Can An Electron Be Two Places At One Time?

MAX PLANCK SOCIETY Press Release News C / 2005 (43)

“Max Planck Researchers in Berlin show that for electrons from nitrogen molecules, the wave-particle character exists simultaneously

The double-slit was voted the most beautiful experiment of all time in a 2002 poll by Physics World, published by the UK’s Institute of Physics. Although each electron seems to go only through one of the two slits, at the end a wave-like interference pattern is created, as if the electron is split while going through the slit, but is subsequently re-unified. However, if one of the slits is closed, or an observer sees which slit the electron went through, it behaves like a perfectly normal particle. The particle is only at one position at one time, and not at both at the same time. Hence, depending on how the experiment is carried out, the electron is either at position A, position B, or at both at the same time.

But Bohr’s Complementarity Principle, which explains this ambiguity, requires that one can only observe one of the two electron’s manifestations at any given time - either as a wave or a particle, but not both simultaneously. This remains a certainty in every experiment, despite all the ambiguity in quantum physics. Either a system is in a state of “both/and” like a wave, or “either/or” like a particle regarding localisation. This is, in principle, a consequence of Heisenberg’s uncertainty principle, which states that for a complementary pair of measurements - for example, position and momentum - only one can be determined exactly at the same time. Information about the other measurement is proportionally lost.

Recently there has been a set of experiments suggesting that these various manifestations of matter can be “carried over” into each other - in other words, there can be switching from one form to the other and, under some conditions, back again. This class of experiment is called quantum markers and quantum erasers. Researchers have shown in the last few years that for atoms and photons - and now, electrons - “both/and” and “either/or” exist side-by-side. In other words, there is a grey zone of complementarity. There are hence experimentally demonstrable conditions where matter appears to be both a wave and a particle.

These situations can be described by a so-called duality relation. It can be viewed as an extended Complementarity Principle for quantum physics and may be more precisely called a Co-existence Principle. It states that manifestations of matter which would normally be mutually exclusive - e.g., local and nonlocal, coherent and non-coherent - are indeed measurable and make themselves evident, in a particular “transition regime”. One can speak of partial localisation and partial coherence, or partial visibility and partial distinguishability. These are measurements that are connected to each other via the duality relation. In this transition regime the Complementarity Principle, and the complementary dualism should be extended to the more general Co-existence Principle, describing the parallel dualism of nature. Nature thus has a more ambivalent character than previously recognized.”

Max Planck Researchers in Berlin show that for electrons from nitrogen molecules, the wave-particle character exists simultaneously. In something akin to a double-slit experiment, scientists at the Fritz Haber Institute of the Max Planck Society, in co-operation with researchers from the California Institute of Technology in Pasadena, California, have shown for the first time that electrons display characteristics of both waves and particles at the same time and, with virtually the push of a button, can be switched back and forth between these states. The researchers provided evidence that disruption of the reflective symmetry of these molecules by introducing two different heavy isotopes, in this case N14 and N15, leads to a partial loss of coherence. The electrons begin to partially localise on one of the two, now distinguishable, atoms. The results could have implications for the building and control of “artificial molecules”, which are made of semiconductor quantum dots and are a possible component of quantum computers (Nature, September 29, 2005).

A century ago, we took the first steps towards recognising, at the level of fundamental physical events, the dual character of nature that had been previously postulated. Albert Einstein was the first to see the implication of this dual character in Max Planck’s quantum hypothesis. Einstein suggested that photons would have the character of particles,although photons had previously been viewed as electromagnetic waves. That was the quintessence of his work on the photoelectric effect. Later in 1926, it was deBroglie who postulated that all building blocks of nature known to us as particles - electrons, protons, etc. - would behave like waves under certain conditions.

In its totality, nature is therefore dual. None of its constituents can be considered as only a particle or a wave. To reconcile this duality, in 1923 Niels Bohr proposed his Complementarity Principle: simply put, every component in nature has particle-like, as well as wave-like character, and which character is observed at a given time depends only on the observer. In other words, the experiment determines which characteristic one is measuring - particle or wave.

His whole life long, Einstein viewed with suspicion that natural characteristics would actually depend on the observer and believed that there must be a reality independent of the observer. Indeed, over time quantum physics has simply come to accept as a fact that there does not seem to be an independent reality. Physics has ceased questioning this, because experiments have confirmed it repeatedly and with a growing accuracy.

The best example is Young’s double-slit experiment. Coherent light is passed through a barrier with two slits. On an observation screen behind it, a pattern of light and dark stripes emerges. The experiment can be carried out not only with light, but also with particles - for example, electrons. If single electrons are sent in one after the other through the open Young double slit, a stripe-shaped interference pattern appears on the photo plate behind it. The pattern contains no information about the route the electron took. But if one of the two slits is closed, an image appears of the other open slit from which one can directly determine the path of the electron. What this experiment does not provide, however, is a stripe pattern and a “which way” report at the same time. That requires a molecular double-slit experiment based not upon position-momentum uncertainty, but on mirror, more precisely, inversion symmetry.

