Text Size
Facebook Twitter More...

PRL 105, 010405 (2010) PHYSICAL REVIEW LETTERS 2 JULY 2010

"Measuring Small Longitudinal Phase Shifts:Weak Measurements or Standard Interferometry?
Nicolas Brunner1 and Christoph Simon2
A cornerstone of quantum mechanics is that a measurement generally perturbs the system. Indeed, during the process of a (standard) quantum measurement, the state of the system is projected onto one of the eigenstates of the measured observable. However, in 1988, in the context of foundational research on the arrow of time in quantum theory, Aharonov, Albert, and Vaidman [1] discovered that quantum mechanics offers a much larger variety of
measurements. As a matter of fact, the only restriction quantum mechanics imposes on measurements is a tradeoff between information gain and disturbance. Therefore, strong (or standard) quantum measurements are only part of the game. There are also ‘‘weak’’ measurements [2], which disturb the system only very little, but which give only limited information about its quantum state. Weak measurements lead to striking results when postselection comes into play. In particular, the ‘‘weak value’’ found by a weak measurement on a preselected and postselected system can be arbitrarily large, where the most
famous example is the measurement of a spin particle leading to a value of 100 [1]. Because of such unorthodox predictions, weak measurements were initially controversial [3] and were largely considered as a strange and purely theoretical concept. However, they turn out to be a useful ingredient for exploring the foundations of quantum mechanics. In particular, they bring an interesting new perspective to famous quantum paradoxes, as illustrated by recent experiments [4] on Hardy’s paradox [5,6]. Furthermore, they also perfectly describe superluminal light propagation in dispersive materials [7,8], polarization effects in optical networks [9], and cavity QED experiments [10]. Weak measurements have been demonstrated in numerous experiments [4,7,8,11] and were recently shown to be relevant in solid-state physics as well [12]. Already in 1990 Aharonov and Vaidman [13] pointed out the potential offered by weak measurements for performing very sensitive measurements. More precisely, when weak measurements are judiciously combined with preselection and postselection, they lead to an amplification phenomenon, much like a small image is magnified by a microscope. This effect is of great interest from an experimental perspective, since it gives access to an experimental sensitivity beyond the detector’s resolution, therefore enabling the observation of very small physical effects"

"Hardy's paradox is a thought experiment in quantum mechanics devised by Lucien Hardy[1][2] in which a particle and its antiparticle may interact without annihilating each other. The paradox arises in that this may only occur if the interaction is not observed and so it seemed that one might never be able to confirm this.[3] Experiments[4][5] using the technique of weak measurement[3] have studied an interaction of polarized photons and these have demonstrated that the phenomenon does occur. However, the consequence of these experiments maintain only that past events can be inferred about after their occurrence as a probabilistic wave collapse. These weak measurements are considered by some[who?] to be an observation themselves, and therefore part of the causation of wave collapse, making the objective results only a probabilistic function rather than a fixed reality." Wikipedia

Category: MyBlog

Categories ...

