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Definition(s) of $\delta$ in quantum phase estimation

I read the chapter on QPE (quantum phase estimation) in Nielsen and noticed that $\delta$ is defined there as follows: $0 \leq \delta \leq 2^{-t}$, see: 5.2.1 Performance and requirements The above ...
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0answers
17 views

Understanding Qiskit's $\texttt{AmplificationProblem()}$ behaviour

This is related to my previous question. To apply amplitude amplification in Qiskit, one needs to use AmplificationProblem() or ...
3
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1answer
39 views

How we can show Lindblad operators are satisfying the following condition?

How can we show that when the Lindblad operators satisfy the condition: $$\sum_{\mu}L_{\mu} L_{\mu}^{\dagger} = \sum_{\mu} L_{\mu}^{\dagger}L_{\mu},\tag{1}$$ the master equation evolution ...
2
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0answers
22 views

How to return phase angles as seen in IBMQ composer using qiskit?

I recently transitioned from using the IBMQ composer and am using qiskit in the IBM lab. To start, I wanted to learn how to reproduce the computational basis states, probabilities and phase angles as ...
3
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1answer
20 views

What is the method to create arbitrary controlled circuits in Qiskit?

I am working on an implementation of an algorithm which uses ampitude estimation and amplification as a subroutine but we are not using qiskit but QuEST. QuEST doesn't have any direct method to ...
1
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0answers
27 views

queueinfo() module in Qiskit

I want to know how to use queueinfo() module in IBM Qiskit. When I type job.QueueInfo(), it says "QueueInfo" is not defined. How to import it? I'm trying to use queueinfo() to know the time ...
1
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2answers
47 views

Setting the $\texttt{state_preparation}$ for $\texttt{AmplificationProblem()}$ in the scope of Grover's algorithm

I am having trouble setting the state_preparation parameter of AmplificationProblem() from ...
3
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0answers
14 views

Is it possible to set quantum volume in IBM Quantum simulator?

A quantum volume serves as a metric of a quantum processor quality. So far, IBM Quantum provides processors with quantum volume up to 128. Freely accessbile processors have QV up to 32. A user using ...
2
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0answers
35 views

Is the boundary of the set of quantum behaviours a polytope?

Consider the standard 2-2 Bell scenario, with two parties each one choosing between two measurement settings, with each measurement setting leading to one of two possible measurement outcomes. ...
2
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1answer
15 views

What is the difference between quantum "system", "register" and "Hilbert space"?

As far as I can tell, these terms are interchangeable but I am not sure of this. What is meant by each of the terms "quantum system", "quantum register" and "Hilbert space&...
2
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1answer
51 views

Why does $H^2=X^2 =I$ not imply $H=X$?

if $HH = I$ and $XX =I$, then is $H=X$? $HH = I = XX$ or, $HH = XX$ then, taking under root, is $H = X$? This is absurd but how to disprove it?
3
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1answer
41 views

Are $(|00\rangle-|11\rangle)/\sqrt2$ and $(|11\rangle-|00\rangle)/\sqrt2$ the same quantum state?

The state $(|00\rangle-|11\rangle)/\sqrt2$ is an entangled state. If we think about the state $(|11\rangle-|00\rangle)/\sqrt2$, is this also entangled, but with maybe a phase change? The above two can ...
1
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1answer
42 views

Factoring Decision Problem - why not in P? [closed]

Nielsen and Chuang, 10th Anniversary Edition, page 142, refers to the following (classical) computation problem: Given a composite integer m and L <m, does m have a non-trivial factor less than L? ...
1
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2answers
70 views

Why doesn't this simpler teleportation idea work?

This circuit: The first (upper) qubit is the one we want to teleport, so could start it any state, call $\alpha|0\rangle+\beta|1\rangle$. Our goal is to teleport it to the third (bottom) bit. After ...
1
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0answers
23 views

Accessing more than 5-qubit IBM Quantum Computer [duplicate]

I'm doing a university project related to Physics using IBM Qiskit. I want to know how to get access to Quantum Computers with more than 5-qubits (preferably more than 10 qubits)? My account ...
2
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1answer
17 views

Why is Measurement Device Independent (MDI) Quantum Key Distribution (QKD) truly MDI?

This is a repost from a question I posted in the physics stack exchange I am having a hard time understanding why MDI-QKD is truly measurement device independent. My current vision is that Charlie (...
7
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1answer
129 views

Is Toffoli a fault tolerant transversal gate of the repetition code on bit-flip-error-only qubits?

