Questions tagged [programming]

For questions relating to the process of assembling quantum programs that can be executed on a quantum computer. For questions using or about a specific programming language, consider using a more specific tag

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12
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2answers
587 views

Does a study guide exist that starts from a “purely CS background” and advances towards “making a new quantum programming language”?

I am from a computer science background and I find it difficult to decide on the resources I should focus on while learning quantum computing, since there is so much to read/watch. My ultimate goal is ...
46
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6answers
2k views

Programming quantum computers for non-physics majors

I come from a non-physics background and I am very much interested in pursuing Quantum Computing - especially how to program them. Any guidance on how to get started will be very helpful.
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3answers
4k views

How can I implement an n-bit Toffoli gate?

I want to create a Toffoli gate controlled by n qubits, and implement it in QISKit. Can this be done? If so, how?
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3answers
806 views

Does a complete list of open quantum software projects exist?

An answer to Is there any source which tabulates quantum computing algorithms for simulating physical systems? mentions the Quantum Algorithm Zoo, a list of quantum algorithms. Several answers to ...
3
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2answers
192 views

Big Endian vs. Little Endian in Qiskit

I've noticed that Q# favors Little Endian. Meaning that most operations are designed for this type of encoding. Is is it the same with Qiskit?
54
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5answers
17k views

What programming languages are available for quantum computers?

From this question, I gathered that the main quantum computing programming languages are Q# and QISKit. What other programming languages are available for programming quantum computers? Are there ...
8
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5answers
827 views

Resources for quantum algorithm basics

I have just started to learn about quantum computing, and I know a little bit about qubits. What is a resource where I can learn a basic quantum algorithm and the concepts behind how it works?
12
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2answers
616 views

Automatic compilation of quantum circuits

A recent question here asked how to compile the 4-qubit gate CCCZ (controlled-controlled-controlled-Z) into simple 1-qubit and 2-qubit gates, and the only answer given so far requires 63 gates! The ...
4
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1answer
1k views

How to create an arbitrary state in QISKit for a local_qasm_simulator?

I would like to play with a quantum circuit local_qasm_simulator in QISKit, but I do not want to implement a separate quantum circuit that would prepare an initial ...
3
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1answer
141 views

Counting in Q#: number of solutions

I have this program derived from Microsoft Quantum Katas for counting (see here): ...
8
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2answers
833 views

Possibility of a “reset” quantum gate

I wish to have a "reset" gate. This gate would have an effect to bring a qubit to the $\mid0\rangle$ state. Clearly, such a gate is not unitary (and so I'm unable to find any reliable implementation ...
11
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3answers
569 views

Are there any quantum software startups?

I am aware of the quantum hardware startup Rigetti and I wonder if there are any quantum startups that build software on top of current quantum computer hardware for commercial applications? Related ...
8
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1answer
194 views

How does the Curry-Howard correspondence apply to quantum programs?

In words of Wikipedia, The Curry–Howard correspondence is the observation that two families of seemingly unrelated formalisms—namely, the proof systems on one hand, and the models of computation ...
7
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4answers
366 views

Which quantum computing programming language should I learn?

Which quantum computing programming language should I learn? What are the benefits of said language? As of Wikipedia, there's quite a bit to choose from. I'm looking to develop end-user applications (...
6
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5answers
2k views

How do I build a gate from a matrix on Qiskit?

I'm creating a gate for a project and need to test if it has the same results as the original circuit in a simulator, how do I build this gate on Qiskit? It's a 3 qubit gate, 8x8 matrix: $$ \frac{1}{...
5
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2answers
296 views

Checking value of variable using quantum approach

A beginner question after watching few videos. Say, var=a; var can be either of two values, ...
4
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3answers
1k views

How to quickly calculate the custom U3 gate parameters $\theta, \phi$ and $\lambda$ for any unitary?

In IBM Qiskit and Quantum Experience, the custom U3 gate is defined as $$ U(\theta, \phi, \lambda) = \begin{pmatrix} \cos\left(\frac{\theta}{2}\right) & -e^{...
6
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1answer
823 views

How would one implement a quantum equivalent of a while loop in IBM QISkit?

