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)

Filter by
Sorted by
Tagged with
1 vote
0 answers
47 views

pennylane: How to carry out MB rotation without CB rotation?

I'm looking at this MBQC tutorial where there's an example that shows that a MB and CB single qubit rotations give the same result. CB version : ...
  • 1,435
0 votes
0 answers
62 views

Conditions for Fault-tolerant QC to work better than not doing any EC (except the ideal decoder)

I've been exploring fault-tolerant QC with the simplest 7-qubit Steane code, yes I'm able to obtain all the predicted thresholds for various transversal gates and the EC gadgets. I then tried to ...
1 vote
1 answer
54 views

Classical register implementation in Amazon Braket

How to implement classical register in a quantum circuit in Amazon Braket ? I am trying to preproduce results of a circuit build in qiskit on AWS braket services. Thanks
  • 11
3 votes
1 answer
67 views

Classes of quantum circuits that can be "efficiently" simulated

Which kind of quantum circuits can be simulated with classical algorithms in a reasonable amount of time (for a large number of qubits)? For example the ones with only Clifford gates. Or the ones with ...
  • 341
5 votes
1 answer
64 views

Why is error correction very different for circuits compared to channels?

Background Suppose one wishes to communicate information using a noisy channel $N$ instead of an ideal channel $I$. The general framework to communicate reliably is Take $n$ copies of $N$. For some ...
  • 2,383
4 votes
1 answer
73 views

Is it possible to implement any random Hamiltonian using quantum circuit

Are there any restrictions on implementing the evolution of any random Hamiltonian? Suppose I want to implement Rabi oscillations using a quantum circuit, I initialize the state and the Hamiltonian ...
0 votes
0 answers
40 views

Applying horizontal dots in a LaTeX Quantum Circuit diagram [closed]

I am almost done with my circuit diagram for the QAOA circuit but the \cdots does not want to cooperate. As seen there exists some wire drawn across the dots from the gate to the right and I can't ...
1 vote
2 answers
102 views

How to repeat the same Qiskit instruction $N$ times (no for loop)?

I need to build the following 1-qubit QuantumCircuit in Qiskit, repeating the pair ($X$ gate, barrier) for $N$ times: The most straightforward way to do this is by ...
3 votes
1 answer
47 views

how to flatten a cirq.Circuit with CircuitOperation

I have a cirq.Circuit that uses a CircuitOperation, something like: ...
  • 325
1 vote
1 answer
47 views

Does the Bell's state entanglement violate the reversibility property of unitary matrices?

I read unitary matrices are reversible, so when we apply a unitary operator $U$ on some input state and got an output state, then if we apply $U^\dagger$ (transpose conjugate) we get back the original ...
1 vote
1 answer
55 views

Commutativity of XY gate

My question is a simple one: Can 2 XY gates commute ? XY gate is a 2-qubit XX+YY interaction also sometimes referred to as iSwap gate.
2 votes
2 answers
91 views

How to translate a 4-qubit Grover's algorithm circuit into a state Matrix?

Grover's algorithm circuit may be implemented as follows: (from here) It is shown very elegantly by @MartinVesely (How to interpret a 4 qubit quantum circuit as a matrix?) how to translate a 4 qubit ...
  • 191
1 vote
0 answers
45 views

qiskit.algorithms.optimizers callback function for all optimizers

I am aware that VQE and VQC factory supports callback functions which can allow us to store intermediate values during optimization through callbacks in its arguments. However my loss function is ...
1 vote
0 answers
51 views

IBM composer deletes my circuit

When I work on the IBM quantum composer and I switch to another circuit, my first circuit is destroyed and replaced by the second one. I thought it was a display bug, but when I restart the composer, ...
  • 23
4 votes
0 answers
66 views

Difference between IBM simulator backends

I'm an Msc student working on a quantum information project (VQEs on 4 qubits). Our group is looking at different IBM simulators on the IBM platform, and have noticed that performance is different for ...
  • 41
3 votes
1 answer
88 views

