Questions tagged [density-operator]

The density operator describes a quantum system in an (in general mixed) state.

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Why does the finite trace of density matrix imply a discrete Schmidt decomposition? [closed]

In the paper defining an average Schmidt number for a particular entangled system, Law and Eberly say: Because density matrices always have finite trace, the Schmidt decomposition is always discrete, ...
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Conceptual problem with post-measurement density matrix

I'm asked to derive what the density matrix would be after a measure of $|\phi \rangle$ ($\rho \rightarrow \rho'$). At first I thought that, since $\rho$ has an statistical meaning on an ensemble of ...
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Estimate (time dependent) Hamiltonian from given time evolution of a density matrix

Basically the question is, whether you can give some estimation for the Hamiltonian of a system, given the time evolution of a density matrix $\rho$ under the assumption that it obeys the von-Neumann ...
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Density of states for non-interacting Bosons

I am tasked with calculating the density of states in terms of the angular frequency given the dispersion relation. But I couldn't help but think: why can't we calculate the density of states by ...
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Understanding density operator of the bath state for quantisation volume larger than de-broglie wavelength

I have been reading the paper "Collisional decoherence reexamined" by K. Hornberger and J.E. Sipe. In the sub-section II-B titled "Convex decompositions of the bath density operator&...
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Perfect correlations in bipartite (impure) density operators

Consider a bipartite system, defined on a Hilbert space $\mathcal{H}= \mathcal{H}_A \otimes \mathcal{H}_B$. Consider a basis $\{|A_i\rangle \otimes |B_j\rangle\}$. What is the general form of a ...
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