The double-slit was voted the most beautiful experiment of all time in a 2002 poll by Physics World, published by the UK’s Institute of Physics. Although each electron seems to go only through one of the two slits, at the end a wave-like interference pattern is created, as if the electron is split while going through themslit, but is subsequently re-unified. However, if one of the slits is closed, or an observer sees which slit the electron went through, it behaves like a perfectly normal particle. The particle is only at one position at one time, and not at both at the same time. Hence, depending on how the experiment is carried out, the electronmis either at position A, position B, or at both at the same time.

But Bohr’s Complementarity Principle, which explains this ambiguity, requires that one can only observe one of the two electron’s manifestations at any given time - either as a wave or a particle, but not both simultaneously. This remains a certainty in every experiment, despite all the ambiguity in quantum physics. Either a system is in a state of “both/and” like a wave, or “either/or” like a particle regarding localisation. This is, in principle, a consequence of Heisenberg’s uncertainty principle, which states that for a complementary pair of measurements - for example, position and momentum - only one can be determined exactly at the same time. Information about the other measurement is proportionally lost.

Recently there has been a set of experiments suggesting that these various manifestations of matter can be “carried over” into each other - in other words, there can be switching from one form to the other and, under some conditions, back again. This class of experiment is called quantum markers and quantum erasers. Researchers have shown in the last few years that for atoms and photons - and now, electrons - “both/and” and “either/or” exist side-by-side. In other words, there is a grey zone of complementarity. There are hence experimentally demonstrable conditions where matter appears to be both a wave and a particle.

These situations can be described by a so-called duality relation. It can be viewed as an extended Complementarity Principle for quantum physics and may be more precisely called a Co-existence Principle. It states that manifestations of matter which would normally be mutually exclusive - e.g., local and nonlocal, coherent and non-coherent - are indeed measurable and make themselves evident, in a particular “transition regime”. One can speak of partial localisation and partial coherence, or partial visibility and partial distinguishability. These are measurements that are connected to each other via the duality relation.

In this transition regime the Complementarity Principle, and the complementary dualism should be extended to the more general Co-existence Principle, describing the parallel dualism of nature. Nature thus has a more ambivalent character than previously recognized. Atomic interferometry provides us with examples of this ambivalence. This was first observed in 1998 in atoms, which consist of an assembly of particles.

In a recent issue of Nature Max Planck researchers in Berlin, together with researchers from the California Institute of Technology in Pasadena, California, report on a molecular double-slit experiment with electrons which are elementary particles, not assemblies of particles, like atoms. Molecules with identical atoms, and thus with inversion symmetry, behave like nature’s own microscopically small double-slit. Nitrogen is one such molecule. In it, each electron, including the highly localised inner electrons, is simultaneously at both atoms. If we ionise such a molecule with soft x-rays, we end up with a coherent - that is, wavelike - strongly coupled electron emission from both atomic sites. This is exactly like a double slit experiment with single electrons.

For the first time, the researchers were able to demonstrate the coherent character of electron emission from such a molecule in analogy to the double slit experiment. They used soft x-rays to destabilise the innermost, and thus most strongly localised, electrons of nitrogen from the molecule, and then followed their movement in the molecular frame of reference using electron-ion coincidence detection. In addition, the researchers were able to prove something that has long been doubted: a disruption of the inversion symmetry of this molecule leads to a partial loss of coherence through the introduction of two different heavy isotopes, in this case N14 and N15. The electrons begin to localise partially on one of the two, now distinguishable, atoms. This is equivalent to partially marking one of the two slits in Young’s double slit experiment. It provides partial “which way” information, because the marking gives information about which path the electron took.

The experiments were carried out by members of the “Atomic Physics” working group of the FHI at the synchrotron radiation laboratories HASYLAB at DESY in Hamburg and BESSY in Berlin. The measurements employed a multi-detector array for combined, coincident electron and ion detection behind undulator beam lines, which deliver soft x-rays with high intensity and spectral resolution. Support for the working group of four scientists and three doctoral students came from the Max Planck Society and from the Federal Ministry of Education and Research, under the programme to promote research in specially chosen topics on fundamental principles of the natural sciences.

