@@ -819,17 +819,17 @@ <h2 id="expectation-values" class="anchor">Expectation values </h2>
819819for a Pauli-\( \boldsymbol{X} \) matrix
820820</ p >
821821$$
822- \boldsymbol{X}=R_{ \sigma}\boldsymbol{Z}R_{ \sigma} = HZH
822+ \boldsymbol{X}=\boldsymbol{R}_{ \sigma}\boldsymbol{Z}\boldsymbol{R}_{ \sigma} = \boldsymbol{ HZH}
823823$$
824824
825825< p > for a Pauli-\( \boldsymbol{Y} \) matrix</ p >
826826$$
827- \boldsymbol{Y}=R_{ \sigma}\boldsymbol{Z}R_ {\sigma}=\boldsymbol{HS}^{\dagger}\boldsymbol{ZHS},
827+ \boldsymbol{Y}=\boldsymbol{R}_{ \sigma}\boldsymbol{Z}\boldsymbol{R}_ {\sigma}=\boldsymbol{HS}^{\dagger}\boldsymbol{ZHS},
828828$$
829829
830830< p > and</ p >
831831$$
832- \boldsymbol{Z}=R_{ \sigma}ZR_ {\sigma}=\boldsymbol{I}\boldsymbol{Z}\boldsymbol{I}=\boldsymbol{Z}.
832+ \boldsymbol{Z}=\boldsymbol{R}_{ \sigma}\boldsymbol{Z}\boldsymbol{R}_ {\sigma}=\boldsymbol{I}\boldsymbol{Z}\boldsymbol{I}=\boldsymbol{Z}.
833833$$
834834
835835
@@ -888,7 +888,7 @@ <h2 id="reminder-on-rotations" class="anchor">Reminder on rotations </h2>
888888
889889< p > Note the following identity of the basis rotator</ p >
890890$$
891- R ^\dagger_\sigma \boldsymbol{Z} R_\ sigma = \sigma,
891+ \boldsymbol{R} ^\dagger_\sigma \boldsymbol{Z} \boldsymbol{R}_\ sigma = \boldsymbol{\ sigma,}
892892$$
893893
894894< p > which follows from the fact that \( \boldsymbol{HZH}=\boldsymbol{X} \) and \( \boldsymbol{SXS}^\dagger=\boldsymbol{Y} \).</ p >
@@ -1084,13 +1084,13 @@ <h2 id="non-interacting-solution" class="anchor">Non-interacting solution </h2>
10841084< h2 id ="rewriting-with-pauli-matrices " class ="anchor "> Rewriting with Pauli matrices </ h2 >
10851085< p > We rewrite \( H \) (and \( H_0 \) and \( H_I \)) via Pauli matrices</ p >
10861086$$
1087- \mathcal{H}_0 = \mathcal{E} I + \Omega \sigma_z , \quad \mathcal{E} = \frac{E_1
1087+ \mathcal{H}_0 = \mathcal{E} I + \Omega \boldsymbol{Z} , \quad \mathcal{E} = \frac{E_1
10881088 + E_2}{2}, \; \Omega = \frac{E_1-E_2}{2},
10891089$$
10901090
10911091< p > and</ p >
10921092$$
1093- \mathcal{H}_I = c \boldsymbol{I} +\omega_z\sigma_z + \omega_x\sigma_x ,
1093+ \mathcal{H}_I = c \boldsymbol{I} +\omega_z\boldsymbol{Z} + \omega_x\boldsymbol{X} ,
10941094$$
10951095
10961096< p > with \( c = (V_{11}+V_{22})/2 \), \( \omega_z = (V_{11}-V_{22})/2 \) and \( \omega_x = V_{12}=V_{21} \).
