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Questions tagged [amplitude-amplification]

For questions about the amplitude-amplitude algorithm. Do NOT use for general Grover's algorithm related question. Amplitude amplification is a technique in quantum computing which generalizes the idea behind Grover's search algorithm and gives rise to a family of quantum algorithms. It was discovered by Gilles Brassard and Peter Høyer in 1997 and independently rediscovered by Lov Grover in 1998. (Wikipedia)

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How to perform amplitude amplification to return $|\psi_{\rm good}⟩$ from $\cos\theta|\psi_{\rm good},\phi⟩+\sin\theta|\psi_{\rm bad},\phi^\perp⟩$?

You are given access to a quantum algorithm $A$ that prepares a state $$|\psi\rangle=cos\theta|\psi_{good}\rangle|\phi\rangle+sin\theta|\psi_{bad}\rangle|\phi^{\perp}\rangle$$ Where $|\phi\rangle=\...
afebs's user avatar
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3 votes
1 answer
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How to perform amplitude amplification when the initial amplitude of aiming state is unknown

Let's say, I want to perform amplitude amplification on the quantum state $$|s\rangle=\sum_{i=0}^{2^n-1}m_i |i\rangle\,,$$ And the aiming state is $|x\rangle\,.$ Usually, when I perform amplitude ...
mingo's user avatar
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working of Variable time amplitude amplification (VTAA) compared to amplitude amplification (AA)

I read the paper by Ambianis on variable time amplitude amplification to improve the $\kappa$ (condition number) dependency for the Quantum linear system algorithm by Childs et al.. I can see VTAA ...
Manish Kumar's user avatar
2 votes
0 answers
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Grover meets Anyone - feasibility

Recently, a variety of algorithms have been proposed to combine Grover algorithm with other quantum algorithms. As an example, given a function $f: \{0, 1\}^n\mapsto \{0,1\}$, the Grover meet Simon ...
tigerjack's user avatar
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How to amplify amplitudes above some threshold, given additional information about the state

Given a quantum state $\left|\Psi\right> = \sum_{i=0}^{2^n-1} \alpha_i\left|i \right>$, for which I know that the probabilities ($|\alpha_i|^2$) follow a sine/cosine like distribution as in the ...
D.D.'s user avatar
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2 votes
1 answer
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Get confused about the implementation of Amplitude Amplifier

I have a circuit $A$, which produces $$A|0^n\rangle _a |00\rangle _b = \phi_0 |00\rangle _b + \phi_1 |01\rangle _b+ \phi_2 |10\rangle _b + \phi_3 |11\rangle _b$$ And only $\phi_0 |00\rangle _b$ is ...
Alexis's user avatar
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Can Amplitude Amplification amplify an unknown state? [duplicate]

If you have for example the basis states $|000\rangle$ and $|xxx\rangle$. The value of the second basis state is unknown, but the amplitude of both states is given. Also the amplitude of the second ...
Manuel's user avatar
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1 answer
144 views

How do I apply Amplitude Amplification for following state?

I have a multi qubit state that consists of two basis states and looks like the following for different number of qubits: 2 qubits: $|00⟩+|xx⟩$ 3 qubits: $|000⟩+|xxx⟩$ 4 qubits: $|0000⟩+|xxxx⟩$ ... (...
Manuel's user avatar
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Grover / amplitude amplification with exponentially high success probability

All the references on Grover / Amplitude Amplification (AA) (Mike&Ike, wiki, Lin Lin lecture notes, etc.) give a recipe for preparing the desired state (or amplifying the state) with probability $\...
mavzolej's user avatar
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Amplitude amplification on each register in a product state

let oracle $U_\psi$ prepare a state $\psi$ with success probability $p$. For simplicity assume that $U$ requires a single ancillary qubit and $\psi$ is itself a single-qubit state: $$ U_\psi |0\rangle|...
mavzolej's user avatar
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1 vote
1 answer
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Amplitude amplification in Grover algorithm

In "Quantum Computation and Quantum Information", they talk about Grover search. One part of the Grover search is Amplitude amplification: But i think the red line is not true. Because i do ...
Huy By's user avatar
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1 answer
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Oracle in Grover's algorithm [duplicate]

In the Grover's algorithm, the solution is already in the Oracle in order to mark winning state(s). I just wonder if we already know the solution, why do we need to run a circuit ?
lenhhoxung's user avatar
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Is amplitude estimation optimal?

