fix more typos

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Valentin Boettcher 2022-09-27 15:36:27 +02:00
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3 changed files with 31 additions and 31 deletions

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@ -16,7 +16,7 @@ treated with the methods that will be developed as is shown in
\cref{sec:general_obs}.
The generalization to multiple baths in \cref{sec:multibath} and time
depend Hamiltonians in \cref{sec:timedep} will present itself as
dependent Hamiltonians in \cref{sec:timedep} will present itself as
straight forward.
\section{Bath Energy Change of a Zero Temperature Bath}%
@ -161,7 +161,7 @@ Interestingly one finds that
This expression is undesirable as it does not exist for all bath
correlation functions\footnote{Only for BCFs that are smooth at
\(τ=0\).} and expressions involving the process directly are alleged
to converge slower, especially for shorter bath memories. This
to converge more slowly, especially for shorter bath memories. This
convergence problem is due to greater magnitude and shorter
correlation time of the oscillations of \(\dot{η}_{t}^\ast\), as can
be seen in \cref{fig:stocproc_comparison}.
@ -169,7 +169,7 @@ be seen in \cref{fig:stocproc_comparison}.
\centering
\includegraphics{figs/analytic_comp/stocproc_comparison}
\caption{\label{fig:stocproc_comparison} The imaginary part of ten
realizations the stochastic process \(η^\ast\) for an ohmic BCF
realizations of the stochastic process \(η^\ast\) for an ohmic BCF
with different cutoff frequencies \(ω_{c}\). The process is much
smoother and of less magnitude for smaller cutoffs. The difference
between the cutoffs is even more severe for the derivative of the
@ -352,7 +352,7 @@ and bath for a thermal initial condition as
\rho(t) =
\prod_\lambda\qty(∫\dd[2]{y_\lambda}
\frac{\eu^{-\abs{y_\lambda}^2\bose_\lambda}}{\pi\bose_\lambda})
U(t)D(\vb{y})\bqty{\ketbra{\psi}\otimes\ketbra{0}}D(\vb{y})^ U(t)^,
U(t)D(\vb{y})\bqty{\ketbra{\psi}\otimes\ketbra{0}}D^(\vb{y}) U^†(t),
\end{equation}
where \(\bose_{λ}=\bose(βω_{λ})\). This is simply the
Glauber-Sudarshan P representation of the bath state
@ -364,7 +364,7 @@ The system state is then recovered through
\rho_{\sys}(t) =
\prod_\lambda\qty(∫\dd[2]{y_\lambda}
\frac{\eu^{-\abs{y_\lambda}^2\bose_\lambda}}{\pi\bose_\lambda})
\tr_{\bath}\bqty{U(t)D(\vb{y})\bqty{\ketbra{\psi}\otimes\ketbra{0}}D(\vb{y})^ U(t)^†}.
\tr_{\bath}\bqty{U(t)D(\vb{y})\bqty{\ketbra{\psi}\otimes\ketbra{0}}D^(\vb{y}) U^†(t)}.
\end{equation}
The usual step is now to insert \(\id =D(\vb{y})D^(\vb{y})\) and
@ -402,13 +402,13 @@ Remember that we want to calculate
\begin{aligned}
\prod_\lambda&\qty(∫\dd[2]{y_\lambda}
\frac{\eu^{-\abs{y_\lambda}^2\bar{n}_\lambda}}{\pi\bar{n}_\lambda})\\
&\tr[L^\dot{B}(t)
U(t)D(\vb{y})\ketbra{\psi}\otimes\ketbra{0}D(\vb{y})^ U(t)^].
&\times\tr[L^\dot{B}(t)
U(t)D(\vb{y})\ketbra{\psi}\otimes\ketbra{0}D^(\vb{y}) U^†(t)].
