# Questions tagged [performance]

For questions about the performance of quantum computers and quantum computer emulators.

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### 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 ...
110 views

### Is it currently more cost effective/efficient to run a general purpose parallel algorithm on an accelerated quantum simulator or on CPUs?

Quantum simulation is advancing and I'm wondering if now or in the future there is a point where its more cost effective and efficient to run general purpose parallel algorithms (e.g. with a mix of ...
52 views

### How to improve embedding process in D-Wave?

I am quite new to the quantum computing field. Currently, I am trying to solve a combinatorial optimization problem on a D-Wave system, which I successfully translated into QUBO form. I also managed ...
2k views

### Why can't quantum computation replace classical computation?

I am not a total novice of quantum computation (have read the first 6 chapters of Nielsen and Chuang, though not familiar with every part), but there are some fundamental questions that I don't know ...
85 views

### When is a Quantum Computer Slower Than a Classical Computer?

Someone offhandedly mentioned to me that quantum computers are sometimes significantly (I guess they meant asymptotically) slower than classical computers. Unfortunately, I didn't get any arguments ...
76 views

### Gate SWAP vs Physical SWAP in Trapped Ions for chain reordering

In trapped ion quantum computers, especially in systems with multiple traps, you may need at some point to perform a "chain reordering", in which you change an ion's position within the ion ...
53 views

### Best way to test the performance of a simulated quantum algorithm in Q#

for a student report about solving graph coloring with Grover's Algorithm, I have to talk about the performance of simulated Grover's Algorithm to solve graph coloring. I don't really know how to ...
231 views

### Does the massive parallelization in Quantum computing imply parallelization of input (as opposed to Turing machine)?

Being a newbie in this field, I'm trying to understand what types of real-life workloads are suitable for migrating to Quantum computers. Intuitively, it seems to me that if a Quantum computer ingests ...
1k views

### Quantum computer vs. supercomputer performance [closed]

Does anybody have any other comparisons between a universal quantum computer and a classical computer that might shed some light into how their performance compares? Below is what I've been able to ...
94 views

### How scalable are quantum computers when measurement operations are considered?

From a high-level point of view, given a quantum program, typically the last few operations are measurements. In most cases, in order to extract a useful answer, it is necessary to run multiple ...
1k views

### Explicit Lieb-Robinson Velocity Bounds

Lieb-Robinson bounds describe how effects are propagated through a system due to a local Hamiltonian. They are often described in the form $$\left|[A,B(t)]\right|\leq Ce^{vt-l},$$ where $A$ and $B$ ...
433 views

### What is the most economical and preferred basis for the qudit?

In Classical Simulation of Quantum Error Correction in a Fibonacci Anyon Code, the authors state on page 2 in section I. Background, A. Topological model: We consider a system supporting nonabelian ...
2k views

### How power-efficient are quantum computers?

Quantum algorithms scale faster than classical ones (at least for certain problem clases), meaning quantum computers would require a much smaller number of logical operations for inputs above a given ...
4k views

### Is Google's 72 qubit device better than D-Wave's machines, which feature more than 2000 qubits? [duplicate]

Google recently announced the Bristlecone 72 qubit quantum computer. However, D-Wave already announced quantum computers featuring more than $2000$ qubits. Why is Google's new device newsworthy then? ...
487 views

### Can classical algorithms be improved by using quantum simulation as an intermediary step?

I'm wondering whether even if we cannot create a fast quantum computer, simulating quantum algorithms can be a reasonable method for classical algorithms. In particular, I'd like to see any results ...
766 views

### How to explain in layman’s terms the significance of the difference of qubits of the D-Wave and IBM QX?

So, @AndrewO mentioned recently that he has had 'encounters' with people wondering why D-Wave has a lot more qubits than IBM. Of course, this comparison is faulty, since the IBM and D-Wave's machine ...
834 views

### Is the common Computer Science usage of 'ignoring constants' useful when comparing classical computing with quantum computing?

Daniel Sank mentioned in a comment, responding to (my) opinion that the constant speed-up of $10^8$ on a problem admitting a polynomial time algorithm is meager, that Complexity theory is way too ...
6k views

### Is there proof that the D-wave (one) is a quantum computer and is effective?

I'm admittedly a novice in this field, but I have read that, while the D-wave (one) is an interesting device, there is some skepticism regarding it being 1) useful and 2) actually a 'quantum computer'....