Potential

The mathematical study of potentials is known as potential theory- The study of harmonic functions on manifolds.
This mathematical formulation arises
from the fact that, in physics, the scalar potential is irrotational, and thus has a vanishing Laplacian — the
very definition of a harmonic function.
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In physics, a potential may refer to the scalar potential or to the vector potential. In either case, it is a field defined in space, from which many important physical properties may be derived.

Quantum Mechanics Latest Visions

Courtesy : Quantum Mechanics

Quantum mechanics is a realm of
weirdness: electrons being linked to each
other even though the vastness of the
universe might separate them, things being
in two places at once, and, of course,
knowledge precluding knowledge. This last
is the standard bearer of quantum oddity:
measuring the momentum of an object
precludes precise knowledge of where that
object is. But I think I have found
something that is stranger than them all.
Researchers have suggested that it might be
possible to make measurements that trick a
photon into thinking it is, in fact, a crowd of
photons.
Let’s imagine that we want to introduce a
phase shift to one single photon through a
control photon. A phase shift is basically a
time delay. In traditional optics this delay is
applied through high-intensity light beams:
a high intensity pulse can modify the
refractive index of the medium through
which it propagates. Our signal photon
traveling through that medium will see that
different refractive index and either be
delayed or sped up.
The problem is that we want to do this all
with single photons, and just one photon
does not fit the definition of high intensity.
It seems a bit hopeless, right? However, in
quantum mechanics, things are not all that
they seem. One type of measurement in
particular—called a weak measurement—
can give very strange results. For instance,
if you measure the spin of an electron using
a weak measurement, you can be
reasonably certain that you haven’t
disturbed the spin state of the electron,
but, you might get a strange value.
Electrons only take on spin values of +1/2
or -1/2, but a weak measurement could
return something like 100. So, under the
right circumstances, that single electron can
behave as if it had the spin effect of 200
electrons.
In our case, we’re using two photons. A
single control photon goes through a beam
splitter where it gets the choice of going
through the medium with a signal photon—
the one we want to phase shift—or go
through a separate channel. These paths
are then recombined at another beam
splitter, but this beam splitter isn’t quite
balanced. In a perfectly balanced splitter,
the control photon will always exit the
beam splitter in the same direction, called
the bright port. In an unbalanced beam
splitter, it’s possible for a photon to
sometimes head off in a different direction,
called the dark port.
When you calculate the possible ways that a
photon could hit a detector looking at the
dark port, one of them is that there are
simply more photons traveling through the
medium with the signal photon than on the
path outside the medium. Even better, the
closer to balanced the detector is, the rarer
the clicks on the detector for the dark port
are. So, to get a click, you need a much
larger number of photons in the medium
with the signal photon . Even if you know
you only send in one photon at a time.
In other words, we are measuring the
number of photons, but getting an answer
that is wrong by several orders of
magnitude. The truly weird thing: nature
believes us rather than reality.
If we make a weak measurement on the
number of photons in the control photon
beam, then a single photon is misreported
as several hundred. And, if everything is set
up correctly—which, in this case, means
that we only look for phase shifts on the
signal photon when the dark port detector
clicks—that lone control photon will have a
much larger effect on the refractive index of
the medium. The end result is that the
phase of the signal photon is shifted by lot
more than would normally be expected.
The catch is that this is a work of theory.
And the phase shifts, even with this
amplification factor, may be really small.
Even so, I can imagine that if you chose
your medium correctly (say an alkali metal
gas), and your wavelengths correctly (right
on the edge of an absorption feature of the
gas), then it might well be possible to
observe the amplification of the phase shift.
Like the Bell inequalities and entanglement,
we will have to wait before this can be
tested. But, unlike some quantum
phenomena, it won’t be decades from
theory to experiment.

Niels Henrik David Bohr

Source – Go “en.wikipedia.org/wiki/Niels_Bohr”
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922
Born: October 7, 1885, Copenhagen
Died: November 18, 1962, Copenhagen
Education: Trinity College, Cambridge, University of Copenhagen, University of Cambridge
Awards: Nobel Prize in Physics, Copley Medal, Franklin Medal

Thus Spoke Bohr :
Prediction is very difficult, especially if it’s about the future.

Your theory is crazy, but it’s not crazy enough to be true.

Einstein, stop telling God what to do!

It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we say about Nature.

An expert is a man who has made all the mistakes which can be made, in a narrow field.

We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough.

A physicist is just an atom’s way of looking at itself.

If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet.

How wonderful that we have met with a paradox. Now we have some hope of making progress.

Never express yourself more clearly than you are able to think

Everything we call real is made of things that cannot be regarded as real.

Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it.

There are trivial truths and the great truths. The opposite of a trivial truth is plainly false. The opposite of a great truth is also true

When it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images.
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