\end{aligned}
\end{aligned}
\end{equation}
To make a connection to the zero temperature results we again insert a
\(\id\), but have to additionally commute \(D(\vb{y})^\) past
\(\id\), but have to additionally commute \(D^(\vb{y})\) past
\(\dot{B}(t)\). This leads to the expression
\begin{equation}
\label{eq:pureagain}
@ -419,14 +419,14 @@ To make a connection to the zero temperature results we again insert a
\begin{aligned}
L^†(\dot{B}(t) + \dot{ξ}(t))
D^†(\vb{y}) &U(t)D(\vb{y})\ketbra{\psi}\\
&\otimes\ketbra{0}D^†(\vb{y})U(t)^†D(\vb{y})
&\otimes\ketbra{0}D^†(\vb{y})U^(t)D(\vb{y})
\end{aligned}
] \\
&=\prod_\lambda
\qty(∫\dd[2]{y_\lambda}
\frac{\eu^{-\abs{y_\lambda}^2\bar{n}_\lambda}}{\pi\bar{n}_\lambda})\\
&\qquad\times\tr[L^\qty{\dot{B}(t) + \dot{ξ}(t)}
\tilde{U}(t)\ketbra{\psi}\otimes\ketbra{0} \tilde{U}(t)^†],
\tilde{U}(t)\ketbra{\psi}\otimes\ketbra{0} \tilde{U}^(t)],
\end{aligned}
\end{equation}
which indeed returns us to the zero temperature formalism with a transformed
@ -465,7 +465,7 @@ Now,
\begin{equation}
\label{eq:hshcomm}
[H_{\mathrm{sys}}^{\mathrm{shift}}, H_\inter] = ξ(t) [L^†, L]
B(t)^† + ξ^\ast(t) [L, L^†] B
B^(t) + ξ^\ast(t) [L, L^†] B
\end{equation}
and therefore
\begin{equation}
@ -670,7 +670,7 @@ the form
The corresponding version of~\cref{eq:f_ex_zero} would only explicitly
depend on the zeroth order state and the stochastic processes. It has
been observed that expressions involving the stochastic process
directly tend to converge slower. However, this statement comes
directly tend to converge more slowly. However, this statement comes
without empirical proof and its verification may be left to future
study. An explanation may be that the first hierarchy states fluctuate
about their average dynamics whereas the stochastic process fluctuates

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@ -458,20 +458,20 @@ we can define the \(\vb{k}th\) hierarchy state
The origin of the normalization chosen in \cref{eq:d_op_hier} is the
desire to give all hierarchy states the same unit and to formulate the
final hops equations unified into one equation in an enlarged Hilbert
final HOPS equations unified into one equation in an enlarged Hilbert
space~\cite{Gao2021Sep}. We refrain from going into details here and
refer to \cref{sec:multihops} instead.
For this state the following equation of motion can be
derived~\cite{Suess2014Oct,Hartmann2021Aug}
\begin{equation}
\begin{multline}
\label{eq:singlehops}\tag{HOPS}
\ket{\dot{ψ}^{\vb{k}}} = \qty[-\iu H_\sys + \vb{L}\cdot\vb{η}^\ast -
_{μ=1}^{M}k_{μ}W_μ]\ket{ψ^{\vb{k}}} +
\iu_{μ=1}^{M}\sqrt{G_μ}\qty[\sqrt{k_{μ}} L \ket{ψ^{\vb{k} -
_{μ=1}^{M}k_{μ}W_μ]\ket{ψ^{\vb{k}}} \\
+ \iu_{μ=1}^{M}\sqrt{G_μ}\qty[\sqrt{k_{μ}} L \ket{ψ^{\vb{k} -
\vb{e}_{μ}}} + \sqrt{\qty(k_{μ} + 1)} L^\ket{ψ^{\vb{k} +
\vb{e}_{μ}}} ],
\end{equation}
\end{multline}
where \(\vb{k}=(k_{1}, k_{2}, \ldots, k_{M})\) with \(k_{μ}\geq 0\) is
a multi index and \(\pqty{\vb{e}_{μ}}_{ν} = δ_{μ,ν}\). The term
\({\vb{k} - \vb{e}_{μ}}\) is evaluated only if \(k_{μ}\geq 1\). The
@ -529,7 +529,7 @@ The main code repository for this work can be found under
\url{https://github.com/vale981/master-thesis}.
The directory \path{python/energy_flow_proper} contains several
project subdirectory with literate programming notebooks in the
project subdirectories with literate programming notebooks in the
\texttt{org} format~\cite{EricSchulte2022Sep}. A detailed listing
linking subprojects to chapters can be found in
\cref{tab:code_structure}.
