Questions tagged [quantum-circuit]
a model in which a computation is a sequence of quantum gates, which are reversible transformations on an n-qubit register (the quantum-mechanical analog of an n-bit register)
570
questions
1
vote
1
answer
69
views
Why does quantum circuit need to be run even though the probability is already in the formula?
In classical computing, it's clear by intuition why we need to run a program code to check whether a large odd integer number is prime or not.
It can be computed manually for such large number, but of ...
0
votes
1
answer
60
views
Modify a quantum state prepared with HHL [closed]
I can prepare a state $|1\rangle|x\rangle|0\rangle$ using HHL. How do I prepare $|1\rangle|x\rangle|0\rangle+|0\rangle|y\rangle|0\rangle$ or simply $|1\rangle|x\rangle|0\rangle+|0\rangle|0\rangle|0\...
0
votes
0
answers
48
views
Find inner product or coefficient from a quantum state in quantum circuit and qiskit [closed]
From a 4 qubit circuit, I prepared state $|w \rangle = a|1000\rangle + b|1010\rangle +c|1110\rangle$. Now I need to find 'a' with sign(+/-), that is I want to find $\langle 1000|w\rangle$. How do I ...
- 1
1
vote
0
answers
32
views
Forward propogation of rotated clifford gates in lattice surgery
In A Game of Surface Codes (arXiv), I have been trying to understand the process that is described for forward propogating rotated clifford gates through other rotated clifford gates, and either I am ...
- 1,095
1
vote
1
answer
41
views
How would you write $ e^{i \frac{\pi}{4} \text{CNOT}}$ in ZX calculus?
How would you write $ e^{i \frac{\pi}{4} \text{CNOT}}$ operation in ZX calculus? Is there any simple method to write gates of the form $e^{i \frac{\pi}{4} \sigma_z^{(1)} \sigma_x^{(2)}}
$?
0
votes
2
answers
54
views
Is there a generalized quantum teleportation for n-qubit entangled states? [duplicate]
Quantum teleportation for single qubit is a fairly simple algorithm to follow. Even its extensions into the transportation of $n$ qubits is fairly simple: repeat the process $n$ times (or run $n$ ...
- 148
2
votes
1
answer
194
views
How to prepare a superposed state?
Given two arbitrary states, $|\psi\rangle\ \text{and}\ |\phi\rangle$ that are possibly unknown to the preparer, is there a way to prepare the superposition $|\psi\rangle+|\phi\rangle$ of them? (If it'...
- 343
-1
votes
1
answer
107
views
Does this quantum circuit reproduce the oracle in Deutsch's algorithm?
This seems to me a fine quantum oracle for the balanced one bit function $f(x)=x$, but putting it in Deutsch's algorithm circuit will give the result $|0\rangle$, i.e. the function is evaluated as ...
0
votes
0
answers
20
views
Encoding electron-phonon interactions in a quantum computer
I am trying to encode superposition of coherent-like states, that represent electron-phonon couplings on a chain, in a quantum computer.
Specifically, I would like to (approximately) generate states ...
- 221
1
vote
0
answers
24
views
Parameterized Gates [duplicate]
I am trying to create my own custom parameterized gate and then transpile it to the AerSimylatorGate. I have been able to create the virtual circuit but in the transpilation to the backend basis set ...
- 41
0
votes
1
answer
45
views
Uniformly sampling a random 3 qubit clifford gate
I try to uniformly sample 3 qubit clifford gates and apply them to my circuit. I'm using python language. I'm following this paper https://arxiv.org/abs/quant-ph/0406196 (Supplementary Materials 1....
- 1
3
votes
1
answer
275
views
Is the outcome of this quantum circuit correct and if so why?
I am very novice with quantum computing and try to understand it. I thought I was getting a handle on it until I built the quantum circuit (1) below. The app I used to build it allows me to measure ...
- 149
0
votes
1
answer
69
views
Decrease the entangled state space
I have a circuit containing two entangled qubits in a 4D vector $\begin{bmatrix} A \\ 0 \\ 0 \\ B \end{bmatrix}$,
Is there a way to encode the amplitudes $A$ and $B$ into a single qubit?
I want to ...
1
vote
0
answers
15
views
How to use GoemansWilliamsonOptimizer from qiskit_optimization.algorithms?
I have created a big instance of a max cut problem, which is in a QuadraticProgram. Now when I try to do this:
...
2
votes
1
answer
95
views
Efficient creation of a modular multiplicative inverse gate using Fermat's Little Theorem
I'm wondering if anyone has ever stumbled upon an efficient way to create a gate that can calculate the multiplicative modular inverse in $\mathbb{Z}_p$, it may even be that somebody has stumbled upon ...
