Collapse of the Wave Function
Why is
it that more than half of the modern "interpretations of quantum mechanics deny the "collapse of the wave
function."
Why
are so many severe physicists and philosophers of science so unhappy with this
concept, which was a fundamental part of the "orthodox" theory
proposed in the late 1920s by the "founders" of quantum mechanics
- Werner Heisenberg, Niels Bohr, Max Born, Paul Dirac, Wolfgang Pauli, and Pascual Jordan.
We can
give the most straightforward answer in a single word - chance. Albert Einstein, the foremost scientist of all time (and ironically
the discoverer of chance in quantum mechanics, which he disliked
but never denied was a part of the quantum theory, as far as it could go in his
time) adamantly disliked the idea of "uncertainty" or
"indeterminism," the thought that some things in the universe were
not caused (or only statistically caused).
The idea of the wave function in quantum mechanics and its indeterministic collapse during a measurement is undoubtedly the most controversial problem in physics today. Of the several “interpretations” of quantum mechanics, more than half deny the collapse of the wave function. Some of these deny quantum jumps and even the existence of particles!
So, it
is essential to understand what Dirac called the projection postulate in
quantum mechanics. The “collapse of the wave function” is also known as the
“reduction of the wave packet.” This describes the change from a system that
can be seen as having many possible quantum states (Dirac’s principle
of superposition) to one that is randomly found in only one of those
possible states.
Although
the collapse is historically thought to be caused by a measurement and thus
dependent on the role of the observer in preparing the experiment, collapses
can occur whenever quantum systems interact (e.g., collisions between
particles) or even spontaneously (radioactive decay).
The
claim that an observer is needed to collapse the wave function has injected a
severely anthropomorphic element into quantum theory, suggesting nothing
happens in the universe except when physicists are making measurements. An
extreme example is Hugh Everett’s Many Worlds theory, which says the universe splits
into two nearly identical universes whenever a measurement is made.
What
is the Wave Function?
Perhaps
the best illustration of the wave function is to show it passing through the
famous slits in a two-slit experiment. It has been known for centuries that
water waves passing through a small opening create circular waves radiating
outward from that opening. If there are two openings, the waves from each
opening interfere with those from the other, producing waves twice as tall at
the crests (or deep in the troughs) and canceling perfectly where a crest meets
a trough from the other.
When we send light waves through tiny slits, we see the same phenomenon.
Most
of the light that reaches light detectors at the back lands right behind the
barrier between the slits. In some places, no light appears in the interference
pattern.
Today,
we know that light consists of large numbers of individual photons, or quanta
of light. Our experiment can turn down the amount of light so low that we know
there is only a single photon or particle of light in the experiment at any
time. We see the prolonged accumulation of photons at the detectors but with the
same interference pattern. And this leads to what Richard Feynman called not just "a mystery” but actually
"the only mystery” in quantum mechanics.
How
can a single particle of light interfere with itself without going through both
slits? We can see what would happen if it went through only one slit by closing
one or the other slit. We get a completely different interference pattern.
Feynman
was right. If you can comprehend, though perhaps not “understand,” this highly non-intuitive
phenomenon that is impossible in classical physics, you are well on your way to
appreciating quantum mechanics.
The
wave function in quantum mechanics is a solution to Erwin Schrödinger’s famous
wave equation that describes the evolution in time of his wave function ψ,
ih/2π δψ/δt = Hψ.
Max
Born interpreted the wave function ψ(x) at
a position x as telling us that the complex square of the wave
function, < ψ(x) | ψ(x) >,
gives us the probability of finding a particle at that position.
So the
quantum wave going through the slits (and this probability amplitude wave ψ(x) does go through both slits) is an abstract number,
neither material nor energy, just a probability. It is information about where
particles of light (or particles of matter if we shoot electrons at the slits)
will be found when we record them.
If we imagine a single particle being sent from a great distance away toward the two slits, the wave function that describes its “time evolution” or motion through space looks like a plane wave - the straight lines of the wave Cresta approaching the slits from below in the figure to the left. We have no information about the exact position of the particle. It could be anywhere. Einstein said that quantum mechanics is “incomplete” because the particle has no definite position before a measurement. He was right. When the particle lands on one of the detectors at the screen in the back, we can represent it by the dot in the figure below.