Simulation files for noisy quantum circuits

For our study with Yosi Rinott and Tomer Shoham we need the following simple data: Starting with a quantum circuit $C$ on $n$ qubits we need two files: a) A file of probabilities (or amplitudes) for ...
  • 201
1 vote
1 answer
40 views

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 ?
1 vote
1 answer
32 views

Alternative Versions of Quantum Fourier Transform (Decimation in Time/Frequency)

Is there a good comparison of alternative versions of the Quantum Fourier Transform (QFT) that mirror the alternative decimation-in-time or decimation in frequency versions for the conventional Fast ...
0 votes
0 answers
28 views

Bound on scaling mixed quantum-classical computer designs

I am familiar with some basics of quantum computation and this makes me wonder, are there any upper bounds known on the size of a quantum circuit, such that quantum circuit + some classical circuit, ...
  • 101
1 vote
2 answers
85 views

Conversion error: from a QISKIT circuit to a QASM string and back

I created a circuit in qiskit and then converted it into a QASM string. When I try to make a circuit out of the QASM string I get the error: ...
  • 1,748
1 vote
0 answers
31 views

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:
  • 37
0 votes
1 answer
40 views

Survival probability quantum circuit

Suppose say that I have a quantum state $\vert\psi\rangle$ at time $t = 0$, which is now evolved by a hamiltonian $H$ $$e^{-iHt}\vert\psi\rangle$$. I can ask the question, how much of initial state is ...
7 votes
0 answers
243 views

What is a gate-level circuit used in the 2022 Jafferis et al. experiment on Sycamore?

A recently published Nature paper of Jafferis et al. describes an experiment with a handful of qubits performed on Google's Sycamore processor to explore the SYK model in the context of AdS/CFT and ...
  • 8,477
0 votes
1 answer
56 views

How do I bound parameters in RawFeatureVector with ParameterizedInitialize in Qiskit?

I'm not sure how to bind the parameters in the Qiskit RawFeatureVector circuit. Here is my code: ...
1 vote
2 answers
68 views

What does circuit-xxx accomplish after circuit gets decomposed by qiskit?

as mentioned in the title, i have a problem with the qiskit decompose function. ...
  • 97
0 votes
0 answers
30 views

How to implement this circuit either using Jupiter notbook or qiskit

I am new to quantum-computaions and learning qiskit. I am trying to construct a two qubits circuit that performs a bell measurement using $\{|\beta_{01}\rangle \langle \beta_{01}| \} $ projectors. ...
  • 1
1 vote
1 answer
32 views

How to create Parametrized Operator

How to transform the U3 gate of parameters (theta, phi, lambda) to an Operator. (in qiskit) The following code don't work ...
0 votes
1 answer
57 views

problem with parametrized circuits

I used a circuit with one parametrized gate U(theta, phi, lambda), than I fixed the parameters with qc.bind_parameters and it's worked well. But the only step that don't work is the execution in a ...
1 vote
2 answers
56 views

Label Qubit Starting State in Qiskit

$ \def \ket#1{|#1\rangle} \def \bra#1{\langle#1|} $Is there a way to set qubits to be a specific value outside of resetting them like so? I understand that all qubits are initialized to the $\ket 0$ ...
1 vote
2 answers
84 views

Draw Circuit with 'latex' with to_gate involved

The circuit draw command doesn't work when there is a custom gate as follows: ...
1 vote
1 answer
35 views

Use state vector simulator with TensorCircuit

Is there a option to use instead of tensor network contraction state vector simulator for quantum circuits? This might be useful for small sized circuits, but I would still like to use TensorCircuit s....
0 votes
2 answers
63 views

How to create superposition of all bitstrings with exactly two ones on 4 qubits?

