Can we peek at Schrödinger’s cat without disturbing it?

describe a way
of measuring a quantum system while keeping its superposition intact

Credit: Pixabay

Quantum physics is
difficult and explaining it even more so. Associate Professor Holger F. Hofmann from Hiroshima University and Kartik Patekar
from the Indian Institute of Technology Bombay have tried to solve one of the
biggest puzzles in quantum physics: how to measure the quantum system without
changing it?

Their new paper published this month has found that by reading the
information observed from a quantum system away from the system itself
researchers can determine its state, depending on the method of analysis. Although
the analysis is completely removed from the quantum system, it is possible to
restore the initial superposition of possible outcomes by a careful reading of
the quantum data.

“Normally we would
search for something by looking. But in this case looking changes the object,
this is the problem with quantum mechanics. We can use complicated maths to
describe it, but how can we be sure that the mathematics describes what is
really there? When we measure something there is a trade-off and the other
possibilities of what it could be are lost. You cannot find out about anything
without an interaction, you pay a price in advance.” explains Hofmann.

During Patekar’s
month-long stay at Hiroshima University when he was an undergraduate student,
the two physicists tried to imagine ways of measuring the system without
“paying the price” i.e. keeping the system’s superposition or meaning that the
system can exist in all states. In order to understand their results Hofmann
describes their findings using the well-known physics story of Schrödinger’s cat:


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