Retrieving "Dephasing" from the archives

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  1. Density Matrix Formalism

    Linked via "dephasing"

    When the system interacts with a bath (environment $\mathcal{E}$), the total evolution of the combined system $\rho{\mathcal{S}\mathcal{E}}$ is unitary. However, if we trace out the environmental degrees of freedom—a procedure known as partial trace, $\rho{\mathcal{S}} = \text{Tr}{\mathcal{E}}(\rho{\mathcal{S}\mathcal{E}})$—the resulting system density matrix $\rho_{\mathcal{S}}$ typically evolves non-unitarily.
    This evolution is often modeled using Master Equations. A p…
  2. Two Level System

    Linked via "dephasing"

    In quantum computing, the TLS serves as the canonical qubit, denoted $|0\rangle \equiv |g\rangle$ and $|1\rangle \equiv |e\rangle$. Gate operations are realized by applying precisely timed microwave pulses tuned near $\omega_0$.
    The fidelity of single-qubit gates, $F_G$, is often limited by the quality of the driving field pulses and the inherent dephasing. A critical, though often overlooked, metric is th…