- 73
3
votes
0
answers
49
views
Do we really apply both single-qubit and two-qubit gates in the same layer in experiments?
I'm doing experiments using superconducting computers, and my question is as follows:
Performing quantum gates requires isolating the coupling between a target qubit and other neighboring qubits.
To ...
- 31
0
votes
0
answers
21
views
Process Tomography and transpiler not running and eventually crashing kernel
I am running a Quantum Process Tomography on a circuit with a custom pulse added to a calibation for a CNOT gate.
Upon running the circuit, running it on the backend takes forever and eventually ends ...
1
vote
0
answers
26
views
QMA-QCMA oracle with quantum gates
While reading the QMA-QCMA paper by Aaronson and Kuperberg I wondered how their result extends to quantum circuits.
Suppose you have an oracle $O$ such that $O\left|\psi\right>=-\left|\psi\right>...
- 1,557
0
votes
0
answers
19
views
Custom pulse with fake backend not running for Cross Resonance Pulse
I am trying to create a cross resonance pulse by driving the control qubit at a non resonant frequency. My code runs but does not stop running.
...
0
votes
0
answers
67
views
Reconstruction of the probability of the uncut state fails
I tried to follow the example from the paper "CutQC: Using Small Quantum Computers for Large Quantum Circuit Evaluations" (https://arxiv.org/abs/2012.02333).
Some hints were also given in ...
- 11
1
vote
1
answer
59
views
States that verify behaviour of Pauli operators in Clifford circuits
I have a circuit composed of Clifford gates and Pauli-basis measurements. I am also told that a set of Pauli operators $P = \{ P_1, P_2, ..., P_n\}$ commute with the circuit. When I say that $P_i$ ...
- 13
1
vote
1
answer
95
views
How does qiskit implement a given superposition in the actual quantum computer?
My question is phrased in 2 parts:
Is there a quantum circuit to implement the following 4-qubit state: $$\frac{1}{2}(|1000 \rangle + |0100 \rangle + |0010 \rangle + |0001 \rangle)$$
When we use the ...
0
votes
1
answer
57
views
How to convert from choi to chi matrix in qiskit
I have done a quantum process tomography experiment on a two qubit system.
...
0
votes
0
answers
44
views
Qiskit's Integer Comparator
Does the IntegerComparator from qiskit.circuit.library works fine, or am I doing something wrong in understanding it's working?
I'm working with this simple ...
2
votes
0
answers
34
views
Why does a random circuit produce an XEB fidelity of $\chi \approx 2$? [duplicate]
Background
In this paper (section 10), the linear cross-entropy benchmark (fidelity) for a random circuit $C$ and samples $s_i$ taken from that circuit is defined as
$$\chi := \frac{2^n}{k}\sum^k_{i=1}...
- 894
1
vote
0
answers
53
views
How is projective measurement usually handled in matrix product state-based simulators?
I decided to write my own matrix product state (MPS)-based quantum circuit simulator. I've got my head all wrapped around the usual things for this like gate application and how Schmidt decomposition ...
- 11
1
vote
1
answer
83
views
Different notations for measurement gates: what is meant by $0$ after a measurement?
I am relatively new to quantum computing I am confused with different notations for measurement gates in quantum computing as shown below https://arxiv.org/pdf/2205.00081
I really donot understand ...
- 53
2
votes
0
answers
97
views
Which 5-qubit QEC circuits can simulate magic state distillation?
Theoretically, any 5-qubit error correction code's decoding circuit should be able to implement magic state distillation, but I have tried many circuits for simulating magic state distillation, and ...
- 21
1
vote
1
answer
61
views
Parametric circuits and QASM3 in Qiskit v1.1.0
I am currently exploring Qiskit v1.1.0 and its handling of QASM3. The following snippet demonstrates the creation of a parametric circuit and the generation of its corresponding QASM3 code. ...
- 293
1
vote
2
answers
58
views
State and observable decomposition into a sequence of native/universal gates
Given a quantum register $q_{0},\dots, q_{n-1}$ composed of $n$ qubits, I wonder if there exists a general mathematical framework to generate the quantum circuit to put this quantum register in a ...
- 321
2
votes
0
answers
42
views
Defining quantum computer without reference to a classical computer
In the definition of an "efficient quantum computer", there is a uniformity condition that suggests to me that the notion of an efficient quantum computer is not independent of the notion of ...
- 519
0
votes
0
answers
30
views
Solving variables in symbolic unitary to get a desired real-valued unitary using qiskit or qympy, qiskit-symb/pytket
I am trying to decompose a 4x4 unitary into 2 qubit circuit using U3 and CNOT gates but the circuit implementation qiskit gives me is not optimized. So I started looking at qiskit-symb and qympy to ...
