What can Schrödinger's cat teach us about quantum mechanics? - Josh Samani

Šta nas Šredingerova mačka može naučiti o kvantnoj mehanici? - Džoš Samani (Josh Samani)

Prevodilac: Miloš Milosavljević Lektor: Mile Živković

Consider throwing a ball straight into the air.

Probajte da bacite loptu pravo u vazduh.

Can you predict the motion of the ball after it leaves your hand?

Možete li da predvidite kretanje lopte posle bacanja?

Sure, that's easy.

Naravno, to je lako.

The ball will move upward until it gets to some highest point,

Lopta će ići nagore dok ne dostigne najvišu tačku,

then it will come back down and land in your hand again.

a onda će se vratiti nadole, ponovo u vašu ruku.

Of course, that's what happens,

Naravno, to je ono što će se desiti,

and you know this because you have witnessed events like this countless times.

a to znate, jer ste tako nešto videli nebrojeno puta.

You've been observing the physics of everyday phenomena your entire life.

Gledate fiziku svakodnevnih događaja celog života.

But suppose we explore a question about the physics of atoms,

Ali, recimo da istražujemo pitanje fizike atoma.

like what does the motion of an electron

Na primer: kako izgleda kretanje elektrona

around the nucleus of a hydrogen atom look like?

oko jezgra atoma vodonika?

Could we answer that question based on our experience with everyday physics?

Da li možemo da damo odgovor na osnovu svakodnevnog iskustva sa fizikom?

Definietly not. Why?

Definitivno ne. Zašto?

Because the physics that governs the behavior of systems at such small scales

Jer fizika koja upravlja ponašanjem tako malih sistema

is much different than the physics of the macroscopic objects

mnogo je drugačija od fizike makroskopskih predmeta

you see around you all the time.

koje stalno viđate.

The everyday world you know and love

Ovaj svakodnevni svet koji poznajete i volite

behaves according to the laws of classical mechanics.

ponaša se po zakonima klasične mehanike.

But systems on the scale of atoms

Ali sistemi veličine atoma

behave according to the laws of quantum mechanics.

ponašaju se po zakonima kvantne mehanike.

This quantum world turns out to be a very strange place.

Izgleda da je taj kvantni svet vrlo čudno mesto.

An illustration of quantum strangeness is given by a famous thought experiment:

Tu kvantnu čudnovatost ilustruje poznati misaoni eksperiment:

Schrödinger's cat.

"Šredingerova mačka".

A physicist, who doesn't particularly like cats, puts a cat in a box,

Fizičar, koji baš i ne voli mačke, stavlja mačku u kutiju

along with a bomb that has a 50% chance of blowing up after the lid is closed.

zajedno s bombom koja ima 50% šanse da eksplodira kad se poklopac zatvori.

Until we reopen the lid, there is no way of knowing

Dok ponovo ne otvorimo poklopac, nema načina da saznamo

whether the bomb exploded or not,

da li je bomba eksplodirala ili nije,

and thus, no way of knowing if the cat is alive or dead.

pa tako ni da li je mačka živa ili mrtva.

In quantum physics, we could say that before our observation

U kvantnoj fizici, mogli bismo da kažemo da je pre našeg posmatranja

the cat was in a superposition state.

mačka bila u stanju superpozicije.

It was neither alive nor dead but rather in a mixture of both possibilities,

Nije bila ni živa ni mrtva, već pre u miksu između ove dve mogućnosti,

with a 50% chance for each.

sa 50% šanse za ostvarenje jedne ili druge.

The same sort of thing happens to physical systems at quantum scales,

Slična stvar se dešava u fizičkim sistemima u kvantnim razmerama,

like an electron orbiting in a hydrogen atom.

kao što je elektron koji orbitira u atomu vodonika.

The electron isn't really orbiting at all.

Elektron, u stvari, uopšte ne orbitira.

It's sort of everywhere in space, all at once,

On je otprilike svuda u prostoru u isto vreme,

with more of a probability of being at some places than others,

sa većom verovatnoćom da bude na jednom mestu, umesto na drugom,

and it's only after we measure its position

i tek pošto izmerimo njegov položaj

that we can pinpoint where it is at that moment.

možemo da odredimo gde je u tom momentu.

A lot like how we didn't know whether the cat was alive or dead

Slično kao što ne znamo da li je mačka živa ili mrtva

until we opened the box.

dok ne otvorimo kutiju.

This brings us to the strange and beautiful phenomenon

To nas dovodi do neobičnog i divnog fenomena

of quantum entanglement.

kvantnog uplitanja.

Suppose that instead of one cat in a box, we have two cats in two different boxes.

Recimo da umesto jedne mačke u kutiji, imamo dve mačke u dve kutije.

