As I have stated repeatedly the inescapable conclusion of light interaction with the retina as explained in this work is that the eye evolved to detect light as a wave and not as photons. The sub-optical wavelength dimensioned nanostructure defined by receptor outer segments operating in femtosecond (10^-15 sec) time “quantizes” the interaction forming a “particle” electron that is subsequently used in an electronic image-forming process.

I would speculate that this interaction can be considered the transition point (described in physics as the “Heisenberg cut”) between the classical and quantum views of reality.

Its “wave reality out there” and “quantized particle reality in here” !

It should  therefore not be thought that “photons go from place to place” but rather that it is the electromagnetic wave that is translated into what should be termed a quantized event (or, alternatively, “turned into a photon”) by the light-accepting nanostructure of  retinal outer segments of the eye.

 

To be more precise:  a.) the retinal nanostructure evolved to interact with the wave nature of electromagnetic radiation, b.)this nanostructure spatially defines the wavelength of the interaction (to three discrete geometrically defined wavelengths in the eye), and, c.) then translates the absorbed energy laterally in the plane of the retina (orthogonal to entrance light direction) using evanescent wave phenomenon and probably a lossless solitonic mechanism to quantum confined electron sites formed by individual receptors. The translation from classical wave to quantized particle is complete.

 

Seemingly relevant thoughts attributed to Albert Einstein (although I have not yet corroborated these!) are contained in a blog by one Dr. Stanley Alterman  (“Stanley’s World” “Optical Waves Wash Photons Aside”).

 

“Despite his success, Einstein and others at the time, viewed the quanta as “perplexing, pesky, mysterious, and sometimes a maddening quirk in the cosmos.” (*) In particular, was the quanta of light a property of the light in a vacuum or the property of the process of light interacting with other materials? (emphasis mine / GCH)

“Even though Einstein’s equation for the photoelectric effect was proven to be accurate, he found the quanta representation so untenable, that he no longer held it to be true. He wrote, even after the advent of quantum mechanics theory in the 1920’s, near his death, “all these 50 years of pondering have not brought me any closer to answering the question, what are light quanta?” (*) Einstein thus represented to his dying days that “the wave theory of light which operates with continuous spatial function, has worked well in the representation of purely optical phenomena and will probably never be replaced by another theory.” (*)”

ADDED IN SUPPORT OF THE ABOVE:

 

We must ask a fundamental question: do we ever really detect single photons? -  a question that is at the heart of the above discussion (or, in the light of my thoughts the term “photon” should be replaced with a “quantized event”).

 

I have some experience in this area of research (described below) but I wonder if we have been misleading ourselves in this regard!

 

I will first discuss the characteristics of the vacuum photomuliplier tube  (PMT)  and Richard Feynman’s use of this device as indeed a very fundamental detector of single photons basing his entire thesis on statements regarding it.

 

First a quote from Feynman’s beautiful treatise “QED (Princeton University Press, 1985)  p.15:.

 

(I assume that R.F’s statements reflect and are not at variance with his deeper thinking)

 

“….where you were probably told something about light behaving as waves. I’m telling you the way it does behave – like particles” (the emphasis is F’s).

 

And a further quote:

 

“You might say that it’s just the photomultiplier that detects light as particles, but no, every instrument that has been designed to be sensitive enough to detect weak light has always ended up discovering the same thing: that light is made of particles” (this time the emphasis mine).

 

And yet another quote (pp.36, 37):

“…but the wave theory cannot explain how the detector makes equally loud clicks as the light gets dimmer.” (again the emphasis again is mine).

 

It is of note that Feynman in his exposition in QED does not generally differentiate between “weak light detection” and “single photon” detection and often uses these terms interchangeably.

 

Now….Feynman’s use of the photomultiplier as an example of a “single photon” detector requires elaboration.

 

I would assert that the photomultiplier tube is actually not a single photon detector but rather a single electron detector.

 

Each light-generated electron released inside the tube from the surface of the photocathode enters a cascading dynode structure where its signal is amplified by a factor of a few thousand arriving finally at the signal output anode. This is the generality and until a few years ago all that we really know about the process.

 

It was discovered only some years ago (1960’s?) and quite by surprise that single electron events could be discerned (“counted”) at the output of the device.

 

How this discovery was made is an interesting story and I believe that I might even have attended an IEEE Nuclear Science symposium in Washington, DC in the 1960’s where this was first reported. I remember well hearing this paper and sensing that it was truly important – single electrons could be detected at room temperature!

 

In essence, an unexpected peak was seen on the low energy electronic “noise tail” appearing at the anode of certain PMT tubes. It could be deduced from the position of this peak that the event that caused it  had undergone the highest amplification with it being recognized peak formation indicated that the initiatory events originated  from one spatial location. It was quickly seen that this location was the photosurface at the light input cathode of the tube.

