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30 votes
Accepted

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

There is still a search for problems where the D-Wave shows improvement over classical algorithms. One might recall media splashes where the D-Wave solved some instances $10^8$ times faster than a ...
Andrew O's user avatar
  • 1,749
11 votes

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

There are two points I'd make here. D-Wave's computer and Google's computer are fundamentally different. D-Wave's computer is a quantum annealer. Imagine a landscape with some grassy hills. If you put ...
auden's user avatar
  • 3,459
11 votes
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Is Google's 72 qubit device better than D-Wave's machines, which feature more than 2000 qubits?

Short explanation: D-Wave implements quantum annealing, while Google has digitized adiabatic quantum computation. Lengthy Explanation: D-Wave advertises their line of quantum computers as having ...
Rob's user avatar
  • 2,327
10 votes
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How power-efficient are quantum computers?

As usual, it is too soon to make comparisons like this. The power consumption of a device will depend strongly on the architecture it uses, for one. However, in principle, there is no reason to ...
glS's user avatar
  • 25.4k
10 votes
Accepted

How much faster is “D-Wave Two” compared to its predecessor?

As Troyer and Lidar saw no speed increase with the D-Wave 1 compared to classical computers, the D-Wave 2 benchmark figure reported in 2013 of 3600 times as fast as CPLEX (the best algorithm on a ...
Rory Alsop's user avatar
9 votes
Accepted

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

The common Computer Science usage of 'ignoring constants' is only useful where the differences in performance of various kinds of hardware architecture or software can be ignored with a little bit of ...
Niel de Beaudrap's user avatar
9 votes

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

Is there proof that the D-wave (one) is a quantum computer and is effective? D-Wave Video - Offers an explanation of: "How do we know ...": https://youtu.be/kq9VqR0ZGNc One analogy you might make ...
Rob's user avatar
  • 2,327
8 votes
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How to explain in layman’s terms the significance of the difference of qubits of the D-Wave and IBM QX?

In the classical case, there is a pretty big difference between digital computers and analogue ones. The methodology and hardware is very much distinct (in all cases I know of, at least). The divide ...
James Wootton's user avatar
7 votes

How much faster is “D-Wave Two” compared to its predecessor?

As far as I know the closest answer to your question for applications is given in the recent (still unpublished) work presented at the March meeting by Bibek Pokharel, where he compares graph 3-...
Davide Venturelli's user avatar
7 votes

Why can't quantum computation replace classical computation?

In the general case, I think the first answer you listed is pretty accurate. At the moment, quantum hardware is expensive and replacing classical with quantum would imply simulating the billions of ...
epelaez's user avatar
  • 2,895
7 votes
Accepted

Explicit Lieb-Robinson Velocity Bounds

Let me first answer the general question how to get a reasonably tight Lieb-Robinson (LR) speed when you are facing a generic locally interacting lattice model, and then I'll come back to the 1D XY ...
Lagrenge's user avatar
  • 185
6 votes

How power-efficient are quantum computers?

The answer to the first question (why is energy efficiency in quantum vs classical not discussed as often as speed?) is: in part because the problem is less univocal and in part because the answer is ...
agaitaarino's user avatar
  • 3,827
6 votes
Accepted

Building a quantum computer in simulation

The first part of your question seems like a duplicate of an existing QC SE post: Are there emulators for quantum computers?. I'm not completely sure what you mean by building a quantum computer from ...
Sanchayan Dutta's user avatar
6 votes
Accepted

Speed versus number of qubits for RSA factorization

[Are] a minimum of 6152 (logical) qubits is required to achieve the capacity of factoring 2048 bit long integers[..]? No, we intentionally used more logical qubits than needed because that reduced ...
Craig Gidney's user avatar
  • 37.9k
5 votes

Building a quantum computer in simulation

I feel like this answer mostly rests on an underlying misunderstanding of what it means to "simulate" something. Generally speaking, to "simulate" a complex system means to reproduce certain features ...
glS's user avatar
  • 25.4k
5 votes

Building a quantum computer in simulation

Well, I'm working on a simulator of a quantum computer currently. The basic idea of quantum computing, of course, is gates represented by matrices applied to qubits represented by vectors. Using ...
auden's user avatar
  • 3,459
5 votes
Accepted

How scalable are quantum computers when measurement operations are considered?

Some near-term quantum algorithms rely on getting lucky with the measurements, and in fact these algorithms will not scale efficiently to large sizes. But most quantum algorithms don't have this ...
Craig Gidney's user avatar
  • 37.9k
4 votes

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

You may be confusing two uses of the word "base". One definition of "base" has to do with how many digits are used to represent a number. For example, base two uses the digits 0 and 1, and the number ...
Simon Burton's user avatar
4 votes

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

You can't ignore the constant factors when comparing quantum computation to classical computation. They're too large. For example, here is an image from some slides I presented last year: The things ...
Craig Gidney's user avatar
  • 37.9k
3 votes
Accepted

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

I will attempt to address the following question only. I'm asking whether the method of 'running' quantum algorithms on a 'quantum computer' 'simulated' on a classical computer would be able to ...
Kiro's user avatar
  • 1,985
3 votes
Accepted

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

The preferred basis problem is essentially something from the many worlds interpretation: If we are to interpret a superposition as representing many universes, what basis should we choose? Since this ...
James Wootton's user avatar
3 votes

Why can't quantum computation replace classical computation?

In my opinion, quantum computers can't replace classical computers, because there are many tasks where classical algorithms are optimized, so why do we replace something which works quickly and ...
Simona99's user avatar
  • 180
3 votes

Gate SWAP vs Physical SWAP in Trapped Ions for chain reordering

Prelim: I am no expert on implementation techniques or the frontier of what gate technology is being used in current renditions of Trapped Ion QC. The Molmer-Sorensen gate is generally what is used in ...
Bertrand Einstein IV's user avatar
3 votes

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

We are not at the point where quantum computers are outperforming classical computers in any practical way so certainly not now. As for the future, there already exist numerous algorithms which have ...
thespaceman's user avatar
3 votes

How does the Qiskit AerSimulator performance scale with the circuit depth?

From my point of view, in the worst case, the computational cost scales linearly with the depth of the circuit. The math behind quantum computer simulation is linear algebra and matrix manipulations ...
Saul_better's user avatar
2 votes
Accepted

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

Validating your solution. Q# offers a variety of methods to test your code, depending on what exactly you want to test. In this case, the main part seems to be validating the oracle you implemented ...
Mariia Mykhailova's user avatar
2 votes

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

do we need to come up with completely different quantum-based solutions for such problems, or is there a way to 'interpret' existing algorithms to the quantum domain and still expect some speedup? ...
glS's user avatar
  • 25.4k
2 votes

Why can't quantum computation replace classical computation?

Sure, you can achieve quantum supremacy, meaning you can do certain tasks way faster on quantum computers than on any classical supercomputers. But the physical implementation of a quantum computer is ...
Jaimin's user avatar
  • 188
1 vote

Why can't quantum computation replace classical computation?

Your question talks about the theoretical capabilities of theoretical computers. Anyone who says that quantum computers won't replace classical computers is probably talking about the actual ...
benrg's user avatar
  • 878

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