The
interfering probability amplitude waves disappear instantly everywhere once the
particle is detected. Still, we have left a small fragment of interfering waves
in the upper left corner to ask a question introduced by Einstein in 1905.
What
happens to the small but finite probability that the particle might have been
found on the left side of the screen? How has that probability instantaneously
(faster than light speed) been collected into the unit probability at the dot?
To be
clear, when Einstein first asked this question, he thought of the light wave as
energy spread everywhere in the wave. So it was energy that he thought might be
traveling faster than light, violating his brand new principle of relativity
(published two months after his light quantum paper).
At the
Solvay conference in Brussels in 1927, twenty-two years after Einstein first
tried to understand what is happening when the wave collapses, he noted;
If | ψ |2 were regarded as the probability
that, at a certain point, a given particle is found at a given time, the same
elementary process might produce an action in two or several places on the
screen. But the interpretation, according to which | ψ |2 expresses the probability that
this particle is found at a given point, assumes an entirely peculiar mechanism
of action at a distance, which prevents the wave continuously distributed in
space from producing an action in two places on the screen.”
Einstein
came to call this spukhafte Fernwerkung “spooky action at a
distance.” It is known as nonlocality.
Niels Bohr recalled Einstein’s description. He drew
Einstein's figure on a blackboard but did not understand what he was saying.
Einstein
referred at one of the sessions to the simple example, illustrated by Fig. 1,
of a particle (electron or photon) penetrating through a hole or a narrow slit
in a diaphragm placed at some distance before a photographic plate.
On
account of the diffraction of the wave connected with the motion of the
particle and indicated in the figure by the thin lines, it is under such
conditions not possible to predict with certainty at what point the electron
will arrive at the photographic plate, but only to calculate the probability
that, in an experiment, the electron will be found within any given region of
the plate.
The
apparent difficulty in this description, which Einstein felt so acutely, is that,
in the experiment, the electron is recorded at one point A of the plate. It is
out of the question of ever observing an effect of this electron at another
point (B). However, the laws of ordinary wave propagation offer no room for a
correlation between two such events.
(Discussions with Einstein, in Albert Einstein: Philosopher-Scientist, P.A.
Schilpp, ed. 1949)
Information
Physics Explains the Two-Slit Experiment
Although
we cannot say anything about the particle’s whereabouts, we can say clearly
that what goes through the two slits and interferes with itself is information.
The wave function tells us the abstract probability of finding the particle
somewhere.
The idea of probability - or possibilities - “collapsing” is much easier to understand. When a die is rolled, and the number 6 shows up, the possibilities of 1 through 5 disappear instantly. When the wave function collapses to unity in one place and zero elsewhere, nothing physically moves from one place to another. Consider a horse race.
When
the nose of one horse crosses the finish line, his probability of winning goes
to certainty, and the finite probabilities of the other horses, including the
one in the rear, instantaneously drop to zero. This happens faster than the
speed of light since the last horse is in a “space-like” separation from the
first.
Although
horse races are not (usually) influenced by quantum mechanics, the idea of
probability collapsing applies to both. The only difference is that we are
dealing with a complex probability amplitude that can interfere with itself in
quantum mechanics.
Note
that probability, like information, is neither matter nor energy. When a wave
function “collapses” or “goes through both slits” in the dazzling two-slit
experiment, nothing material is traveling faster than the speed of light or
going through the slits. No messages or signals can be sent using this collapse
of probability. Only the information has changed.
This
is similar to the Einstein-Podolsky-Rosen experiments, where the measurement of one
particle transmits nothing physical (matter or energy) to the other “entangled”
particle. Instead, instantaneous information has come into the universe at the
new particle positions. That information, together with the conservation of
angular momentum, makes the state of the coherently entangled second particle
certain, however far away it might be after the measurement.
The
standard “orthodox” interpretation of quantum mechanics includes the projection
postulate. This is the idea that once one of the possibilities becomes
actual at one position, the probability of actualization at all other positions
becomes instantly zero. New information has appeared.
