Questions tagged [quantum-gate]
For questions regarding usage, performance, implementation, application or theory related to quantum gates.
188
questions with no upvoted or accepted answers
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Find the desire state with a set of gates?
I encoded a state |000> applied by a U3 gate, resulting in state: a|000>+b|100>. I need to create a circuit to achieve the desired state (a'|**0>+b'|**1>) with * as any 0 or 1 state. ...
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modify Shor’s quantum order finding algorithm in such a way that it uses as few qubits as possible
I am supposed to modify Shor’s quantum order finding algorithm in such a way that it uses as few qubits as possible.
Beforehand, I already did an exercise where I showed that the inverse Quantum ...
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Computation for threshold of CNOT gate
I'm trying to reproduce some threshold results using 7-qubit Steane code in those legacy papers. I managed to obtain the graph for circuit noise and single qubit gate
e.g. the pseudocode for computing ...
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Trying to construct modular exponentiation gate in Qiskit
https://qiskit.org/textbook/ch-algorithms/shor.html in this tutorial I don't understand especially in how they define for the modular exponentiation gate with only swap gate (inside c_amod15 function)....
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how do x, y, z, and h gates transform amplitude, phase, and magnitude? Affect of one gate to others?
I have been taking the qiskit and I am having trouble understanding how they work.
How does the phase affect the actually probability of the output?
The course also talks about the amplitude trees of ...
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How to apply CNOT with control qubits in first register and target qubit in second register
I would like to know how to mathematically describe the states of the qubits in both registers in the following circuit:
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How to extract the entanglement fidelity from an arbitrary quantum operation?
I have an arbitrary process matrix that does an entangling operation (a controlled-pi/2 rotation) plus some additional phase rotations that are not of interest. I am curious to find a way to extract a ...
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Universality : Working with one qubit
I am working on the Pennylane's code camp problems and I'm stuck with the challenge 4.
I am utterly clueless about this question, as in what is it asking from me, they provide us with a $2\times 2$ ...
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Calculate the single qubit unitary (U) created by the sequence of gates: U=XZH
I don't know how are we going to proof this by using tensor product of XZH
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Quantum Algorithm to Solve a Maze
I am trying to understand the paper "Quantum Algorithm to Solve a Maze - Converting the Maze Problem into a Search Problem" by Debabrata Goswami and Niraj Kumar (here the reference https://...
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Decompose 8x8 Unitary Matrix into tensor product of three phased gate
We try to decompose 8x8 unitary matrices
\begin{pmatrix}
e^{ia} & & & & & & \\
& e^{ib} & & & & & \\
& & e^{ic} & & ...
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How to read data from multiple qubits and feed it to a MLP
Being new in the field of quantum computing, I tried with the implementation of "https://qiskit.org/textbook/ch-machine-learning/machine-learning-qiskit-pytorch.html" using a single qubit. ...
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How MCMT is implemented in Qiskit, what is the initiution behind it?
I have read about and used the MCMT qiskit gate (Multiple Control Multiple Target).
But I wonder how they have implemented it, how is a gate (like CCCZ for example) is decopmosed into basic gates and ...
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How to apply mid-circuit measurement and measurement based conditional operations in `amazon-braket`?
Is there any method to apply mid circuit measurements in amazon-braket? I'm implementing a circuit that has few operations conditioned to measurement. In ...
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CNOT gate path interference
I have a question on paper https://doi.org/10.1038/nature02054.
In this paper, the CNOT gate is realized using a beam displacer for higher stability. The figure below shows a 1:1 mapping from (a) to (...
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The relationship between number of shots and performance of quantum agent
What is the relationship between number of shots and the performance of quantum agent in Quantum neural network? and what is the limit of number of shoots in QASM simulator?
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Faithful description of a photonic setting with the circuit model
The above picture comes from this paper.
The circuit on the left and the one on the right are equivalent (up to the basis).
However, there is an important difference: the circuit makes the input -- i....
