All Questions
Tagged with density-matrix programming
20 questions
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Discarding a Quantum register to extract kernel matrix in practical quantum computer
Question: How to extract a kernel matrix from a quantum state on a real quantum computer through discarding a register?
I am trying to understand the paper "Quantum Support Vector Machine for Big ...
- 9
0
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36
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How to generate random quantum states in matlab?
I was wondering if there is some academic standard/any way of generating random n times n q-states/density matrices in Matlab without using any other package then QETLAB.
- 325
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40
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Applying 2-qubit noise to a multi qubit system using local operations in Python
I am trying to create a simulation of 2-qubit dephasing noise that acts on the first two qubits of a multi qubit system. I would like to do this locally rather than expanding my kraus operators into $...
1
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38
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Why is my mutual information negative in Python, and how can I accommodate that?
I'm calculating the mutual information between two 1 qubit subsystems in a quantum state using Python. Theoretically, mutual information should always be non-negative. However, I'm encountering very ...
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Is there a theoretical method to achieve a positive semi-definite density matrix in QST?
The problem of encountering negative eigenvalues in the density matrix during Quantum State Tomography (QST) is well-explained in this Quantum Computing Stack Exchange post.
However, I am seeking ...
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42
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Tests of entanglement between one and many qubits
I have a 5-qubit state $|\psi \rangle$, which has a physical interpretation that the middle qubit is the "impurity" with spin $s_{imp} = 1/2$. The rest 4 qubits highlight the presence of ...
2
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2
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106
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Can non-linear operations be implemented as a circuit on a quantum computer?
Suppose I have a Quantum circuit, which gives an output state $|\psi \rangle$ let's say. I wish to obtain the reduced density matrix by tracing out subsystem B, i.e. $\rho = |\psi \rangle \langle \psi ...
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Particle number expectation value in QuTip
I am learning now to use QuTiP by going through their documentation site. I am trying to understand what does the argument - particle number expectation value in thermal density matrix do? How does it ...
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279
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Create qnode with density matrix on pennylane
I'm using pennylane.
What I want to do is
Create a qnode with the 2*2 density matrix of a single qubit one. It has the parameter as phi
Given density matrix:
$$\...
- 115
2
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1
answer
104
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Converting a Matrix to a Gate in OpenQasm 2
I am a beginner when it comes to quantum computing so forgive me if this is a dumb question. Does anyone know how to create a gate from any matrix on OpenQasm2? Specifically, can anyone provide any ...
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How are $\theta, \phi$ and $\lambda$ for the U3 gate derived in Abhijith et al. 2018?
I am looking to implement Quantum PCA from this paper (page 62). They have their code on Github.
I have gone through the paper multiple times but failing to understand how they got numbers (for theta, ...
- 135
1
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321
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QuTiP VS RK45: Which one gives the correct results for time-dependent systems?
I am writing a code for a quantum thermal machine which includes both coherent and dissipative time evolutions in its different stages of operation. However, evolving the system with "mesolve&...
- 111
5
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1
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363
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What is the superop simulator in Qiskit for?
I'm trying to understand what the use case of a superop simulator would be. My understanding is that density matrix is generally more resource intensive than state vector, but it has additional ...
- 153
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1
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477
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Produce a quantum state with its density matrix an identity matrix up to an constant
For a n-qubit quantum state $|\psi\rangle=\displaystyle\sum_{i=0}^{2^N-1}|i\rangle$, by definition it's density matrix is $|\psi\rangle\langle\psi|=\displaystyle\sum_{i,j=0}^{2^N-1}|j\rangle\langle i|$...
- 998
1
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1
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464
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Initialising impure density matrices
I wish to initalise the state $\rho=(1-\frac{p}{2})|0\rangle \langle0|+\frac{p}{2}|1\rangle\langle1|$, where p is some measure of decoherence. This is a mixed state. There are some suggestions on here ...
- 373
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1
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113
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Information about two algorithms of Matrix product state
In qiskit backends, there is Matrix_product_state.
With this backend, I can simulate circuit for several qubits. And I found some mysterious problem about MPS. With 25,26,27 qubits, the simulating ...
- 967
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348
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Numerical methods for finding an eigen basis of a degenerate Liouvillian
I'm trying to find the steady-state of a master equation,
$$\dot{\rho}(t) = \mathcal{L}\rho(t),\tag{1}\label{1}$$
In the form where we vectorise the density matrix and matrixify (??) the Liouvillian ...
- 11
3
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1
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1k
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What is "Lindblad Superoperator" in Stochastic Master Equation
I was reading a paper titled "Using a Recurrent Neural Network to Reconstruct Quantum Dynamics of a Superconducting Qubit from Physical Observations" and was confused about a stochastic master ...
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2
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2
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5k
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How do I construct a Density Matrix corresponding to a Hamiltonian?
I have a Hamiltonian and I want to know the corresponding density matrix. The matrix I'm interested in is the one in this question.
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7
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2
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1k
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From Q# measurements to Bloch sphere
I would like to represent the state of a qubit on a Bloch sphere from the measurements made with Q#.
According the documentation, it is possible to measure a qubit in the different Pauli bases (...
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