 

The fact that a peak was seen was a spatial effect related to the geometry of the construction of the tube All initiatory events from a uniform surface being subjected to the same gain resulted in the formation of a peak. The detection of single electrons in the PMT is fundamentally the result of the spatial geometry of the PMT!

It then becomes crucial to note that these electronic output signals from the PMT were all of the same size .In essence, a standard or constant pulse height was measured from single electron events.

 

I will note again the quote from Feynman above:

 

“…but the wave theory cannot explain how the detector makes equally loud clicks as the light gets dimmer.” (again the emphasis again is mine).

 

This has been absolutely explained – and it is not single photons but single electrons that yield the standardized output – or in F’s terms “equally loud clicks”.

 

I should note that single electron response represents the ultimate in sensitivity of this or any detector. One cannot achieve any greater sensitivity. The standard or “equally loud” signal is exactly what one should expect.

And…single electron response – the ultimate sensitivity! – is also characteristic of the light detection centers of the retina and of the photosynthetic organelles of plans and algae.

 

Now to the subject of a “single photon response” of the PMT. Feynman would have to assume that a 1:1 correspondence must exist between the incidence of a single photon and the release of a single electron into the vacuum of the PMT. This to my knowledge has never been demonstrated either theoretically or experimentally. Quite the contrary, there seemed to be an “anomalous” yield of single electrons released to the number of incident photons. As I remember (and I stand to be corrected) the best that could be discerned was that a statistical number of photons (30?)reslted in the release of a single electron.

 

What is the physical situation here? The light interaction process within the photosurface of a PMT occurs in an atomically thick “low work function” (i.e. electron emitting) layer that has been vacuum deposited on the inside of the light entrance glass thickness. As I remember, cesium compounds are used but there are others. The physics of this interaction were studied at the time and there seemed to be many troubling aspects to our understanding of the process and, in summary, it was never really understood.

There was certainly not a one-to-one correspondence between a single incident photon and the release of a single electron.

 

In reality a PMT therefore detects and “counts” single electrons and not single photons.

 

Finally, focus again on the two separate aspects of the light detection process in a PMT:

 

a.) Spatial/geometrical concerns are at the basis of identification of the event.

 

b.) That a constant signal amplitude, Geiger counter-like, “quantization” of the process results for the case of single electron detection.

 

___________________________________________

 

I mentioned above that I have had some experience in single electron detection. My research into, what are termed, the silicon “avalanche” photodetector (actually, a “solid state PMT”) at their best possessed electronic gain values approximating a thousand (10³). This was not quite sufficient to detect single electrons. Vacuum PMT detectors with the ability to detect single electrons possess gains of perhaps twice this number. We therefore conceived of the idea of replacing the structural dynode structure of the PMT with an avalanche detector for amplifying the single electron released from the vacuum photosurface. A voltage of a thousand volts or so was applied between the photosurface and the avalanche electron-detecting device. This made for a very compact single electron detector that we proposed would ultimately replace some PMT’s. We made the significant single electron response measurement of the device at a Hughes Aircraft facility in San Diega,Ca. I have that curve somewhere and will dig it if proves necessary. I received a U.S. patent for the concept (No. 5,146,296 “Devices for Detecting and/or Imaging Single Photoelectrons”, Sept. 8, 1992). The last time I looked they are now marketed as “Hybrid Photodetectors” by Applied Photonics, Inc. in Ann Arbor, Michigan.

 

A drawing describing the device made at the time:

 

It becomes obvious from this work that the eye evolved to detect light as the electromagnetic wave of classical physics and not the traditionally held view that “photons interact with pigments within individual retinal receptors”.

 

The photon is shown actually to be a “quantized wave-to-particle transition” that occurs at the point of the nanostructure of retinal outer segments. It has historically been wrong to assume that “photons go from place-to-place”.

 

It is fascinating that these statements do not violate the tenets of either classical or quantum physics! The translation process can be viewed from either direction - as classical waves or quantum particles!.”

 

The millions of individual nanostructural light detection sites formed by appositions at the plane of retinal outer segments (that much has been correctly understood) perform this fundamental transition from electromagnetic wave to the quantized electron particle.

 

This means, in summary, that  it logically must follow that the vision process interfaces the vision system with the domain of quantum physics.  This is the point that has been termed in physics the “Heisenberg Cut” and calls into focus the possible existence of a “quantum reality out there” whatever that term turns out to mean.

 

The sub-optical wavelength size of these detection sites and evidence that they operate in the very fast femtosecond (10^-15 sec) time domain is consistent with this statement. It has been experimentally shown that isomerization (the electronic “signal producing event”) of the retinal molecule contained within receptors occurs in this fast time domain.