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What's the best way to design a circuit with logic gates that use the same input lines?
I am implementing a Carry Select Adder, the problem is that the circuit is quite complex to translate in Qiskit.
I need to use one (or multiple) line(s) as input for two (or more) gates.
In particular,...
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CNOT chain vs CNOT fountain in qiskit
I was going through qiskit's synthesis module, their methods take an argument called cx_structure which has two possible values, ...
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Slight issue with QFTing two qubits
Let's consider two qubits and the corresponding computational basis $\{|0\rangle\, |1\rangle, |2\rangle, |3\rangle\}$. In binary form, any of these vectors can also be written as a product $|x_1\...
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How to simulate $H(\theta) = B(\sin\theta S_1^x +\cos\theta S_1^z +\sin\theta S_2^x +\cos\theta S_2^z)+aS_2^zI_z$ on IBM Qiskit
I am trying to simulate this Hamiltonian on IBM Qiskit, for varying values of $\theta$:
$H(\theta) = B(\sin\theta S_1^x +\cos\theta S_1^z +\sin\theta S_2^x +\cos\theta S_2^z)+aS_2^zI_z$
Where S is ...
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Qiskit library.gaussian() does not accept parametric expression
I'm trying to build a gaussian pulse in qiskit where I keep the amplitude as a parameter but for the followig code
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Sequential Circuits in IBMQ and Qiskit and generating a clock pulse
I am trying to implement the Peres Gate with Feedback from Feynmann Gate feeding back into the third input to Peres Gate. This sequence needs to be repeated. There is also a clock pulse that needs to ...
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How do I construt a mixed state for an arbitrary symmetric matrix?
A symmetric matrix can be seen as a density matrix. If I have an arbitrary symmetrical matrix, can I use a quantum random access memory to construct a corresponding mixed state? What kind of quantum ...
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How should I think about circuit metrics like "qubit count," "circuit depth," and "gate count" when dealing with the OpenQASM 3 `ctrl` modifier?
It seems like circuit metrics like qubit count, circuit depth, and gate count are pretty useful. Qubit count determines whether a it's even possible to run a program on resource-limited quantum ...
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How many physical qubits are needed to encode a logical qubit on ion trap, superconducting, neutral atom, photonic QC?
How many physical qubits are needed to encode a logical qubit on an
-- ion trap,
-- superconducting,
-- neutral atom,
-- photonic,
-- spin
quantum computer based on today's technologies?
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How many single and double qubit gates are required to create a uniform superposition of vertices of a Johnson Graph J(n,r)?
Can I in $\tilde{O}(r)$ number of gates (single and double qubit) create a uniform superposition of vertices of Johnson Graph $J(n,r)$? I would like to create a state $|\psi\rangle = \frac{1}{\sqrt{n \...
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How to measure the error rate (or fidelity) of a particular gate (such a H, T) by Qiskit
We know the calibration data of IBM's quantum devices can be retrieved through the randomized benchmarking method, which is included in Qiskit. However, the calibaration data about gates just gives ...
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Matrix for $U^{2^j}$ from Shor's algorithm for any $a$ and $N$
I'm implementing Shor's algorithm from scratch and therefore want to implement a unitary gate $U$ such that $U^{2^j}|y\rangle = |a^{2^j}y \: \text{mod} \: N\rangle$. I know that an efficient way of ...
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In (O'Brien et al. 2004), why is the target qubit not affected when the control is $\vert 0\rangle$?
I'm currently reading this paper https://arxiv.org/abs/quant-ph/0403062 but I fail to understand how the input of the control qubit affects the output of the target qubit. I do understand that when ...
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How do I get sate vector for each shot running on a quantum computer?
I was running this code on a quantum computer how can I generate a state vector for each shot while running on a quantum computer?
qikit code
...
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3-qubit phase shift gate/circuit implementation without any Ancilla qubits
Hi, I need help me with figuring out the 3-qubit phase shift circuit without any ancillas similar to the 2-qubit circuit shown in below attached picture....... Please do let me know! Thanks in advance!...
