This talk makes me very suspicious of "quantum computers": https://its.unc.edu/wp-content/uploads/sites/337/2021/06/Introduction_to_Quantum_Computers.pdf

In my personal opinion: If a result cannot be explained, it should not be trusted. "Artificial Intelligence" and "Machine Learning" are already being presented as smoke-and-mirrors whose results are extremely difficult to explain. Yet we are asked to trust those results, sometimes with our lives. Science can and should do better than that.

Thank you Peter Raeth .Beautifully explained.

Quantum science isn't about small scales (and possibly less an less mysterious").

It somewhat used to be, since we only recently (say, in the 1990s) learned to create massive quantum objects with macroscopic, or at least mesoscopic, coherence lengths allowing for more subtle interference phenomena than self-interference of a single objetc, etc.

So the so-called "second quantum revolution" is all about nonlocality and entanglement effects, and definitely not limited to small scales. Hence its potential technological applications.

Quantum computers are, or will be, one of such applications. Since they use nonlocal "qubits" instead of the local "bits" of classical computers, they may be able to explore rather large and complex circuits all at once, in single pass, where a classical computer would have to use a lenghty sequential process (even if massive parallelism obviously helps). For _some_ problems, such as the factorization of very large numbers, the speed of a specifically designed quantum processor might thus surpass those of classical supercomputers, indeed.

As for reliability... the future will tell. But at the current state of the art, the reliable exploitation of a single qubit might call for several thousands of ancillary qubits for error correction.

Moreover, while quantum supremacy might be soon achieved on a few class actual computations, with specifically designed quantum computers, we remain very far for a "universal" quantum computer. For the vast majority of computations, Classical supercomputers are thus likely to remain both faster and more reliable for a few decades.

Thank you Eric Picholle . Sir, I am so happy to go through your explanation. Please explain to me how nonlocal qubit helps to resolve complex parallel computation.

Dear Sovan Mohanty

From what I observed, ever since the idea of quantum computers started to be researched decades ago, as far back as the 1950's , all articles relating any "progress" in quantum computing development, always end up alluding to expected future accomplishment, or relate to actual developments easily explainable with normal electron behavior in circuit design presented as novelties.

The very underlying concept of polarity entanglement of 2 particles located away from each other, lost among a plenum of other interacting particles at the subatomic level, dear to Copenhagen interpretation aficionados, makes little sense in my view, given that these particles will by structure preferably interact with particles closer to them than with the other member of any such pair.

Best Regards, André

Thank you André Michaud for giving insight into the influence of subatomic quantum particles.

Peter Raeth Thanks for the link to the interesting presentation from North Carolina!

Let me first comment on the presentation: I do not believe a single word from someone who misses the importance of putting a date on his/her publication!

The problem with that, and all other quantum-computing-worship papers, is that they sweep under the carpet all obvious problems and live in an intellectual vacuum in which only good characteristics of QC exist.

To grasp the central problem (although there are others), consider one difference between classical and quantum computing.

A classical, pen-and-paper multiplication is perfect in theory. One can calculate with arbitrary precision. You can work with one decimal place. You can work with 10, and you can work with 100. All you need is a piece of paper, a pen, and the algorithm.

Now, quantum computing also works on paper. After all, it has been invented by a theorist and a mathematician,. Unfortunately, both with a significant lack of experimental skills, namelly a sense for the physical reality. So, it works on paper, indeed! Good for them! The problem is that it is absolutely un-usefull on a paper. If you want it to be usefull (faster than classical) than it must work on physical qubits. THAT is the big difference: your pen-and-paper calculation works perfectly well on paper, but QC works only on physical objects and they must be precise enough. So, if you want to be 1 bit precise you use 1 qubit and some quantum gates to manipilate the qubit. That probably works to a some precision, but IBMs public QC is not even very precise on 1 qubit. If you want precision of 10 bits, you must have very precise qubits to begin with, and very precise physical logic gates to manipulate them, or you won't be presenting the correct number and any calculation would go far astray. With 270 qubits, you already surpass precision of 1 atom in the whole Universe. How could one possibly hope for or expect such a physical precision? While at the same time your classical pen-and-paper works at 100, 200, 300, thousand, and many thousand of bits, with absolutely no sweat. And it can run on your smatrwatch or even a "smart" credit card.

In summary, an INCREDIBLY HIGH and therefore IMPOSSIBLE analog precision of physical objects, called qubits and gates, is what would make a QC more powerful than a smartwatch. In fiction.

The speed and power of quantum computers are incomparable to that of supercomputers. They are ideal for addressing complex problems that need effectively processing vast amounts of data since they can handle multiple computations at once.

Jagbeer Singh This is not true! Memory of QC's today is so small that they can barely encode the sentence: "Quick fox jumps over the lazy dog" !

Thank you Mario Stipčević Jagbeer Singh for answering.

"Quantum supremacy" so far has only been shown in one dubious case of Google's calculation of "something". Nobody understands what was solved and therefore they can safely claim that normal computerts would take ages to do the same. If quantum computyers continue to solve quickly only problems that are useless or even not well defined, it is soon going to be their end!