[EC]
Original work: Daniel Rolles, Markus Braune, Slobodan Cvejanović, Oliver Ge ner, Rainer Hentges, Sanja Korica, Burkhard Langer, Toralf Lischke, Georg Prümper, Axel Reinköster, Jens Viefhaus, Björn Zimmermann, Vincent McKoy and Uwe Becker Isotope-induced partial localization of core electrons in the homonuclear molecule N2

Nature 437, 711-715, September 29, 2005
Contact:
Prof. Uwe Becker
Fritz Haber Institute of the Max Planck Society, Berlin
Tel.: +49 30 8413-5694
Fax: +49 30 8413-5603
E-mail: becker@fhi-berlin.mpg.de



4 Responses to “Can An Electron Be Two Places At One Time?”

1. Tony Dubshot says:

   June 15, 2009 at 10:36 am

   R. Buckminster Fuller says:

   “Universe means “toward oneness” and implies a minimum of twoness.”
   (Synergetics 307.03)

   “Universe and its experiences cannot be considered as being physical, for they balance out as weightless. Every positively weighted “particle” has its negatively weighted complementary, but non-mirror-imaged, counterpart behavior. The integrated weights of physical Universe add up to zero.”
   (Synergetics 310.03)

   “Because we start with whole Universe we have left out nothing: There is no multiplication by amplification of, or addition to, eternally regenerative Universe; there is only multiplication by division”
   (Synergetics 304.00)

   “Just when you think you are negative, you find you are positively so. This is the eternal wellspring of positive-negative regeneration of acceleratingly heating entropy and cooling-off syntropy, which is synergetically interoperative between the inherently terminal physical differentiating and the inherently eternal metaphysical integration.”
   (Synergetics - 310.14)

   “It is reasonable to suppose that there must be an overall physical-metaphysical cosmic accounting system that is always omniconsiderately integrative of all the a priori set of generalized interrelationship principles that we have found scientifically to be unfailingly operative in Universe. It may well be that each of us humans is an important function in sustaining the eternally regenerative integrity of Universe. The invention of the game of limited and terminal local awareness that we call “life” is in contradistinction to the concept of eternally total cosmic knowledge, intellect, and wisdom, whose totality of comprehensive comprehension would answeringly cancel out all questions and all problems, which would result in the eternally timeless, sublime 0=0 equation of absolute perfection.”

   “Humanity being a macro -> micro Universe-unfolding eventuation is physically irreversible yet eternally integrated with Universe. Humanity cannot shrink and return into the womb and revert to as yet unfertilized ova. Humanity can only evolve toward cosmic totality, which in turn can only be evolvingly regenerated through new-born humanity.”
   (Synergetics - 311.03)

   More over here: http://www.rwgrayprojects.com/synergetics/s03/p0000.html
2. doc says:

   June 15, 2009 at 10:54 am

   Thanks for the great Bucky quotes. Brilliant! A great cross-association of quantum mechanics, complementarity, coordination dynamics and ’synergetics’ is found in the synergetics of Hermann Haken, ‘father of laser theory’ Here is a wiki:

   http://en.wikipedia.org/wiki/Synergetics_(Haken)

   fyi - J. A. Scott Kelso worked with Haken to apply this kind of synergetics to human brain~behavior. This history should definitely be more visible here at TSS and will eventually be so.

   Being a long time fan of Bucky Fuller and his synergetics, then being trained under Kelso on Haken Synergetics (and as a squiggler) I find it useful to think of the two synergetics this way:

   Haken Synergetics ~ Fuller Synergetics, which simplifies to

   dynamical synergetics ~ structural synergetics. This isn’t a stretch, as Haken synergetics is based in nonlinear dynamics, while Bucky was an architect, concerned with ‘pattern integrity’. As this digresses from particle~wave complementarity, let me make a post on TSS of Buckminster Fuller for us to explore further…

   Thanks again for the comments. Appreciate the effort.

   mtsbwy! (may the squiggle be with you!)
3. Tony Dubshot says:

   June 19, 2009 at 11:27 am

   Thanks a lot for your view on the two brands of synergetics. To be honest i didn’t like it the first time i noticed that Haken had ‘borrowed’ Bucky’s terminology, especially because Bucky has also coined ’synergy’ but after reading Kelso’s Dynamic Patterns and reading a bit more about Hakens work i began to appreciate the great potential for synergy

   By the way Bucky always points out that his definition of universe is 100% dynamic, he calls it ’scenario universe’! That’s why Robert Anton Wilson’s favourite Buckyquote is “Universe is apprehended non-simultaneously”
4. doc says:

   June 28, 2009 at 12:04 pm

   Yes, scenario universe is without doubt one of my favorite Fullerian concepts, and is another interesting crossover point with both Quantum Mechanics of particle~wave and Coordination Dynamics, as in all three cases, as context (observer~observing) is an inextricable, dynamical, and complementary aspect of universal law. One of my favorite down to earth descriptions of context (in this context, ha ha) is one we used in TCN:

   “Fuller astutely points out that there is nothing about the earth itself or the moon itself that will help a person intuit the invisible gravitational bond between them. Perception of both the earth and moon moving together is necessary to even conceive of gravity in the first place. Of course, once it is conceived, it seems so incredibly obvious.”

   TCN p180

   We look forward to more comments! May the squiggle be with you!