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How can I achieve single-qubit $T$ operation using spin resonance?
We know that $T$ gate is as follows
$T=\left(\begin{array}{cc}1 & 0 \\ 0 & e^{i \pi / 4}\end{array}\right)$
And on the other resultant spin-resonance hamiltonian is
$\frac{H}{\hbar}=\frac{1}{2}...
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Is there a quantum gate that can do this?
Is there a quantum gate that can do the following?
Given a first set of N qbits, mutually entangled in such a way that each state in the superposition meets a given condition, generate a second set of ...
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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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There seems to be a bias against states with more 1s, in IBM's calibration matrix generator: What are the consequences and possible solutions?
Qiskit's function CompleteMeasFitter builds a calibration matrix in this way (2 qubit case):
Everything is initialized in the state $|00\rangle$, which is the ...
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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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A question about quantum noise model
Now, I try to understand some concept of Quantum Noise Model and Quantum Channel. The Quantum Noise can be represented as a quantum operator with their own probability. As far as I concerned,(I dont ...
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Screening procedure in an iterative qubit coupled cluster (iQCC) ansatz
The paper Iterative Qubit Coupled Cluster approach with efficient screening of generators describes a new screening procedure for generators of the QCC ansatz.
How does one get from defining the ...
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Error in qiskit.aqua.operator
I want to implement this thing:
Operator([[3, Pauli([1,0,0], [0,0,0])], [2, Pauli([0,0,0],[0,0,3])]])
But while doing this there is an error in ...
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IBM quantum circuit - order of tensor product for equivalent matrix
I'm trying to understand how to apply tensor products on 3-qubit systems (or well at least 2 qubits). Let's take a basic example:
where $$\lvert \psi \rangle = \lvert q_2q_1q_0\rangle $$ with $q_2$ ...
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How to implement controlled u3 gate from Qiskit using simpler gates?
I am trying to implement the u3 controlled gate (able to rotate the qubit in any specified direction in 3 dimensions if the control is 1, for two qubits) using simpler gates. The simpler gates ...
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About a Qiskit Function
I want to understand this Qiskit function (a function for creating the gate CNX with Python): more specifically i don't understand what's the rotations (Y and Z) over the qubits for ?
I added inline ...
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Kronecker notation of an operator
Suppose I have the state $|A\rangle=|x\rangle^l\otimes |y\rangle^l \otimes |z\rangle^l \otimes |0\rangle_x^l\otimes |0\rangle_y^l\otimes |0\rangle_z^l$. I perform the transformation between the $|x\...
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Quantum circuit simplification using classical computers
Suppose that we have this kind of circuit where the first unitary operator U is used for the state preparation while the Hadamard operator is used of state detection.
Let's say we try to run this ...
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Half-wave plate (HWP) Hadamard gate implementation
The transformation of a qubit encoded in the polarization state from $|H\rangle$ to the state $|+\rangle$ is theoretically achievable with an HWP@π/8. However, I rarely see this solution in ...
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Qiskit_machine_learning QNNEstimator 'Estimator job failed' when using CU-Gates
I'm trying to construct a QNN using controlled arbitrary unitary gates. While some simple code versions work perfectly for controlled single rotations, the moment I add CU gate with parameters, the ...
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How does using a controlled rotation gate , with the slope of the linear function as a parameter, loads that function onto the amplitude?
I was going through the paper Quantum Risk Analysis in the section III they came up with a technique, in which they represented the analytical function into a polynomial and then used the slope of ...
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Derivation of complexity for data encoding schemes
Could anyone help to derive the space-time complexities of the following different data encoding schemes ?
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Understanding the meaning of [2, 2] for input_register and target_register in a custom Cirq gate
I'm learning a custom gate implementation from google Cirq official tutorial of shor algorithm(https://colab.research.google.com/github/quantumlib/Cirq/blob/master/docs/experiments/shor.ipynb#scrollTo=...
