you want to go to Rome the city
eternal could they go by boat
making a stopover in Sardinia and then
crossing the Tyrrhenian sea or they could go
road doing stopping in bologna or
before in genoa that would seem to them if
could go at the same time for the two routes
would be something wonderful truth or is it
Enjoy both of them at the same time
alternatives because this is what
let’s talk because when I was 20
years
and some time ago and
they told me that a particle could
be at the same time in two places
that caught my attention
it seemed somewhat disconcerting and I thought that
I had to understand a little more
that story not then why
studied quantum mechanics mechanics
quantum is the part of physics that
study that deals with the smallest of the
world of the atom and the particles
subatomic quantum mechanics was created
the first third of the twentieth century in its
application is now for all
sides are all the devices of
electronics that surround us are based
in quantum mechanics or lasers with
those that read barcodes or
that allow operations to be carried out
Precision surgery in hospitals
all of that is based on quantum mechanics
It is true that their principles
fundamentals are both disconcerting
it seems that logic and inclusion
ordinary be and stay a little
deteriorated remains a little surprised
actually when he studied mechanics
quantum I realized that there was no
trick that is true that a particle
can be at the same time in the most places
even that is another expression of a
more general principle of nature
which it is to come and speak here
called the principle of superposition
is that nature when
I always talk about the atomic and
its atomic
when nature those levels
You have several alternatives to obtain
a result has several ways to
arriving at a result it turns out that it does not
decant does not choose chooses all at once
all to all roads at once that’s
what happens to nature to
understand this a little more let’s see
that experiment that is there in the
screen
in this experiment what we have is a
To be
I have hidden here a thousand do for
the occasion and my little crystal and iu with
this laser
if I plugged it in here towards the glass
I see that there are two images I do not know if the
you see is the transmitted beam that
is fixed down and the reflected that I
I can move when I move the crystal
I’m spinning and I have the reflected beam
truth is worth that crystal that I have
here is similar to what the figure is
flame mirror semi reflector the mirror is
I reflector is a crystal like that in
the one that the intensity of lightning
transmitted is the same as that of lightning
reflected a and b the rays the transmitted
and reflected the king has transmitted arrives
to the conventional mirror that is in the background
to the right and it comes bouncing there to
detector superior to that of two lightning
reflected after voting on the glass
comes to the conventional mirror that is
up on the left and at the end
the one detector
those are the two routes that follow
transmitted and reflected rays that I have
seen before with the laser pointer that
had and you can reduce the intensity
of the laser
this can be done laboratories by
course and you can reduce the
intensity of the laser until a
Photon photon increasing the particle
the simplest the particle
visible from the one that is made to light
then I can reduce the intensity
and a photon comes out every time we go to see the
simulation
here the photon is a bit fat but already
you see one goes and it is transmitted and
comes from two others is reflected we have
seen and arrived they went to the story mind
because the photon when it reaches the mirror
no effect because you can not divide some
will cross and others will reflect and the
50% probability for each of
the situations then I have huh
detections n 1 and n 2
but the interesting thing happens when I
placed at the point where they concur
transmitted az and age reflected
placed a mirror if I reflector equal
that the iee that is called efe
then what happens now good what
we hope is that the photons that go by
the lower route the route that we’re going to
call be from now on when
come to efe
can be transmitted or reflected by
both can reach two or one
the same thing happens with the photons that are
reflect in e
they go by the route that we are going to call ay
can reach efe and also
be transmitted reflected and therefore
will come from one of two or what one
expected to get is that there are detections
random alternatives in both
sectors
but it turns out that when the
experiment you can get that
happen the following all photons
they come to one
how is it possible that all photons
come to a good one because we have
introduced the semi- reflecting mirror
efe and the routes that I have there are
indistinguishable because the principle of
overlay says
e that when I have several alternatives
to get a result in the
nature the atomic levels and their
atomic
follow all but with one condition and it is
that nobody foot no trace or
trace of none of the alternatives
the condition is that the alternatives
are indistinguishable and that’s what
it happens when I
