Wave-particle duality of nature challenged at Kelaniya University
Posted on February 2nd, 2012

Janaka Wansapura, Ph.D.

In 1807, Thomas Young demonstrated that light had wave properties by using a simple experiment now famously known as the YoungƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s double slit experiment. Young showed that the pattern of bright and dark fringes that forms on a screen when light passes through two narrow slits can be explained using the wave theory. Since YoungƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s revelations, the wave theory of light (of electromagnetic radiation in general) took firm root and dominated the physics world for nearly a century. Until Max Plank, in 1901, showed that the energy of the radiation emitted by heated objects was discretized as if light was actually composed of particles! Since the wave nature of light as demonstrated in the YoungƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s experiment could not be discarded, scientists reconciled that light had both wave-like and particle-like properties.ƒÆ’-¡ƒ”š‚  As it turned out just as light possess particle like properties, particles such as electrons, neutrons and even large molecules like fullerenes possess wave like properties. In 1989 experiments conducted by Tonomura demonstrated that a beam of electrons passing through a double slit, as in YoungƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s experiment, actually forms a dark and bright fringe pattern on a screen next to it. It is believed that these interference patterns, as they are called, arise because of the wave nature of electrons.ƒÆ’-¡ƒ”š‚ ƒÆ’-¡ƒ”š‚ ƒÆ’-¡ƒ”š‚ ƒÆ’-¡ƒ”š‚ 

YoungƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s double slit experiment is still an active research topic among physicists as they have not fully embraced the strange behavior of nature implied by it. Physicists have been particularly bothered by the fact that when a single electron, instead of a beam of electron is sent through the double slit what is observed on the screen is not a faint interference pattern but a single dot on the screen depicting an electron striking the screen. If an electron represented a physical wave of some sort then one would expect a series of bright and dark fringes, however faint it might be on the screen but not a single dot. This unexplained phenomenon is the focus of recent theoretical and experimental work conducted by Dr. Nalin de Silva and his student Suraj Chandana at University of Kelaniya.

Dr. de Silva rejects the wave nature of particles. According to him what gives rise to a bright and dark fringe pattern in the YoungƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s double slit experiment is not the so called wave nature but the particle nature itself though not necessarily those of ordinary classical particles. Dr. de Silva theorizes that each particle that hit the screen on a double slit experiment appears at both the slits simultaneously prior to reaching the screen. This view contrasts with what physicists believe to date. They believe that particles come thorough one of the slits in the YoungƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s experiment but not both. But particles coming through individual slits cannot explain the bright and dark fringe pattern forming on the screen. Therefore to account for the fringe pattern they theorize that particles behave like waves.ƒÆ’-¡ƒ”š‚  However this so called wave property cannot be inferred when only a single particle is fired through the double slit, which results in a single dot on the screen and not a fringe pattern.

In the case of the double-slit experiment, quantum physics dictates that at the level of the slits, a particle is in a superposition of states corresponding to the position of the two slits. The particle is in this superposition as long as it is not disturbed. Placing a screen causes to collapse the superposition into one single state (position). Dr. de Silva interprets the superposition of positional states to mean that the particle actually exists at multiple positions prior to striking the screen. Using the super-positional states quantum physics can predict the probability of finding the particle at the screen or anywhere else between the screen and the double slits. The fringe pattern merely corresponds to the probability of finding the particle at various points of the screen. Dark fringes are where there is a zero probability of finding the particle and bright fringes are where there is higher probability of finding the particle. According to this interpretation, there is no interference of sort taking place as there are no waves to be considered. Why there is only a dot on the screen when a single electron is fired through the double slit is simply because the superposition of positional states collapses into one single position at the screen.

To prove that quantum particles do not have wave properties, Dr. de Silva designed an ingenious yet a simple experiment using a laser beam and double slit apparatus. Here, a series of aluminum sheets are placed along the zero probability positions as predicted by quantum physics, between the slits and the screen. Since light cannot penetrate aluminum sheets, no interference pattern should form on the screen if light behaved like a wave. On the other hand if light behaved as quantum particles, placing aluminum sheets at zero probability positions should not affect the fringe pattern since there is no particle present at those positions to interact with the sheet. The experiment was carefully set up by his student, Suraj Chandana. When the laser was turned on, the fringe pattern appeared on the screen as they had expected confirming the hypothesis that light consists of particles that did not have wave properties.