 

These thoughts have major implications to the subjects of vision, consciousness, and, in fact, our entire view of what constitutes reality. I will be writing about this.

 

The historically held idea taught in every textbook that the eye acts as the camera that we understand with a reaction time in terms of milliseconds (10^-3 sec) must be given up!

 

Moreover, it follows from the well known fact the eye is sensitive to “single photon interactions” (never explained)  means that each  if detection sites described above  possess the sensitivity to detect what will now be termed “single quantized events”.  Such localization of quantized electrons are subsequently used in electronic processes to form the visual image. (I have presented electronic noise reduction scenarios that may explain this capability)

 

It is crucial to note that each of these single quantized events – determined by the nanostructure of the retina as explained in this work - produce identical output signals or, in electronic terms, the same “pulse height.” This is analogous to the output of a nuclear Geiger counter where the result of an interaction is  a constant output pulse size.

 

To summarize,  the eye reveals a heretofore unobserved nanostructural interaction between light and matter that comprises;

 

 a.) A sub-micron dimensioned (i.e., smaller than the wavelength of light) spatial region of variable dimensions to absorb the electromagnetic wave and, as shown in this work, to geometrically discriminate between wavelengths.

 

With this region being immediately adjacent to:

 

b.) An absorbing material-related space of fixed dimensions that quantum confines the absorbing electron following understood physics principles. ( I understand that the subject of quantum confinement certainly has many ramifications. I simply point to the “electron-in-a-box” approximation of quantum physics.)

 

__________________________________

 

ADDED IN PROOF:

 

I have discussed the recent discovery of a “porous silicon” visible light interactive nanostructure (that strongly resembles the morphology of the receptors of the retina!). This structure is composed of high aspect ratio silicon “pillars” (no pigments in site!) and intervening “pores”. Visible light only interacts with this structure only when the pillars have been reduced (laterally) to nanometer electron quantum confinement dimension.

 

__________________________________________

 

AND FURTHER IN PROOF:

 

A recent paper “EVIDENCE FOR WAVELIKE ENERGY TRANSFER THROUGH QUANTUM COHERENCE IN PHOTOSYNTHETIC SYSTEMS” (Nature, Vol. 446, April 2007)  beings with the sentence “Photosynthetic complexes are exquisitely tuned to capture solar light efficiently, and then transmit the energy to reaction centers…….”  Further on the authors note the”extreme efficiency.. of the photosynthetic process.”. The extraordinary light detection efficiency of biological photosynthetic systems and the retina of the eye is well known but never explained. In  vision this efficiency  manifests itself in the well understood results that the eye/retina can discern single photon (or “quantized”) interactions. This is discussed above - there can be no “greater sensitivity”.  In this paper the authors employ the concept of “quantum coherence” that  inherently posits that the initiatory step in the interaction has a wave nature and that these quantum waves display coherence occurring in (real) space. This result opens up many avenues for thought in finally understanding the processes of vision.

 

I would note that I have also proposed that the same “classical/quantum” nanostructure of theretinaof the eye is present in the photosynthetic organelles of plants and algae. Search “chloroplast” on the main page.

 

GCH

10.29.08

In Science Daily of yesterday  I note a paper  “Atomic-resolution Views Suggest Function Of Enzyme That Regulates Light-detecting Signals In Eye” authored  a team of University of Washington and Rutgers investigators.

Quoting from the release:

 

“The enzyme, phosphodiesterase 6 (PDE6), is central to the way light entering the retina is converted into a cascade of signals to the brain”

 

I would propose that this enzyme may be “central” in the vision process but not in the biochemical sense that the authors believe.(see below).

 

A further quote from the release:

 

“This particular form of the enzyme comes from the cone photoreceptors of the retina and has not been well-researched, in contrast to its rod form. Rods are involved in night vision and motion sensation; the cones are responsible for color sensitivity, visual acuity, daylight vision, and adjustment to bright light.”.

 

It simply amazes me that this belief is still held and that it forms the basis for thrust of research!

 

For the record – it is the interreceptor spacing of rods ( importantly exactly forming the short wavelength limit of vision) and the totality of rod area of the peripheral retina acting in concert (there has long been experimental evidence of this) that controls  pupillary constriction and thus entrance of light into the eye. Thus rods, in a sense, do control low light level (or night) vision but not in the way usually and erroneously thought!

 

It is my contention that the role of protein must be viewed in a structural physics sense controlling the spatial dimensionality of receptors – at the inner segment. It is the inner segment diameter, and the proteins that code for and form this structure, that sets the wavelength determining separation of the light interactive outer segments.

 

There are obviously other enzymes and uses for same, but the role of the inner and outer segments of receptors can be defined as follows:

 

THE INNER SEGMENT: In addition to providing the structural spatial separation of outer segments, forms the “factory” for constantly producing thylakoid disks for use in the outer segments.

