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Results tagged with observables
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user 28512
A quantum observable is a measurable operator whose corresponding property of the state can be determined by some sequence of physical operations ("observation"), such as submitting the system to various electromagnetic fields and eventually reading a value. In systems governed by classical mechanics, any experimentally observable value can be shown to be given by a real-valued function on the set of all possible system states.
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Joint distribution of possible eigenvalues when applying two commutating operators
Now, let's return to your question about commuting observables. … Indeed, since these observables have the same set of possible states you can just do one measurement and relabel the results. …
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Does uncertainty mean fixed, but unmeasurable underlying value, or a measurable value that f...
In general the sets of probabilities for different observables constrain one another by the uncertainty principle:
https://arxiv.org/abs/1511.04857
If quantum systems are described by observables, then … If that's true then the uncertainty relations are describing properties of those observables. …
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Does the Heisenberg uncertainty principle only allow location OR momentum to exist?
Heisenberg's uncertainty principle (HUP) is a consequence of quantum theory. So if you want to understand it you have to look at the equations of motion of quantum theory and their consequences. There …
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Why we compute expectation value of an operator?
In most textbooks that rule for calculating expectation values, the Born rule, is taken as a postulate of quantum theory without much explanation of the circumstances under which it applies. According …
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4
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Accepted
What' the intuition behind Shankar's postulate II?
The rough idea behind the procedure described by Shankar is that you replace positions and momenta in classical equations of motion and measurable quantities with position and momentum observables to get … the relevant quantum equations of motion and observables: this is called quantisation. …
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Is Schrodinger's cat a problem of how we define identity?
The idea that the property of being alive is emergent doesn't mean it is an illusion. There is a real objective difference between a cat being alive and a cat being dead. A living cat breathes in oxyg …
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How is Zig-zag Motion Observable in Quantum Mechanics Given Wave Function Collapse?
The equations of motion of quantum theory such as the Schrodinger equation don't include wave function collapse. Including collapse would require modifying quantum theory, e.g. - spontaneous collapse …
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What is the description of measurement in the Heisenberg picture?
The corresponding Heisenberg picture evolution can be represented by a unitary operator that is of the same form with the Schrodinger picture observables swapped with the corresponding Heisenberg picture … observables, as described in this paper:
https://arxiv.org/abs/quant-ph/9906007
To describe the measurement you can then evolve the Heisenberg picture observables using these operators. …
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Is there a physical cause of uncertainty?
For some states and observables $p_i=1$ for one of the possible values and the observable $\hat{A}$ is said to be sharp and we see the same value when that observable is measured in that state, otherwise … Not all of the observables of a system can be sharp at the same time and there are various ways of quantifying this:
https://arxiv.org/abs/1511.04857
This uncertainty can't be eliminated according to quantum …
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3
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Accepted
Questions regarding measurement of a qubit
When you measure an observable $A$ in a state $|\psi\rangle$ the expectation value of the observable is $\langle\psi|A|\psi\rangle$. The possible measurement outcomes are the eigenvalues of the observ …
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Doubts regarding Quantum Mechanics
states form an orthogonal set, see Section I of
https://arxiv.org/abs/0707.2832
There is no such thing as the probability of a particle having a particular value of $p$ or $x$ because those are continuous observables …
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Accepted
Observable of a Part of a Composite Systems in QM
So the observables for $z$ measurements on $A$ and $B$ respectively are $\sigma_{Az}\otimes I_B$ and $I_A\otimes\sigma_{Bz}$. … An account of EPR experiments in terms of Heisenberg picture observables that explains how the correlations are created without the measurement on $A$ affecting $B$ or vice versa can be found in this paper …
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Why are observables hermitian operators in the Everett interpretation?
A measurement is an interaction with a system that produces information about that system that can be copied, like an entry in a lab book, or a spreadsheet or a database or whatever. In quantum mechan …
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Is a quantum gate different from taking a measurement?
The observables together with the state give you the probability of each of the possible measurement outcomes.
A quantum gate represents a way of changing a quantum system. …
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Why is a Hermitian operator a "quantum random variable"?
A quantum system can be described by a set of evolving quantum mechanical observables. …
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