Physicists had to artificially attach a wave property to quantum particles to explain the fringe pattern in the YoungƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s experiment because they did not think that the superposition of positional states meant particles were at both the slits at the same time. According to the Copenhagen interpretation of quantum mechanics formulated by Niels Bohr and others, nothing can be said about the superposition of positional states before a measurement is made; it is the act of measurement that creates the knowledge of the position of the particle. According to Dr. de SilvaƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s interpretation or Vidyalankara interpretation as he prefers to call it, a particle actually exist at number of positions in superposition until the superposition is disturbed by an observer. Western physicists could not have considered this possibility since according to the Aristotelian logic a particle is either here or not here. But for people of many eastern cultures it is not a problem to believe that a particle can be at multiple locations at the same time, as they can relate to certain deities and supernatural beings that can manifest at different places at the same time. Today, the existence of such superposition of states is not just a legend but is supported by experiments. In 1996 Monroe and his colleagues had demonstrated the simultaneous existence of two spin states of Beryllium cation. Since then similar experiments have been carried out by others to prove the existence of superposition of states.

The Vidyalankara interpretation also resolves other paradoxes in quantum physics such as the SchrƒÆ’†’ƒ”š‚¶dinger’s cat, the results of ƒÆ’‚¢ƒ¢-¡‚¬ƒ…-which wayƒÆ’‚¢ƒ¢-¡‚¬ƒ”š‚ experiment and the WheelerƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s delayed choice experiment. For long physicists have been forced to understand quantum physics using particle and wave properties which are essentially classical ideas. Dr. de Silva expels these and introduces a nature that is more akin to quantum physics. He has created a paradigm shift in the knowledge of quantum nature.ƒÆ’-¡ƒ”š‚ 


Janaka Wansapura, Ph.D.

30 Responses to “Wave-particle duality of nature challenged at Kelaniya University”

  1. Wickrama Says:

    PHEW !!
    My brain is in a severe spin after reading this !!

  2. Ranjith Soysa Says:

    Thanks for proceeding ahead to discover fresh information etc in conducting research /experiments.
    Dr Nalin De Silva and his team has opened new vistas for Sri Lankan people interested in the
    capability of real Sri Lankan scientists who are equipped to think out of the box of Western science.
    We hope the peak Science Orgs in Sri Lanka will encourage scientists and their new concepts
    without attempting to strengthen the vested interests in Sri Lankan science fora.

  3. aloy Says:

    Thanks for writing this. First time I have seen such an excellent write up. What about NARA (or NAQDA) or IFS. I have never seen anything from them although they have been in existence for a very long time. Can they justify their existence?.

  4. Bodhi Says:

    To AloY;
    NARA, IFS and NAQD are not claiming that Afshar’s work is Nalin de Silva’s work. This writer Janaka has made a big mistake. The Afshar experiment has been on the Cornell website for more than 5 years.
    Besides NARA, NAQD are administrative agencies and NOT research agencies. The Science faculty of Kelaniya and IFS can do independent research. But Kelaniya cannot plagiarize – or more likely, this write Janaka has made a hugh blunder.
    Can the Kelaniya people be ignorant of that?

  5. radha Says:

    So many theorists, challengers and adversaries! Academics are fighting over who knows best and who is cleverer. For the benefit of the laymen who are not really involved in the world of cutting and pasting, could someone tell what is the benefit of this knowledge to the mankind. What is in it for me and the average Joe Bloggs? This is a serious question and would benefit the readership, if we know what is this all about from a practical and useful point of view.

  6. Janaka Wansapura Says:

    Dr. de Silva and his student did not plagiarize Afshar’s work. If Bodhi had actually read Shahriar Afshar’s paper he/she would have realized that the experiment and the conclusions derived in his study are markedly different to Dr. de Silva’s work. Incidentally Dr. de Silva’s work is also published in the same Cornell website and can be found at http://arxiv.org/pdf/1006.4712v1.pdf. I invite you to read it. In this paper Dr. de Silva sites Afshar’s excellent work and discusses the difference between the two. In short, Afshar places thin wires where dark fringes would form only at the level of the screen which he had replaced by a lens. His results do not lead him to deny the wave property of particles. In contrast, Dr. Silva and Chandana places thin sheets of Aluminum extending from the screen all the way to the double slit. Since the fringe pattern is not disturbed by this, they can rightly conclude that light particles did not possess wave properties. The idea that quantum particles do not carry a so called wave property is a paradigm shift in how we think about quantum nature. Although Afshar’s work is innovative, neither his experiment nor his interpretation of the results comes close to it.

    Plagiarism is a serious accusation. Bodhi is not only accusing Dr. de Silva but the Kelaniya University and the student who had performed this experiment as part of his dissertation who could be stripped of his diploma if found guilty. Unless Bodhi intends to follow through with this accusation which I think hinges on malice rather than merit, I suggest he/she withdraw his/her comments.

    I do not know if there is a personal benefit from this knowledge to anybody. When it says that a particle can exists at both the slits at the same time, the Vidyalankara interpretation allies with the intuition of the Sri Lankan culture but runs against the culture that created quantum physics. It takes years for people to deviate from their comfort zones and accept a new idea but Dr. de Silva’s theory agrees with existing experimental evidences. Therefore his theory will eventually win the intellectual battle, when it does the knowledge based in our culture will win a small battle against its adversaries. Whether such a gain has anything in it for somebody or not is subjective.

