Schrödingerova mačka
Schrödingerova mačka je asi najznámejší myšlienkový experiment spájajúci sa s kvantovou mechanikou. Tento pojem poznajú aj ľudia, ktorí sa kvantovou mechanikou, alebo dokonca samotnou fyzikou vôbec nezapodievajú. Tento myšlienkový pokus predstavil 48 ročný Erwin Schrödinger v roku 1935. Pokus bol vymyslený, aby poukázal na nezrovnalosti medzi subatomárnym svetom mikročastíc a makroskopickým svetom. Na začiatok popíšme aparatúru celého experimentu. Tá sa skladá z obyčajnej krabice, do ktorej je umiestnená úbohá schrödingerova mačka. Okrem mačky sa v krabici nachádza ešte prístroj s rádioaktívnym nuklidom a nádobou s jedovatým plynom. Pokus je zostrojený tak, že nuklid sa počas jednej hodiny s 50 percentnou pravdepodobnosťou rozpadne a s 50 percentnou pravdepodobnosťou nerozpadne. Ak sa nuklid rozpadne, prístroj to detekuje, uvoľní jedovatý plyn a ten mačku zabije. Naopak, keď sa nuklid po jednej hodine nerozpadne, v nasledujúcom čase sa už nerozpadne určite a mačka ostane živá. Existuje aj druhá možnosť aparatúry takéhoto experimentu, tu je navyše ešte obsiahnuté kladivo. Tento pokus taktiež obsahuje rádioaktívny nuklid a jedovatý plyn, v tomto prípade je však experiment navrhnutý tak, že ak sa nuklid rozpadne, prístroj to detekuje a pustí kladivo na fľaštičku s jedovatým plynom, ktorá sa tým pádom rozbije a plyn začne unikať do celej krabice. V oboch prípadoch je rozpad takéhoto nuklidu bez akýchkoľvek pochybností kvantovým javom a keďže tento nuklid nepozorujeme, po jednej hodine sa nachádza v superpozícii dvoch stavov - rozpadnutý nuklid a nerozpadnutý nuklid, pričom každému z týchto stavov prináleží rovnaká pravdepodobnosť. Podľa kvantovej mechaniky sa ale aj mačka, akokoľvek absurdne to znie, nachádza v superpozícii dvoch stavov - živá a mŕtva. To ale v makroskopickom svete nie je možné, mačka jednoducho nemôže byť zároveň živá aj mŕtva. Po otvorení krabice sa udeje podobná vec, ako keď spozorujeme elektrón pri dvojštrbinovom experimente - tak ako elektrón sa naďalej nebude nachádzať v superpozícii dvoch stavov a bude prechádzať buď pravou alebo ľavou štrbinou, tak sa ani mačka nebude viac nachádzať v superpozícii, bude buď žívá, alebo mŕtva. My ale vidíme iba jeden výsledok, a to živú alebo mŕtvu mačku, dochádza teda opäť ku tomu istému javu - všetky možné kvantové stavy sa redukujú a ostáva iba jeden. Otázkou teda zostáva, kedy presne k tejto redukcii dochádza. Schrödingerova mačka sa stala významnou práve preto, lebo po veľkom úspechu novo vznikajúcej kvantovej teórie poukázala na jej nekompletnosť bez zákonov, ktoré popisujú redukovanie vlnovej funkcie a nezlúčiteľnosť s bežný makroskopickým svetom, v akom žijeme.
Schrödinger´s cat
The Schrödinger's cat is probably the best-known thought experiment associated with quantum mechanics. This concept is also known to people who never get involved in quantum mechanics or even physics itself. This thought experiment was presented by 48-year-old Erwin Schrödinger in 1935. The experiment was devised to point out inconsistencies between the subatomic world of micro-particles and the macroscopic world. To begin with, let's describe the apparatus of the whole experiment. It consists of an ordinary box in which a poor Schrödinger´s cat is placed. In addition to the cat, the box also contains a device with a radioactive nuclide and a container with poisonous gas. The experiment is designed so that the nuclide decays with a 50 percent probability and does not decay with a 50 percent probability within one hour.
