Linked Questions

31
votes
4answers
9k views

Is there a layman's explanation for why Grover's algorithm works?

This blogpost by Scott Aaronson is a very useful and simple explanation of Shor's algorithm. I'm wondering if there is such an explanation for the second most famous quantum algorithm: Grover's ...
30
votes
3answers
2k views

Can a quantum computer simulate a normal computer?

Similar to the question Could a Turing Machine simulate a quantum computer?: given a 'classical' algorithm, is it always possible to formulate an equivalent algorithm which can be performed on a ...
15
votes
3answers
3k views

Grover's algorithm: a real life example?

I'm fairly confused about how Grover's algorithm could be used in practice and I'd like to ask help on clarification through an example. Let's assume an $N=8$ element database that contains colors ...
9
votes
3answers
650 views

What is the simplest algorithm to demonstrate intuitively quantum speed-up?

What's the simplest algorithm (like Deutsch's algorithm and Grover's Algorithm) for intuitively demonstrating quantum speed-up? And can this algorithm be explained intuitively? Ideally this would be ...
9
votes
3answers
1k views

Grover's algorithm in a nutshell

I am trying to understand Grover's algorithm. I read that this algorithm is able to find an entry in an unsorted list in just $\sqrt N$ steps, and needs only $\log N$ space. I understand entanglement ...
9
votes
3answers
909 views

Does the oracle in Grover's algorithm need to contain information about the entirety of the database?

Grover's algorithm is often described as a way to search a database in $O(\sqrt{N})$ time. For using it we need an oracle gate that represents some function $f$ such that $f^{-1}(1)$ is the answer. ...
5
votes
1answer
1k views

How does an oracle function in Grover's algorithm actually work?

I have lately been studying quantum algorithms. I have gone through the Deutsch algorithm and Grover's algorithm. There's always a function in the oracle which somehow 'recognizes' the solution ...
2
votes
3answers
160 views

What is the point of Grover's algorithm, really?

This is a question desguised as a rant. There is a similar question here, What's the point of Grover's algorithm if we have to search the list of elements to build the oracle?, but the answers have ...
2
votes
1answer
187 views

How does the Grover's Algorithm work with a real example? [duplicate]

I am new to this field and I have been baffled by the idea of Oracle for a long time. I am aware of the procedure, but I am very confused about how we choose the oracle. Let say we have 4 poker ...
3
votes
1answer
62 views

How can one evaluation of $U_f$ in Grover's algorithm use only one query of $f$?

I am very much new to quantum computation and do not have a background in quantum mechanics, which I believe is at the root of my confusion around Grover's algorithm. Suppose that we have a search ...
1
vote
1answer
53 views

How is the oracle physically implemented in Deutsch algorithm?

In the Deutsch algorithm, the oracle implementation for the function f is taken as a black box, but physically, how is the oracle implemented? Why can we assume such a black box exists for the ...
1
vote
0answers
55 views

In Grover's oracle, how is the matrix $U_f$ derived for a generic $n$?

Grover's algorithm works by iteration of the operator $$\tag{1}G:=U_S^\perp U_f=H^{\otimes n}U_0^\perp H^{\otimes n}.$$ I know how to write down the matrix for $U_S^\perp$ (the inversion about the ...