  7. NeelaMahaYoda Says:

    I am glad that Bodhi’s original comment is now removed by the moderator and further request Bodhi to refrain from posting future comments based on knowledge purely acquired through google search. Lankaweb is for academics and professionals to post valid and responsible comments, but Lanaweb should not let anybody to post cheap and abusive comments to ridicule the writer .

  8. DrPadmaWijesekara Says:

    Dear Bodhi
    Are you a physicist who is engaged in research into particle physics?. If not, please shut up.

  9. Bodhi Says:

    I am glad that Janaka W has given the reference to Dr. Nalin de Silva’s atricle at the arXive as that now clarifies everything. he should have mentioned that right then.
    In that reference if the Kelaniya people have given due credit to Afshar’s expt and so the suspicion that there was plagiarism is removed. The error was in Janaka W not giving the reference. WITHOUT that, it did look very suspicous, and I have a right to voice my suspicions. And you should be glad that I voiced my suspicions, as others all over the world who would read it, and know something of the subject, would immediately have the same suspicions.

    Science progresses by transparency and scepticsm. removing my posting and obfuscation do not help. The answering of my posting by Janaka W has helped.

    Thank you very much for the clarification. I will read the article and comment as soon as I can.

    In reply to DrPadmaWijesekara let me tell her that science does not respect status and prestige. Any one can discuss a given topic, do experiments etc., and get the views published in a peer-reviwed journal if the material presented is up to standard. By the way, the Cornell website is NOT a peer-reviewed journal (any one can send in a preprint there, as it is simply a pre-print archive).

    Further more let me point out to PadmaWijesekera that Einstein was “a mere Patent clerk” if we go by her approach, and “not doing research into particle physics” when Einstein wrote his papers.

    Also the topic handled here (wave-particle duality) is not research in particle physics. It becomes research ONLY IF new experimental conclusions (new phenomena) can be drawn from the “new paradigm”. If it has no new observable conclusions different from the Copenhagen interpretation, then it is just philosophy, or let us say “interpretations of physics as I said in my post to Radha.


  10. radha Says:

    Thanks Janaka and Bodhi for responding helpfully to my query. Janaka, your response (in the last para) was nearer to my anticipated answer; clearly you had read my mind. Bodhi too touched upon this aspect when referring to the philosophical nature of the discussion.

    Looking at a scientific result through the eyes of a belief system might be helpful at personal level in trying to reconcile with a phenomenon for which there is insuffcient evidence. But in academic circles I am a little dubious about the value of mixing science with cultural beliefs. The phenomenon about a deity appearing in two places at the same time is only a belief and has no scientific basis, right? I mean we cannot quote religious scripture as a proof when we have no clear idea of what the basis for the scripture was. It might be OK purely for personal visualiztion of the phenomenon, but in scientific circles it is not a good idea to rest a scientific case on a belief.

    If the scientifc evidence is insufficient, it is better to leave the issue open rather than trying hastily to jump into conclusions, or to speculate the phenomenon through beliefs. The student has clearly presented his methods and recorded his results; in doing so he has contributed to the knowledge-base and so deserves credit for that.

  11. Bodhi Says:

    I have discussed the Nalin de Silva preprint with some of my friends and added a section to my blog on particle-wave duality.
    Please see:

    I am afraid, in our view this preprint is based on incorrect physics.

    It is experimentally found that nature populates the detector screen of the two-slit experiment with electrons in a random fashion, but with a distribution that satisfies the intensity formula for an interference pattern of a wave. This interference happens even with just one electron, with the blip most likely to appear in the high-intensity region of the interference pattern which acts like some hidden hand guiding the electron. So it is natural to ask if there is some field indirectly guiding the electrons to reach the screen. After all, we don’t see a magnetic field, but if we place a paper and put iron filings at random, then the field rearranges the filings to fit with the pattern of intensity of the field.

    Louie de Broglie thus came up with the idea of a pilot wave directing the electrons, and remaining in the background as some invisible field.

    However, such ad hoc models based on physical intuition became unnecessary when Schrodinger introduced his wave equation. According to Schrodinger, whether it be one electron or many electrons, there exists a field ψ which is a function of all the coordinates of all the electrons and time. The energy (i.e., sum of kinetic plus potential energy) of the system, re-written as as operator is the Hamiltonian operator of the system. The ψ function is an eigenfunction of this operator. The probability of finding an electron at some point X=(x,y,z) is simply the squared modulus of ψ at X, i.e., |ψ(x,y,z,t) |2.