introduce the mirror effector look efe
why then the factors that are going to
you do not know where it comes from
visible by the route or by the route b not
you know you can not even know
I have no idea if it comes by the route and
they have been transmitted either by the route and
iu have been reflected in efe
and as that principle is not acting his
replacement
so what is happening here what
what happens is that the photon when it arrives
ae
has two alternatives truth two
roads has two routes the key and that
does the photon when it has two routes
possible if they are indistinguishable and not
leaves a mark on none of them
the shots 23 photo what it does is that it goes
at the same time by both ways
is what happens in that sense it
it behaves like waves a wave that
get to e would be divided into two
would continue and another would bounce in the
mirror
well, the waves may have
constructive interference that is what
you see two probes above and vibrate to the
Once free phase is called increases
decreases each time they create a bigger sling
but if they lived as you see the part of
down one phase opposition of the other
if when one increase to the other decreases
its effects are canceled and in the end
result is null because that seems to be
what happens in our experiment what
what happens
this experiment is that the photon is a
single particle there is a click on the
detector but it goes at the same time for both
routes and if one analyzes only requires a
little more effort but it can be done
if you analyze the reflections of the
mirrors and such discovers what happens what
I’m telling you only here as the
summary that there is interference
destructive towards fingers and constructive
towards one is to say that it does not arrive
no photo na of two but all
they come to one
so what is happening is that
as I say a single particle goes at once
by the two routes it is said that it is a
state of overlap and it presents itself
by a more go to this route up and see
as given below and simultaneously the two
puts more ve is an impossible state in
classical physics classical physics are
Incompatible routes but if given is
normal in the atomic and subatomic world
and
but how is the photon going because in the
simulation that I have put disappears
the photon ny appears in efe
why do not I put it in between
simply because I do not know how it goes
but not only that I do not know if not that
I can know why if I knew
if I look where you are going if the photon
I put some device that detects if it goes
by a route or not at that time and a
of the routes leaves a trace
the routes are no longer indistinguishable are
distinguishable and the
superposition the magic is over
at that time already the photon instead of going
the two routes go through one of them the
superposition of fact is a very state
delicate there lies its beauty that’s why
this talk is called the beauty of what
inscrutable because he has to stay
hidden inscrutable because if I of
the way that it scrutinized a state of
overlay I want to know if there is a
of the alternatives
whether or not one of the alternatives is given and
I want and I want to know that
at that moment the assumption breaks down
technically says that collapses collapses
one of the alternatives to one of the
possibilities
in fact if I place a detector here
as you can see on the lower route you see
at that moment
I break like I said before the
overlay and then what will
happen the photon would behave like a
ordinary particle and steam for by
as such if going by the hour can bounce
in efe it will arrive two or can
be transmitted and b can happen what
same
here we see the photons some are reflected
ivana of one
others are transmitted and down from 2 our
simulation other matches that goes there
because it ‘s random then another bounces
I was going to finger xetra go as I said to the
two detectors alternately already
equal number of arrests in each
from them
the detection anyway the
overlay in two ways it gets
especially interesting when instead
to refer to a particle a photon in
this case that goes by two roads is
refers to two particles
let’s analyze the case here the
electrons an electron for what we
interesting here is nothing more than a little ball
which is rotating and the axis of rotation of the
ball that new address space
which is called the spin of the electron is
for us an electron is a little ball
with an arrow
Well, there are experiments in which
the electrons fired in
opposite senses and they move away the
one from another
the laws of physics impose that if the
electron that is on the left has the
spin up from the right
have to have the spin down or
vice versa but then what will be the
joint state of the two electrons
Well let’s see
could be
or electron from the left to the top
electron from the right down or
it could be electron from the left
down electron from the right towards
up but let’s not forget our
superposition principle if the
nature has two possibilities and they are
as in this case and distinguishable is not
decant by none of them does not choose
none of them stays in a state
suspended as it happened with the photon that
