All Questions

I referred to the following Qiskit's document: state_fidelity. The inputs of state_fidelity are quantum state vectors or density matrices. For example, $|00\rangle$...

I have a quantum circuit and the job has been run on the "statevector" backend, which runs only 1 shot. Therefore is there a way to return the qubit state (0 or 1) specifically when selected ...

Being a newbie in this field, I'm trying to understand what types of real-life workloads are suitable for migrating to Quantum computers. Intuitively, it seems to me that if a Quantum computer ingests ...

The coherent information of a channel $\mathcal{E}_{A'\rightarrow B}$ is defined as the maximum value obtained by the following function where the maximization is over all input states $$I_{\rm{coh}}(...

The most general single qubit gate is $\mathrm{U3}$ given by matrix $$ \mathrm{U3}= \begin{pmatrix} \cos(\theta/2) & -\mathrm{e}^{i\lambda}\sin(\theta/2) \\ \mathrm{e}^{i\phi}\sin(\theta/2) & ...

I'm a noob in quantum computing and I'm trying to get Shor's algorithm working on Q# (the language is unrelated). However, I'm stuck on computing $f(x)$s in the quantum circuit. Let $N\sim \log_2(n)$ ...

I'm using Qutip to plot some basic two level dynamics using hamiltonians with a temporal envelope defined as the sum of two error functions, designed to make it more representative of experimental ...

Consider two quantum states $\rho_A$ and $\sigma_A$, and define the classical-quantum state over a classical binary system $B$ and $A$, $$\omega_{AB}^\epsilon :=\epsilon \vert 0 \rangle \langle 0 \...

I cannot see any libraries for Qiskit to calculate md5 hashes, is there one? How could I go about calculating the md5 hash of text?

I am trying to implement the Grover's search algorithm using Q# and I am not able to implement the oracle (black box) part for the search of state $|1010\rangle$. How to implement the controlled NOT ...

I've started playing around with circuits only recently and decided to try out and implement a 4-qubit Grover's search using qiskit. When I run my python script using the qasm_simulator, I get the ...

I am following this qiskit workshop from https://colab.research.google.com/github/mtreinish/qiskit-workshop/blob/master/Workshop.ipynb . After adding my API key I had encountered the error ...

Let's say I start with the following arbitrary qubits: $$ \color{red}{\vert Q_1 \rangle = \alpha_1 \vert 0 \rangle + \beta_1 \vert 1 \rangle}\\ \color{green}{\vert Q_2 \rangle = \alpha_2 \vert 0 \...

I'm trying to run a simulation of the following circuit: on the ibmq_qasm_simulator, but it only shows the "Circuit diagram" without the "Circuit Implementation" and "Results tab". Did someone had ...

Quantum algorithms are inherently probabilistic. Let's say I run Shor's factoring algorithm on some number. There's a chance that the output I observe is incorrect. Does the many-worlds theory suggest ...

I am trying to check the way qiskit has the noise implemented. I have read how is this theoretically done using quantum channels (see Nielsen and Chuang chapter 8) and I want to verify if qiskit ...

I sometimes see the "Fubini-Study distance" between two (pure) states $|\psi\rangle,|\phi\rangle$ written as $$ d(\psi,\phi)_1=\arccos(|\langle\psi|\phi\rangle|), $$ for example in the Wikipedia page. ...

I've seen many articles in the popular press saying that quantum computers will enable searching through huge amounts of data in an instant. But I can't figure out how the current architectures can do ...

I have been experimenting with Qiskit lately, but I have found the implementation of algorithms in Aqua extremely confusing. Currently I am trying to implement a very simple circuit that will return ...

Consider a state $\rho_{AB}$. Let it have purification $\psi_{A'AB}$. I am interested in the coherent information of this state which is given by $$I(A\rangle B)_\rho = S(B)_\rho - S(AB)_\rho$$ I ...

Sender and receiver use teleportation protocol,where sender teleport a quantum state $\left| \varphi \right>=\alpha\left| 0 \right> + \beta \left|1\right>$ to receiver . I want to implement ...

Consider the $X$ gate. Mathematically, we have $X=i e^{-i\frac{\pi}{2} X}$ But as global phase of unitaries don't matter because they will simply act a global phase to the wavefunction, we can ...

This is the exercise 4.23 from Nielsen and Chuang, asking that if it is possible to construct $C^1(U)$ for $U=R_{x,y}(\theta)$ with TWO single qubit gates and CNOT gate. My answer is no, and I would ...

I am doing an state of the art study about the existing quantum computer technologies and one of the parameters of interest is the gate delay value, as it determines the time expected from a gate from ...

