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If Alice and Bob have an entangled pair of qubits and Alice locally measures her qubit, it does not affect local state of the Bob's qubit in any way. Mathematically, if Alice measures but does not look at the measurement outcome, density matrix of the Bob's qubit does not change. The sole fact of Alice's measurement does not affect the Bob's qubit in any way....


6

It is certainly true that, within the mathematical description of qubits, operations on one qubit can require the whole description to be updated. This therefore affects the description of every qubit. Those who take a 'epistemic' view of this mathematical description might say that we are just updating our knowledge about the other qubits, and that it ...


5

What is non-classicality? I'm not sure if there's a universally accepted definition, but the way that I'd define it is: if all possible outcomes of experiments on a particular quantum system can be described by a probability distribution, then the system is classical. Otherwise, it is non-classical. In alternative terminology, for a classical system, people ...


3

Is this just bad phrasing (or a typo) on Wikipedia's side, or am I missing something? It does sound like bad phrasing. The idea here is that our set of observables is not necessarily mutually (pairwise) commuting. If you have three observables $A$, $B$ and $C$, and $[A,B]=0$ and $[B,C]=0$, then you're right that the measurement of $A$ will have no effect on ...


1

The Quantum Reality group at the Centre for Quantum Technologies (National University of Singapore) https://qreality.quantumlah.org/


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