Suppose you have physical qubits that only have bit flip noise (no phase flip noise, no unwanted measurements, no leakage, no amplitude decay, etc; just unwanted X rotations). Such qubits can be kept ...
1
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0answers
11 views

Openfermion state transformation from Bravyi-Kitaev basis to occupation number

I'm working in the Bravyi-Kitaev basis implemented by the openfermion.bravyi_kitaev() function to find the ground state of a fermionic operator in the BK ...
6
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1answer
62 views

What are the vertices of the no-signalling set $\mathcal{NS}$?

Consider the standard 2-2 Bell scenario, with two parties each one choosing between two measurement settings, with each measurement setting leading to one of two possible measurement outcomes. ...
1
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1answer
39 views

For the circuit below, could anyone explain the results I get?

This was sent to qasm_simulator, and the results look like: It seems qasm has added classical bits but why there are gates on the right side of the line. What do they mean? Also, what does the result ...
2
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1answer
41 views

Why does measurement in computational basis result in classic probability?

I am working on a problem related to finding the limits on the joint probability distributions/correlations of three or more quantum systems who share entangled states, after measurement. I have been ...
1
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1answer
29 views

In "from qiskit import *" , how can I check the entire spectrum of imports available

In some codes, I have seen "from qiskit import QuantumCircuit, aer, execute". Some say "From qiskit import *". This is python related, I understand, but with respect to Quantum ...
2
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1answer
33 views

What is the $K_i$ in Fubini-Study tensor?

Following this paper and tutorial from Pennylane, I'm trying to re-calculate the Fubini-Study tensor: $$ g_{i j}^{(\ell)}=\left\langle\psi_{\ell-1}\left|K_{i} K_{j}\right| \psi_{\ell-1}\right\rangle-\...
1
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2answers
43 views

Confusion about the Grover algorithm

Suppose I have a list of items: $(a, b, c, d, e, f, g, h)$. I could encode these letters in $3$ qubits such that $a = \vert 000\rangle, b = \vert 001\rangle, \cdots, h = \vert 111\rangle$. If I'm ...
0
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0answers
26 views

I am a beginner and therefore, these three H terms are confusing. "Hemitian", "Hamiltonian", and "Hilbert"

I am a beginner and therefore, these three H terms are confusing. "Hemitian", "Hamiltonian", and "Hilbert". Could someone give proper context and explain these terms . ...
2
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1answer
46 views

What is the difference between the two entanglement circuits?

For a three qubits system to be in an entanglement(GHZ) state, the circuit can be built as per Qiskit, Here, the control bit of the second X gate is on q0. what if the control bit is shifted to q1. ...
2
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1answer
87 views

How many minimum Quantum Rats are needed to figure out which bottle contains poison?

For the classical Poison and Rat puzzle, we need at least $\lceil\log_2({\rm bottles})\rceil$ rats to figure out the poisoned bottle. If we have Schrödinger’s quantum rats, can we use fewer rats(...
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0answers
23 views

How to create uniform superpostion of N states where N is not power of 2 [duplicate]

Many textbooks only consider superposition of N states where N is a power of 2. For example, H|0> is a uniform superpostion of |0> and |1> and N=2. How to construct quantum circuit for a ...
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0answers
31 views

How to to build/simulate Toffoli gate using CSWAP (Fredkin) gates? [duplicate]

I have seen a question about the other way (CSWAP from CCNOT). Both are 3 qubit gates. Is there a way to simulate CCnot from Fredkin gates?
2
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1answer
53 views

What is the difference between Qiskit Terra, Aer, Ignis and Aqua?

I am going through the Qiskit tutorials and they have an article on each of the above 4. however, As a beginner, I am not very clear. Could anyone share some insights on these?
2
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1answer
45 views

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 ...
2
votes
1answer
66 views

Amplifying entangled qubits

Suppose I have a three-qubit entangled state of the following form: $$ |00\rangle|\psi_1\rangle + |01\rangle|\psi_2\rangle + |10\rangle|\psi_3\rangle + |11\rangle|\psi_4\rangle $$ I refer to the ...
2
votes
1answer
21 views

Properties of the generalized fidelity for subnormalized states

The generalized fidelity for quantum states that may be sub-normalized is given by (Defn 3.12) $$F_{*}(\rho, \tau):=\left(\operatorname{Tr}|\sqrt{\rho} \sqrt{\tau}|+\sqrt{(1-\operatorname{Tr} \rho)(1-\...
2
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1answer
34 views

How can I add readout error in constructing a quantum noise model?