On a quantum circuit, how would I create an equal superposition of the states: $$|\psi\rangle=|0011\rangle + |0101\rangle + |0110\rangle + |1001\rangle + |1010\rangle + |1100\rangle.$$
2 votes
1 answer
51 views

Quantum In-place Modular Addition Circuit

Can anyone explain this in-place modular addition circuit from the paper "Quantum Resource Estimates for Computing Elliptic Curve Discrete Logarithms" by Martin Roetteler et. al (https://...
1 vote
2 answers
49 views

Vanishing expectation value $|\langle Z_1Z_2...Z_N \rangle|$

I'm doing a research involving expectation values of different observables. I've observed that, given a random Quantum Circuit $U$ with $N$ qubits acting on an inital state $|0\rangle$ in such a way ...
  • 341
2 votes
1 answer
75 views

How to calculate a matrix difference in a quantum circuit in the form $A - BAB$

In quantum circuits, every gate is a unitary, and these gates get multiplied together. For example, a simple circuit that performs $X$ on the least significant qubit (i.e., $I \otimes X$), and $CNOT$ ...
1 vote
1 answer
69 views

How to interface stim to a generic qiskit decoder?

I can generate encoder/decoder circuits for arbitrary QECC in qiskit. I tested a number of codes : $[[5,1,3]], [[7,1,3]],[[8,3,3]],\cdots$ and everything seems to work fine. The problem is that the ...
  • 1,435
1 vote
2 answers
41 views

Plot circuit within TensorCircuit

Given an arbitrary TensorCircuit, is there a convient way to get a plot of the circuit?
0 votes
0 answers
35 views

Method to use nonlinear operators within quantum circuits

I recently learned of a technique known as "block-encoding" which embeds any $M \times N$ matrix into a unitary matrix, given that the spectral norm is at most $1$. This type of result is ...
1 vote
1 answer
43 views

How $X\otimes X^{1/2}$ propagates through $CZ$

I am trying to find out how the $X\otimes X^{1/2}$ operator propagates through a $CZ$ one. Below a circuit example.
0 votes
0 answers
47 views

How to use more than 3 classical registers in a single quantum circuit in Qiskit without getting error: not enough memory slots?

I'm trying to run a quantum circuit on qasm simulator which has more than 3 classical registers. It gives error when I try to execute it. The circuit looks ...
  • 53
4 votes
1 answer
49 views

gradient estimations on variational quantum algorithms

Other than the two famous parameter-shift rule and finite difference method, is there any other (perhaps simple) methods to estimate gradients of a cost function in variational quantum algorithms?
  • 391
1 vote
1 answer
72 views

Is there a way to decompose a quantum circuit into layers?

For example, if take the following circuit as the input (either QASM or Qiskit): ...
  • 33
1 vote
1 answer
43 views

Is there any shortcut to create a controlled gate or any technique?

I was solving Controlled H gate from qiskit textbook -> Basic Circuit Identities There I tried to find the unitary matrix for CH gate but it get's really complicated when I use tensor product or ...
  • 123
0 votes
2 answers
58 views

How $X$ noise propagates through controlled-$S$ gate

I am struggling to find how an $X$ noise propagates through a controlled-$S$ gate. Here`s the circuit.
2 votes
0 answers
52 views

How to use stabilizers to simulate the circuit?

Sorry for this easy questions. That is a simple textbook question but I don't know how to solve it. I have the following circuit: The question was "use stabilizers to simulate the circuit" ...
  • 544
0 votes
1 answer
60 views

How can we represent a CNOT gate using a cascade of rotation gates?

I have been working using qiskit to implement the CNOT decomposition into a cascade of rotation gates from this source. After computing the unitary matrix, the resultant matrix is not the same as the ...
0 votes
0 answers
9 views

Size of output and post selection registers

Let $\mathcal{A} =\{\mathsf{Q}_n\}$ be a quantum circuit, taking $n$ input qubits to $n$ output qubits. It is known that \begin{equation} \mathsf{Post}\mathcal{A} = \mathsf{Post}\mathsf{BQP}, \end{...
1 vote
1 answer
38 views

ModuleNotFoundError when running Qiskit RNG

I'm trying to generate random numbers using IBMQ backends with the following code: ...
1 vote
1 answer
47 views

Is there an alternative algorithm to extract a probability of states of qubit after measuring?

Let a simple quantum circuit consist of one qubit and one classical bit. Initially, a qubit has the $|0\rangle$-state and then goes through some sequence of quantum gates, see the circuit below. The ...
  • 131
1 vote
2 answers
144 views

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?

1
2 3 4 5
7