- 1
1
vote
2
answers
203
views
How to implement a quantum multiplier in Qiskit 1.0
I am looking at the homepage of Qrisp, and they have an example of how to multiply two registers with Qiskit:
...
- 39
1
vote
1
answer
48
views
Verifying block encoding by computing inner products
Assume that we know each matrix element $A_{ij}$ of a $n$-qubit matrix $A$, and we are given an $(n+m)$-qubit unitary $U_A$ that we would like to verify is a $(1,m)$-block encoding of $A$. To do this, ...
- 559
-5
votes
1
answer
90
views
Why is the matrix representation of CNOT gate valid
$\begin{bmatrix}1&0&0&0\newline 0&1&0&0\newline 0&0&0&1\newline 0&0&1&0\end{bmatrix}$
Obviously, given any $4\times 1$ matrix, it fixes the first two ...
- 99
1
vote
0
answers
38
views
Will my custom gate actually spin when I run it on real hardware?
I am trying to create a custom gate using Qiskit Pulse and use it in my quantum circuit. Below is the code I have written so far.
...
- 21
1
vote
1
answer
108
views
An equivalent classical circuit for Hadamard gate
In principle, we can simulate any Quantum circuit via a classical circuit. However, this simulation could be inefficient. (Church-Turing thesis)
Together, Hadamard and Toffolli are universal gate sets ...
- 827
0
votes
1
answer
125
views
Unable to extract the quantum registers information from qiskit quantum circuit data
Consider the following code:
...
3
votes
0
answers
33
views
methodology for design quantum circuits according to a given unitary
This is a general question. Given an arbitratry unitary matrix.
How to desigin a quantum circuit to implement it?
I am not asking for a specific unitary matrix, but for a general methodology to tackle ...
- 171
0
votes
0
answers
17
views
How to plot a histogram of a pulse-level quantum circuit simulation in QuTiP?
The qutip_qip package allows for pulse-level quantum circuit simulation, compared to for instance the gate-level quantum circuit simulation found in Qiskit (to understand the difference, scroll to the ...
- 101
0
votes
2
answers
811
views
3
votes
3
answers
73
views
Interpretation of a circuit that yields the same result for initializations $|+\rangle$ and $|-\rangle$
How can I interpret a quantum circuit that results in the same state for the initialization $\newcommand{\ket}[1]{|#1\rangle}\newcommand{\bra}[1]{\langle #1|}\ket{+}$ and $\ket{-}$?
For example, the ...
- 311
1
vote
0
answers
24
views
Highly-efficient $n(n+1)$?
Appendix G of this paper provides a highly-efficient way of squaring integer numbers. (LMK if anything more advanced is already available.) I'm wondering if this approach can be easily modified to ...
- 2,081
1
vote
0
answers
39
views
A maximally distant unitary from a parameterized circuit
I have a parameterized circuit that includes a certain number of rotation gates, each parameterized by an angle. By sampling over these angles, I can obtain various unitaries. What are the unitaries ...
- 141
2
votes
0
answers
42
views
Is there a fix for the varying numerical gradients calculated in the optimizer with qiskit?
I am currently trying to train a quantum circuit on Qiskit using an Azure QPU. I have some parameterized gates that I optimize using ADAMs. However, as the output of the circuit $f(x)$ is not ...
- 53
2
votes
1
answer
90
views
Showing the Toffoli gate can be constructed from one-qubit gates using computer matrix multiplication
I need help coming up with the code that I can use in a computer algebra system like Sage, Python, or Mathematica that can evaluate the circuit.
I am not a programmer and used ChatGPT to try to help ...
- 351
0
votes
1
answer
34
views
Two Quantum State Density Matrices with Unequal Off-Diagonal Elements but Equal Magnitudes
I recently read Kitaev's paper on magic state distillation. I want to verify whether the circuit for the [5,1,3] encoder can map a single qubit state T_0 to the logical state T_1 in the encoded space. ...
- 21
0
votes
0
answers
28
views
Difficulties Encountered in Simulating Quantum Purification Circuits for Magic State Distillation
Recently, I've been studying Kitaev's paper on magic state distillation. Referring to Nathan Babcock's presentation, I wrote a program in MATLAB to simulate the purification circuit. Instead of the ...
- 21
0
votes
0
answers
20
views
How can I find out how compatible a quantum circuit is to a backend without executing the circuit
Say I have multiple backends, I need a score to determine how well a backend is suitable for that particular circuit, I have it's noise model too, I tried transpiling the circuit and calculating noise ...
1
vote
1
answer
57
views
Quantum circuit of stateful oracle
Suppose I have operator $U_f$ that maps state $|x\rangle|y\rangle|0\rangle$ to another state $|x\rangle|y\rangle|f(x, y)\rangle$.
The function $f$ has its internal state, that changes on each ...
- 147