The principle
of superposition tells us that before a measurement, a system may be
in any of many possible states. The two-slit experiment includes all the
possible positions where |ψ(x)|2 is not zero. All other possibilities vanish once
the quantum system (the photon or electron) interacts with a specific detector on
the screen. It is perhaps unfortunate that the word “collapse” was chosen since
it suggests some significant physical motion.
Just
as in philosophy, where the language used can be the source of confusion, we
find that thinking about the information involved clarifies the problem.
collapse
of the wave function
The collapse of the wave function is the transformation from a spread-out wave function to a
localized particle. One must understand this phenomenon's
meaning of “wave function,” described in its own article.
Measurement
in Double Slit Experiment
Let’s
start with the example of the wave function for a photon shot
from a laser aimed at a photographic plate. The photon must pass through a
barrier with two slits before it hits the photographic plate. This is the
famous Double Slit Experiment.
The
wave function is the equation that describes the changing or “evolving”
photon. It is an equation that derives from the Schrodinger Equation.
Sometimes, scientists describe the wave function as an equation and an actual physical object. However, this approach leads to
difficulty in understanding the physical meaning of quantum mechanics. Considering the wave function as no more than an equation is more straightforward.
In our
example, the wave function describes the evolution of the photon. But it does not
tell us the trajectory of the photon. Instead, it tells us the evolving
probabilities of where we would find it if the photon were to be detected. The
wave function might tell us at any one moment that there’s a 20% probability of
the photon landing at this spot on the photographic plate, a 30% probability
there, a 40% probability there, and a 10% probability there on the plate. The
probabilities total 100% as this experiment has been set up, so there’s a
100% chance that we’ll find the photon somewhere on the photographic plate.
quantum
decoherence & quantum superposition
The
possible trajectories are in a superposition. That is, at any moment in time,
many trajectories are possible. Each possible trajectory determines the probabilities of where we will detect the photon. Each
possible trajectory has more influence than we are used to attributing to the
idea of “a possibility.” In the quantum world, each possibility influences what
happens in the physical universe. It is as if there were an underlying
Quantumland in which the possible trajectories play out and determine what happens in the physical universe.
The
accompanying animation shows a different example of wave function collapse. An
entire atom rather than a tiny photon is shown. The animation shows a
superposition of two possible energy levels that the atom might adopt. These
energy levels are shown as if they are actual physical things. However, they are
possibilities described by the wave function and are not part of our physical
reality. The video gives substance to the options defined by the wave
function to better communicate. The wave function collapses when the atom interacts with an object
(is “measured”). The atom is
measured as having one of the two possible energy levels upon collapse. In this animation,
the collapse of the wave function is called “decoherence.” More about
decoherence will be discussed later in this article.
Collapse
of the Wave Function
Getting
back to the photon shot from the laser gun. Soon enough, the photon is detected
as a little dark dot on the photographic plate. Physicists would say that it
has been “measured.” “Measured” means that the photon has interacted with something in the physical universe. This interaction allows us
to detect the photon. In this case, the photon is absorbed by an electron in
the photographic plate, creating a dark spot. Upon
measurement, that is, this interaction, the probabilities calculated by the
wave function instantaneously convert to a 100% probability for the specific
dark spot and 0% everywhere else. The wave function has “collapsed.”
Quantum
Field Theory--what is it?
The
wave function does not calculate when the collapse will occur. On the contrary,
the wave function tells us that the photon continues to evolve and grow indefinitely. Nothing in the wave function gives us a hint
that the evolution of the photon’s trajectories will soon come to an abrupt
halt. The wave function accurately describes the photon only so long as it
remains free of interaction with the physical things.
Nor
does the wave function calculate the position where the photon will leave
its mark. The selected position appears to be random. Physicists must “write in
by hand” the detected position of the photon rather than being able to
calculate it.
The
failure of the wave function to describe what happens when the photon interacts
with the physical universe and is detected is called the “Measurement Problem.”
