Quantum Computing Stack Exchange
Quantum Computing Stack Exchange

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)

516 questions
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How to reason about absorbing Pauli Product rotations into measurements?

In this image, the orange box refers to the operator $\exp(-i P \frac{\pi}{4})$ and the blue box refers to the Pauli Measurement $P'$. The idea behind these rules is to show how all the Pauli Product $\frac{\pi}{4}$ rotations at the end of the…
shashvat
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Help Implementing a 4-qubit super dense coding algorithm

I am new to quantum computation, I have seen examples of super-dense coding; however, I am struggling in my attempts to scale the 2-qubit system to a 4-qubit, here is a visual of the 2-qubit super-dense coding protocol I have implemented. My…
ajhill1
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Building a controlled NOT gate which is controlled by the qubit it is acting on

I have a question, which I have thought about for a while now, and can't seem to figure out. I have a quantum circuit and I would like to construct a unitary gate acting on a qubit $q$ that acts as a NOT gate on $q$ if $q = |1\rangle$, and leaves…
Q.Ask
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Simplifying quantum circuits

I am very new to quantum circuits and am unsure how to simplify them. Say I'm given a very simple circuit: and I want to simplify it using basic quantum gates. I'm not looking for an answer, but more just how to go about it. I started by computing…
Spike Spiegel
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Can any matrix be translated into a quantum circuit?

Can any matrix be translated into quantum circuit? Is there any limitation to the qubits length or any other constraints to the matrix? Can any matrix be presented by a unique quantum circuit or are there several options to present it?
Avi
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How are quantum circuits constructed on cloud-based quantum computers?

I've been trying to wrap my head around quantum computing, with mixed success. I have a reasonable understanding of how quantum circuits work and the basic principles. However, there is one big missing piece in my understanding, which I've not been…
ColinE
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Is there a clear, understandable example of Quantum Circuit Cutting I can use to understand the process?

I'm working my way through the ASPLOS paper "CutQC: Using Small Quantum Computers for Large Quantum Circuit Evaluations". At the heart of the paper is, of course, the technique of circuit cutting. A first derivation in the paper was already…
rhundt
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Is a quantum circuit without measurements, a unitary operator?

Is it true that the whole circuit, viewed as a map from the input registers to the end is a unitary operator ?
eternalstudent
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How to calculate CNOT gate for three-qubit (1-control, 2-target) states as a matrix?

How can I calculate CNOT gate with 1 control and 2 target qubits as matrix?
Seokhyeon Lee
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Steps to build a 3 qubit Quantum circuit based on final statevector

I need to build a Quantum circuit in Qiskit as shown below. Does anyone know the formal steps to approach the design?
Joydeep Bhattacharjee
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What is the relationship between cX gate and measurment?

I'm currently working with the cX gate but I have the question: This gate is a projection to sigmax axis on the bloch sphere if y partially trace the target qubit? Or i mean, what is the relationship between this gate and the measurement?
felipechoy
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How can I measure output distributions at different count intervals? (i.e. measure output at 100 shots, at 200, etc...)

So, this is more of a code question rather than a theoretical question. I am working on project and I need to measure the output distributions at various shot intervals. I am currently using a simple while loop, but is there a way to simulate the…
lookreachbrush
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What are the purposes of circuit gates in addition to matrix presentation

If quantum circuit gates can be presented as a matrix, are there any other qualities for the circuit gates except for a compact presentation of a matrix?
Avi
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Would anything change if a qubit was made out of anti-matter?

If you had a QC system with an arbitrary number of qubits and an arbitrary number of anti-qubits (qubits made of anti-matter, e.g. a positron), how would the interactions (e.g. gates) and the circuit model in general change? (If at all?)
K0mp0t1k
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How does superposition enables the detection and correction of a phase error?

In the phase error correction code for three qubits, why do we need to use the hadamard gate? Can someone explain this with math.
LittleBlue
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