Amplitude estimation requires $O(1/\epsilon)$ measurements if we want to estimate an amplitude to absolute precision $\epsilon$. Is this optimal? Why can't we do better than this? I'm trying to see if ...
confusion's user avatar
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Amplitude Estimation/Counting - unsatisfiability

The Amplitude Amplification paper states in Theorem 13: For any positive integers $M$ and $k$, and any Boolean function $f: \{0,1,\ldots,N-1\}\rightarrow\{0,1\}$, the algorithm Count $\left(f,M\right)...
inq's user avatar
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2 votes
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Find the number of iterations for Amplitude Amplification to get the correct states amplified

I'm trying to use Grover operator in Qiskit (more precisely to perform Amplitude Amplification) but I'm facing some problems. I'm experimenting the Quantum Amplitude Amplification in order to amplify ...
Tommaso's user avatar
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Defining an oracle with Qiskit

I have a 8-qubits circuit whose final vector state may be for instance: $$ \frac{\sqrt{2}}{4} |00010101\rangle+\frac{\sqrt{2}}{4} |00101010\rangle+\frac{\sqrt{2}}{4} |01010110\rangle+\frac{\sqrt{2}}{4}...
Maurice Clerc's user avatar
1 vote
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Which applications of quantum singular value transformation use block-encodings in apriori unknown bases?

Quantum singular value transformation (QSVT) algorithm allows performing polynomial transformations on matrices that are block-encoded in a unitary. Typically, block encoding is assumed to be 'the top-...
Nikita Nemkov's user avatar
1 vote
1 answer
294 views

Grover's algorithm for complex phases

Grover's algorithm traditionally inputs a phase oracle, $U_\omega$ such that $U_\omega | x \rangle = (-1)^{f(x)} | x \rangle$. The task is to find some $x$ such that $f(x) = 1$. In other words, the ...
Andrew Baker's user avatar
1 vote
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Quantum Amplitude Estimation formulations (Brassard et. al. vs Montanaro)

I am puzzled on the relation between the two approaches (old and new). (a) The original approach of QAE as described by Brassard et. al. uses two operators to form ${Q}$: $$ {Q}={A} {S}_0 {A}^{\dagger}...
Marion's user avatar
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2 votes
0 answers
109 views

Converting from amplitude encoding to basis encoding

The question is inspired from Preparing a quantum state from a classical probability distribution which shows how basis encoding $\frac{1}{\sqrt n}\sum_{x=0}^{n-1}|x\rangle|p(x)\rangle$ may be ...
Philips's user avatar
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Amplitude amplification when an exact input state is unknown but amplitude is known

Let initial quantum state be $|s\rangle = a|0\rangle|d_a\rangle + b|1\rangle|d_b\rangle$. I know value of amplitude $a$, but I do not know $|d_a\rangle$ and $|d_b\rangle$. These unknown states can be ...
Philips's user avatar
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An improved search algorithm based on weak value amplification?

I am having difficulties understanding this paper (arXiv:1910.12390), so asking this question. As far as what I see from mathematics of this paper, all improvements over Grover's search disappear when ...
Zimmermann's user avatar
1 vote
1 answer
69 views

In the quantum mean computation circuit, how to apply the controlled rotation to the extra qubit?

I'm trying to implement quantum mean computation via amplitude estimation, as suggested in Example 8.3.5 in Kaye, LaFlamme, Mosca. I wonder about the actual circuit to accomplish this. This previous ...
rhundt's user avatar
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7 votes
2 answers
221 views

How to increase the probability of successful measurement to find out the largest amplitude?