I'm writing a simple multiplication algorithm that uses the Quantum Fourier Transform to repetitively add a number (the multiplicand) to itself and decrements another number (the multiplier). The ...
9
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1answer
282 views

Submitting jobs to IBM devices without Python

Qiskit can be used to submit jobs to IBM devices using Python (or Swift and JavaScript). But what if I want to use a different language? For example, suppose I have a specific circuit I want to run. ...
8
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1answer
2k views

Visualization of Quantum Circuits when using IBM QISKit

I have followed the installation steps, regarding QISKit working environment. For circuit visualization, I've installed latex as in addition to poppler to convert from PDF to images. Afterwards, I ...
7
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2answers
132 views

How does one obtain amplitude information in Q#?

Is it possible to obtain amplitude information (in lexicographic ordering) for a particular qubit register in Q#? For example, in the following code: ...
6
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1answer
292 views

What is the purpose of the TDG gate in QISKit?

The QISKIT documentation doesn't explain what a TDG gate does and I can't find it anywhere else online.
6
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1answer
772 views

How many logical qubits are needed to run Shor's algorithm efficiently on large integers ($n > 2^{1024}$)?

First, I know there are differences in logical qubits and physical qubits. It takes more physical qubits for each logical qubit due to quantum error. Wikipedia states that it takes quantum gates of ...
5
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2answers
378 views

How do we code the matrix for a controlled operation knowing the control qubit, the target qubit and the $2\times 2$ unitary?

Having n qubits, I want to have the unitary described a controlled operation. Say for example you get as input a unitary, an index for a controlled qubit and another for a target. How would you code ...
4
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1answer
391 views

How can noise on a device be simulated using measured noise parameters?

The real devices used as backends for Qiskit have calibration data that quantifies errors ($T_1$ and $T_2$, gate fidelities, etc). This can be accessed by, for example ...
3
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2answers
318 views

Why won't Qiskit ccx gate accept registers?

In Qiskit, they have the concept of a Toffoli gate (ccx). However, the following code throws an error: ...
3
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1answer
142 views

How does the cnx gate work in Qiskit (Python)?

Could somebody explain the cnx operator, and how it operates on its qubit parameters to flip the target qubit in Qiskit (Python)?
3
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1answer
222 views

Implementing a complex circuit for a Szegedy quantum walk in qiskit

Problem definition I'm implementing a quantum circuit in qiskit for a Szegedy quantum walk, (reference, Fig 21.). It uses two registers of dimension $N$ ($N=3$) each one. The challenges I'm facing ...
2
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1answer
100 views

Newbie Project: Calculate a Mersenne Prime with Quantum Computing

I am new to the quantum world and wondering the bounds of which the technology is at the current state of the art: specifically in computing prime numbers. I would like to, if possible, create a ...
2
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1answer
99 views

How to define custom controlled unitaries in OPENQASM 2.0?

According to the OPENQASM 2.0 documentation, it's possible to define custom unitary gates using the format: gate name(params) qargs { body } where the optional ...
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0answers
76 views

Decomposition of an arbitrary gate using given matrix in Qiskit

If I have an arbitrary non-unitary matrix of say $$ U = \begin{pmatrix} 1.5 & 0 & 0 & 0 \\ 0 & 0 & 0 & 1.6 \\ 0 & 0 & 1 & 0 \\ 0 & 1 & 0 & 0 \\ \end{...
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0answers
45 views

A question about qiskit's WeightedPauliOperator.evolve method for IPEA (IQPE) implementation

I'm doing an implementation/tutorial of the iterative phase estimation algorithm (IPEA) and have a problem. My Hamiltonian is a diagonal matrix $H = \begin{pmatrix} E_1 & 0 \\ 0 & E_2\end{...
1
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2answers
152 views

How can the state $\lvert0\rangle+M^{-1/2}\sum_{j=1}^M\lvert j\rangle$ be generated?

I was wondering if anybody to help me to generate the following state. It would be preferable if you use only Hadamard, CNOT and T-gates, on $\lceil\log_2(M+1)\rceil$ qubits: $$|\psi\rangle = \frac{1}{...
1
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1answer
425 views

Cannot load account with Qiskit

I just got started with Qiskit. When I tried to save my account with the API token from IBMQ website, I got the error: ...
0
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2answers
90 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 ...