already by two roads, here, exactly
As a state that could stays
describe as before was the most see here
is the sum of the two possibilities and is
a very special state because as I say
I can say that the electron of the
left to be effective not up or
down does not have the spin either
defined until it is measured up
then it seems to me a state of
superposition of a state where no
a suspended state is defined and
another thing happens when I measure
really the spin of the electron that’s going to
happen then that if an electron I measure it
and it has destiny up
the partner of the other who has
far away may be hundreds of millions
of kilometers has to be placed
immediately with the spin upside down
down so there’s a way here
fastest instant communication
that the light it takes how fast it travels
in our world for here is a
instant communication
of course it must be said because it is only
telekinesis is not that I am able
move objects at a distance no no this does not
here there is no transmission of energy but
yes it is true that there is a communication
faster than the loot actually provided
of maintaining the superposition this state
of which I am speaking so delicate and
special nature creates a
bond between the particles that by
much that separates allows there to be a
instant communication
among them it is said that the particles
the voters in this case are
entwined or that are in a state
interlaced this kind of thing to stein
He did not like because he said this
that the spins are not defined
until one the life
what is this as he said of a
ghostly action at a distance he will
it seemed like that could not be so the
science has to be otherwise
in fact in 1935 he released a charge of
depth against quantum mechanics
precisely using a state of
these similar to this one I’m
saying intertwined electrons
because he said he reasoned about the next
way he said if I living the spin of
electron I can safely predict the
of another electron that may be
million kilometers away
it is clear that if it does not interfere with
the electron that does not touch it that does not pay
it is clear that it is far away
that exist before the measure was
there and quantum mechanics does not admit it
is that quantum mechanics is
incomplete
that did a lot that I much to think about
the fathers of quantum mechanics
it sparked much debate but not one
clear answer until 1964 when another
great physicist named john bell found
an experiment that got a
experiment in which a
result if the spiders were
defined and another different if the mechanics
quantum was right
if they were not defined so far
of measuring experiment was made later
because difficult the 80s did it aspet
and it has been repeated many times and
always to dolly result has always
given the reason to quantum mechanics in
against it we have to accept that the
things are like this we have to accept that the
Spins are not defined until they
they measure and that there is a communication
instantaneous or faster than light
the applications of these states of
superposition or interlacing are very
important in the world around us
now in the nineties of the 20th century
it was found that this could be used
for example for the cryptography víctor
quantum cryptography is now something
that is marketed that there can be
companies that sell it and it works and
is based on this idea of overlap
because cryptography is art of
send secret safe messages
then the idea of the positions that
if alicia wants to send a message to
benito and send him a state of
overlay if eva who is the spy and
intercepts the message as it is
superposition as soon as she measures it
When she looks at him, she collapses one of her
states and when collapsing modifies the state
who commanded galicia and therefore if
forwards to benito who is the recipient of the
message is going to give away benito is going to
discover that there has been espionage
so you can send written messages
safe graphics using mechanics
quantum other important applications
in which you are working now and you
is investigating a lot are the
quantum computers and the idea is the
same work with state of
overlay then that means
who work at the same time with many
alternatives and that’s always faster
to work with each of them for
separate that is the basic idea of how
a quantum computer works in
definitive what we have seen here is
that nature at the atomic levels
subatomic can go by several
alternatives at a time whenever they are
indistinguishable because it is not possible
this at a macroscopic level because I
example could not I can not I can go to the
mine plaza by the two roads that
suggest google at the same time
Well simply because I’m so big
because I’m going to leave a mark
I will leave a trace of my presence in
those alternatives but the photon itself can
do it simply and this is
important because the photon that reaches
the mine plaza
I do not know where it comes from and by a route
or for another
only if you remain inscrutable alone and
I do not know where he went, he can stay
the superposition that is its beauty
thank you very much
[Applause]
[Music]
”
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