@@ -1221,7 +1221,7 @@ <h2 id="measurements-and-computational-basis" class="anchor">Measurements and co
12211221and the identity matrix \( \boldsymbol{I} \). Let us make this Hamiltonian that involves only one qubit somewhat more general
12221222</ p >
12231223$$
1224- \left\langle \psi \right| \mathcal{H} \left| \psi \right\rangle = a \cdot \left\langle \psi \right| I \left| \psi \right\rangle + b \cdot \left\langle \psi \right| Z \left| \psi \right\rangle + c \cdot \left\langle \psi \right| X \left| \psi \right\rangle + d \cdot \left\langle \psi \right| Y \left| \psi \right\rangle.
1224+ \left\langle \psi \right| \mathcal{H} \left| \psi \right\rangle = a \cdot \left\langle \psi \right| \boldsymbol{I} \left| \psi \right\rangle + b \cdot \left\langle \psi \right| \boldsymbol{Z} \left| \psi \right\rangle + c \cdot \left\langle \psi \right| \boldsymbol{X} \left| \psi \right\rangle + d \cdot \left\langle \psi \right| \boldsymbol{Y} \left| \psi \right\rangle.
12251225$$
12261226
12271227
@@ -1254,7 +1254,7 @@ <h2 id="in-more-detail" class="anchor">In more detail </h2>
12541254< p > We have</ p >
12551255$$
12561256\begin{align*}
1257- &\text{Z eigenvectors} \qquad
1257+ &\text{\boldsymbol{Z}- eigenvectors} \qquad
12581258\left| 0 \right\rangle = \begin{bmatrix}
125912591\\
126012600
@@ -1272,7 +1272,7 @@ <h2 id="for-the-other-two-matrices" class="anchor">For the other two matrices </
12721272
12731273$$
12741274\begin{align*}
1275- &\text{X eigenvectors} \qquad
1275+ &\text{\boldsymbol{X}- eigenvectors} \qquad
12761276\left| + \right\rangle = \frac{1}{\sqrt{2}} \begin{bmatrix}
127712771\\
127812781
@@ -1282,7 +1282,7 @@ <h2 id="for-the-other-two-matrices" class="anchor">For the other two matrices </
12821282-1
12831283\end{bmatrix},
12841284\\
1285- &\text{Y eigenvectors} \qquad
1285+ &\text{\boldsymbol{Y}- eigenvectors} \qquad
12861286\left| +i \right\rangle = \frac{1}{\sqrt{2}} \begin{bmatrix}
128712871\\
12881288i
@@ -1309,11 +1309,11 @@ <h2 id="explicit-eigenvalues" class="anchor">Explicit eigenvalues </h2>
13091309
13101310$$
13111311\begin{align*}
1312- \left\langle \psi \right| Z \left| \psi \right\rangle &= \left( {c_1^z}^* \cdot \left\langle 0 \right| + {c_2^z}^* \cdot \left\langle 1 \right| \right) Z \left( c_1^z \cdot \left| 0 \right\rangle + c_2^z \cdot \left| 1 \right\rangle \right) = {\left| c_1^z \right|}^2 - {\left| c_2^z \right|}^2,
1312+ \left\langle \psi \right| \boldsymbol{Z} \left| \psi \right\rangle &= \left( {c_1^z}^* \cdot \left\langle 0 \right| + {c_2^z}^* \cdot \left\langle 1 \right| \right) Z \left( c_1^z \cdot \left| 0 \right\rangle + c_2^z \cdot \left| 1 \right\rangle \right) = {\left| c_1^z \right|}^2 - {\left| c_2^z \right|}^2,
13131313\\
1314- \left\langle \psi \right| X \left| \psi \right\rangle &= \left( {c_1^x}^* \cdot \left\langle + \right| + {c_2^x}^* \cdot \left\langle - \right| \right) X \left( c_1^x \cdot \left| + \right\rangle + c_2^x \cdot \left| - \right\rangle \right) = {\left| c_1^x \right|}^2 - {\left| c_2^x \right|}^2,
1314+ \left\langle \psi \right| \boldsymbol{X} \left| \psi \right\rangle &= \left( {c_1^x}^* \cdot \left\langle + \right| + {c_2^x}^* \cdot \left\langle - \right| \right) X \left( c_1^x \cdot \left| + \right\rangle + c_2^x \cdot \left| - \right\rangle \right) = {\left| c_1^x \right|}^2 - {\left| c_2^x \right|}^2,
13151315\\
1316- \left\langle \psi \right| Y \left| \psi \right\rangle &= \left( {c_1^y}^* \cdot \left\langle +i \right| + {c_2^y}^* \cdot \left\langle -i \right| \right) Y \left( c_1^y \cdot \left| +i \right\rangle + c_2^y \cdot \left| -i \right\rangle \right) = {\left| c_1^y \right|}^2 - {\left| c_2^y \right|}^2.