I have built a state $$A|0\rangle = |\Psi \rangle = \sum _n c_n |n\rangle$$ Where $A$ is a circuit. And I need to known, where is the largest $|c_n|$. I find out that, I can simply do many ...
Alexis's user avatar
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1 answer
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Can one obliviously reflect about the *initial* state in fixed-point amplitude amplification?

It is normal to extend fixed-point amplitude amplification to an oblivious version, i.e., $1 - (1-e^{i \beta})|t\rangle \langle t | \rightarrow 1 - (1-e^{i \beta}) 1 \otimes |0\rangle \langle 0|$, ...
kηives's user avatar
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For the superposition state of a composite system, how to use the quantum amplitude amplification algorithm to simultaneously amplify several of them

For the superposition state $|\Phi \rangle =\frac{1}{16}\sum\limits_{i=0}^{15}{(|i\rangle |{{a}_{i}}\rangle )}$ (The second quantum system ${a}_{i}$ is not necessarily all orthogonal) of a composite ...
Ren-Xin Zhao's user avatar
1 vote
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158 views

Amplitude Amplification applied to HHL Algorithm

I’m trying to understand and implement the amplitude amplification algorithm described in the HHL paper. I’m using the cirq implementation of the HHL algorithm as my starting point. I have a couple of ...
Markivaira's user avatar
3 votes
1 answer
216 views

Qiskit: Get number of iterations for Iterative Amplitude Estimation

Trying to count the number of uses of my circuit $A$ in Grover iterate circuit $Q= -AS_0A^{\dagger}S_x$. However, Qiskit's amplitude estimation algorithms such as IAE or FAE accept only precision ...
consthatza's user avatar
2 votes
1 answer
208 views

Reflection operator in amplitude amplification for block encoding

I am trying to figure out equation (2.33) here. Given that \begin{gather} U_{\psi_0}|{0^m}\rangle|{0^n}\rangle=\sqrt{p_0}|{0^m}\rangle|{\psi_0}\rangle+\sqrt{1-p_0}|{\perp}\rangle,\\ (\Pi\otimes I_n)|{\...
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1 vote
0 answers
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Using rotation gates instead of Grover

I have a conceptual question about Grover's algorithm. In the textbook case, we always assume to have an oracle that singles out the correct states by giving them a negative phase. Then, we use phase ...
Gemeis's user avatar
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4 votes
0 answers
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Why does QAA need QPE to estimate the probability of the good state?

I have some trouble understanding some aspects of the Quantum Amplification Algorithm (QAA). I am using this reference for the following discussion (section 4). The QAA applies a certain operator $Q :=...
Marion's user avatar
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3 votes
1 answer
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Amplitude amplification with or without ancilla state

I am trying to understand amplitude amplification and I am able to find two formulations (almost identical). (A) No ancilla Usually, and what I do understand quite well, is that you start with the ...
Marion's user avatar
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2 votes
0 answers
60 views

Amplifying states using partial information

Assume we have an initial state $(H^{\otimes n}|0\rangle)|0\rangle = \frac{1}{\sqrt{N}}\sum_{i=0}^{N-1}|i\rangle|0\rangle$ in two $n$-qubit registers (let $N=2^n$). Then we feed this state through a ...
Gemeis's user avatar
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1 answer
188 views

Using Grover on entangled states

I am trying to implement Grover's algorithm on an entangled state. The idea is that I will have a state $\sum_x\alpha_x|f(x),x\rangle$ and I want to measure the $x$, for which $f(x)=0$. Note that $f$ ...
Gemeis's user avatar
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2 votes
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Oblivious Amplitude Amplification

I've been looking for the OAA paper but I've been unsuccessful in finding it. (so any links will also be helpful) My question is essentially this, given the state: $$\vert 0good \rangle + \vert 1bad \...
Dani007's user avatar
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3 votes
1 answer
259 views

In generals Amplitude Amplification algorithm, the initial state does not need to attain equally superposition?