    If an electron is created at time t0 at the electron emitter located at X0, we describe this process by the operator A+0. Let the electron propagate to the slit S1  at time t1. Then its presence can be sampled using the operator As1. The mean-value of the Wick product of operators, denoted by G=<T A+0As1 >, where T is the Wick-time ordering operator is known as the propagator of the electron. It is shown in books on quantum field theory that that this propagator is simply the Green’s function of the Schrödinger equation. It can be shown that the Green’s function is single valued, and hence the electron cannot be in two places at the same time. Thus the electron must pass through just one slit, and we need the quantum field as well, to bring in the interference effect. We cannot do without the field. This is a mathematical consequence of the nature of the Schrodinger equation.

  12. Janaka Wansapura Says:

    A single blip is a blip not an interference pattern; only a large collection of blips that gives the appearance of an interference pattern.

    It is accepted that when you make a measurement on the position, which is equivalent to the function of an operator, the Schrödinger function collapses to a single state representing a single location (as if at one slit) but that does not in any way mean that the particle was in only one position before the measurement (which is the case when a fringe pattern is visible). In fact it is in a superposition of positional state. Now Copenhagen interpretation does not say anything about this superposition but Vidyalankara interpretation says that these superpostional states exist (as if a particle is at both the slits) before any measurement. This fact has been validated by Monroe et al.

    By the way, that a particle goes through only one slit is also a belief (of which culture nobody question; out of fearful respect I guess) as quantum particles are not sensory perceptible. But this belief does not hold true since it cannot explain the fringe pattern.

  13. brahamin Says:

    Bodhi has put in a good effort and written a whole section into his wave-particle blog which is politely
    and seriously written. That is how things should be done.

    Now it is up to Janaka W and Nalin de Silva to present their discussion.

    I am no expert in the subject, but here I see a short reply from Janaka W who says that a
    A single blip is a blip not an interference pattern”.

    Indeed, but I see that the quantum theory also does not claim it to be so. The quantum theory
    attempts to explain why the many blips, including the very first one , fall into a distribution given
    by an interference pattern, rather than, say, two normal distributions at the exit side of the two

    No one expects a single data point to demonstrate a law. Think of the school physics parcticles. If you
    are studying Boyle’s law, where P is proportional to 1/V, you plot P versus 1/V. But the
    moment you put the first data point, you cannot say it is on a straight line. For that you need at least
    three points.

    So I think your hang up on a single blip is not scientific and also not what is claimed by the
    existing theory.

  14. Bodhi Says:

    Thanks Brahamin.

    To Janaka. Thank you for your most recent comment. You say:
    “that a particle goes through only one slit is also a belief “
    Let me first ask, does JanakaW regard the Schrödinger equation to be also just a
    All quantum physicists accept that The Schrödinger Equation describes the observed pheonomena for non-relativistic equations.
    The Schrödinger equation is a 2nd order differential equation, and hence its one-particle propagators are single valued.
    Hence an excitation of the field has to be single valued and cannot exist simultaneously at two places, because in that case the propagator has to be multi-valued.
    I explained much of that in the blog, where I can write mathematics.
    Also I noted that when the Schrodinger equation is transformed into a Hamilton-Jacobi equation, there too one can prove mathematically that the electron has to necessarily go by a singel slit. This proof was given by Hiley and Bohm.
    So, that a particle goes through only one slit is not just a belief, but a necessary consequence of the
    nature of the Green’s function associated with the Schrödinger differential operator.

    As for Munroe’s experiment, I don’t have have time or space to explain that – and most people reading this e-jounal have probably not read the Munroe paper. So let u stick to just what is in the Nalin de Silva paper.

  15. Bodhi Says:

    One more question to JanakaW. You say:
    “the Schrödinger function collapses to a single state representing a single location…”

    So you seem to accept the “Schrodinger wavefunction”, and yet you all say there is no wave property.

    From sec. 7 of the Nalin pre-print, I see that he accepts that we are dealing with an amplitudes.
    That is what is loosely called the waveproperty of the electron. So in what sense are you claiming that there is no wave property? You can’t say one thing in one place, and another thing in another place.

    Once an electron is emitted by the electron gun we don’t know where it is. All we can do is to make some precise statements about the probability amplitude function. This function is called a wavefunction because the second order differential equation is in the same class as other wave equations. There is absolutely no hint of a particle anywhere in it.

    The time evolution of the Schrodinger wave function w(x, t) allows us to predict the electron density probability at any point as |w(x,t)|2. So, if you evaluate it on the screen, it just gives a probability, and that has the shape of an interferenc epattern. As each electron lands on the screen, it confirms that predicted probability pattern. Quatum Mechanics says NOTHING about what happened in between the emission of the electron, and its observation.
    But it also says that the propagators (Greens functions) are single valued.


