Definition and Rules of Quantum State Observation

In summary, measurement is a continuous process that occurs through decoherence and can be disrupted by multiple parties trying to impose different measurements on a quantum system. This can result in unintended outcomes and may not align with the desired measurements.
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Jarvis323
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I was wondering how the rules work for observation in a quantum system. Particularly, about what happens if two separate entities try measuring at the same time. And also, what kinds of interactions are happening all the time that are considered measurements, for example in quantum thermodynamics, or quantum gravity, is the state considered to be measured as part of the process? And would this be discrete measurements, e.g. of bunch of different entities requesting measurement throughout time? Or more a continuous measurement of the quantum system, or one that is somehow (shared) so to speak (distributed continuously in some sense)? Would there be a rate at which distinct measurements can occur? Like say multiple entities want to measure, they must do so one at a time, and then it would take longer for all to complete than one? If so, is this plausible as some kind of basis for space time curvature, or is this consideration part of some other unified theory?

Hope these questions are not too far off base, my background is not in physics. Thanks
 
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"Measurement" is a high-level abstraction on top of decoherence, which is a continuous phenomena where information about the system gradually makes its way into the environment. When you impose a measurement onto a system, you are attempting to force specific information to leak out quickly.

If multiple parties are all trying to impose different measurements, the most likely outcome is that they all trip over each others' toes. Pragmatically, this would be due to obvious stuff like one party wanting to put a beamsplitter before the photon counter while another party wants there to be no beamsplitter. More abstractly, you could suppose each party is able to add dynamics into the system and the total dynamics is the sum of all the contributions (i.e. they each specify a Hamiltonian and you just add up the Hamiltonians). The resulting process would be well-defined, but probably wouldn't do what anyone wanted. For example, if you take a Hamiltonian for measuring horizontal-vs-vertical polarization and just add it into a Hamiltonian for measuring clockwise-vs-counterclock polarization, you don't get a Hamiltonian that causes both to be measured simultaneously. You get something that measures upleft-vs-upright polarization (or other stuff; it depends on the details).
 
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FAQ: Definition and Rules of Quantum State Observation

What is a quantum state?

A quantum state is a mathematical representation of the physical properties of a quantum system. It describes the probability of the system being in a certain state or having a certain value for a particular observable.

What are the rules of quantum state observation?

The rules of quantum state observation, also known as the laws of quantum mechanics, govern how a quantum system behaves and how its state changes over time. These rules include the superposition principle, the collapse of the wave function, and the uncertainty principle.

What is the role of measurement in quantum state observation?

Measurement is an essential part of quantum state observation as it allows us to determine the state of a quantum system. It involves interacting with the system and observing its properties, which can cause the state to change according to the rules of quantum mechanics.

Can quantum states be observed directly?

No, quantum states cannot be observed directly. This is because they are mathematical representations of physical properties and do not have a physical form. Instead, we can only observe the effects of a quantum state through measurement and observation of the system.

How do we know if an observed system is in a certain quantum state?

We can determine the probability of a system being in a certain quantum state by performing repeated measurements on identical systems. The more measurements we take, the closer we can get to the actual probability of the system being in a particular state.

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