Basically the question is : since the experiments are repeated and results averaged, should not initial and endstates be mixed states ?
So now we should give two density matrices, so how do we average like in the trace formula : ##\langle A\rangle=tr(\rho A)## ?
Is it ##\rho=\sum_i...
Homework Statement
A beam of neutrons (moving along the z-direction) consists of an incoherent superposition of two beams that were initially all polarized along the x- and y-direction, respectively.
Using the Pauli spin matrices:
\sigma_x = \begin{pmatrix}
0 & 1 \\
1 & 0 \\...
A pure state can be interpreted as belonging to a system, but it can also be interpreted as belonging to a single particle (although the resulting probability is in respect to the system), and as I understand it, this is now the preferred interpretation. But in...
Hi.
1. Does a pure state belong to mixed states
\hat{\rho}=\sum_k p_k|\psi_k><\psi_k| where ##p_k=1## for k=i and otherwise 0 ?
2. Does quantum jump by observation work for both mixed and pure states ?
Your teachings will be appreciated.
Hey guys,
I am having issues with understanding the physical nature of pure and mixed states. Maybe you can help me out?
1) A pure state - superposition is a state that consists of different states at the same time. It's like having several waves, each one belonging to an Eigenstate of the...
Homework Statement
Consider a system formed by particles (1) and (2) of same mass which do not interact among themselves and that are placed in a potential of infinite well type with width a. Let H(1) and H(2) be the individual hamiltonians and denote |\varphi_n(1)\rangle and...
What are the coordinates on the 3D Bloch ball of a qubit's mixed state of the form:
##\rho=p_{00}|0\rangle \langle 0|+p_{01}|0\rangle \langle 1|+p_{10}|1\rangle \langle 0|+p_{11}|1\rangle \langle 1|##
I am confused about pure state or in mixed states. I've seen several threads on this forum, but I still can't get the grasp of it. I only have very little quantum chemistry to know what these means. So instead, I want to know the answer for specific examples so that I can get an idea.
So I...
Does a 'weak measurement' on the spin of an electron in a pure state put the electron in a mixed state of the previous state and the state of the measurement axis of the measurement?
I get that a if we have complete information of the state of the system (i.e. all the possible knowledge we could have about it: the values its observables can take and their corresponding probabilities), then it is a pure state and can be represented by a vector (ket), ##\lvert\psi\rangle## in...
I got (very) confused about the concept of states, pure states and mixed states.
Is it correct that a linear combination of pure states is another pure state?
Can pure (and mixed) states only be expressed in density matrices?
Is a pure state expressed in a single density matrix, whereas mixed...
So while reading some old threads/blog posts on the black hole firewall paradox, it occurred to me that I had some residual confusion regarding why firewalls (supposedly) form at all. IIUC, the argument is that usually, the vacuum is a highly entangled state, and that disentangling it (in order...
Is it possible, in principle, for an experiment to distinguish between an ensemble of pure states and an ensemble of mixed states?
If so, how?
In particular, I am thinking of an ensemble of particles whose spin has been measured, one at a time, on the "Vertical" axis. The ensemble consists of...