    As for the cultural aspects, in the West people are used to believing that God is omnipresent – present every where. So is St. Joseph, the holy spirit, Satan etc. Beliefs in spirits, witches, etc., is so prevalent in the west that there are days like “Haloween”. Harry Potter books sell in millions. Santa Claus is present in every chimney on Christmas night.
    The kelaniya interpretaion is essentially a “Santa Clause” cultural interpretation.
    Note that in Lanka, gods and deities are localized people. Saman Deiyo is in the Samantha Kuta and Dadimundi is not found on Galle Face Green. Sakraya sits on his Paandukambala-Sailasana and has to take a divine look.

    And most quantum physicists use the loose language that the electron entangled in two states |a> and |b> are in both states. Such talk is most common among experimental physicists who use intuitive language. Such usage is OK for discussions, as long as we remember that if we push it too much we get wrong answers.

    The “Kelaniya interpretation” is to claim that the loose language that the electron is “at the same time in several places” is the correct “ontology”, and also make the mistake that that electrons do not show diffraction patterns. The whole field of electron microscopy is based on the wave property of the electron.

    What Kelaniya is trying to is to pretend that we are still in the early 1920s.

  16. Janaka Wansapura Says:

    It is true that when a position operator acts on the Schrödinger function it results in a single value for the position (This is what Bodhi is trying to say with all his quotations from text books) but it is not relevant here. If you placed an observer at the level where the slits are located and make a measurement you will get a single position. But making a measurement on the position disturbs the coherence and results in no fringe pattern further down on the screen. That is, when you know that a particle is passing through just one slit you don’t get a fringe pattern. In other words, the fringe pattern does not correspond to a particle passing through just one slit. But in the Young’s experiment there is no measurement made on the particles that get through the slit (i.e. these particles are not disturbed) and form a fringe pattern on the screen. In other words a position operator does not act on these particles; if it did, the particles would not have formed a fringe pattern. Therefore what result when an operator act on the Schrödinger function at the slits (what Bodhi says) is not relevant in this particular case. The appropriate question is: what can be said about the positional state of these particles that get through the slits undisturbed and form a fringe pattern? QM says they are in a superposition of Schrödinger functions. In the case of the Young’s experiment, particles can only be in two positions (corresponding to the two slits) before striking the screen. Therefore they are in a superposition of positional states corresponding to the slits. The Vidyalankara interpretation of this superposition is that when a fringe pattern is formed the particles exist at both the slits. How does Bodhi interprets it?
    The fact that such superpositional states do exist, as proved by Monroe and others in the 90’s, (which Bohr was not aware when he formulated the Copenhagen interpretation) cannot be ignored.
    If quantum particles represented a physical wave in space it should form a faint interference pattern on the screen with a single particle. It does not. The Schrödinger function predicts the probability density of the particle in space it does not say that particles carry wave properties. It is the interpretation that Quantum particles have wave properties that is challenged in Dr. de Silva’s experiment.

  17. Bodhi Says:

    Janaka W says:If quantum particles represented a physical wave in space it should form a faint interference pattern on the screen with a single particle

    No significant physicist since 1925 has said that quantum particles represented a physical wave in space. Even in Louie de broglie’s papers the pilot wave is unobservable, and merely guides the electron, and that is why it was called a “pilot wave”.

    This is I think the big misunderstanding that is in the NdeS pre-print
    The quantum theory says that the quantum particle is AN EXCITATION IN A QUANTUM FIELD, and no metaphysics.

    When JanakaW says “The Schrödinger function predicts the probability density of the particle in space it does not say that particles carry wave properties”.
    that is the CORRECT statement.

    When JanakaW says
    It is the interpretation that Quantum particles have wave properties that is challenged ” ,
    JanakaW has perhaps forgotten that Bohr had already said that particles CANNOT have wave properties, and waves cannot have particle properties at the same time This is the OLD COMPLEMENTARITY PRINCIPLE, so there is nothing to challenge here, as all that has been looked after in the 1920s.
    Waves and particles are complementary manifestations of the underlying quantum field. These excitations can be described by the corresponding field operators acting on the underlying field. Such excitations cannot be observed simultaneously unless the operators commute. But the field operators for particles, and those for waves, do not commute. That is old hat.

    There is no need to restate a narrow the complementarity principle again and call it a new interpretation. But this is not the only problem in the NdeS preprint as I have discussed them clearly in my blog.

    But if you read NdeS you get the feeling that he has thrown out the quantum field, and then brings it back through his hilbert space without being aware of it.

    This is what I had taken great pains to explain in my blog.
    The quantum field in the case of the Schrodinger equation is typified by the psi-function.

