Quantum Computing Stack Exchange
Quantum Computing Stack Exchange

Questions tagged [initialization]

For questions regarding the initial state of a system for quantum computation and their preparation.

26 questions
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Threshold and practical requirements for initial state preparation?

At the beginning of a quantum computational process we generally want to start in a perfectly known initial state, and evolve from there. This cannot be done perfectly, for fundamental reasons, but I strongly suspect there has to be a practical…
agaitaarino
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Projective measurements: aftermath and restoration

I have some practical difficulties with projective measurements, so I'd welcome inspiration from others. This is beyond the question "Are true Projective Measurements possible experimentally?" in that I'm not aiming for perfection but for something…
agaitaarino
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How is the state preparation Unitary in initialize selected?

Normally, in order to prepare the Bell state $\frac{1}{\sqrt{2}}(|00\rangle+|11\rangle)$, we can simply make a circuit with a Hadamard gate on $|0\rangle$ followed by a CNOT gate on $|1\rangle$. However, initializing the Bell state and then using…
sven
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Survey of which 'physically interesting' many-body states can be efficiently prepared on a quantum computer?

For digital quantum simulation of many-body problems, efficiently preparing an initial state of 'physical interest' (e.g. ground states, thermal states, topologically ordered states etc.) is very relevant. There is quite an extensive amount of…
lm1909
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Qiskit: Initializing $n$ qubits with binary values ($0$s and $1$s)

Is there a way in Qiskit to initialize $n$ qubits with binary values (0s and 1s)? For example, how can I initialize two qubits in the state $|11\rangle$? Here is a code snippet: from qiskit import QuantumCircuit import numpy as np n = 2 circuit =…
Dr. Prasanna Date
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Is there a "parameterized initialization" that I can apply to a QuantumRegister to re-use a circuit?

I'm working on a QuantumCircuit which measures the fidelity of one point (my "test vector") and two other points (my "data set", containing of states phi_1 and phi_2) at once. I'm using Afham; Basheer, Afrad; Goyal, Sandeep (2020) to reproduce their…
GroenteLepel
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How to pick number of simulation qubits for finding eigenvalue of fermionic Hamiltonian?

I am having some trouble understanding how the number of simulation qubits are chosen when finding the eigenvalue of a fermionic Hamiltonian. For the phase-estimation algorithm, is the number of simulation qubits the same as the number of particles…
QCQCQC
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Why after transpiling a Qiskit circuit we obtain a different result?

I am trying to obtain the correct circuit transpiled for the ibmq_london device, as I want to know what the real gates applied in the quantum computer are. I am implementing the QFT circuit for 5 qubits. My code is the following one (DAQC and qnoise…
Paula G
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What are the mathematics and theory behind Initializing a quantum state vector?

I do not understand how the initialize function in QiSkit is working. I know that it is used to put a qubit in a specific custom state. My question is - how is it implemented or how to do such a thing mathematically, which gates to use and why? Hope…
Yousef Zook
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From the final quantum state to the quantum circuit composition

When I build a quantum circuit and my initial state is the one composed only by zeros ($|000\ldots 0\rangle$), I have a final state $|\psi\rangle$ that is the result of the application of the quantum circuit to $|000\ldots 0\rangle$. My question is:…
stopper
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Why wont my custom controlled gates in Cirq work on a simulator?

To initialize a state in Cirq, I created a custom controlled rotation and a custom rotation gate. The effect of applying the custom controlled gates to the qubits doesn't seem to affect the state. Here's the definition of the custom controlled…
user14860
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Using QuantumCircuit.initialize() on a real quantum computer

Can the qiskit function QuantumCircuit.initialize be used to initiate any number of qubits (which exist currently on the quantum computers) and can it be used on a real quantum computer?
AL_P
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VQE restart from a previous computation

I'm running VQE algorithm on ibmq-qasm-simulator. I'm trying to implement a restart mechanism in order to be able to start a new computation from the result of a previous one. To do so I've tried to set VQE' s initial_point parameter to…
Valentina
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Prepending initial state to a quantum circuit in Qiskit

I am trying to generate a Quantum Phase Estimation (QPE) circuit in QISKIT the following way. 1 - First, I generate a QPE circuit with the following code: ### building inverse quantum fourier transform circuit iqft = StandardIQFTS(2) iqft_circ =…
NikPapadopoulos
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Default value for a state created by QuantumRegister

What's the default value for a state created by QuantumRegister(1,'name_of_the_register')? Is it a $|0\rangle$ or a $|1\rangle$?
user1319236
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