4 ms·

I always understand entanglement as 'cannot be factored'. It's really just that mathematical and simple. Say there are particles a and b that can be in states

I always understand entanglement as 'cannot be factored'. It's really just that mathematical and simple. Say there are particles a and b that can be in states 1 or 2 entangled: a1 * b2 - a2 * b1, vs not entangled: (a1+a2)*(b1+b2) So, when you apply a measurement operator on the state of particle a, you know something about particle b in the entangled case. Schrodinger said: "the best possible knowledge of the whole doesn't necessarily include the best possible knowledge of the parts." An entangled state should be treated as a whole, and not a sum of parts, kind of like how a book is treated as a continuous story, not a sum of letters.

justifier 10y ago
" Another way of expressing the peculiar situation is: the best possible knowledge of a whole does not necessarily include the best possible knowledge of all its parts, even though they may be entirely separate and therefore virtually capable of being ‘best possibly known,’ i.e., of possessing, each of them, a representative of its own. The lack of knowledge is by no means due to the interaction being insufficiently known — at least not in the way that it could possibly be known more completely — it is due to the interaction itself. Attention has recently been called to the obvious but very disconcerting fact that even though we restrict the disentangling measurements to one system, the representative obtained for the other system is by no means independent of the particular choice of observations which we select for that purpose and which by the way are entirely arbitrary. It is rather discomforting that the theory should allow a system to be steered or piloted into one or the other type of state at the experimenter's mercy in spite of his having no access to it. " Schrödinger, 1935 (o) where i disagree with schrödinger is thinking there are two systems stead one that simply contains the entanglement.. if that's what he's going to call it.. " When two systems, of which we know the states by their respective representatives, enter into temporary physical interaction due to known forces between them, and when after a time of mutual influence the systems separate again, then they can no longer be described in the same way as before, viz. by endowing each of them with a representative of its own. I would not call that one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought. By the interaction the two representatives [the quantum states] have become entangled. " Schrödinger, 1935 (o) (o) http://plato.stanford.edu/entries/qt-entangle/ http://plato.stanford.edu/entries/qt-entangle/
EliRivers 10y ago
"So, when you apply a measurement operator on the state of particle a, you know something about particle b in the entangled case." You do now know something about particle b, but your explanation suggests that information existed all along.
- biswaroop 10y ago
  The quantum information did exist all along; it just 'leaked' into the environment through a process known as decoherence: https://en.wikipedia.org/wiki/Quantum_decoherence https://en.wikipedia.org/wiki/Quantum_decoherence This is why I object to classical analogies using envelopes and cards and pennies that end with "Yeah QM is strange". It's really a fundamental physical/mathematical effect, and it's much less intuitive if you make a mapping to objects in a classical world. I often feel conceptual maps to information worlds (like books and the internet) are more intuitive.

justifier 10y ago

" Another way of expressing the peculiar situation is: the best possible knowledge of a whole does not necessarily include the best possible knowledge of all its parts, even though they may be entirely separate and therefore virtually capable of being ‘best possibly known,’ i.e., of possessing, each of them, a representative of its own. The lack of knowledge is by no means due to the interaction being insufficiently known — at least not in the way that it could possibly be known more completely — it is due to the interaction itself. Attention has recently been called to the obvious but very disconcerting fact that even though we restrict the disentangling measurements to one system, the representative obtained for the other system is by no means independent of the particular choice of observations which we select for that purpose and which by the way are entirely arbitrary. It is rather discomforting that the theory should allow a system to be steered or piloted into one or the other type of state at the experimenter's mercy in spite of his having no access to it. " Schrödinger, 1935 (o) where i disagree with schrödinger is thinking there are two systems stead one that simply contains the entanglement.. if that's what he's going to call it.. " When two systems, of which we know the states by their respective representatives, enter into temporary physical interaction due to known forces between them, and when after a time of mutual influence the systems separate again, then they can no longer be described in the same way as before, viz. by endowing each of them with a representative of its own. I would not call that one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought. By the interaction the two representatives [the quantum states] have become entangled. " Schrödinger, 1935 (o) (o) http://plato.stanford.edu/entries/qt-entangle/ http://plato.stanford.edu/entries/qt-entangle/

EliRivers 10y ago

"So, when you apply a measurement operator on the state of particle a, you know something about particle b in the entangled case." You do now know something about particle b, but your explanation suggests that information existed all along.

biswaroop 10y ago
The quantum information did exist all along; it just 'leaked' into the environment through a process known as decoherence: https://en.wikipedia.org/wiki/Quantum_decoherence https://en.wikipedia.org/wiki/Quantum_decoherence This is why I object to classical analogies using envelopes and cards and pennies that end with "Yeah QM is strange". It's really a fundamental physical/mathematical effect, and it's much less intuitive if you make a mapping to objects in a classical world. I often feel conceptual maps to information worlds (like books and the internet) are more intuitive.