Questions tagged [circuit-construction]
For questions about the construction of complex circuits using elementary quantum gates.
331
questions
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Composing teleportation circuit in Qiskit Circuit Composer
I'm trying to create the teleportation circuit in IBM Qiskit Circuit Composer.
...
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1answer
23 views
Which method of executing a multi-control gate is more efficient?
I am interested in executing multi-control gates and I have found two methods to do so as explained below.
The first is taken from Nielsen and Chuang (2010) from their Figure 4.10. This method ...
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2answers
58 views
Optimizations in quantum circuits
In a paper called On quantum circuits employing roots of the Pauli matrices, I found this figure, where I couldn't understand the equality in the circled circuits. I need an explanation of how the ...
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0answers
28 views
How to build a multicontrolled cnot without auxilary qubits?
How can I build a multicontrolled cnot without auxilary qubits?
When I am using multicontrolled cnots, then I always need many auxilary qubits.
Can one build a multi controlled cnot without auxilary ...
1
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3answers
37 views
How can I obtain transformation matrix of a quantum circuit in the Qiskit?
I need to draw a quantum circuit in Clifford+T library and obtain automatically its transformation matrix. Is there any feature on Qiskit in this case?
0
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1answer
46 views
Odd behavior with Qiskit Pauli operators
I was creating a simple implementation of the Hadamard test when I came across the following, what seems like, strange behavior.
Consider the following snippet, which is part of the computating the ...
2
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0answers
30 views
Preparing arbitrary two- and multi-qubit states with real amplitudes
Is it correct that the following circuit can produce any two-qubit state with real amplitudes? (Meaning that for any set of the four real amplitudes there exists a set of angles...)
If so, should I ...
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0answers
17 views
Issue with running a circuit: Cannot read property 'idCode' of null
I have been trying to run simple circuits from the Circuit Composer, both on a real quantum comp and on a simulator. Every time I get this error message:
...
1
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1answer
48 views
Is there any difference between a quantum- and classically-controlled gate if I know my basis?
Consider an unrealistic 2-qubit plus 1 ancilla bit-flip error correction code (images generated by quirk), where I know by some means or other that an error may have happen on qubit0 (represented by ...
4
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2answers
156 views
Is there a circuit to compare two quantum states?
Lets have two quantum states (single qubits ones for simplicity) $|\psi\rangle$ and $|\phi\rangle$:
$$
|\psi\rangle = \alpha_\psi|0\rangle+\mathrm{e^{i\varphi_\psi}}\beta_\psi|1\rangle
$$
$$
|\phi\...
0
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1answer
31 views
Converting 'string' to a function/gate in QisKit
I want to give a list of Quantum gates in a .txt file from user an apply them to a Quantum circuit but the gates in notepad .txt file have 'string' type while in Qiskit I need functions/methods. For ...
2
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2answers
82 views
Generate a 3-qubit SWAP unitary in terms of elementary gates
I wish to generate the following unitary
...
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0answers
26 views
Reducing the depth of quantum circuits with ancilla qubits
This question is two-fold and considers general $n$-qubit operations on a quantum computer.
First, can a general $n$-qubit operation be implemented on a quantum computer without the use of ancilla ...
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1answer
28 views
Implementing Cirq Coding Gates
Can someone please help me making these gates on CIRQ programming:
Decrement Gate (-1)
Splitter Gate (If possible)
I was having trouble implementing these and was not sure if it's possible either.
...
2
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1answer
52 views
How can I convert the unitary matrix $e^\frac{i\pi}{2}$ into a quantum circuit in Qiskit?
How can I put the unitary matrix $$e^\frac{i\pi}{2}I$$ to the quantum circuit?
I don't know if it is belong to $$U3(\theta, \phi, \lambda), U2(\phi, \lambda), U1(\lambda)$$
Thanks a lot.
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0answers
64 views
What is the thought process for circuit making after seeing input and output of a matrix?
Here is an exercise (4.27) from Nielsen and Chuang and I found the answer (given in the figure below) online without any explanation. The question was to construct a circuit by seeing a matrix (given ...
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1answer
54 views
Quantum Circuit Optimization with Machine Learning [closed]
I read some paper about Quantum Circuit Optimization but I am on a low level.