  18. Janaka Wansapura Says:

    I appreciate Bodhi’s interest in this topic and hope he will continue to engage in the discussion. However I am not entirely convinced that he has a basis for his arguments as he appears to be throwing stones in many directions in last couple of his posts. Bodhi’s initial opposition to Dr. de Silva’s work was that it plagiarized Afshar’s work. He should have realized that both were independent to each other had he read and understood Afshar’s paper and my review of Dr. de Silva’s work. When I pointed this out to him Bodhi changed the basis for his opposition. This time, he claimed that according to quantum physics a particle can go through only one slit. This is an utter lie. Quantum physics dictates no such thing. According to standard Copenhagen interpretation nothing can be said about the position of the particle before it is measured though it is true that you get only one position when a measurement is made. What Bodhi should understand is that whenever a position operator acts on a wave function it produces a single value but that does not mean that particles have single values for position when a position operator is not acting on them. Since no measurements are done at the slits when a fringe pattern is visible, the standard interpretation does not allow one to claim that particles go through only one slit. Western physicists only assume that it is so following what they know about classical objects like baseballs and airplanes.

    I am not sure whether he understood or accepted my point nevertheless he changed his argument once again. This time he questions why we use the term wave function if we say that particles do not have wave properties. To argue about the use of terms without referring to what is meant is really silly.

    We reject the idea of a wave property. But we accept that solutions to the Schrodinger equation predict the probability of finding the particle in space in line with the Born interpretation. (Bodhi should have known this if he read my review article). These solutions represent classical waves hence the term wave function. Using this term to identify solutions to the Schrodinger equation does not mean that we associate any wave properties with the particles. But western physicists do.

    The probability density at the screen corresponds to an interference pattern of two classical waves. Now western physicists have to interpret what this means. Since they assume that particles come through only one slit they cannot account for two waves. To explain this, they say that in addition to them being particles (that behave like classical objects) particles have wave properties. When a classical wave interacts with a wall with two slits in it, it spawns two waves which interfere with each other beyond the wall. So according to western physicists the two waves at the slit arise because of the wave property of the quantum particles. They need this property in order to justify the probability density at the screen which is derived by summing up two waves. According to them particles do interact like waves giving rise to an interference pattern.

    But for us, plane waves are just the solution to the Schrodinger equation and do not represent a property of the particle. The two waves are there because they represent a single particle appearing at both the slits at the same time. This is the major difference between standard quantum physics and Dr.de Silva’s theory. In other words the particle is represented by a superposition of solutions to the Schrodinger equation. Beyond the slits, the probability of finding the particle is predicted by the superposition of these solutions.

    Two prove that Dr. de Silva’s theory is correct two issues needed to be resolved. First he has to prove that such superposition of states do exists. The standard interpretation says that you cannot say anything about it. Dr. de Silva’s interpretation says that they do exist. But in the last decade or so physicists have already shown that superpositional states exist.

    Next issue is that if particles do not have wave properties they shouldn’t interact like waves. Meaning the probability density at the screen should not have anything to do with a wave like interference. Dr. de Silva had to demonstrate this with experiments. This is what his student Chandana did. He showed that placing Aluminium sheets along the zero probability points between the slits and the screen does not alter the fringe pattern. Since light cannot penetrate Aluminum sheets, this means that there is no interference of waves happening. Particles do not have wave properties.

    If Bodhi or any of his friends wants to reject Dr. de Silva’s theory either they have to repeat this experiment and show that it does not work or they have to explain how waves interfere with each other even though their path is obstructed.

    Finally I should mention that Dr. de Silva’s paper appeared in the 50th anniversary commemoration volume of the University of Kelaniya which is a peer reviewed journal. Dr. de Silva also presented this work at the department of physics at University of Cincinnati and was well received by fellow physicists who like him have contributed to science and know when a good piece of science is presented to them and finally M. Phil degree has been awarded to Chandana, his student by the University of Kelaniya. As you can see many learned people have reviewed this material. (may I add that I too have a doctorate in physics and know something about this topic). Criticism is good but anyone who wishes to do so should hold themselves to a similar high standard.

  19. Janaka Wansapura Says:

    Before anybody misunderstands it, by high standard I meant clear thoughts, logical reasoning and above all intellectual honesty. Most of us are capable of these.

    Complementarity is Bohr’s excuse for using classical concepts for understanding quantum physics. We have rejected the wave property of particle hence there is no room (or need) for a Complementarity Principal. It is amazing how Bodhi concluded that Dr. de Silva’s work was about this. Either he is trying to mislead the readers or he has no clue about anything.

  20. Bodhi Says:

    Come on, I said that the Schrodinger equation transformed into the Hamilton-Jacobi equation allows us to plot the trajectory, and then you see that the electron goes through just one slit. See my blog.

