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500 | 500 | "source": [
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501 | 501 | "$$\n",
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502 | 502 | "\\boldsymbol{P}_a=\\vert \\psi_a\\rangle \\langle \\psi_a\\vert = \\begin{bmatrix} \\vert \\alpha_0\\vert^2 &\\alpha_0\\alpha_1^* \\\\\n",
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503 |
| - " \\alpha_1\\alpha_0^* & \\vert \\alpha_1\\vert^* \\end{bmatrix},\n", |
| 503 | + " \\alpha_1\\alpha_0^* & \\vert \\alpha_1\\vert^2 \\end{bmatrix},\n", |
504 | 504 | "$$"
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505 | 505 | ]
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506 | 506 | },
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519 | 519 | "source": [
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520 | 520 | "$$\n",
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521 | 521 | "\\boldsymbol{P}_b=\\vert \\psi_b\\rangle \\langle \\psi_b\\vert = \\begin{bmatrix} \\vert \\beta_0\\vert^2 &\\beta_0\\beta_1^* \\\\\n",
|
522 |
| - " \\beta_1\\beta_0^* & \\vert \\beta_1\\vert^* \\end{bmatrix}.\n", |
| 522 | + " \\beta_1\\beta_0^* & \\vert \\beta_1\\vert^2 \\end{bmatrix}.\n", |
523 | 523 | "$$"
|
524 | 524 | ]
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525 | 525 | },
|
|
558 | 558 | "source": [
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559 | 559 | "$$\n",
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560 | 560 | "\\boldsymbol{A}=\\lambda_a\\begin{bmatrix} \\vert \\alpha_0\\vert^2 &\\alpha_0\\alpha_1^* \\\\\n",
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561 |
| - " \\alpha_1\\alpha_0^* & \\vert \\alpha_1\\vert^* \\end{bmatrix} +\\lambda_b\\begin{bmatrix} \\vert \\beta_0\\vert^2 &\\beta_0\\beta_1^* \\\\\n", |
562 |
| - " \\beta_1\\beta_0^* & \\vert \\beta_1\\vert^* \\end{bmatrix}.\n", |
| 561 | + " \\alpha_1\\alpha_0^* & \\vert \\alpha_1\\vert^2 \\end{bmatrix} +\\lambda_b\\begin{bmatrix} \\vert \\beta_0\\vert^2 &\\beta_0\\beta_1^* \\\\\n", |
| 562 | + " \\beta_1\\beta_0^* & \\vert \\beta_1\\vert^2 \\end{bmatrix}.\n", |
563 | 563 | "$$"
|
564 | 564 | ]
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565 | 565 | },
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742 | 742 | "metadata": {},
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743 | 743 | "source": [
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744 | 744 | "$$\n",
|
745 |
| - "\\sum_{i=0}^1\\boldsymbol{P}_i^{\\dagger}\\boldsymbol{P}_1=\\boldsymbol{I},\n", |
| 745 | + "\\sum_{i=0}^1\\boldsymbol{P}_i^{\\dagger}\\boldsymbol{P}_i=\\boldsymbol{I},\n", |
746 | 746 | "$$"
|
747 | 747 | ]
|
748 | 748 | },
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|
1500 | 1500 | "source": [
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1501 | 1501 | "## Simple Hamiltonian models\n",
|
1502 | 1502 | "\n",
|
1503 |
| - "In order to study get started with coding, we will study two simple Hamiltonian systems, one which we can use for a single qubit systems and one which has as basis functions a two-qubit system. These two simple Hamiltonians exhibit also something which is called level crossing, a feature which we will use in later studies of entanglement.\n", |
| 1503 | + "In order to get started with coding, we will study two simple Hamiltonian systems, one which we can use for a single qubit systems and one which has as basis functions a two-qubit system. These two simple Hamiltonians exhibit also something which is called level crossing, a feature which we will use in later studies of entanglement.\n", |
1504 | 1504 | "\n",
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1505 | 1505 | "We study first a simple two-level system. Thereafter we\n",
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1506 | 1506 | "extend our model to a four-level system which can be\n",
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1507 | 1507 | "interpreted as composed of two separate (not necesseraly identical)\n",
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1508 | 1508 | "subsystems.\n",
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1509 | 1509 | "\n",
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1510 |
| - "We let our hamiltonian depend linearly on a strength parameter $z$" |
| 1510 | + "We let our hamiltonian depend linearly on a strength parameter $\\lambda$" |
1511 | 1511 | ]
|
1512 | 1512 | },
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1513 | 1513 | {
|
|
1668 | 1668 | "is $\\vert 0 \\rangle$. At $\\lambda=1$ the $\\vert 0 \\rangle$ mixing of\n",
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1669 | 1669 | "the lowest eigenvalue is $1\\%$ while for $\\lambda\\leq 2/3$ we have a\n",
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1670 | 1670 | "$\\vert 0 \\rangle$ component of more than $90\\%$. The character of the\n",
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1671 |
| - "eigenvectors has therefore been interchanged when passing $z=2/3$. The\n", |
| 1671 | + "eigenvectors has therefore been interchanged when passing $\\lambda=2/3$. The\n", |
1672 | 1672 | "value of the parameter $X$ represents the strength of the coupling\n",
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1673 | 1673 | "between the model space and the excluded space. The following code\n",
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1674 | 1674 | "computes and plots the eigenvalues."