And have some experience in ML.
But what I don't understand is it possible that ML can help to optimize Quantum Circuits ...
3
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1answer
106 views
How to implement linear combination of two unitary gates in a quantum circuit?
I wanted to implement a non-unitary operation. I came to know that I can do it as a linear combination of unitaries from this paper (published version). Let us say I want to implement an operation ...
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1answer
131 views
Implementing a circuit that returns $|01\rangle$ and $|10\rangle$ with equal probability
Using Python how can I implement a quantum circuit that returns $|01\rangle$ or $|10\rangle$ using only $CX$, $RX$ and $RY$ gates, starting with random parametric gates as parameters and optimizing it ...
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0answers
97 views
Can one use a quantum circuit as a pathfinding algorithm?
I've been learning about quantum computing, and I noticed that another way to describe the state vector is as a path in a binary tree where each level of tree represents another qubit, each node ...
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3answers
211 views
Google Colab - ImportError: The class MatplotlibDrawer needs pylatexenc
When I run the following command
qc.draw(output='mpl')
for my circuit qc, I get this error:
...
2
votes
1answer
73 views
Test equivalence of circuits exactly on qiskit
I have two circuits that I believe are equivalent. How can one check this on qiskit? Currently, I am executing both circuits and verifying that the counts are close (which they are) but I would like ...
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1answer
32 views
Is there a way to generate random circuits in qiskit with only certain allowed gates?
It seems like I can use https://qiskit.org/documentation/stubs/qiskit.circuit.random.random_circuit.html but I would like to control the gates that are allowed.
What is an efficient way to make random ...
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0answers
39 views
qiskit - MCMT - base gate acting on only one qubit
I want to reduce the depth of a ucrz gate acting on multiple qubits with ancilla qubits in qiskit. One way to do this could be the mcmt implementation with ...
0
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2answers
36 views
How to remove last n layers of Quantum Circuit in Qiskit?
Let's say I have a QuantumCircuit with depth $d$ layers. How can I generate a new ...
1
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1answer
37 views
How to split a Quantum Circuit on a barrier in Qiskit?
Let's say I have a QuantumCircuit with multiple barriers as shown in the visual below:
How would I split up the ...
2
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1answer
196 views
How to measure in another basis
I am new to qiskit and I have to simulate a quantum circuit. I read this documentation https://qiskit.org/textbook/ch-states/single-qubit-gates.html where it is left as an exercise to the reader to ...
2
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1answer
80 views
What is the best way to handle parametric circuits in Qiskit?
What is the best way to handle parametric circuits in Qiskit? When I create a variational form like TwoLocal and then do ...
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0answers
25 views
Difference between a Non-Gaussian Circuit and Gaussian Circuit
I am fairly new to this topic and I couldn't find resources that were beginner-friendly. So basically what are the differences between these two?
2
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0answers
19 views
Can low-rank factorizations approximate quantum circuits?
Quantum circuits can be expressed as the matrix product of each gate in the circuit, where each gate is a unitary matrix (say) $G_i$. So, the whole circuit is $S = G_n G_{n-1} \cdots G_1$.
Since $S$ ...
0
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0answers
32 views
Why QuantumCircuit.diagonal does not provide global phase when it is used in a controlling circuit
When it is used in a controlling circuit, QuantumCircuit.diagonal() decomposition in Qiskit does not provide global phase (as a relative phase), but instead only identity operator is used. Here the ...
2
votes
1answer
41 views
Circuit of quantum error correction code
I read an interesting paper of QEC with only two extra qubits.
In the paper, there is a circuit. Note that .
Here are some contexts of the paper:
"The stablizer is $XZZXI$. If the second gate ...
1
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0answers
26 views
Gate definitions for quantum random access codes
I would like to know how the gates are defined in quantum random access codes? Consider the $2 \to 1$ code described in Lemma 3.1 of this paper.
The section defines the encoding and decoding circuits. ...
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1answer
42 views
What is the analysis of the Bell Inequality protocol in Cirq's 'examples'?
This question is taken from https://github.com/quantumlib/Cirq/issues/3032.
The "standard" protocol measures Alice's and Bob's qubits in different bases, while the one in Cirq measures in ...