This is the problem that the Schrodinger Cat thought experiment (as described
below) was designed to highlight. The measurement problem has additional
aspects, including an inability to define “measurement” rigorously. In the
Copenhagen Interpretation, the interpretation that this article focuses on is that measurement is described in a general way as the quantum particle interacting
with a macroscopic object. The Copenhagen Interpretation itself provides no
mathematical description of this interaction. However, other interpretations
do. When added to the Copenhagen Interpretation, the decoherence theory also provides a mathematical description of the interaction.
Wave
Function Collapse and the Speed of Light
Yet
another aspect of the Measurement Problem is that wave function collapse
appears to violate the universe's speed limit, the speed of light. Albert
Einstein and two colleagues pointed this out in a famous paper, nicknamed “The
EPR Paper,” for the last names of the three authors. As noted above, when the
wave function collapses, all positions except one instantaneously adopt a
probability of 0%. One position, the position in which the photon is detected,
adopts a probability of 100%. How can all the other positions described by the
wave function instantaneously get the news that the photon has just been
detected in one position? The conversion of the probabilities appears to be
instantaneous, and “instantaneous” is faster than the speed of light. This
violates the Special Theory of Relativity, a theory well-confirmed by empirical
observations.
This description of the wave function violates “locality.” Locality is the
principle that objects are affected only by those things that touch them. And
anything that can feel something else must not exceed the speed of light. Even
when we hear a radio broadcast of a symphony created halfway across the world, the locality is preserved. The sound has traveled as vibrations of air molecules
and as vibrations of electromagnetic radio waves. These are considered physical
“things” which travel by touching things. At the journey's end, vibrating
air molecules touch our eardrums. At no point do any of these waves travel
faster than the speed of light.
This
is in contrast to wave function collapse. The quantum world,
Quantumland, is not bound by the principle of locality. Experiments on
entanglement and Bell’s Theorem indicate that the quantum world is non-local.
That is, quantum particles can act in a perfectly coordinated manner regardless
of their distance from each other.
Non-locality
can be absorbed by the Copenhagen Interpretation. It simply ignores the issue.
The Copenhagen Interpretation needs to address what quantum particles are doing
before detection, and it argues that doing so would be unscientific. It
argues that since what occurs in Quantumland cannot be detected, even in
principle, it is not a proper subject for scientific investigation. Other
interpretations of quantum mechanics explicitly address the issue of
non-locality. The de Broglie-Bohm Interpretation is explicitly non-local, as is
the Transactional Interpretation. Other interpretations vary regarding
locality.
Does
the wave function really describe a wave?
Measurement
in the Double Slit Experiment
Double
slit experiment
Let’s
return to the Double Slit Experiment. If we keep sending photons through the
slits, more and more dots mark the photographic plate. The dots seem to land in
random positions. But dot by dot, a pattern builds up. After thousands or
millions of photons hit the plate, we see light and dark stripes.
The
accompanying photos (left) show this build-up of stripes. Gradually, the dots build Frameame Frameame until the stripes are clearly visible Frameame (e).
(It should be noted that these Frames ofFrameos were created by electrons rather than photons. As the electrons hit,
light dots formed on a dark background. But were photons used, a striped
pattern would also appear.)
This
striped pattern is a signature pattern of waves meeting waves. Waves that meet
superimpose themselves upon each other, creating a “superposition.” The image
above of two water waves meeting and interfering with each other shows a
superposition of waves. Waves in superposition can form the familiar crisscross
pattern of two boat wakes meeting or ripples from two pebbles thrown in a pond.
The crisscrosses create a striped “interference pattern” on the detection
screen.
The
interference pattern formed by quantum particles in the Double Slit Experiment
is the empirical clue that the photon acts as a superposition of waves before
detection. The other evidence that the photon acts as a superposition of waves
is that the probabilities of its detection are calculated by the wave function.
This equation is similar to those that calculate the behavior of
water, sound, and other ordinary waves.
Wave
Function Collapse and Schrodinger’s Cat Experiment
In the
1920s and 1930s, physicists speculated about the collapse of the wave
function. What was it about detecting the subatomic particle that ended the
evolution of the wavelike behavior of the photon? What caused it to transform
into a particle with a specific position? While the mathematics of the wave
function said that the “photon wave” should continue to evolve,
experiments showed that it adopted a particular position instead. Worse, it
adopted a position that could not be predicted: In the same experimental setup,
particles that were run through the experiment adopted different, apparently
random, positions. The wave function calculates only the total distribution of
particle positions.