|
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1785 | 1785 | "metadata": {},
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1786 | 1786 | "source": [
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1787 | 1787 | "$$\n",
|
1788 |
| - "\\vert 10\\rangle = \\vert 1\\rangle_{\\mathrm{A}}\\otimes \\vert 0\\rangle_{\\mathrm{B}}=\\begin{bmatrix} 0 & 1 & 0 &0\\end{bmatrix}^T,\n", |
| 1788 | + "\\vert 01\\rangle = \\vert 0\\rangle_{\\mathrm{A}}\\otimes \\vert 1\\rangle_{\\mathrm{B}}=\\begin{bmatrix} 0 & 1 & 0 &0\\end{bmatrix}^T,\n", |
1789 | 1789 | "$$"
|
1790 | 1790 | ]
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1791 | 1791 | },
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1803 | 1803 | "metadata": {},
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1804 | 1804 | "source": [
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1805 | 1805 | "$$\n",
|
1806 |
| - "\\vert 01\\rangle = \\vert 0\\rangle_{\\mathrm{A}}\\otimes \\vert 1\\rangle_{\\mathrm{B}}=\\begin{bmatrix} 0 & 0 & 1 &0\\end{bmatrix}^T,\n", |
| 1806 | + "\\vert 10\\rangle = \\vert 1\\rangle_{\\mathrm{A}}\\otimes \\vert 0\\rangle_{\\mathrm{B}}=\\begin{bmatrix} 0 & 0 & 1 &0\\end{bmatrix}^T,\n", |
1807 | 1807 | "$$"
|
1808 | 1808 | ]
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1809 | 1809 | },
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1849 | 1849 | "metadata": {},
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1850 | 1850 | "source": [
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1851 | 1851 | "$$\n",
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1852 |
| - "H_0\\vert 10 \\rangle = \\epsilon_{10}\\vert 10 \\rangle,\n", |
| 1852 | + "H_0\\vert 01 \\rangle = \\epsilon_{01}\\vert 01 \\rangle,\n", |
1853 | 1853 | "$$"
|
1854 | 1854 | ]
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1855 | 1855 | },
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1859 | 1859 | "metadata": {},
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1860 | 1860 | "source": [
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1861 | 1861 | "$$\n",
|
1862 |
| - "H_0\\vert 01 \\rangle = \\epsilon_{01}\\vert 01 \\rangle,\n", |
| 1862 | + "H_0\\vert 10 \\rangle = \\epsilon_{10}\\vert 10 \\rangle,\n", |
1863 | 1863 | "$$"
|
1864 | 1864 | ]
|
1865 | 1865 | },
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|
1914 | 1914 | "source": [
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1915 | 1915 | "$$\n",
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1916 | 1916 | "\\boldsymbol{H}=\\begin{bmatrix} \\epsilon_{00}+H_z & 0 & 0 & H_x \\\\\n",
|
1917 |
| - " 0 & \\epsilon_{10}-H_z & H_x & 0 \\\\\n", |
1918 |
| - "\t\t 0 & H_x & \\epsilon_{01}-H_z & 0 \\\\\n", |
| 1917 | + " 0 & \\epsilon_{01}-H_z & H_x & 0 \\\\\n", |
| 1918 | + "\t\t 0 & H_x & \\epsilon_{10}-H_z & 0 \\\\\n", |
1919 | 1919 | "\t\t H_x & 0 & 0 & \\epsilon_{11} +H_z \\end{bmatrix}.\n",
|
1920 | 1920 | "$$"
|
1921 | 1921 | ]
|
|
1936 | 1936 | "metadata": {},
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1937 | 1937 | "source": [
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1938 | 1938 | "$$\n",
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1939 |
| - "\\rho_0=\\left(\\alpha_{00}\\vert 00 \\rangle\\langle 00\\vert+\\alpha_{10}\\vert 10 \\rangle\\langle 10\\vert+\\alpha_{01}\\vert 01 \\rangle\\langle 01\\vert+\\alpha_{11}\\vert 11 \\rangle\\langle 11\\vert\\right),\n", |
| 1939 | + "\\rho_0=\\left(\\alpha_{00}\\vert 00 \\rangle\\langle 00\\vert+\\alpha_{01}\\vert 01 \\rangle\\langle 01\\vert+\\alpha_{10}\\vert 10 \\rangle\\langle 10\\vert+\\alpha_{11}\\vert 11 \\rangle\\langle 11\\vert\\right),\n", |
1940 | 1940 | "$$"
|
1941 | 1941 | ]
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1942 | 1942 | },
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