Download
quantum entanglement nonlocality and back in time messages n.
Skip this Video
Loading SlideShow in 5 Seconds..
Quantum Entanglement, Nonlocality, and Back-In-Time Messages PowerPoint Presentation
Download Presentation
Quantum Entanglement, Nonlocality, and Back-In-Time Messages

Quantum Entanglement, Nonlocality, and Back-In-Time Messages

356 Vues Download Presentation
Télécharger la présentation

Quantum Entanglement, Nonlocality, and Back-In-Time Messages

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Quantum Entanglement,Nonlocality, andBack-In-Time Messages John G. Cramer Professor Emeritus of Physics University of Washington Norwescon 33 April 3, 2010

  2. Causality & Retrocausality The Law of Causality:A cause must precede its effects in all reference frames. In quantum mechanics, there are apparent violations of this principle. One example is Wheeler’s Delayed Choice Experiment, in which a photon of light is made to pass either through one slit or two slits, depending on which measurement action that is taken after the light has already passed the slit system. This is called retrocausality, an effect that appears to precede its cause. Norwescon 33

  3. Evidence for Retrocausality:Publicity Precedes the Experiment Seattle Post IntelligencerNovember 15, 2006 New ScientistSeptember 30, 2006 Norwescon 33

  4. … and Even More Evidence Men’s Journal October, 2007 Seattle Metropolitan Magazine October, 2007 Norwescon 33

  5. Quantum Entanglement and Nonlocality “Spooky Actions-at-a-Distance” Albert Einstein

  6. Entanglementand Nonlocality Measurement 1 M1 Entangled photon 1 Entangled Photon Source Nonlocal Connection Entangled photon 2 M2 Measurement 1 Entanglement:The separated but “entangled” parts of the same quantum system can only be described by referencing the state of other part. The possible outcomes ofmeasurement M2 depend of theresults of measurement M1, andvice versa. This is usually aconsequence of conservation laws(conservation of momentum, angularmomentum, energy, …). Nonlocality:This “connectedness” between the separated system parts is called quantum nonlocality. It should act even of the system parts are separated by light years. Einstein called this “spooky actions at a distance.”

  7. Interference of Waves Light travels as a wave, but leaves and arrives as a particle.(E = hn) We can select wave-like behavior or particle-like behavior by choosing what to measure. Wave-like behavior shows up as interference. Norwescon 33

  8. One-Slit Diffraction Norwescon 33

  9. Two-Slit Interference Norwescon 33

  10. Two-slitInterference Pattern No Two-slitInterference Pattern H V Turning InterferenceOn and Off Waves that cannot be distinguished will interfere. Waves that can be distinguished (e.g., by polarization) will not interfere. Norwescon 33

  11. Shih Ghost Interference Experiment (1995) Note the useof coincidence

  12. Klyshko Reflection

  13. Dopfer Position-MomentumEPR Experiment (1998) Note the useof coincidence. LiIO3 Down-ConversionCrystal “Heisenberg” Lens f = 86 cm “Heisenberg”Detector D1 UV LaserBeam 28.2o Laser BeamStop 28.2o f 2f Auxiliary Lens Double Slit System a= 75 mm, d = 255 mm Momentum Position Double-SlitDetector D2 Birgit Dopfer PhD Thesis U. Innsbruck, 1998. CoincidenceCircuit or f 2f

  14. Detecting Interference CramerHalf-SlitInterferometer Mach-ZehnderInterferometer MZ Advantages:Interference with full incident beam. MZ Disadvantages:(1)Extremely difficult to align(4 reflecting surfaces aligned to wavelength-scale precision); (2) Path is momentum-independent.

  15. Periodically PoledNonlinear Crystal ppKTP = periodically poled KTiOPO4(potassium titanyl phosphate) Phase Matching: kP = kS + kI + 2p/L

  16. The D-mirrors intercept and deflect one-half of each of the beams of entangled photons. Mark III NonlocalQuantum Communication Test Signal is sent by moving splitter in/out. In = interference (wave) Out = no interference (particle) 90° Pentaprism 1 APD Detectors Receive 2 Splitter Half-Slit Interferometer V 3 APD Detectors D-mirror 90° Pentaprism 405 nm Pump Laser Send Half-Wave Plate 4 90° Pentaprism Crystal Oven Splitter In/Out ʘ Sacher TEC- 100-0405-040 Mirror ppKTP Crystal 810 nmVertical Polarization Half-Slit Interferometer H Longpass Filter 810 nm Horizontal Polarization Hot Mirror ʘ Lens D-mirror 90° Pentaprism Aperture Polarizing Splitter Pump Beam Monitor f

  17. The Far-Fetching Implicationsof Nonlocal Communication:Faster than Light &Backwards in Time

  18. Faster-Than-Light Signaling In this test, we would string equal lengths of fiber optics cables to separate the two ends of the experiment by a line-of-sight distance of ~1.4 km. We would then send bits at a photon rate of 10 MHz over this link. Assuming a 10-photon decoding “latency”, this would demonstrate a signal transmission speed of about 5 times the speed of light. 1 3 2 4 90° Pentaprism 90° Pentaprism Splitter In/Out Splitter Send Receive Mirror Mirror 90° Pentaprism 90° Pentaprism 90° Pentaprism 405 nm Pump Laser 1.0 km 1.0 km Half-Wave Plate Crystal Oven ʘ Sacher TEC- 100-0405-040 ppKTP Crystal Mirror Mirror Mirror D-mirror D-mirror 810 nmVertical Polarization 810 nm Horizontal Polarization Longpass Filter Hot Mirror ʘ Lens Mirror Polarizing Splitter Aperture Norwescon 33 Norwescon 33 18/28 April 3, 2010

