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1answer
7 views

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, $|00\rangle$...
0
votes
1answer
21 views

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 ...
1
vote
1answer
23 views

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 ...
0
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0answers
15 views

Forbidden/allowed outputs of a quantum channel

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}}(...
1
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1answer
24 views

$U3$ gate and global phase

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) & ...
0
votes
1answer
35 views

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 $N\sim \log_2(n)$ ...
1
vote
1answer
24 views

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 ...
1
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0answers
33 views

Quantum state discrimination and lower bound for conditional von Neumann entropy

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 \...
-1
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0answers
26 views

Calculating the md5 of a text

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?
1
vote
1answer
32 views

Controlled NOT gate using multiple control qubits in Q#

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 ...
1
vote
1answer
63 views

Vey different results between qasm_simulator and quantum computer

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 ...
0
votes
2answers
70 views

'IBMQFactory' object has no attribute 'load_accounts'

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 ...
1
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3answers
69 views

Unentangling a qubit from a system: can we convert $\alpha|000\rangle+\beta|111\rangle$ into $\alpha|00\rangle+\beta|11\rangle$?

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 \...
1
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0answers
27 views

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 ...
2
votes
1answer
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 ...
1
vote
1answer
43 views

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 ...
5
votes
1answer
61 views

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. ...
2
votes
2answers
52 views

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 ...
0
votes
2answers
33 views

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 ...
2
votes
0answers
43 views

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 ...
-1
votes
1answer
61 views

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 ...
5
votes
1answer
50 views

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 ...
3
votes
1answer
46 views

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 ...
1
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2answers
60 views

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 ...
0
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0answers
23 views

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 ...
2
votes
1answer
64 views

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 ...
2
votes
1answer
54 views

Partial trace condition in Choi state

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\...
4
votes
1answer
112 views

Why is the size of the top register for Shor's algorithm chosen as it is?

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)\...
3
votes
1answer
91 views

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, ...
1
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0answers
40 views

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 ...
1
vote
2answers
65 views

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 ...
2
votes
1answer
41 views

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 ...
1
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0answers
33 views

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 ...
0
votes
1answer
37 views

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 ...
5
votes
2answers
158 views

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 ...
0
votes
0answers
24 views

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 ...
1
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0answers
29 views

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 \begin{equation} ...
0
votes
1answer
42 views

More broken older Qiskit code

I am persuing some older code as below ...
0
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2answers
25 views

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
1
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0answers
50 views

IBM qiskit vs Microsoft QDK [closed]

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.
2
votes
2answers
45 views

How many real-valued coefficients does it take to specify an $n$-qubit state?

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>, \...
3
votes
1answer
128 views

What does it mean “less than identity” in the operator sum representation?

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 ...
-1
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2answers
51 views

How to find eigenvalues and eigenvector for a quantum gate? [closed]

I need to know how can I find eigenvalues and eigenvectors for a quantum gate, for example $X$ gate.
1
vote
0answers
34 views

Quantum computing in finance - list of articles

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 ...
2
votes
1answer
81 views

Problem 2.2 in Nielsen & Chuang - Properties of the Schmidt number

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 ...
-1
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2answers
67 views

What are the properties of qubit transformation?

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 ...
0
votes
1answer
65 views

Problems with Q# installing

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 ...
2
votes
4answers
54 views

Implementing four oracles for the Deutsch Algorithm (preferably on IBM Q Experience)

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 ...
3
votes
1answer
78 views

Optimizing over quantum channels

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 ...
1
vote
0answers
54 views

Can we apply Grover to meet-in-the-middle attack?

$\newcommand{\Ket}[1]{\left|#1\right>}$ 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,...

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