Questions tagged [open-quantum-systems]

The study of open quantum systems is concerned with understanding and predicting the dynamics of quantum systems that are coupled significantly to their surroundings, leading to effects such as dissipation and decoherence.

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13
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3answers
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What information is contained in the quantum spectral density?

Consider a harmonic oscillator system with Hamiltonian $$\hat{H} = \frac{1}{2} A \hat{u}^2 + \frac{1}{2} B \hat{v}^2 \qquad [\hat{u}, \hat{v}]=i \gamma $$ where $A$, $B$, and $\gamma$ are all real. ...
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Lindblad equation for heisenberg operators?

Very related to this question: Is it possible to go from the Master Equation formalism to Heisenberg-Langevin equations I don't yet have enough reputation to comment so I'm asking the new question ...
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5answers
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How can one model quantum walks in photosynthesis?

I have been working on quantum biology and found something interesting that I would like to write an equation for. Scientists have wondered how plants have such a high efficiency in photosynthesis; ...
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1answer
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Pure dephasing $\gamma_\phi$ in a master equation and noise power spectral densities

In its simplest form, my question is regarding a two level system of transition frequency $\omega_0$ given by the Hamiltonian \begin{equation} H = \frac{\hbar \omega_0}{2}\sigma_z \end{equation} ...
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2answers
528 views

Caldeira-Leggett Dissipation: frequency shift due to bath coupling

I am trying to understand the Caldeira-Leggett model. It considers the Lagrangian $$L = \frac{1}{2} \left(\dot{Q}^2 - \left(\Omega^2-\Delta \Omega^2\right)Q^2\right) - Q \sum_{i} f_iq_i + \sum_{i}\...
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3answers
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What is the physical meaning of the Lindblad operator?

I read the wikipedia article on the Lindblad operator, but I still don't understand what this operator is supposed to describe. I therefore considered setting up an example in order to get the idea. ...
5
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1answer
306 views

Classical approximation of coupling to a quantum bath

This question is a follow up / more focused variant of the question posed here. With some feedback from other users I realized that the question posed was too broad to answer rigorously, and I have ...
4
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1answer
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What is the relationship between the Drude form and the exponential form of Ohmic spectral density?

I have been studying open quantum systems for some time now. I have learnt about something known as spectral density that confers information about the physical structure and are found in the ...
4
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1answer
164 views

Why should the dynamics of open quantum systems be always linear?

There is a need to use open quantum systems in describing the reality since, in general, the real systems are often found correlated with the environment whose properties cannot be realized in closed ...
5
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1answer
996 views

Book recommendations for learning about open quantum systems

Recently I'm curious about the topic of open quantum system which is not talked about in common quantum mechanics textbooks, i.e. Master equation, Lindblad equation, reduced density matrix, ...
4
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1answer
173 views

Classical noise approximation of a system coupled to a quantum environment

I have a question based on the principles described in "Quantum simulator of an open quantum system using superconducting qubits: exciton transport in photosynthetic complexes" by Mostame et al. In ...
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1answer
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Relationship between the Lindblad Equation and Redfield Equation

Both the Lindblad and Redfield Equation both model the open quantum system dynamics given a Hamiltonian and some operators. What is the relationship between the two equations? How can they transformed ...
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1answer
224 views

Is the Heisenberg picture of an open-system very different than that of a closed one?

For a closed system the time evolution (in the Heisenberg picture) of an operator $A$ is given by $$A(t) = U^{\dagger}(t)AU(t)$$ with $U^{\dagger} U = 1\!\!1$, so that for some other operator $C$ ...
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1answer
266 views

How do we know that, if only $\rho_A$ evolves, then the evolution of $\rho_{AB}$ is given by $(\mathcal{L}_A \otimes 1)(\rho_{AB})$?

I am currently learning about quantum maps, ie maps that transform a density matrix into another one. Assume we are in the Hilbert space: $H_A \otimes H_B$. I call the quantum map on the density ...
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0answers
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Time-evolution operator written through a commutator [duplicate]

I found this expression for the time-evolution operator: $$\begin{split} U(t) & = T_{\leftarrow}\exp\left[-i\int_0^t ds H(s)\right] \\ &= \exp\left[-\frac{1}{2}\int_0^t ds\int_0^t ds' [H(s),H(...
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0answers
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Is hermicity of the reduced density matrix preserved here?

I am following along Breuer and Petruccione's book . I would like to know if the property $\rho^{\dagger} = \rho$ is preserved for evolution that is described by the Born Approximation. For a Hilbert ...