In
fact, the mathematics was saying even more. The wave function has a
mathematical property called “linearity.” This property means that when the
photon superposition interacts with the photographic plate, the superposition
should “infect” the photographic plate. The plate itself is composed of
quantum particles. Mathematically, it appears that the particles in the plate
should become correlated with the photon. The plate should go into a
superposition like the photon, a superposition of all the positions where
the photon might land.
Instead,
the wave function collapses to a particle, making a single dot on the
plate. Rather than going into a blurry superposition, the photographic plate
stays solidly in place.
The
Schrodinger Cat thought experiment highlights the problem of our ignorance of
the cause of the collapse of the wave function. Here’s the experiment: A
radioactive atom is in a superposition of two states: 1) decay, in which it
emits an electron, and 2) stability, in which it doesn’t. The atom is in a box
with a hapless cat and a Geiger counter. If the atom decays and emits the
electron, it triggers the Geiger counter, which releases a hammer, which breaks
a vial, which releases a poison gas, which kills the cat.
The
property of the wave function's linearity tells physicists that the atom's superposition, both decayed and undecayed, would put the Geiger
counter into a superposition of triggered and not triggered. The superposition
of the Geiger counter would, in turn, infect the hammer, which would go into a
superposition of smashing the vial and not breaking the vial. And so on, until
the cat is in a superposition of being dead and alive. But this
does not describe the reality that we experience. What actually happens in the
physical universe that saves us from zombie cats?
Early
on, some physicists proposed that consciousness collapses the wave function.
Upon the human experimenter looking at it, the entire cat-killing machine is
solidified, and the cat is found dead or alive, but not both. The decoherence theory was developed in later decades to explain wave function
collapse. Both of these explanations are described below.
Some interpretations of quantum mechanics do not hold that
the wave function actually collapses. The Many Worlds Interpretation and the de
Broglie-Bohm Interpretation are the most well-known.
Collapse
of the Wave Function and Consciousness
In the
1920s and 1930s, some quantum physicists considered the possibility that
consciousness collapses the wave function. This possibility is suggested by an
odd aspect of the Double Slit Experiment. When the “which path” information is
discovered about the quantum particle in any manner whatsoever, the wave
function collapses. In other words, if we can determine either directly
or indirectly the path of the quantum particle through the slits, the waviness
of the particle disappears. It becomes a particle.
A chain of reasoning raises the possibility that consciousness could
play a role in wave function collapse. This reasoning can be illustrated regarding the Schrodinger’s Cat Experiment: The box in the Schrodinger Cat
Experiment might hold a cat infected by the radioactive atom's superposition, is both dead and alive. But we know from experience that when
the physicist opens the box and looks, she will see either a live cat or a dead
cat, not a blurry superposition of both. Possibly, the physicist’s
looking, her consciousness, causes the instantaneous collapse of the wave
function to either a live cat or a dead cat.
wave
function collapse
Collapse
of the Wave Function by Consciousness. [Image source: David Chalmers and Kelvin
McQueen, “Consciousness and the Collapse of the Wave Function”
http://consc.net/slides/collapse.pdf]
All
the objects in the box are composed of quantum particles. Due to the linear
property of the wave function (see above section), the objects would be
expected to enter into superpositions of states correlated with the undecayed
atom and states correlated with the decayed atom. Given the tendency of the
atom’s superposition to infect everything composed of quantum particles that it
interacts with, only something not consisting of quantum particles could actually
collapse the wave function. Consciousness could be this thing. This is the Von
Neumann-Wigner Interpretation.
Consciousness
and Collapse of the Wave Function—Von Neumann-Wigner Interpretation
In
1932, John Von Neumann, one of the leading mathematicians of the 20th Century,
wrote the first comprehensive presentation of the mathematics of quantum
mechanics, The Mathematical Foundations of Quantum Mechanics. This became the
standard textbook for quantum mechanics. In this volume, Von Neumann proposed
that the wave function could collapse at any point in the causal chain from the
measurement device to the human perception of the measurement. In the 1960s,
Nobel Laureate Eugene Wigner proposed that precisely human consciousness collapses the wave function. However, in later years, he
distanced himself from this proposal.