    Other formulations do not allow one to plot the path, except for the Feynman path-integral method. But Feynman’s path integral approach also allows all possible paths. But there are NO multivalued paths possible with a linear-differential equation and that has nothing to do with quantum or classical etc. It is mathematics. So, even with Feynman paths, the electron does not go through both slits.

    Just demonstrate mathematically that such two-valued propagators (Greens functions) are possible for the two-slit system, leaving aside the question of observability. You have a differential equation with two source-sink terms AND EXAMINE WHAT ITS GREEN’S FUNCTIONS ARE, for a second-order linear differential operator.

    You said that you expect to see a very faint interference pattern TOGETHER WITH with the blip according to your (and Nalin’s) understanding of wave-particle duality. That is not quantum mechanics. Wave (position) and particle (momentum) cannot exist together because the corresponding operators do not commute. This is the complementarity principle.

    To use classical concepts Bohr used the correspondence principle, and not the complementarity principle. They are two different things.

  21. Janaka Wansapura Says:

    Although the concepts behind Young’s experiment are rooted in the heart of quantum physics an average person with some science background can easily understand it without having to use too many mathematical tools. Unfortunately, some like to surround themselves with scientific jargons and mathematical expressions hoping to impress others though with little or no knowledge about them, which brings me to the question of Schrodinger propagators.

    This is a tool in quantum physics that let you assess the chance (magnitude of the probability) that a certain quantum particle may end up at some place given its initial position. In the case of the Young’s experiment the initial position is where the particles are emitted and the final position is somewhere on the screen. Now when you say a propagator is single valued this means that for one particle emitted you get one blip on the screen. That’s all. It does not say anything about the path it took.

    In the path integral approach to quantum mechanics the magnitude of the probability is calculated by summing up all the possible paths of the particle. In the case of the Young’s experiment there are two possible paths that a particle can get from the emitter to the screen (through slit one and slit two). The propagator is the sum of the two paths. Contrary to Bodhi’s understanding this approach too does not say that particles can go through only one slit. In fact, if you discard the wave property and say particles behave like quantum particles (unlike classical particles) one might infer the opposite that is particles go through both the slits. Of cause western physicists assume that particles go through one list and say they have wave properties to account for the two paths.

    At this point I have no confidence in Bodhi to come up with a rational argument against Dr. de Silva’s
    theory but I hope he learnt something from the exercise.

  22. brahamin Says:

    Leave aside the mathematics, You have still said nothing about the complementarity principle which says that no interference pattern (wavee property) when a particle property (blip) is observed. But you and Nalin Silva say that you expect to see a faint interference pattern.
    The whole point is, the wave-particle duality does NOT mean that waves and particles exist at the same time. In fact it is just the opposite – namely, they are complementary manifestations of quantum reality. This simple point has not been appreciated and a high claim has been made.

    Please look up “Bohr’s complementarity principle”, or just Google it.

    I mentioned the mathematics and propagators etc., because you go on saying it is only a belief that the particle goes thorugh one slit.

    If you have N slits, now the particle has to go through all of them at once according to your view, and you need the trajectory to have N branches . If you don’t like my propagators, you need to show by your own methods that such N-branched trajectories exist. It is not enough to merely say it loud in physics .
    Bohm argued that his particles go through just one slit even if there are N slits, and he proved it mathematically .

  23. Janaka Wansapura Says:

    So Bodhi, you are your own cheering squad eh?
    Well that’s alright…. Just don’t hurt yourself..

    Did you actually read any of these articles? Neither I nor Dr. de Silva has said that a single particle should result in a faint interference pattern plus a blip. We say that if particles have wave properties physicists should expect a faint interference pattern from a single particle. In my review I specifically say “If an electron represented a physical wave of some sort then one would expect a series of bright and dark fringes, however faint it might be on the screen but not a single dot” Why do you make things up?

    The propagators are just fine. As I mentioned in my last post, it was you who did not understand the meaning of it. The mathematics does not stipulate that a particle must go through only one slit. In fact if you take Feynman’s path integral approach to the propagators you will see that it is the sum of all possible paths that gives the correct probability amplitude. So if you didn’t have a problem with particles being at multiple places at the same time you would interpret multiple paths as such. It is the western physicist who chose to interpret multiple paths as a wave property of particles and assumed that particles go through just one slit.

