinning • black holes (as treated in this paper) and spinning ones.1–4 Demonstrations that all vacuum perturbations of a black hole, except changes of its • mass and spin, get radiated away as gravitational waves, leaving behind a quiescent black hole described by the Schwarzschild metric (if non-spinning) or the Kerr metric (if spinning).5 This is a dynamical, evolutionary version of Wheeler’s 1970 aphorism “a black hole has no hair”; it explains how the “hair” gets lost. Formulations of the concept of quasinormal modes of a black hole with complex • eigenfrequencies,6 and extensive explorations of quasinormal-mode -
Mad Genius Or Rotten Apple? Exploring Time Travel Through Wormholes
Mad Genius or Rotten Apple? Exploring Time Travel Through Wormholes Gayatri Dhavan “They had to travel into the past to save the future”— Timeline (2003) That’s the tagline from the 2003 movie Timeline. The film itself was forgettable but it was based on a premise that has intrigued humanity for generations: time travel. In the movie, characters were able to identify a wormhole, which allowed time travel between present day and medieval France. I thought this was an interesting idea but I knew it bordered on ridiculous, so I decided to take a closer look at whether time travel through wormholes could indeed be possible. First things first, what is a wormhole? Here is an easy way to picture wormholes without a Physics PhD: imagine that you fold a piece of paper so that one end hovers a couple of inches above the other end. Now punch a hole with a pen on the top part of the paper so the point of the pen reaches the lower part of the paper. Your pen now represents the wormhole. In principle, the wormhole could be used as a shortcut so that, from the point of view of observers outside of the wormhole, travel between the two points could appear to take place faster than the speed of light. The essence of the idea was originally put forth in 1935 by Albert Einstein and Nathan Rosen, who suggested the possibility of “bridges” in the space-time continuum. Once I learned that Einstein had something to do with the concept behind wormholes, I actually felt that wormholes might not be so ridiculous after all. -
Spooky Action at a Distance Is Not Spooky-It Is Knowledge: Combining Entanglement and Negative Observation to Show How the EPR E
How Knowledge Can Lead to the Demise of Schrodinger’s Cat Through a Negative Measurement/Null Measurement (A Quantum Mechanical Measurement in Which There is No Physical Interaction Between a Physical Measuring Apparatus and the System Measured) Douglas M. Snyder 2020 APS March Meeting, Denver, Colorado http://meetings.aps.org/Meeting/MAR20/Session/C71.261 DOI: 10.13140/RG.2.2.27582.43843 forpsyarxiv_cat 5/26/2020 Copyright 2020 Douglas Michael Snyder 1 Abstract The Schrodinger cat experiment (SCE) is presented. An alteration follows where the LACK of radioactive decay leads to the demise of the cat instead of the ACT of radioactive decay. The lack of radioactive decay is a negative (null) measurement (where there is NO physical interaction between the radioactive material and the Geiger counter). The negative (null) measurement is non-trivial because all knowledge about the radioactive material (rm) is derived from its associated wave function which itself has no physical existence. The wave function is how we make probabilistic predictions regarding systems in quantum mechanics. So when the wave function changes in a negative (null) measurement, that is exactly what happens in a positive measurement where there is a physical interaction between entity measured and a physical measuring apparatus. (continued on next slide) 5/26/2020 2 Copyright 2020 Douglas Michael Snyder Abstract Before the box in the original SCE is opened, the wave function for the radioactive material is: ψrad_mat = 1/√2 [ψrad_mat_does_not_decay + ψrad_mat+_does_decay] -
General Relativity 05/12/2008 Lecture 15 1
General Relativity 05/12/2008 UCSD Physics 10 UCSD Physics 10 So Far, We Have… • Decided that constant velocity is the “natural” state of things General Relativity • Devised a natural philosophy in which Einstein Upsets the Applecart acceleration is the result of forces • Unified terrestrial and celestial mechanics & brought order to the Universe Spring 2008 2 UCSD Physics 10 UCSD Physics 10 Frames of Reference Science is Fraught with Assumptions This is all fine, but accelerating • The Earth is at the center of the universe... with respect to what?? • The Earth is at the center of the solar system... • The world is flat... • The geometry of the Universe is flat... • The surface of the Earth is the “natural” reference frame... • Time and space are independent concepts These assumptions can have a dramatic impact on our views of Nature Why the Earth, of course! Spring 2008 3 Spring 2008 4 Lecture 15 1 General Relativity 05/12/2008 UCSD Physics 10 UCSD Physics 10 Recall the Rotating Drum Example Imagine Being in a Car • Windows are painted black • Move the car to outer space • An accelerating frame of reference feels a lot like • Now imagine placing a few objects on the dashboard of gravity this blacked-out car, still in outer space. – In fact, it feels exactly like gravity • If the car accelerates forward, what happens to these • The essence of General Relativity is the objects on the dashboard? (Why?) recognition that “gravitational force” is an artifact • If you didn’t know the car was accelerating, what of doing physics in a particular reference frame! would you infer about a “force” acting on the objects? • How would that force depend on the masses of the objects? Spring 2008 5 Spring 2008 6 UCSD Physics 10 UCSD Physics 10 Gravity vs. -
QUANTUM ENTANGLEMENT and Locality
QUANTUM ENTANGLEMENT and lOcalitY * Miriam Blaauboer , * Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands * E-mail: [email protected] * DOI: 10.1051/ epn /2010602 Can a measurement at location A depend on events taking place at a distant location B, too far away for the information to be transmitted between the two? It does seem too mysterious to be true. Even Einstein did not believe so. But experiments seem to prove him wrong. t is well-known that until the end of his life Einstein was at B travelling at the speed of light cannot possibly reach ᭡ John Bell dissatisfied with quantum mechanics as a fundamental A before the measurement at A has been performed. thinking - ahead of his theory [1]. He strongly believed that the real world eories satisfying both of these criteria are called‘local’ time - about should consist of “systems” (particles, fields) that pos - and‘realistic’. Quantum mechanics, in contrast with ear - Bell tests with I electrons in sess objective properties, i.e. , properties that do not lier developed classical theories, does not satisfy either nanomaterials depend on measurements by external observers. A second of these criteria: properties of a quantum-mechanical essential aspect of these objective properties is that the system do depend on the experimental conditions outcome of a measurement at location A cannot depend under which they are measured, and a measurement at on events taking place at another location B, if B is suffi - A can be influenced instantaneously by an event happe - ciently far away from A that information about the event ning at B via the mechanism called entanglement (see III EPN 41/6 17 Article available at http://www.europhysicsnews.org or http://dx.doi.org/10.1051/epn/2010602 fEaturEs quaNtum ENtaNglEmENt III box).