Noted
physicist Henry Stapp continued with the idea that consciousness
collapses the wave function. He wrote:
“From
the point of view of the mathematics of quantum theory, it makes no sense to
treat a measuring device as intrinsically different from the collection of
atomic constituents that make it up. A device is just another part of the
physical universe… Moreover, the conscious thoughts of a human observer ought
to be causally connected most directly and immediately to what is happening in
his brain, not to what is happening out at some measuring device… Our bodies
and brains thus become … parts of the quantum mechanically described physical
universe. Treating the entire physical universe in this unified way provides a
conceptually simple and logically coherent theoretical foundation….”
The
cartoon image above illustrates this view of the collapse of the wave function. In
this illustration, the universe is a collection of interacting waves. Our consciousness collapses to fundamental solid particles forming houses, trees,
the sun, and a family picnic. This view of the role of consciousness in
collapsing the wave function is sometimes espoused by people who are into
spirituality. They sometimes look back at statements along this line by early
quantum physicists like Eugene Wigner and Werner Heisenberg, not realizing that
this is no longer mainstream physics. However, some physicists consider the possibility that consciousness gives physicality to our universe.
Physicists interested in the possibility that we live in virtual reality may
be especially interested in the role of consciousness in giving flesh to the
equations that govern the universe. For a discussion, see the final section of
this article.
Today,
most physicists dismiss the idea that consciousness collapses the wave
function. Of course, there is no theoretical understanding of the physics of
consciousness and the mechanics of how consciousness might collapse the wave
function. Instead, today (2019), many physicists look to the mathematical
theory of decoherence as the explanation or, at least part of the explanation,
for the collapse of the wave function. (See next section.) Other physicists
subscribe to interpretations of quantum mechanics, such as the Many Worlds and
Bohmian Interpretations, which do not involve the wave function collapse.
This, in fact, is one of the main attractions of these two interpretations.
Experimental
Results on Consciousness and Collapse of the Wave Function
While
many physicists have moved away from considering consciousness as a possible
cause of the wave function collapse, a few have done actual
experiments. In addition to other potential causes of collapse, could conscious
attention to the path of a quantum particle collapse the wave function? This
possibility was investigated by physicists at Princeton University and York
University in 1998. Participants were asked to observe with their mind’s eye
light traveling through a Double Slit Experimental set-up. The possibility of
any physical contact with the set-up was eliminated.
Experimenters
at Princeton University used subjects experienced with maintaining
focused intention in these experiments. This experiment found a small
but statistically significant effect of visualization on collapsing the wave
function. The York University experiment used a random group of
subjects but found no significant impact.
In
2012, a team of parapsychologists led by Dean Radin conducted six
experiments on consciousness and the collapse of the wave function. These
experiments found that the results depended heavily on the selection of the
subjects. When experienced meditators were asked to see the path of quantum
particles in their mind’s eye, wave function collapse was slightly more likely.
The results were statistically significant: odds against chance were 107,000 to
1. However, non-meditators were not effective in creating wave function
collapse. These studies' results and the earlier ones in 1998 were
published in peer-reviewed physics journals.
This
is an exciting research area; hopefully, more experiments will be
conducted on the issue.
Decoherence
and Collapse of the Wave Function
So,
what is decoherence? First, I must explain what coherence is. When a quantum
particle is coherent, we’re just saying it’s in a
superposition. It’s the wavelike state of the particle that the wave function
describes. (It can be confusing to keep calling it a “particle” when
it’s wavelike, but that’s how physicists speak about it.)
To
explain decoherence, let’s return to the example of the photon moving
towards the photographic plate. When it hits the plate, it’s absorbed by an
electron in the plate. With this interaction, its position is definite. It’s
no longer simply a set of possibilities. It has changed things in the physical
universe. Information has been created and recorded by the photographic plate.
This can’t be undone. The wave function has decohered. Decoherence has
occurred.