In the beginning of this paper about amplitude amplification algorithm, the author stated the conventions of amplitude amplification which I quoted the important part for your convenience as follows: ...
narip's user avatar
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3 votes
0 answers
134 views

Understanding Qiskit 0.32 's $\texttt{AmplificationProblem()}$ behaviour

This is related to my previous question. To apply amplitude amplification in Qiskit, one needs to use AmplificationProblem() or ...
26118in's user avatar
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1 vote
2 answers
155 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 ...
26118in's user avatar
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1 answer
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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 ...
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2 votes
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How to understand picking a random subcube in the Aaronson/Ambainis spatial search algorithm?

I am referring to the Quantum Search of Spatial Regions paper. I must confess that the paper itself is a bit heavy for my level of mathematical fluency. Trying to understand it nevertheless and having ...
Stanislaw's user avatar
6 votes
1 answer
443 views

BHT algorithm implementation

Summary of Method Amplitude Amplification Summary The BHT algorithm uses amplitude amplification, a nice generalisation of Grover's algorithm, where there is a subset $G\subset X$ of good elements in ...
Chris Long's user avatar
2 votes
1 answer
156 views

Noise-induced amplitude amplification?

I wanted to share some results from an experiment which I find thought were deeply surprising. The basic idea is to prepare a superposition in a main register then conditionally apply lots of random ...
Edwin Agnew's user avatar
0 votes
0 answers
328 views

How does the amplitude amplification in Grover's algorithm work?

As the question says - how does the amplitude amplification in Grover's algorithm work? I am fine with adding the negative phase on the winning state, but how does one generate the diffuser to ...
YoungBoi's user avatar
2 votes
0 answers
76 views

Managing memory while running a high depth circuit simulation (amplitude amplification) using Qiskit

I am running an instance of amplitude amplification using Qiskit (v 26) on Google Colab. The circuit is approximately 17 qubits in space and $O(ck)$ in depth where $k \in \left \{1,2,3....,22 \right \...
César Leonardo Clemente López's user avatar
2 votes
1 answer
190 views

Amplitude Amplification for searching $|0\rangle$ in an unknown state

For one known (invertible) function that does: $$f:H^{\otimes 2n}\times H^{\otimes 2n}:|x⟩|0⟩\mapsto|x⟩|y⟩$$ I want to find a similar (invertible) function that does: $$g:H^{\otimes 2n}\times H^{\...
Lei Zhang's user avatar
3 votes
1 answer
233 views

Combining Amplitude Amplification with HHL

I'm recently learning about how to apply Grover search techniques to other places. An example I've come across is to amplify the probability of measure a $\lvert 1 \rangle$ of the ancilla qubit in HHL ...
genesis gcd's user avatar
2 votes
1 answer
131 views

Manipulating the amplitude of state based on the state information

In the past, I thought I have seen quantum circuits/algorithm techniques to change the amplitude of state based on the state? $\lvert \psi \rangle = \sum_x \ C_x \lvert x \rangle$, here $C_x$ is just ...
John Parker's user avatar
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1 vote
0 answers
239 views

How to load time-series stock data into quantum amplitude estimation

Now I got some time-series data as showing example below: I have spent a period of time realizing the QAE from qiskit, and I found that the tutorial used uncertainty model to reproduce data, while I ...
RonaldHo's user avatar
0 votes
1 answer
134 views

In the amplitude amplification algorithm in Nielsen and Chuang's book, why is the error probability $M/N$?

I was able to follow til the yellow-highlighted sentences, which seems to be important to understand. Why M/N is the probability of error? If so 1 - M/N would be the probability of success?
John Parker's user avatar
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8 votes
2 answers
643 views

What is the difference between amplitude amplification, amplitude estimation, and phase estimation?

I'm confused about the difference among Amplitude amplification (AA) , phase estimation (PE), and Amplitude Estimation. I thought I understood AA and PE somewhat but when I heard the amplitude ...
John Parker's user avatar
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