@ -564,7 +564,7 @@ merged into the original repository
The extensive and well tested existing HOPS code of the Theoretical
Quantum Optics group\footnote{Available upon reasonable request.} was
created by Richard Hartmann. Some improvements have been made in the
course of this work this work. Documentation, type hints and unit
course of this work. Documentation, type hints and unit
tests have been introduced. The parallelization mechanism was
overhauled and now uses the \href{https://www.ray.io}{\texttt{Ray}}
library. The structure of the code was further modularized, allowing

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@ -11,7 +11,7 @@ verify the results of \cref{chap:flow} in
\cref{sec:hopsvsanalyt}. Excellent consistency of the analytical and
numeric solutions for the QBM models will be demonstrated. A common
feature of the short time behaviour of the bath energy flow that is
visible in all simulations will be discussed and explained in
visible in all simulations that will be discussed and explained in
\cref{sec:pure_deph}.
In the generic case where no analytic solution is known we
@ -80,7 +80,7 @@ For the estimation of mean and standard deviation from trajectory
data, Welford's online algorithm is employed to avoid catastrophic
numerical cancellation~\cite{Welford1962Aug,Knuth1997}.
In all simulations discussed use an Ohmic spectral density
In all simulations, we will use an Ohmic spectral density
\begin{equation}
\label{eq:ohmic_sd}
J(ω)=η ω \eu^{-\frac{ω}{ω_{c}}}\quad (ω>0)
@ -567,7 +567,7 @@ We solve the model with the Hamiltonian (Schr\"odinger picture)
\label{eq:puredeph}
H = L^†(t) B + L(t) B^† + H_\bath
\end{equation}
with \(L(t)=L(t)^\), \([L(t), L(s)] = 0\;\forall t,s\) (so that the
with \(L(t)=L^(t)\), \([L(t), L(s)] = 0\;\forall t,s\) (so that the
Heisenberg Hamiltonian matches \cref{eq:puredeph}) and \(B,\,H_\bath\)
as in \cref{sec:nmqsd_basics}.
@ -630,9 +630,9 @@ match the zero temperature case in which the bath has minimal energy
in the initial state.
A thermodynamically useful model should feature significant system
dynamics which is always given, assuming that the coupling is no too
dynamics which is always given, assuming that the coupling is not too
strong. Non hermitian coupling may also have this effect, but in the
literature most effective qubit models tend to favour Hermitian
literature most effective two-level models tend to favour Hermitian
couplings
\cite{Aurell2019Apr,Hita-Perez2021Nov,Hita-Perez2021Aug,MacQuarrie2020Sep,Andersen2017Feb,Mezzacapo2014Jul}. For
the spin-boson model, non Hermitian coupling is the result of the
@ -793,11 +793,11 @@ be witnessed in the inset of \Cref{fig:stocproc_systematics}.
Only in the simulation with precision \(\varsigma=10^{-6}\) (blue)
however, the compatibility condition of \cref{sec:meth} is satisfied
for the given trajectory count. This is due to the fact that multiple
quantities are being obtained in different ways, namely system energy
and the flow. The system energy can be calculated directly from the
system state whereas the flow has to be integrated numerically to
obtain the total bath energy change.
for the given trajectory count. The system energy can be calculated
directly from the system state whereas the flow has to be integrated
numerically to obtain the total bath energy change and depends
directly on the first hierarchy states. The accuracy must be high for
the results to be consistent.
\begin{figure}[htp]
\centering
\includegraphics{figs/one_bath_syst/stocproc_systematics_bath_energy}
@ -821,7 +821,7 @@ plotted in \cref{fig:stocproc_consistency_dev}. Only for the highest
precision (blue) case good consistency is given continually. For lower
precision (green, orange), the consistency fluctuates and only
occasionally surpasses \(68\%\). Initially compatibility is being
demonstrated (until about \(N=10^4\)) but a divergence diverge from
demonstrated (until about \(N=10^4\)) but a divergence from
the most precise result occurs. It is therefore important to consider
the dependence of the compatibility on the sample count \(N\) to judge
the veracity of the simulation results.
@ -854,7 +854,7 @@ convergence as is also demonstrated in
\subsection{Hierarchy Truncation}
\label{sec:trunc}
As the systematics of the truncation depth has already been studied
As the systematics of the truncation depth have already been studied
thoroughly in~\cite{RichardDiss,Hartmann2021Aug}, we will keep the
discussion short. We chose \(N=4.5 \cdot 10^5\) trajectories and an
Ohmic BCF with \(α(0)=0.8\) and \(ω_c=2\). Again, a BCF expansion with