1316+ \left\langle \psi \right| \boldsymbol{Y} \left| \psi \right\rangle &= \left( {c_1^y}^* \cdot \left\langle +i \right| + {c_2^y}^* \cdot \left\langle -i \right| \right) Y \left( c_1^y \cdot \left| +i \right\rangle + c_2^y \cdot \left| -i \right\rangle \right) = {\left| c_1^y \right|}^2 - {\left| c_2^y \right|}^2.
13171317\end{align*}
13181318$$
13191319
@@ -1334,18 +1334,18 @@ <h2 id="unitary-transformation-of-boldsymbol-x" class="anchor">Unitary transform
13341334
13351335< p > If we use the Hadamard gate</ p >
13361336$$
1337- H = \frac{1}{\sqrt{2}}\begin{bmatrix}
1337+ \boldsymbol{H} = \frac{1}{\sqrt{2}}\begin{bmatrix}
133813381 & 1\\
133913391 & -1
13401340\end{bmatrix},
13411341$$
13421342
13431343< p > we can rewrite</ p >
13441344$$
1345- X= HZH.
1345+ \boldsymbol{X}=\boldsymbol{ HZH} .
13461346$$
13471347
1348- < p > The Hadamard gate/matrix is a unitary matrix with the property that \( H ^2=\boldsymbol{I} \).</ p >
1348+ < p > The Hadamard gate/matrix is a unitary matrix with the property that \( \boldsymbol{H} ^2=\boldsymbol{I} \).</ p >
13491349
13501350<!-- !split -->
13511351< h2 id ="generalizing " class ="anchor "> Generalizing </ h2 >
@@ -1393,7 +1393,7 @@ <h2 id="multiple-ansatzes" class="anchor">Multiple ansatzes </h2>
13931393</ p >
13941394
13951395$$
1396- \langle \psi \vert (c+\mathcal{E})\boldsymbol{I} + (\Omega+\omega_z)\boldsymbol{\sigma}_z + \omega_x\boldsymbol{\sigma}_x \vert \psi \rangle.
1396+ \langle \psi \vert (c+\mathcal{E})\boldsymbol{I} + (\Omega+\omega_z)\boldsymbol{Z} + \omega_x\boldsymbol{X} \vert \psi \rangle.
13971397$$
13981398
13991399
@@ -1410,13 +1410,13 @@ <h2 id="rotations-again" class="anchor">Rotations again </h2>
14101410</ p >
14111411
14121412$$
1413- R_x(\theta)=\cos{\frac{\theta}{2}}\boldsymbol{I}-\imath \sin{\frac{\theta}{2}}\boldsymbol{\sigma}_x ,
1413+ R_x(\theta)=\cos{\frac{\theta}{2}}\boldsymbol{I}-\imath \sin{\frac{\theta}{2}}\boldsymbol{X} ,
14141414$$
14151415
14161416< p > and</ p >
14171417
14181418$$
1419- R_y(\phi)=\cos{\frac{\phi}{2}}\boldsymbol{I}-\imath \sin{\frac{\phi}{2}}\boldsymbol{\sigma}_y .
1419+ R_y(\phi)=\cos{\frac{\phi}{2}}\boldsymbol{I}-\imath \sin{\frac{\phi}{2}}\boldsymbol{Y} .
14201420$$
14211421
14221422
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