 

THE OUTER SEGMENT: A physics based region where the fundamental light interaction process occurs. This is via a classical wave / quantum particle mechanism that I have proposed. The retina can be considered in essence as a logically spaced, wavelength- determinative array of generic quantum confined electron centers. The isomerization of the retinal molecule is the femtosecond time domain, electronic signal producing, center of all receptors both cone and rod.  It is the role of the rhodopsin protein to form the spatially-determinative structure to constrain the retinal molecule to quantum confinement dimension.

 

Back to the paper, the authors attempt to relate this particular enzyme to the extreme (quantum event sensitive) of the eye is not persuasive – or evenin evidence!

 

There is certainly a role for biochemistry downstream in an understanding  of the fate of the electronic signal from the outer segment but this region seems a concern of physics.

 

And I would add that “color” and “pigments” have been taken out of the picture in my explanation!

 

GCH

10.08.08

 

  

DISCLAIMER: Lest I be accused of poor scholarship (that has happened!), I will generally not in my Comments include references that I have previously used in other sections of this work. GCH

 

A recent paper ( Nature, “Quantum Secrets of Photosynthesis Revealed”April 12, 2007) supports my contention that femtosecond (10^-15 sec) time and quantum effects are involved in the initial light interaction in photosynthetic structures. Quoting from the release:

BERKELEY, CA —Through photosynthesis, green plants and cyanobacteria are able to transfer sunlight energy to molecular reaction centers for conversion into chemical energy with nearly 100-percent efficiency. Speed is the key – the transfer of the solar energy takes place almost instantaneously so little energy is wasted as heat. How photosynthesis achieves this near instantaneous energy transfer is a long-standing mystery that may have finally been solved.

 

Their results go further finding that quantum coherence is involved –another quote: “We have obtained the first direct evidence that remarkably long-lived wavelike electronic quantum coherence plays an important part in energy transfer processes during photosynthesis”. The underlines are mine as they represent the three terms that I have associated with light interaction.

 

“Wavelike -  quantum -  coherence” -  one should take note of the association of these terms with one another!

 

Another paper authored by Fleming and quoted in the Berkeley news release: “Evidence for Wavelike Energy Transfer Through Quantum Coherence in Photosynthetic Systems”.

 

I will be writing more about this but for the time being I will enclose text that describes my nanostructural explanation for this “wavelike energy transfer”:

 

I have written often in the body of this work that the fundamentally defining element in the vision process occurs at the point of light interaction with retinal outer segments and, contrary to traditional thought, this interaction occurs in the femtosecond (i.e., 10^-15 sec) time domain. There is a great deal of emerging high speed spectrometric experimentation that supports this contention (well referenced), notably, that the signal-producing isomerization of the retinal molecule occurs in this time. In addition to proposing that inter receptor light detection “devices” possess electronic properties that should be capable of detection in this domain, I have noted that this result must imply that quantum physics must be introduced into the vision process. The entire old thinking about the eye acting as a “camera” and that slow, millisecond “reaction times” of the eye must be discarded.

 

The eye, and the specific classical/quantum receptor nanostructure that it teaches, define it as the point where the human system interfaces with the quantum regime. To me, there can be no doubt of this!

 

Another point that must be considered in this light is the ability of the eye to discern (i.e., detect and produce a usable signal from) single photons (or as I would rather say it, “single quanta”). There can be no doubt about this and I have noted many references in the history of vision science to this point. See the references contained in Rose’s “Vision Human and Electronic”. Of note here is that detection efficiency of the eye at the retina must be very high – approaching 100%. I will include a portion of a Wikipedia entry that I have come upon that makes this point very well”

“It was found that the emission of only 90 photons was required in order to elicit visual experience. However, only 45 of these actually entered the retina, due to absorption by the optic media. Furthermore, 80% of these did not reach the fovea. Therefore, it only takes nine photons to be detected by the human eye. Moreover, as the chance of any one rod receiving more than one photon is very small, we can assume that it only takes one photon to excite a rod receptor.”

The fundamental point is that if vision can be shown to visualize single quanta, as it has been, then single receptor light detection sites must be sufficiently sensitive to accomplish this. I have proposed a logical scenario using quantum and electron device thought as how this comes about.

And, I must further note that, in the entire history of vision science, this ability of the eye has never been explained. The physics here have somehow been ignored and swept under the rug!

And, I must note that I have proposed that the same classical/quantum nanostructure principle evolved in the retina of the eye to effect the process of vision evolved in the photosynthetic organelles of plants and algae although optimized in a different direction towards light collection efficiency (as in a solar cell). I have written about this under “chloroplast”.

GCH

10.06.08