3
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1answer
40 views
Can you take infinitely many square roots of Pauli-X?
I am trying to find the cost for a n-bit Toffoli gate based on the recurrent circuit presented on Barenco's Work in Lemma 7.5 (Elementary gates for quantum computation)
The construction requires that ...
7
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1answer
205 views
Consequences of $MIP^\ast=RE$ Regarding Quantum Algorithms
The (pending-peer review) proof of $MIP^\ast=RE$ in this pre-print has been hailed as a significant breakthrough. The significance of this result is addressed by Henry Yuen (one of the authors) in ...
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1answer
531 views
Can anyone provide me with an example of the for Grover's algorithm on one qubit?
I'm having trouble understanding Grover's Algorithm, so I'd like to start with the case with 1 qubit. But I don't see anyone build it for 1 qubit, only 2 is the minimum. Is it because that's ...
4
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1answer
51 views
Defining a custom parametric gate in Qiskit in terms of standard gates?
Here it is explained how to define a custom non-parametric gate in Qiskit. How do I define a new parametric gate?
For example, I want to have the $CCR_y$ gate defined as
in order to use it as
...
7
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1answer
84 views
Preparing any superposition of fixed Hamming weight states
There exists a nice way of preparing any superposition (with real amplitudes ā this is the case I'm interested in) of states $\{\ldots0001\rangle,\,|\ldots0010\rangle,\,|\ldots0100\rangle,\ldots\}$, ...
4
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3answers
117 views
How can we implement controlled-T gate using CNOT and H, S and T gates?
In general, is there any way to implement a controlled version of an arbitrary gate U if we are given only CNOT and U gate?
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0answers
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What is the maximum circuit depth for Qiskit Aer Simulator?
I'm running some simulator circuit on my computer, and I see that (using 3 qubits, and thousands of classical registers), the max cap seems to be about qc.depth() ...
2
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2answers
58 views
How can I load a probability distribution using a quantum circuit in Qiskit?
Can someone suggest me a way to load a distribution (for example a discretized Gaussian distribution) into a quantum computer using a quantum circuit?
I tried to implement the code using Qiskit.
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0answers
47 views
Generalized construction of W basis
Although this question deals with the construction of a W-state, I was looking for a general way to find all the orthogonal W-states, given a number of qubits. For example, for three qubits, the first ...
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0answers
64 views
Preparation of states that correspond to efficiently integrable probability distributions
I have been trying to implement methods from paper Creating superpositions that correspond to efficiently integrable probability distributions by Grover and Rudolph.
It is stated that there exists an ...
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0answers
224 views
The analogous IBM circuit representation for the quantum scheme
I am trying to implement a quantum scheme of sharing a secret via EPR states. Here is my initial state of 6 qubits \begin{equation} |\psi\rangle=\left(\dfrac{|0\rangle_1|0\rangle_2+ |1\rangle_1|1\...
4
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1answer
79 views
How to implement an Oracle
Often when reading about QC algorithms the Authors assume the existence of an Oracle. I understand this is so that they can focus on the overall structure of the algorithm, and an Oracle can be seen ...
4
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1answer
61 views
How to transform a state with amplitude squared or to any power?
Suppose I have an unknown state $|\psi\rangle = \sum_i \alpha_i|{\lambda_i}\rangle$, is it possible that I can transform it into $|\psi\rangle = \frac{1}{\sqrt{\sum_i|\alpha_i|^{2r}}} \sum_i \alpha_i^...
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Equivalence checking of quantum circuits up to error
Suppose you are given two circuit descriptions $A$ and $B$ where by a circuit description I mean a sequence of gates (in the order they are applied) and the qubits they are applied on. (For the sake ...
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1answer
57 views
Is there a tool to get the quantum circuit corresponding to a sparse matrix?
If I know a sparse matrix, is there any tool that allows me to get the corresponding quantum circuit directly?
If not what should I do?
For exampleļ¼I want to try hamilton simulation and I have the ...
1
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1answer
72 views
How to construct quantum circuit to count number of 0-qubits and 1-qubits
Suppose we have a 3-qubit input; each bit is either 0 or 1. How to decide if there are more 1's than 0's? Only 1 extra qubit may be used for the output. (Yes I know this can be achieved using 3 ...