't Hooft 100 Year Star Ship Abner Shimony accelerometers action-reaction principle Aephraim Sternberg Alan Turing Albert Einstein Alpha Magnetic Spectrometer American Institute of Physics Andrija Puharich Anthony Valentin Anton Zeilinger Antony Valentini anyon Apple Computer Artificial Intelligence Asher Peres Back From The Future Basil Hiley Bell's theorem Ben Affleck Ben Libet Bernard Carr Bill Clinton black body radiation Black Hole black hole firewall black hole information paradox black holes Bohm brain waves Brian Josephson Broadwell Cambridge University Carnot Heat Engine Central Intelligence Agency CIA Clive Prince closed time like curves coherent quantum state Consciousness conservation laws Cosmic Landscape Cosmological Constant cosmology CTC cyber-bullying Dancing Wu Li Masters Dark Energy Dark Matter DARPA Daryl Bem David Bohm David Deutsch David Gross David Kaiser David Neyland David Tong de Sitter horizon Dean Radin Deepak Chopra delayed choice Demetrios A. Kalamidas Demetrios Kalamidas Dennis Sciama Destiny Matrix Dick Bierman Doppler radars E8 group Einstein's curved spacetime gravity Einstein's happiest thought electromagnetism Eli Cartan EMP Nuclear Attack entanglement signals ER=EPR Eric Davis Ernst Mach ET Eternal Chaotic Inflation evaporating black holes Facebook Faster-Than-Light Signals? fictitious force firewall paradox flying saucers FQXi Frank Tipler Frank Wilczek Fred Alan Wolf Free Will G.'t Hooft Garrett Moddel Gary Zukav gauge theory general relativity Geometrodynamics Gerard 't Hooft Giancarlo Ghirardi God Goldstone theorem gravimagnetism gravity Gravity - the movie gravity gradiometers gravity tetrads Gravity Waves Gregory Corso gyroscopes hacking quantum cryptographs Hagen Kleinert Hal Puthoff Hawking radiation Heisenberg Henry Stapp Herbert Gold Higgs boson Higgs field hologram universe Horizon How the Hippies Saved Physics I.J. Good ICBMs Igor Novikov inertial forces inertial navigation Inquisition Internet Iphone Iran Isaac Newton Israel Jack Sarfatti Jacques Vallee James F. Woodward James Woodward JASON Dept of Defense Jeffrey Bub Jesse Ventura Jim Woodward John Archibald Wheeler John Baez John Cramer John S. Bell Ken Peacock Kip Thorne Kornel Lanczos La Boheme Laputa Large Hadron Collider Lenny Susskind Leonard Susskind Levi-Civita connection LHC CERN libel Louis de Broglie Lubos Motl LUX Lynn Picknett M-Theory Mach's Principle Mae Jemison Making Starships and Star Gates Martin Rees Mathematical Mind MATRIX Matter-AntiMatter Asymmetry Max Tegmark Menas Kafatos Michael Persinger Michael Towler microtubules Milky way MIT MOSSAD multiverse NASA Nick Bostrum Nick Herbert Nobel Prize nonlocality Obama organized-stalking Origin of Inertia P. A. M. Dirac P.K.Dick P.W. Anderson Paranormal parapsychology Paul Werbos Perimeter Institute Petraeus Physical Review Letters Physics Today Post-Quantum Physics pre-Big Bang precognition presponse PSI WARS Psychic Repression qualia Quantum Chromodynamics quantum computers quantum entanglement quantum field theory quantum gravity Quantum Information Theory Quantum Theory RAF Spitfires Ray Chiao Red Chinese Remote Viewing retrocausality Reviews of Modern Physics Richard Feynman Richard P. Feynman Rindler effect Robert Anton Wilson Robert Bigelow Roger Penrose rotating black holes Roy Glauber Rupert Sheldrake Russell Targ Ruth Elinor Kastner S-Matrix Sagnac effect Sam Ting Sanford Underground Research Facility Sarfatti Lectures in Physics Scientific American Second Law of Thermodynamics Seth Lloyd signal nonlocality Skinwalker Ranch social networks space drive space-time crystal SPECTRA - UFO COMPUTER spontaneous broken symmetry SRI Remote Viewing Experiments Stanford Physics Stanford Research Institute Star Gate Star Ship Star Trek Q Stargate Starship Stephen Hawking Steven Weinberg stretched membrane string theory strong force gluons Stuart Hameroff superconducting meta-material supersymmetry symmetries telepathy Templeton The Guardian Thought Police time crystal time travel topological computers Topological Computing torsion UFO Unitarity unitary S-Matrix false? Unruh effect Uri Geller VALIS virtual particle Virtual Reality Warp Drive weak force Wheeler-Feynman WIMP WMAP WMD world crystal lattice wormhole Yakir Aharonov Yuri Milner