Quantum
world works on probabilities. This is the golden rule of survival in Quantum
world. When there are probabilities, there are many chances to survive, to
evolve, and to change future. When you are certain or fixed on something, this
destroys other possibilities and so the hope too. It's your choice or act of
measurement that makes quantum qualities definite and we visualise their effect in
Classical world.
Quantum physics show us the real world as it exist. Quantum physics is more profound. It is
absolutely not weird as people assumed.
Quantum
world and Classical world are not a different world rather one is a leap
forward to other. Quantum qualities expand your limit, add new dimension to
your world and change your approach to see the world as it exist in reality. Quantum
world exists beyond the boundary of a Classical world.
Einstein was
right in his interpretation of the behaviour of classical world. His General
theory of relativity changed our approach to see physical phenomenon clearly.
Most of his theories explained the classical world correctly. Classical physics
and Quantum physics don't interpret different things. Quantum physics helps us
to recognise and understand the new
dimensions beyond the Classical world.
The
realities that we experience every day are at macroscopic level and every
object behave as we expect from them. Quantum physics deal with the realities
that exist at microscopic level and their effects are negligible for us. But
everything is made up of quantum
particles and to realise this we need to cross our three dimensional delusional
realities.
I would take
well known fascinating experiment "Delayed
Choice Quantum Eraser" as an example to dig into Quantum mechanics. It investigates altering behaviours of
wave-particle phenomenon of a photon/electron. It was an extension of an Delayed
Choice experiment with the basic of Double-Split experiment.
In a Double Slit
experiment, when they shoot electrons from both the slits, at random, it shows
wave nature of electrons and display fringe patterns on the wall. When
they shoot marble, instead, from both the slits it always shows 2 straight
lines on the wall. Marble is easily noticeable because of its heavy mass. So it
always show its particle nature.
Electrons or photos are the basic element of
any particle and having negligible mass. Speed of the particle determines the
magnitude of the wave function. Waves
are the vibrations generated by the energy distribution from a particle. Every
particle if run with high speed (even if not with the speed of light), they forms
waves and every particle is on the state of a superposition to each other. As
you locate particle position, the wave function disappears. Propagation of a
particle through space is a wave function.
This we
observe in our real world also. When we see something running with super-fast
speed, we observe contraction in its length and we are unable to identify its
part separately.
There are many probabilities that could be true but as you choose one, instantaneously other probabilities get dissolved. The act of observation/measurement converts many probabilities into one definitive output. This definite result we observe in Classical world.
In a Double Slit
experiment, when we place observer, whether at the slit or at wall, we locate
the electron's position. Instantaneously, wave function is collapsed and observer
measures it as a particle. Wave form emerges when electrons are in a
superposition state to each other. When you locate an individual particle, the superposition
state disappears and wave form is collapsed.
For example,
when we throw a stone in water, ripples generate and scatter around. Particle created due to given
energy in water and then waves are formed depending upon the density and speed
of a particle.
Image Credit:Wikimedia Commons [Kim EtAI Quantum Eraser.svg]
In a Delayed
Choice Quantum Eraser experiments, they used a nonlinear optical crystal in the
path of slit A and slit B. It converts the electron/photon into two identical
pair. They get an entangled pair of each electron/photon that pass through from
either slit.
The quantum
state of each entangled pair cannot be described independently of the state of
the others.
One entangled
pair of photon is send directly to the detector D0 and the other photon is
diverted to detector D3 or detector D4 , depending on which slits they have
been pass through. The other entangled pair of photon that reaches at D3/D4 embodies
the which-way information. The
optical path of detector D3 and detector D4 from the source is longer than the
optical path of detector D0 from the source.
Detector D3 and detector D4 recorded diffraction
pattern because these entangled pair of photons had "which-path
information" that have broken their superposition states.
There were
some more arrangements have been done to this experiment, they placed 2 mirrors
in the way where 50 % of photons reflected to detector D3 or detector D4 and
50% of photons transmitted to detector D1 or detector D2. Here we have no idea
about which way (slit A or slit B) photons pass through. This time photons displayed
an interference pattern on detector D1 and detector D2.
Humm, this amazed physicist
about photon's behaviour as they do time travel in past and inform their
entangled pair about the future action of being not watched.
Nothing of
this sort can ever be happened. You can never change past action but to learn
not to repeat the same in future.
In a scientific experiment, observation doesn't
mean it is directly being observed by any one at a particular time period. It could
be done in the presence of scientists or in an empty lab. Observation means measurement!! They get records from experiments,
and then compare all records and give the final result. Comparing and
measurement of recorded outputs would be called an Observation.
Detector D0
has recorded a cluster of photons
whose entangled pairs were sent at multiple detectors. You don't get any
idea by simply looking at graph available at detector D0.
After the
experiments, they filtered all the records collected at multiple detectors and
compare the available graphs. There they observed visual impression of
interference pattern or diffraction pattern on the detector D0.
The
diffraction events recorded at detector D3 and detector D4 because of the available
path information (slit A or slit B). They got a graph of single maxim at
detector D0 which signifies impact of cluster of photons. They filtered corresponding
entangled pair of photons that have hit detector D3 and detector D4.
You observed
the photons, single out entangled pair of photons. It disturbed the
superposition state of a photon as you locate the position of a photon! Photon
was in its superposition state when it hit detector D0. During observation, you
filtered corresponding entangled pair of photon that hit detector D3 and
detector D4.
The outcome
at detector D3 and detector D4 determine outcome at detector D0 though they arrived
late.
While for detectors D1 and D2, you don't know
which path information for photons. You get fringe patterns on detector D1 and detector
D2. You recorded a fringe pattern at
detector D0 also. Because, photon was not single out (located) from its
superposition state at detector D1 and detector D2. The corresponding entangled
pair of photon is also recorded in a superposition state at detector D0. Thus,
the wave like interference pattern appears.
It's an act of observation that destroys the
wave function of an electron or a photon. The moment you have a knowledge of
the system, it destroys other probabilities that could have been true too. You conscious choice determines your future.
