# All Questions

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### How to obtain the noise of a circuit in Qiskit?

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

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 ...
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### Does the massive parallelization in Quantum computing imply parallelization of input (as opposed to Turing machine)?

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 ...
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### How to implement modular exponentiation efficiently in Shor's algorithm?

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 $N\sim \log_2(n)$ ...
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### Strange Behaviour of MeSolve, McSolve

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 ...
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### Problem with circuit composer results tab

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 ...
52 views

### Quantum computing w.r.t. the many-worlds theory

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 ...
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### How is quantum error applied to the qubits?

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 ...
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### What is the difference between the “Fubini-Study distances” $\arccos|\langle\psi|\phi\rangle|$ and $\sqrt{1-|\langle\psi|\phi\rangle|}$?

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. ...
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### How will quantum computers access large amounts of storage?

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 ...
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### Right way to use Quantum Phase Estimation using aqua

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 ...
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### Convexity of coherent information - erroneous argument!

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 ...
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### Quantum Circuit teleportation

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 ...
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### Global phase and single qubit gate: does it actually matter for two (or more) qubit gates?

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 ...
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### Constructing a circuit for $C^1(U)$ for rotation operators with TWO single qubit gates and CNOT gate

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 ...
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### IBM quantum computers gate delay values

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 ...
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### Depth of quantum algorithm: definition [duplicate]

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 ...
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### How to interpret a 4 qubit quantum circuit as a matrix?

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 ...
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### Where are the physical gates in the Google processor?

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, ...
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### Openfermion to qiskit

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 ...
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### Measuring T1 and T2 constants on IBM Q

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 ...
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### Quantum teleportation between two computer chips, how relevant?

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 ...
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### Can two intrinsic angular momentum directions (spin) be used for future entanglement after collapse? [closed]

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 ...
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### How can I build up an arbitrary quantum circuit given a certain unitary matrix operation?

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 ...
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### Is there anything practical that can be done with a single qubit?

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 ...
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### Code for a simple optimization problem in Criq

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 ...
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### Are there different orderings of the fifteen SU(4) generators in common use?

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 ...
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### More broken older Qiskit code

I am persuing some older code as below ...
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### UCCSD in qiskit deprecated?

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