  19. Back-In-Time Signaling We would use 10 km of high-quality optical fiber coiled in the corner of the laboratory. We split the horizontally polarized entangled photon beam with a D-mirror and pass each of the two paths through 10 km of fiber coils. The vertically polarized entangled photons have no optical delay, and the signal is received as soon as these photons are detected at D1,2, which is about 50 ms before the signal is transmitted, when the twin entangled photons arrive at D3,4. Back-in-time signaling! 3 4 90° Pentaprism 90° Pentaprism 1 Splitter In/Out APD Detectors 2 Send Splitter Receive Mirror 90° Pentaprism D-mirror 90° Pentaprism 405 nm Pump Laser 10 km 10 km Half-Wave Plate Crystal Oven ʘ Sacher TEC- 100-0405-040 Mirror ppKTP Crystal 810 nmVertical Polarization D-mirror Longpass Filter 810 nm Horizontal Polarization Hot Mirror ʘ Lens Mirror Polarizing Splitter Aperture April 3, 2010 Norwescon 33 Norwescon 33 19/28

  20. Time-TravelParadoxes April 3, 2010 Norwescon 33 Norwescon 33 20/28

  21. The Bilking Paradox Suppose that we constructed a million connected retrocausal links of the type just shown (or used 107 km of fiber optics). Then the transmitted message would be received 50 seconds before it was sent. Now suppose that a tricky observer receives a message from himself 50 seconds in the future, but then he decides not to send it. This produces an inconsistent timelike loop, which has come to be known as a “bilking paradox”. Could this happen? If not, what would prevent it? April 3, 2010 Norwescon 33 Norwescon 33 21/28

  22. Chronology Protection:The Hawking Bomb “The Chronology Protection Hypothesis”, suggested by Steven Hawking, asserts that, in the context of timelike loops made with wormholes, the quantum fluctuations of the vacuum should rise without limit as the timelike loop was about to be produced, smiting the experimenter and his apparatus and preventing the formation of the timelike loop. In quantum field theory there are equations that appear to support this idea. Thus, retrocausal communication could in principle lead to the creation of a “Hawking Bomb”, a device that, by approaching the creation of a timelike loop, causes disruption of molecules, atoms, and fundamental particles due to excessive vacuum fluctuations. This has interesting implications - both for hard SF and for the military. As a working hypothesis in thisa work, we assume that this will not be a problem, since we see Nature doing retrocausal things all the time in the quantum domain. April 3, 2010 Norwescon 33 Norwescon 33 22/28

  23. Anti-Bilking Discussions of bilking paradoxes have been published in the physics literature from the 1940s by Wheeler and Feynman (advanced waves) to the 1990s by Kip Thorne and his colleagues (timelike wormholes). The consensus of such discussions is that Nature will forbid inconsistent timelike loops and will instead require a consistent set of conditions. Thorn and coworkers showed that for any inconsistent paradoxical situation involving a timelike wormhole, there is a “nearby” self-consistent situation that does not involve a paradox. As Sherlock Holmes told us several times, “When the impossible is eliminated, whatever remains, however improbable, must be the truth.” April 3, 2010 Norwescon 33 Norwescon 33 23/28

  24. Bilking &Probability Control These speculations suggest that equipment failure producing a consistent sequence of events is more likely than equipment operation producing an inconsistency between the send and receive events. The implications of this are that bilking itself is impossible, but that very improbable events could be forced into existence in order to avoid it. Thus, using the threat of producing an inconsistent timelike loop, one might “bilk” Nature into producing an improbable event. For example, you might set up a highly redundant and reliable system that would produce an inconsistent timelike loop unless the number for the lottery ticket you had purchased was the winning number. April 3, 2010 Norwescon 33 Norwescon 33 24/28

  25. The “ImmaculateConception” Paradox The other issue raised by retrocausal signaling might be called the “immaculate conception” paradox. Suppose that you are using the setup described above, and you receive from yourself in the future a .pdf file of a wonderful novel with your name listed as the author. You sell it to Tor Books, it is published, it becomes a best-seller, you become rich and famous, and are the Writer Guest of Honor at Norwescon 38. When the time subsequently comes for transmission, you duly send the .pdf file back to yourself, thereby closing the timelike loop and producing a completely consistent set of events. But the question is, just who actually wrote the novel? Clearly, you did not; you merely passed it along to yourself. Yet highly structured information (the novel) has been created out of nothing. And in this case, Nature should not object, because there are no inconsistent timelike loops. April 3, 2010 Norwescon 33 Norwescon 33 25/28

  26. Present Status • The experiment has been in testing phases since mid-January, 2007. Our initial attempt to produce down-converted photons with LiIO3 and BBO and detect them with a cooled CCD camera or APDs did not work. We have demonstrated that the production rate is too low and the detectors too noisy. In 2009-10 we have substituted a new crystal, laser, and interferometers. • The experiment was recently moved from the basement UW Laser Physics Facility to the 2nd Floor Optics Lab, where we can turn off the lights without interfering with other experimenters. • We are now testing the Mark III configuration. Our main problem seems to be the small quantity of entangled photons produced. (Zeilinger in Vienna makes 106 pairs per second with a crystal and laser similar to ours.) April 3, 2010 Norwescon 33 Norwescon 33 26/28

  27. Conclusions • There are no obvious “show stoppers” that would seem to prevent our proposed measurements. Nevertheless, because of their implications, the experiment has a low probability of success. • We have so far received about $46k in contributions from foundations and individuals in support of this work . We have spent most of this on the Mark III system. • This experiment is a rare opportunity to push the boundaries of physics with a simple tabletop measurement. We are pushing hard. April 3, 2010 Norwescon 33 Norwescon 33 27/28

  28. TheEnd April 3, 2010 Norwescon 33 Norwescon 33 28/28