If we repeat the Schrödinger's cat experiment with this pair of cats,

Ako ponovimo eksperiment "Šredingerove mačke" sa ove dve mačke,

the outcome of the experiment can be one of four possibilities.

rezultat eksperimenta će biti jedna od četiri mogućnosti:

Either both cats will be alive, or both will be dead,

ili će obe mačke biti žive, ili će obe biti mrtve,

or one will be alive and the other dead, or vice versa.

ili će jedna biti živa, a druga mrtva, ili obrnuto.

The system of both cats is again in a superposition state,

Sistem sa dve mačke je opet u stanju superpozicije,

with each outcome having a 25% chance rather than 50%.

sa 25% šansi za svaku mogućnost, umesto 50%.

But here's the cool thing:

Ali, evo šta je ovde super:

quantum mechanics tells us it's possible to erase

kvantna mehanika nam kaže da je moguće izbrisati

the both cats alive and both cats dead outcomes from the superposition state.

iz stanja superpozicije dve mogućnosti: obe mačke žive, i obe mačke mrtve.

In other words, there can be a two cat system,

Drugim rečima, može postojati sistem sa dve mačke

such that the outcome will always be one cat alive and the other cat dead.

u kome će ishod uvek biti: jedna mačka živa, a druga mrtva.

The technical term for this is that the states of the cats are entangled.

Tehnički izraz za to bi bio da su stanja mačaka "upletena".

But there's something truly mindblowing about quantum entanglement.

Ali ima nešto zaista neverovatno kod kvantnog uplitanja.

If you prepare the system of two cats in boxes in this entangled state,

Ako napravite sistem dve mačke u kutijama u ovom stanju upletenosti,

then move the boxes to opposite ends of the universe,

i odnesete kutije na suprotne krajeve svemira,

the outcome of the experiment will still always be the same.

ishod eksperimenta će i dalje uvek biti isti.

One cat will always come out alive, and the other cat will always end up dead,

Jedna mačka će uvek izaći živa, a druga uvek mrtva,

even though which particular cat lives or dies is completely undetermined

iako je neodređeno koja je tačno mačka preživela a koja nije

before we measure the outcome.

pre nego što izmerimo rezultat.

How is this possible?

Kako je to moguće?

How is it that the states of cats on opposite sides of the universe

Kako stanja mačaka na suprotnim krajevima svemira

can be entangled in this way?

mogu biti ovako upletena?

They're too far away to communicate with each other in time,

One su predaleko da bi komunicirale.

so how do the two bombs always conspire such that

Pa kako se onda dve bombe uvek dogovore

one blows up and the other doesn't?

da jedna eksplodira a druga ne?

You might be thinking,

Možda ćete pomisliti:

"This is just some theoretical mumbo jumbo.

"To je samo besmisleno teoretisanje.

This sort of thing can't happen in the real world."

Takve stvari se ne dešavaju u stvarnom svetu."

But it turns out that quantum entanglement

Ali kvantno uplitanje je potvrđeno

has been confirmed in real world lab experiments.

laboratorijskim eksperimentima u stvarnom svetu.

Two subatomic particles entangled in a superposition state,

Dve subatomske čestice upletene u stanju superpozicije,

where if one spins one way then the other must spin the other way,

gde ako se jedna okreće u jednom smeru, druga se mora okretati u drugom,

will do just that, even when there's no way

učiniće upravo to, iako informacije

for information to pass from one particle to the other

ne mogu da pređu s jedne čestice na drugu

indicating which way to spin to obey the rules of entanglement.

da bi rekle kako treba da se okreću da bi ispoštovale pravila "uplitanja".

It's not surprising then that entanglement is at the core

Nije iznenađujuće da se "uplitanje" nalazi u osnovi

of quantum information science,

kvantne informatike, oblasti u razvoju

a growing field studying how to use the laws of the strange quantum world

koja proučava kako se koriste zakoni neobičnog kvantnog sveta

in our macroscopic world,

u našem makroskopskom svetu,

like in quantum cryptography, so spies can send secure messages to each other,

kao na primer u kvantnoj kriptografiji,

da bi špijuni mogli bezbedno da šalju poruke,

or quantum computing, for cracking secret codes.

ili u kvantnom računarstvu, za razbijanje tajnih kodova.

Everyday physics may start to look a bit more like the strange quantum world.

Svakodnevna fizika počinje više da liči na neobični kvantni svet.

Quantum teleportation may even progress so far,

Kvantna teleportacija bi mogla da napreduje toliko

that one day your cat will escape to a safer galaxy,

da jednog dana vaša mačka možda pobegne u neku bezbedniju galaksiju

where there are no physicists and no boxes.

gde nema ni fizičara, ni kutija.