98

Your question is sort of "opinion-based", but yet, there are a few important points to be made. Theoretically, there's no convincing argument (yet) as to why quantum computers aren't practically realizable. But, do check out: How Quantum Computers Fail: Quantum Codes, Correlations in Physical Systems, and Noise Accumulation - Gil Kalai, and the ...


40

Is quantum computing just pie in the sky? So far it is looking this way. We have been reaching for this pie aggressively over the last three decades but with not much success. we do have quantum computers now, but they are not the pie we wanted, which is a quantum computer that can actually solve a problem faster or with better energetic efficiency than a ...


35

Classical computing has been around longer than quantum computing. The early days of classical computing is similar to what we are experiencing now with quantum computing. The Z3 (First Turing complete electronic device) built in the 1940s was the size of a room and less powerful than your phone. This speaks to the phenomenal progress we have experienced in ...


21

Early classical computers were built with existing technology. For example, vacuum tubes were invented around four decades before they were used to make Colossus. For quantum computers, we need to invent the technology before we make the computer. And the technology is so beyond what had previous existed, that just this step has taken a few decades. Now we ...


18

TL,DR: Engineering and physics arguments have already been made. I add a historical perspective: I argue that the field of quantum computation is really only a bit more than two decades old and that it took us more than three decades to build something like the MU5. Since you mention the timeline, let's have a closer look: The beginnings First of all, the ...


15

When you ask whether it is pie in the sky, that rather depends on what promises you think quantum technologies are trying to fulfil. And that depends on who the people are making those promises. Consider why you are even aware of quantum computation, given that it hasn't yet managed to produce any devices (or to be more fair, not very many devices) which ...


13

First we should take a step back. Is there any machine learning done a quantum computer that cannot be efficiently simulated on a classical computer? The answer currently (2020) is no. In this respect quantum machine learning (which has many variants) is at the fundamental research phase. None of this is at a stage where it is at all considered something ...


12

To answer part of the question, "will I ever buy a quantum computer", etc. I think there is a fundamental misunderstanding. Quantum computing isn't just classical computing but faster. A quantum computer solves certain kinds of problems in a short time that would take a classical super computer a thousand years. This isn't an exaggeration. But regular kinds ...


11

TL;DR: I've been working on the theory of quantum computers for about 15 years. I've seen nothing convincing to say that they won't work. Of course, the only real proof that they can work is to make one. It's happening now. However, what a quantum computer will do and why we want it does not match up with the public perception. Is quantum computing just ...


10

Like all good questions, the point is what you mean. As the CTO of a startup developing a quantum computer, I have to emphatically disagree with the proposition that quantum computing is just pie in the sky. But then you assert "You won't be buying one in PC World any time soon." This I not only agree with but would suggest that in the foreseeable future, ...


10

You have two different questions here: 1) Can quantum computing be profitable without quantum hardware? In the comments people have said this is an opinion based question, but the truth is that there's already people (and companies!) making profits off of quantum computing. In 2016 Doug Finke made a website with his own money, which kept track of the ...


9

A couple years ago it was shown in Quantum algorithms and the finite element method by Montanaro and Pallister that the HHL algorithm could be applied to the Finite Element Method (FEM) which is a "technique for efficiently finding numerical approximations to the solutions of boundary value problems (BVPs) for partial differential equations, based on ...


9

See the timeline on Wikipedia, and ask yourself where's the parallel adder? It seems to me that your answer lies in your question. Looking at the timeline on Wikipedia shows very slow progress from 1959 until about 2009. It was mainly theoretical work until we went from zero to one. In the only 9 years since then, the pace of progress has been ...


9

Why would you expect two different technologies to advance at the same rate? Simply put, quantum computers can be immensely more powerful but are immensely harder to build than classical computers. The theory of their operation is more complicated and based on recent physics, there are greater theoretical pitfalls and obstacles that inhibit their scaling up ...


8

The sad truth for most of the people here is that John Duffield (the asker) is right. There is no proof that a quantum computer will ever be of any value. However, for the companies that have invested in quantum computing (IBM, Google, Intel, Microsoft, etc.), it is entirely worth it to try to build one, because if they are successful they will be able to ...