My question is really simple: what is the depth of a quantum algorithm ? Is it the number of gates that are ran in sequence ? When I am googling it I only find article using the word without defining ...

This is part of Simon Algorithm (Initial state + some Oracle function) There is a post that explains how to interpret circuits (How to interpret a quantum circuit as a matrix?), but I'm not sure how ...

Consider Hilbert spaces $\mathcal{X}, \mathcal{Y}$. For any quantum channel $\mathcal{E}_{\mathcal{X}\rightarrow \mathcal{Y}}$, the bipartite Choi state $J(\mathcal{E}) \in L(\mathcal{Y}\otimes\...

Let $N$ be the number we're trying to factor. In Shor's algorithm, the top register then has $2 \lceil\log_2(N)\rceil+1$ qubits, while the bottom register (the ancilla qubits) has $\lceil\log_2(N)\...

Google's article Quantum supremacy using a programmable superconducting processor states that the processor "53 qubits, 1,113 single-qubit gates, 430 two-qubit gates, and a measurement on each qubit, ...

Is there a direct way to go from an object generated in openfermion to objects usable in Qiskit. I can't find anything about any plugin. It's not too hard to translate into pyQuil and then to Qiskit ...

We have been asked to measure relaxation and dephasing times T1 and T2 on the IBM Q using the composer only, Qiskit not allowed. I am a bit confused about the way to do so. Can someone explain the ...

After stumbling upon this recent news article: Information teleported between two computer chips for the first time (which references a "Nature Physics" publication Chip-to-chip quantum teleportation ...

Persuant to all contributors, here I will use a coin toss analogy since the vector direction is either up or down (heads or tails). Two coins will be used for each of two tosses. It's assumed that the ...

Suppose I want to put a qubit whose initial state is $|0\rangle$ to the final state $\frac{1}{\sqrt{3}}|0\rangle + \sqrt{\frac{2}{3}}|1\rangle$. Well, in that case, the unitary matrix that performs ...

Is there anything practical that can be done with a single qubit? And by "practical," I mean a problem that can be solved or information that can be stored. I realize that one practical thing that ...

For a demonstration, I would like to code a simple optimization problem in Cirq. I don't care what the problem is, but I want it understandable to someone who has had only basic algebra. One idea is ...

I've recently performed certain analyses (Archipelagos of Total Bound and Free Entanglement) pertaining to eq. (50) in Separable Decompositions of Bipartite Mixed States , that is \begin{equation} ...

I am persuing some older code as below ...

Is this now deprecated or moved? I've been looking for it. It was in from qiskit.chemistry.aqua_extensions.components.variational_forms import UCCSD

I am new to both IBM Qiskit and Microsoft QDK. I wish to understand which framework would be best suited for someone new to this field. I am lookig for the pros and cons of both frameworks.

Let a quantum register of size $n$ be in the following state, expressed in the computational basis for $n$-qubit states: $$\left| \psi \right> = \sum_{i=0}^{2^n-1} \alpha_i \left| i \right>, \...

In Quantum Computation and Quantum Information by Isaac Chuang and Michael Nielsen, section 8.2.3, $\mathcal{E}=\sum_{k}E_k\rho E_k^{\dagger}$ gives the operator-sum representation. In general, it ...

I need to know how can I find eigenvalues and eigenvectors for a quantum gate, for example $X$ gate.

I am trying to find application of a quantum computing in finance. So far I found these papers: Quantum computing for finance: Overview and prospects Quantum computational finance: quantum algorithm ...

This question has been asked here: "Problem 2.2 in Nielsen & Chuang - Properties of the Schmidt number", but no answer has been provided there yet, thus I move it here. The problem is stated ...

I have a question about the properties of the closed quantum system's state transformation. For example, when a qubit is transformed by the application of certain operators, we know that one property ...

I don't know if this is the right place to ask this question. I just thought it would be a place where people knew what they are doing. If there is a better place to look for answers (stackoverflow ...

I guess, I understood simple Deutsch Algorithm (if unary function is balanced or constant) as described here: Introduction to quantum computing: The Deutsch algorithm I need to test it. I was ...

I am given fixed quantum states $\rho_X$ and $\sigma_Y$ and some function of the form $\text{Tr}(N_{X\rightarrow Y}(\rho_X)\sigma_Y)$. I would like to maximize this function over all completely ...

$\newcommand{\Ket}[1]{\left|#1\right>}$ If we have the superposition $$\displaystyle \sum \dfrac{1}{2^n} \Ket x \Ket{ f(x)} \Ket 0 \Ket y \Ket{g(y)} \Ket 0 \Ket {\delta_{x,y}} ,$$ here $\delta_{x,...