  24. . Says:

    Important Observation- LankaWeb
    See below how one could use the same computer for posting comments under two different names and complementing each other. How deceiving that can be?
    brahamin Submitted on 2012/02/10 at 6:59 am IP address
    Bodhi’s apology accepted. It is partly my fault as I asked Bodhi if he could help me with my Quantum Mech course unit tutorials that I need to do for myelectronic devices course. I gave him access to my laptop which was logged onto Lankaweb.
    So the erudite comment starting with ” Leave aside the mathematics”, under the name of “Brahamin” hasto be understood as being from Bodhi
    Bodhi Submitted on 2012/02/09 at 5:38 pm IP address
    Apologize to Brahamin at Laval University for using his computer that he has left logged on.
    Thanks Bodhi
    Brahamin Submitted on 2012/02/09 at 5:19 pm IP address
    Leave aside the mathematics, You have still said nothing about the complementarity principle……..
    brahamin Submitted on 2012/02/09 at 6:43 am IP address
    Bodhi has brought in a lot of new stuff (I mean not new to science, but not germane to the issue)
    I meant to say : Bodhi has brought in a lot of new stuff (I mean not new to science, but germane to the issue).WE all did some physics, but I moved to engineering for my degree, so these basic things like “wave-particle duality” are replaced by more useful, down to earth things in engineering studies. As Radha had said, this topic is of practical importance, but then so is poetry, or art, or music.
    Brahamin Submitted on 2012/02/09 at 6:31 am IP address
    So, you guys are still debating this? Great………..
    Bodhi Submitted on 2012/02/08 at 9:57 pm IP address
    Bodhi Submitted on 2012/02/08 at 9:11 pm IP address
    Bodhi Submitted on 2012/02/08 at 9:50 am IP address
    Bodhi Submitted on 2012/02/06 at 12:40 pm IP address
    Brahamin Submitted on 2012/02/06 at 8:09 am IP address
    Bodhi Submitted on 2012/02/06 at 6:53 am IP address
    Bodhi Submitted on 2012/02/05 at 8:38 pm IP address
    Brahamin Submitted on 2012/02/05 at 7:29 pm IP address
    Bodhi Submitted on 2012/02/05 at 9:12 am IP address
    Bodhi Submitted on 2012/02/03 at 8:28 pm IP address
    Brahamin Submitted on 2012/02/03 at 8:29 am IP address
    Brahamin Submitted on 2012/02/03 at 8:25 am IP address
    Bodhi Submitted on 2012/02/03 at 11:17 am IP address
    Bodhi Submitted on 2012/02/03 at 12:07 pm IP address
    Bodhi Submitted on 2012/02/03 at 8:19 am IP address
    Bodhi Submitted on 2012/02/03 at 8:13 am IP address
    Bodhi Submitted on 2012/02/02 at 8:46 pm IP address
    Bodhi Submitted on 2012/02/02 at 8:26 pm IP address
    Bodhi Submitted on 2012/02/02 at 8:09 pm IP address

  25. jasonsociety Says:

    What is this guy’s agenda? Why can’t one have a coherent honest discussion on this like real acadamics? All your (Bodhi/Brahmin) comments to Janaka are ‘yanne koheda malle pol’ type asnwers/questions.

  26. Janaka Wansapura Says:

    Just as us human beings can exist in various forms in the cyber space it is said that devas can exist in multiple places at the same time. Is it that strange that an electron that nobody can see, hear, smell or touch can be at multiple places at the same time?

  27. jasonsociety Says:

    Janaka, according to Vidyalankara Interpretation, when the quantum particle “exist” at both slits (in superposition) and hit the screen, only a spot appears on the screen?

  28. Janaka Wansapura Says:

    Yes. Spots are what appear on the screen. Nobody denies it. And that particles are in a state of superposition with respect to position at the slits is also a fact according to quantum physics. The difference is that quantum physics does not interpret the superposition as being at two locations at the same time whereas according to vidyalankara interpretation, particles do exist at both the locations. This is the difference. It may look like a minor philosophical difference but when you consider the quantum nature described by it, it is a paradigm shift.

    Dr. de Silva’s experiment confirms that the probability distribution of the particle in space cannot arise because of a wave like interference (because light cannot penetrate Al sheets). I think, the fact that it coincides with the predictions of the wave theory is just a coincidence. Taken together with the vidyalankara interpretation it gives credibility to the assumption that particles can exist at multiple positions at the same time.

  29. Dham Says:

    Why not check Ben Silva=Radha=Bodhi. You wil be surprised with motives of these anti-buddhists.

  30. AnuD Says:

    We know that particles are compounded “things” I mean, theoretically, the superstring is the most basic particle. Instead of considering a particle as one “particle” if a particle is considered a CLOUD COMPOSED OF OTHER SMALLER PARTICLES the problem in explaining the discrepancy of the doubler slit experiment ight at least partially be solved. We know, a particle exists only when a wave front is stopped. Then it can be considered a cloud of particles as a pair of photons do it’s best to keep together. Yet it spread through both holes, or causing an interference even with one hole.

    Can you imagine how a Galaxy is seen – a dense cloud as whole and a collection of billions of stars, planets, asteroids, comets and many more when considered one by one and most probably it contains dark matter and a one or more black holes too. If a similar concept at the basic particle level too.

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