# Questions tagged [circuit-construction]

For questions about the construction of complex circuits using elementary quantum gates.

469 questions
Filter by
Sorted by
Tagged with
29 views

### What is the method to create arbitrary controlled circuits in Qiskit?

I am working on an implementation of an algorithm which uses ampitude estimation and amplification as a subroutine but we are not using qiskit but QuEST. QuEST doesn't have any direct method to ...
24 views

### 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 ...
18 views

### How to perform controlled rotations similar to what is done in HHL

How does one do the conditional rotation based on a binary encoding of the input? The rotation of D_i^t has to be done in the image below and I know that similar rotations can also be found in HHL and ...
68 views

### Compute the output of this Approximate Quantum Cloning three-qubit circuit

Above is a circuit for "Approximate Quantum Cloning" The preparation state is given by $$|\psi\rangle =\alpha|0\rangle+\beta|1\rangle$$ The gates labelled $\theta_i$ denote single qubit ...
57 views

### How to multiply two vectors (kets) in qiskit?

Hi does anyone know how i could write a program to get the product of something like |1>|0>|0>?
33 views

### Could the Hamiltonian of a Rubik's Cube be simulated with a NISQ device?

Consider the four cells on each of the six faces of the 2x2x2 Rubik's cube (the pocket cube), with front, up, and right twists being labelled as $\langle F,U,R\rangle$. Each move uses fifteen SWAP ...
32 views

50 views

### Why do we care about the number of $T$ gates in a quantum circuit?

When reading this question and quickly reading some of the linked papers, I wondered why was the number of $T$ gates specified along the number of controlled-$X$ gates. I've often read that ...
48 views

356 views

### Implement a projection operator as a quantum circuit

Let the state $|\Psi\rangle\equiv a|0\rangle\otimes|\psi_0\rangle + b|1\rangle\otimes|\psi_1\rangle$, where $|\psi_0\rangle$ and $\psi_1\rangle$ belong to a multi-qubit register $R$ and the ...
755 views

### Why do we have to measure the circuit before sending it to the real quantum computer?

If I want to run a circuit on a real quantum computer, I have to measure it before running it. For example: ...
60 views

### How to perform a plot histogram for a circuit?

I have created a circuit and I don't know how to plot a histogram. I tried to plot a histogram but it gives me output for 0000 case only, how to get to know the probability for all of the cases. The ...
30 views

65 views

### An algorithm to perform Gram-Schmidt orthogonalization of linearly independent state vectors

In the first paragraph of the 2nd section of this article, it is stated that given a set of linearly independent $n$-qubit state vectors, Alice can perform the Gram-Schmidt procedure to obtain ...
36 views

### Marginal output probability of first bit for constant-depth circuits

Consider a constant depth $1\text{D}$ quantum circuit, which is applied to the input state $|0^{n}\rangle$, and whose output is measured in the standard basis. You can assume that the gates of the ...
232 views

### Complexity of $n$-Toffoli with phase difference

I'm interested in the $n$-Toffoli gates with phase differences. I found a quadratic technique in section 7.2 of this paper. Here's the front page of the paper. Here's an image of the section that I'm ...
142 views

### Understanding Grover’s Oracle for 3-SAT

First of all I'm very new to the quantum computing world so this might seem trivial to you, but it's a hump I was unable to get over for days now. So I'm talking about the version that Qiskit has ...