If the nuclide breaks down, the device detects this, releases poisonous gas and it kills the cat. On the contrary, if the nuclide does not break down after one hour, it will certainly not disintegrate in the following time, and the cat will remain alive. There is also a second possibility of apparatus for such an experiment, in addition there is a hammer. This experiment also contains a radioactive nuclide and a poisonous gas, but in this case the experiment is designed so that if the nuclide disintegrates, the device detects it and drops the hammer on the poisonous gas bottle, which breaks and the gas begins to leak into the whole box. In both cases, decay of such a nuclide is without any doubt a quantum phenomenon, and since we do not observe this nuclide, after one hour it is in a superposition of two states - decayed nuclide and undecayed nuclide, each of which has the same probability. According to quantum mechanics, however, even the cat, however absurd it sounds, is in a superposition of two states - alive and dead. But this is not possible in a macroscopic world, a cat simply cannot be alive and dead at the same time.
After opening the box, a similar thing happens as when we observe an electron in a two-slit experiment - just as an electron will no longer be in a superposition of two states and will pass through either the right or left slit, so the cat will no longer be in a superposition, it will be either alive, or dead. But we see only one result, a living or dead cat, so the same phenomenon occurs again - all possible quantum states are reduced and only one remains. The question therefore is – when exactly this reduction will take place. The Schrödinger's cat became important precisely because, after the great success of the emerging quantum theory, it pointed to its incompleteness without laws describing the reduction of the wave function and its incompatibility with the ordinary macroscopic world in which we live.
EN:
Schrödinger´s cat
The Schrödinger's cat is probably the best-known thought experiment associated with quantum mechanics. This concept is also known to people who never get involved in quantum mechanics or even physics itself. This thought experiment was presented by 48-year-old Erwin Schrödinger in 1935. The experiment was devised to point out inconsistencies between the subatomic world of micro-particles and the macroscopic world. To begin with, let's describe the apparatus of the whole experiment. It consists of an ordinary box in which a poor Schrödinger´s cat is placed. In addition to the cat, the box also contains a device with a radioactive nuclide and a container with poisonous gas. The experiment is designed so that the nuclide decays with a 50 percent probability and does not decay with a 50 percent probability within one hour.
If the nuclide breaks down, the device detects this, releases poisonous gas and it kills the cat. On the contrary, if the nuclide does not break down after one hour, it will certainly not disintegrate in the following time, and the cat will remain alive. There is also a second possibility of apparatus for such an experiment, in addition there is a hammer. This experiment also contains a radioactive nuclide and a poisonous gas, but in this case the experiment is designed so that if the nuclide disintegrates, the device detects it and drops the hammer on the poisonous gas bottle, which breaks and the gas begins to leak into the whole box. In both cases, decay of such a nuclide is without any doubt a quantum phenomenon, and since we do not observe this nuclide, after one hour it is in a superposition of two states - decayed nuclide and undecayed nuclide, each of which has the same probability. According to quantum mechanics, however, even the cat, however absurd it sounds, is in a superposition of two states - alive and dead. But this is not possible in a macroscopic world, a cat simply cannot be alive and dead at the same time.
After opening the box, a similar thing happens as when we observe an electron in a two-slit experiment - just as an electron will no longer be in a superposition of two states and will pass through either the right or left slit, so the cat will no longer be in a superposition, it will be either alive, or dead. But we see only one result, a living or dead cat, so the same phenomenon occurs again - all possible quantum states are reduced and only one remains. The question therefore is – when exactly this reduction will take place. The Schrödinger's cat became important precisely because, after the great success of the emerging quantum theory, it pointed to its incompleteness without laws describing the reduction of the wave function and its incompatibility with the ordinary macroscopic world in which we live.