I'm trying to construct a quantum noise model with readout error only: qiskit.providers.aer.noise.NoiseModel.add_readout_error. However, when I try to specify the ...
1
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1answer
46 views

Hamiltonian of Qiskit QFT is not hermitian

I am trying to generate the Hamiltonian of a quantum Fourier transform by taking the log of the corresponding unitary using qiskit and scipy. I don't find a hermitian matrix. Why? ...
3
votes
1answer
32 views

Soundness of Grover's search application

I find that some algorithms can be sped up using Grover's search, but I have a question about the soundness of new algorithms. Since Grover's search is a probabilistic method, it has a chance to make ...
4
votes
1answer
56 views

Register size in factoring 15 using Shor's algorithm

In Nielsen and Chuang's book: Quantum computation and quantum information (2016), there is an example in Box 5.4 which shows how to factor $15$ using Shor's algorithm. I am confused about a ...
4
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1answer
53 views

Derivation of efficiency of Phase Estimation Algorithm

In the section Performance and requirements of the phase estimation algorithm of Page 224, Quantum Computation and Quantum Information by Nielsen and Chuang In order to obtain Eq. 5.27 we have ...
1
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0answers
23 views

How do I construt a mixed state for an arbitrary symmetric matrix?

A symmetric matrix can be seen as a density matrix. If I have an arbitrary symmetrical matrix, can I use a quantum random access memory to construct a corresponding mixed state? What kind of quantum ...
1
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0answers
13 views

Is there any software package tracking Pauli errors in stabilizing circuits with GUI?

I want to track the Pauli errors propagating in stabilizer circuits like surface code. I wonder whether there is any developed package that can do this elegantly. It will be better if it has GUI that ...
2
votes
0answers
14 views

Max-relative entropy quasi-convexity inequality under partial trace

The max-relative entropy between two states is defined as $$D_{\max }(\rho \| \sigma):=\log \min \{\lambda: \rho \leq \lambda \sigma\}.$$ It is known that the max-relative entropy is quasi-convex. ...
0
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0answers
42 views

AttributeError: 'UCC' object has no attribute 'set_max_evals_grouped' [closed]

I'm trying to run the VQE algorithm using an Aer backend simulator. However, whenever I run the algorithm I Receive this error: "AttributeError: 'UCC' object has no attribute '...
2
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1answer
40 views

Coupling maps in quantum computation

Perhaps a bit naive question from my side, but I could not find any satisfactory answer elsewhere: What exactly are the coupling maps in quantum computation and, more particularly, how do those maps ...
1
vote
1answer
86 views

Expected value of Z operator in GHZ state

I'm following this notebook written using amazon-braket, and there's a statement I don't understand ... To reiterate, the following output is expected: $$\left|\mathrm{GHZ}\right> = \frac{1}{\sqrt{...
3
votes
3answers
908 views

Why can't we simulate a Qubit using classical computer?

I am completely a noob in terms of quantum computing, have watched several videos to understand what Quantum computers are trying to achieve. I am a programmer of classical computers. We have a ...
2
votes
1answer
81 views

VQE from scratch, what have I got wrong?

I've been working on a code to run VQE with a grouped measurement. For some reason, my expectation values are slightly off from those computed by pennylane, the software I decided to use for this ...
1
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0answers
23 views

How should I think about circuit metrics like "qubit count," "circuit depth," and "gate count" when dealing with the OpenQASM 3 `ctrl` modifier?

It seems like circuit metrics like qubit count, circuit depth, and gate count are pretty useful. Qubit count determines whether a it's even possible to run a program on resource-limited quantum ...
3
votes
1answer
44 views

Is it possible to use a quantum algorithm to optimize quantum chips

I'm really new to QC, so please excuse if this is a dumb question. I was looking at the different Qubit configurations/arrangments in chips and was wondering if it is possible to create an algorithm ...
2
votes
1answer
43 views

Using Quantum Bit String Comparision inside Grover's algorithm

Intro I am trying to implement a quantum bit string comparator (QBSC) circuit (based on this paper) into a simple Grover's algorithm but I am unfortunately running into issues. The paper has two ...
-3
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0answers
23 views

Quantum teleportation using a type of mixed state [closed]

Alice and Bob are performing the teleportation protocol.[]

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