8

I won't be giving any precise statements about which problems can be solved more efficiently using quantum algorithms (compared to existing classical algorithms) but rather some examples: Discrete Fourier transform (DFT) is used in pretty much all modern day music systems, for example in iPods. That algorithm single-handedly changed the world of digital ...


7

The difficulty with explaining quantum computing is that quantum objects and processes have no direct classical analogue; they're an entirely new ontological category. For example, you might have learned in high school physics that light "is both a particle and a wave" in an attempt to relate it to two classical objects you can intuitively understand. In ...


7

There are many technical challenges to developing a universal quantum computer consisting of with many qubits, as pointed out in the other answers. See also this review article. However, there may be workaround ways to get certain nontrivial quantum computing results before we get to the first truly universal quantum computer. Note that classical computing ...


7

In my view, if artificial general intelligence (AGI) is ever 'solved', it likely won't be because of the development of a quantum AI algorithm. Rather, it will be because of a breakthrough in the training of existing classical algorithms. That said, much like in the classical case (i.e. classical machine learning), research on quantum algorithms with ...


6

There are a lot of interesting applications that use similar technology. A lot of labs that work towards quantum computing also publish papers with these applications. Here are some: All-optical computation. Personally, I think this has more potential than quantum computing, as it has already been shown to be useful for quickly processing neural networks ...


5

No. Chaos (as described in chaotic systems) is deterministic, and the evolution of such a system can be calculated using classical deterministic equations. The problem is the strong divergence of the different trajectories that even small differences in initial values can lead to large differences in the final values. Quantum computing does not help in ...


5

Given that the QFT is exponentially faster than the FFT, The problem with quantum computing is that they are not actually parallel computers: One is tweaking the qubits in such a way that when reading out the result, the desired result gets a high probability. The power of quantum computing comes from the vast phase-space that grows exponentially with ...


5

There are several startups that have formed around QC-assisted drug discovery. The ones listed below have resources on their websites that you might find helpful. ProteinQure Qulab HQS Kuano For a general understanding of molecular simulation, Simulating Molecules using VQE from the Qiskit Textbook is a great resource if you're generally familiar with QC (...


5

"IonQ is claiming to have a potential application in machine learning by 2023. What applications could they have in mind?" None. The plot you showed has no units on the y-axis. It doesn't even have numbers. The choice of 2023, 2025, and 2027 for "inflection points" (which they didn't define, and based on their graph has nothing to do ...


4

In complement to the other answer from @user1271772: 1) Can quantum computing be profitable without quantum hardware? I can add another two elements. First companies that can sell/develop anti-quantum security protocols because as you may know, RSA is threatened by quantum computers (at least in theory but it can be enough to transition to new protocols)...


4

I was not able to find references specifically in quantum biology. I found however a review called Quantum Assisted biomolecular modeling. You may find it interesting but this is from 2010. The field has evolved since but I guess the ideas remain similar. The authors focus more on the idea of the ability of a quantum computer to try every classical paths ...


4

Perform and checking basic quantum-mechanic experiments Before the IBM and alibaba quantum cloud computers, you would need an expensive lab to do simple CHSH or GHZ experiments. Of course the qubits in the IBM computer are not loophole free but many institutes and also collegeschools could not have better experiment facilities purchased within their physics ...


4

Not always. Some problems are non-deterministic (their solution). Apart from that, some problems are, as you say, so sensitive to changes in initial conditions, that most solutions are too localized. But there are cases where quantum computers can provide insightful results, that might shed light on different approaches to solutions. Another point to ...


4

I'm not sure if the 286 qubit estimate has ever been fully explained, but we can backwards reason about how to get to the figure. First off, accuracy of quantum chemistry simulations via Trotterization is a function of the basis set (in both classical and quantum simulations). The basis set is kinda like a coordinatization the electron orbitals. There are a ...


4

There is good reason to believe that quantum computers will eventually play an important role in drug discovery. Perhaps the best way to show that it's not science fiction is to talk about the startups forming that are focused on QC-enabled drug discovery. The companies that I know of that fit this description are ProteinQure HQS GTN Qulab Riverlane


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