Questions tagged [quantum-advantage]

"Quantum advantage" or "quantum supremacy" is the potential ability of quantum computing devices to solve problems that classical computers practically cannot.

Filter by
Sorted by
Tagged with
11
votes
2answers
713 views

Understanding Google's “Quantum supremacy using a programmable superconducting processor” (Part 1): choice of gate set

I was recently going through the paper titled "Quantum supremacy using a programmable superconducting processor" by NASA Ames Research Centre and the Google Quantum AI team (note that the paper was ...
7
votes
3answers
828 views

What exactly makes quantum computers faster than classical computers?

What feature of a quantum algorithm makes it better than its classical counterpart? Are quantum computers faster than classical ones in all respects?
29
votes
1answer
1k views

Quantum machine learning after Ewin Tang

Recently, a series of research papers have been released (this, this and this, also this) that provide classical algorithms with the same runtime as quantum machine learning algorithms for the same ...
6
votes
1answer
587 views

Understanding Google's “Quantum supremacy using a programmable superconducting processor” (Part 3): sampling

In Google's 54 qubit Sycamore processor, they created a 53 qubit quantum circuit using a random selection of gates from the set $\{\sqrt{X}, \sqrt{Y}, \sqrt{W}\}$ in the following pattern: ...
25
votes
2answers
992 views

When will we know that quantum supremacy has been reached?

The term "quantum supremacy" - to my understanding - means that one can create and run algorithms to solve problems on quantum computers that can't be solved in realistic times on binary computers. ...
8
votes
4answers
1k views

Grover algorithm for a database search: where is the quantum advantage?

I have been trying to understand what could be the advantage of using Grover algorithm for searching in an arbitrary unordered database D(key, value) with N values instead of a classical search. I ...
8
votes
1answer
741 views

Understanding Google's “Quantum supremacy using a programmable superconducting processor” (Part 2): simplifiable and intractable tilings

In Google's 54 qubit Sycamore processor, they created a 53 qubit quantum circuit using a random selection of gates from the set $\{\sqrt{X}, \sqrt{Y}, \sqrt{W}\}$ in the following pattern: ...
3
votes
2answers
318 views

Do quantum supremacy experiments repeatedly apply the same random unitary?

It is my understanding that, given a quantum computer with $n$ qubits and a way to apply $m$ single- and 2-qubit gates, quantum supremacy experiments Initialize the $n$ qubits into the all-zero's ket ...
30
votes
4answers
1k views

Are there problems in which quantum computers are known to provide an exponential advantage?

It is generally believed and claimed that quantum computers can outperform classical devices in at least some tasks. One of the most commonly cited examples of a problem in which quantum computers ...
19
votes
2answers
4k views

What does Google's claim of "Quantum Supremacy" mean for the question of BQP vs BPP vs NP?

Google recently announced that they have achieved "Quantum Supremacy": "that would be practically impossible for a classical machine." Does this mean that they have definitely proved that BQP ≠ BPP ?...
15
votes
1answer
5k views

What exactly is "Random Circuit Sampling"?

Many people have suggested using "Random Circuit Sampling" to demonstrate quantum supremacy. But what is the precise definition of the "Random Circuit Sampling" problem? I've seen statements like "the ...
10
votes
2answers
1k views

What are the real advantages of superdense coding?

In superdense coding, two qubits are prepared by Eve in an entangled state; one of them is sent to Alice and the other is sent to Bob. Alice is the one who wants to send (to Bob) two classical bits of ...
7
votes
1answer
436 views

How to benchmark a quantum computer?

Using a simple puzzle game to benchmark quantum computers is the most clever approach I have seen so far. The author of the aforementioned article, James, makes a nice analogy to buying a laptop ("...
2
votes
1answer
114 views

How does successfully sampling from a random quantum circuit invalidate the Extended Church-Turing Thesis?

According to these lecture notes from Berkeley, the Extended Church-Turing Thesis (ECT) asserts that: ...any "reasonable" model of computation can be efficiently simulated on a standard model such ...
7
votes
1answer
128 views

List of practical quantum computing algorithms that have speed-up higher than quadratic speed-up?

From this link (provided by @KAJ226's comment in this question), it appears as though current error correction methods are not enough to get practical speedup out of algorithms that have quadratic ...
4
votes
2answers
193 views

How exactly is solving the random circuit sampling problem a computation in the Church-Turing thesis sense?

Note: This has been cross-posted to CS Theory SE. If we assume $\mathsf{BQP} \neq \mathsf{BPP}$, then we can say with reasonable certainty that Google's random sampling experiment falsifies the ...
3
votes
2answers
275 views

Question regarding integration of Haar random state

I am trying to understand the integration on page 4 of this paper. Consider a Haar random circuit $C$ and a fixed basis $z$. Each output probability of a Haar random circuit (given by $|\langle z | C |...
2
votes
2answers
95 views

Generally speaking, are quantum speedups always due to parallelization of a given problem?

We know that quantum computers use the wave-like nature of quantum mechanics to perform interference. Sometimes we can use this interference to perform specific algorithms that will cause enough ...
1
vote
1answer
136 views

What is the difference between classical and quantum computers as well as computing (permuting) itself?

Theoretically and for sure physically (I know the quantum physics behind it) I know something about it. But not that much. That's why I ask the question here. I'm very interested. The only answer to ...