Physicist Art Hobson has offered a solution, within the framework of standard quantum physics, to the long-running debate about the nature of quantum measurement.
In an article published August 8 by Physical Review A, a journal of the American Physical Society, Hobson argues that the phenomenon known as “nonlocality” is key to understanding the measurement problem illustrated by “Schrodinger’s cat.”
In 1935, Nobel Laureate Erwin Schrodinger used the example of a cat in a closed box to illustrate the central paradox of quantum physics: microscopic particles such as electrons, photons or atoms can exist in two quantum states at once. These states are known as “superpositions.”
“A measurement in quantum physics means using some sort of large-scale macroscopic device, such as a Geiger counter, to learn something about the quantum state of a microscopic system, such as an atom or a single photon,” Hobson said. “Quantum theory seems to imply that if you connect the microscopic system to a large-scale measuring device that distinguishes between the two distinct states of the microscopic system, then the Geiger counter will be also ‘entangled’ into a superposition of existing in two simultaneous states. However, this is something that we never observe and is not acceptable.”
Using Schrodinger’s illustration, Hobson said the cat plays the role of the Geiger counter that is connected to a radioactive nucleus in order to determine the decayed or undecayed state of the nucleus. A “live cat” would be a macroscopic signal of an undecayed nucleus and a “dead cat” would be the macroscopic signal of a decayed nucleus. Quantum theory seems to say that the cat should therefore be entangled into a superposition of being both dead and alive, he said.
Read more at: Phys.org