diff --git a/content/CSE5313/CSE5313_L24.md b/content/CSE5313/CSE5313_L24.md index 9eddab0..9b25a4a 100644 --- a/content/CSE5313/CSE5313_L24.md +++ b/content/CSE5313/CSE5313_L24.md @@ -2,7 +2,7 @@ ## Continue on coded computing -[!Coded computing scheme](https://notenextra.trance-0.com/CSE5313/Coded_computing_scheme.png) +![Coded computing scheme](https://notenextra.trance-0.com/CSE5313/Coded_computing_scheme.png) Matrix-vector multiplication: $y=Ax$, where $A\in \mathbb{F}^{M\times N},x\in \mathbb{F}^N$ diff --git a/content/CSE5313/Exam_reviews/CSE5313_F1.md b/content/CSE5313/Exam_reviews/CSE5313_F1.md index c059f9f..d3d0b0f 100644 --- a/content/CSE5313/Exam_reviews/CSE5313_F1.md +++ b/content/CSE5313/Exam_reviews/CSE5313_F1.md @@ -30,7 +30,7 @@ Please refer to the syllabus for our policy regarding the use of GenAI. > [!WARNING] > -> This notation system is annoying since in mathematics, $A^*$ is the transpose of $A$, but since we are using literatures in physics, we keep the notation of $A^*$. In this report, I will try to make the notation consistent as possible and follows the **physics** convention in this report. So every vector you see will be in $\ket{\psi}$ form. And we will avoid using the $\langle v,w\rangle$ notation for inner product as it used in math, we will use $\langle v|w\rangle$ to denote the inner product. +> This notation system is annoying since in mathematics, $A^*$ is the transpose of $A$, but since we are using literatures in physics, we keep the notation of $A^*$. In this report, I will try to make the notation consistent as possible and follows the **physics** convention in this report. So every vector you see will be in $\ket{\psi}$ form. And we will avoid using the $\langle v,w\rangle$ notation for inner product as it used in math, we will use $\langle v|w\rangle$ or $\langle v,w\rangle$ to denote the inner product. A quantum error-correcting code is defined to be a unitary mapping (encoding) of $k$ qubits (two-state quantum systems) into a subspace of the quantum state space of $n$ qubuits such that if any $t$ of the qubits undergo arbitary decoherence, not necessarily independently, the resulting $n$ qubit state can be used to faithfully reconstruct the original quantum state of the $k$ encoded qubits. @@ -170,9 +170,33 @@ In practice, we ignore the subscript of the vector space and just write $\langle Decoherence process +#### No-cloning theorem + +> Reference from P.532 of the book + +Suppose we have a quantum system with two slots $A$, and $B$, the data slot, starts out in an unknown but pure quantum state $\ket{\psi}$. This is the state which is to be copied into slot $B$m the target slot. We assume that the target slot starts out in some standard pure state $\ket{s}$. Thus the initial state of the copying machine is $\ket{\psi}\otimes \ket{s}$. + +Assume there exists some unitary operator $U$ such that $U(\ket{\psi}\otimes \ket{s})=\ket{\psi}\otimes \ket{\psi}$. + +Consider two pure states $\ket{\psi}$ and $\ket{\varphi}$, such that $U(\ket{\psi}\otimes \ket{s})=\ket{\psi}\otimes \ket{\psi}$ and $U(\ket{\varphi}\otimes \ket{s})=\ket{\varphi}\otimes \ket{\varphi}$. The inner product of the two equation yields: + +$$ +\langle \psi|\varphi\rangle =(\langle \psi|\varphi\rangle)^2 +$$ + +This equation has only two solutions, either $\langle \psi|\varphi\rangle=0$ or $\langle \psi|\varphi\rangle=1$. + +If $\langle \psi|\varphi\rangle=0$, then $\ket{\psi}=\ket{\varphi}$, no cloning for trivial case. + +If $\langle \psi|\varphi\rangle=1$, then $\ket{\psi}$ and $\ket{\varphi}$ are orthogonal. + + + #### Proposition: Encoding 8 to 9 that correct 1 errors -Recover 1 qubit from a 9 qubit quantum system. (Shor code) +Recover 1 qubit from a 9 qubit quantum system. (Shor code, 1995) + +![Shore code](https://notenextra.trance-0.com/CSE5313/Shore_code.png) ### Tools and related topics @@ -229,16 +253,6 @@ $\mathcal{C}^{\perp}\coloneqq\{v\in\mathbb{F}_2^n:v\cdot w=0\text{ for all }w\in Consider the $[7,4,3]$ Hamming code with generator matrix $G$. -$$ -G= -\begin{bmatrix} -1 & 0 & 0 & 0 & 1 & 0 & 1\\ -0 & 1 & 0 & 0 & 1 & 1 & 1\\ -0 & 0 & 1 & 0 & 0 & 1 & 1\\ -0 & 0 & 0 & 1 & 0 & 1 & 1\\ -\end{bmatrix} -$$ - #### Proposition: Encoding $k$ to $n$ that correct $t$ errors diff --git a/public/CSE5313/Shore_code.png b/public/CSE5313/Shore_code.png new file mode 100644 index 0000000..892ef4b Binary files /dev/null and b/public/CSE5313/Shore_code.png differ