Starting
in the 1950s, physicists realized they needed to consider the
environment in which particles functioned. In ordinary environments, there
are lots of macroscopic particles everywhere. At ordinary atmospheric pressure,
so many air molecules float around that the photon needs to travel only the width
of a human hair before bumping into a nearby air molecule. This means that many
opportunities are provided for quantum particles to decohere and leave the
superposition state. For this reason, quantum particle experiments are often
conducted within vacuums.
This
tendency for a quantum particle to quickly leave its superposition (decohere)
is the primary barrier to developing useful quantum computers. Quantum computers
depend upon the quantum nature of particles–their ability to exist in a
superposition. Interactions with the environment bring a quick end to
superpositions. Physicists must place quantum particles in containers that
prevent the particles from touching the sides of the container. One way is to
create magnetic fields that hold electrically charged particles away from the
sides of the container. The containers must also be emptied of air and kept at
near-zero temperatures. All of these measures help to prevent decoherence.
This
is an area of active research. Physicists are doing experiments and developing math to better understand the interactions between quantum particles
and the environment. A 2013 experiment on the interactions of photons with
atoms is a good example. Both atoms and photons have the quantum property of
spin. The spin of a photon can either be aligned with the spin of an atom it encounters or not aligned. The experimenters found that if the photon's spin is aligned with the atom's spin, the two will not interact; the photon's wave function will not collapse. It will remain in a
superposition. However, if the spin of the photon and the atom are aligned,
they will interact. The wave function will collapse, and the photon will lose its superposition and be measured. It will experience decoherence.
The
collapse of the wave function is a central problem that physicists continue to
explore. It has become a problem with essential implications due to its role as
a significant barrier to the development of quantum computing.
Another
Role for Consciousness in Physics
While
today, consciousness is not generally thought by physicists to explain the
collapse of the wave function, it has emerged in another role. Some physicists
propose that we live in a virtual reality. They see physical reality as
fundamentally a set of interacting “wavinesses.” Upon interaction, the wave function
collapses. But this is only a mathematical change. It is a change from one
equation to another. Suppose it’s a photon being absorbed by an electron upon the collapse
of the wave function. In that case, the photon's wave function switches to an equation
describing how photons and electrons interact. But how do we get from
mathematical equations to physical reality? How does the math become a dark
spot on a photographic plate? As Stephen Hawking put it: What “breathes fire”
into the equations?
The
entire universe might be seen as interacting equations, one equation’s output
providing the input for another equation, and so on. Continuing the process of
the photon being absorbed by an electron in the photographic plate, an entire
chain of equations governs the interactions, which end with equations for
electromagnetic waves in the brain of the physicist who looks at the
photographic plate. These electromagnetic waves describe a dark spot on the
photographic plate. But how do we get from these equations describing
electromagnetic waves in the brain to the physicist having the subjective
experience of seeing a dark spot? This is where consciousness comes in. The
consciousness of the physicist decodes the equations and provides the
experience of seeing a dark spot.
Rather
than focusing on equations, we might see the universe as the “computer code”
that the equations generate. This is the world that the enslaved humans in the
movie “The Matrix” live in. They live in a virtual reality, essentially an
interactive video game created by computers, into which their brains are hooked. However, this view of reality doesn’t necessarily imply that we are
characters in a computer video game. Physicists like Amit Goswami have proposed
instead that the coding is in one mind that we are all hooked into.
BIBLIOGRAPHY
1. Griffiths, D. J. (2005). Introduction to quantum mechanics (2nd ed.). Prentice Hall.
2. Shankar, R. (1994). Principles of quantum mechanics (2nd ed.). Springer.
3. Feynman, R. P., Leighton, R. B., & Sands, M. (1965). The Feynman lectures on physics (Vol. 3). Addison-Wesley.
4. Bohm, D. (1952). A suggested interpretation of the quantum theory in terms of "hidden" variables. Physical Review, 85(2), 166-193.
5. Schlosshauer, M. (2007). Decoherence and the quantum-to-classical transition. Springer.
Konstantinos P. Tsiantis
Physicist - Teacher of Physics
16-4-2024
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου