IBM quantum computer is useless, No advantage.

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Quantum computer is hopeless

IBM quantum computer, which is too error-prone to give right answers, relied on illegitimate error-mitigation using classical computer for masking quantum computer's errors.

(Fig.1) IBM quantum computers were outperformed by classical computers.

IBM quantum computers showed No quantum advantage.

The recent overhyped news claimed IBM quantum computer called "eagle" with (just) 127 qubits might show quantum utility by mitigating their errors.

But actually, to jump to the conclusion, this IBM quantum advantage or utility, which claim was wrong from the beginning, turned out to be fake even officially.

Classical computers easily outperformed IBM 127-qubit quantum computer, even in a very unfair condition unfavorable to classical computers.

This 9~10th-paragraphs say
"By adopting a (classical) tensor network approach, we can perform a classical simulation that is significantly more accurate than the results obtained by the quantum device."

This p.1-left-lower says
"IBM team simulated the dynamics of .. (useless) Ising model (= just manipulating qubits in some ways ) on a 127-qubit...
However, and unlike originally thought, they are still far from any sort of quantum advantage"

First of all, today's quantum computers including IBM are too error-prone to give right answers, and error corrections of quantum computers is impossible (forever).

This 1st-paragraph says
"Despite steady improvements in quantum computers, they're still noisy and error prone, which leads to questionable or wrong answers. Scientists predict that they won't truly outcompete today's classical supercomputers for at least five or 10 years, until researchers can adequately correct the errors"  ← quantum error correction will never happen

The impossibility of quantum error correction shows there is No quantum advantage nor supremacy from the beginning.

This 1st-paragraph says "quantum computing, but so far it has Not surpassed conventional computers"  ← No quantum advantage

This key takeaway says "Quantum computing today provides No tangible advantage over classical computing in either commercial or scientific applications."

This 1~2nd-paragraphs say "pouring billions of dollars into quantum computing, despite the technology still being years away from practical applications"  ← No quantum utility

Real quantum advantage or supremacy needs more than millions of qubits ( this-summary,  this-4th-paragraph ), which is far more than IBM's just 127 qubits (= one qubit can take only 0 or 1 values ).

The error-prone IBM quantum computer had to rely on illegitimate error-mitigation (= Not error correction ) using classical computer.  ← relying on classical computer means No quantum advantage.

(Fig.2) Today's quantum computers are too error-prone to give right answers

IBM relied on illegitimate error mitigation using classical computer.  ← No quantum advantage

IBM tried to obtain right answers in some tasks by using illegitimate methods called error mitigation ( this p.2-2nd-paragraph ), which relied heavily on an ordinary classical computer to seemingly mask errors without legitimate quantum error correction ( this-lower-quantum error mitigation ).

This p.1-right-2nd-paragraph says
"The high error rates of these current quantum devices usually prevent the realization of quantum applications,... error correction is generally not possible on them. As such, quantum error mitigation provides a potential alternate pathway..., which utilize classical (= computer ) post-processing approaches to mitigate error"

This p.1-right-1st-paragraph (+ p.2-Fig.1 ) says
"In QEM (= quantum error mitigation ), the correct result of a calculation is generally estimated by post-processing the output from multiple quantum circuits using a classical computer"

↑ The fact that today's quantum computers have to rely on ordinary classical computers for mitigating errors means there was No quantum advantage nor supremacy from the beginning.

This or this 2nd-last-paragraph says
"Some researchers are less optimistic about the potential of noise mitigation, and expect that only quantum error correction will (= still quantum error correction is impossible ) enable calculations.. "  ← quantum error mitigation is illegitimate

Classical computer unfairly forced to imitate the non-existent quantum superposition or parallel worlds, outperformed quantum computer after all.

(Fig.3) There is No evidence of the error-prone IBM quantum computer using quantum superposition or parallel universes for (fake) quantum advantage

IBM 127-qubit tried to use 2¹²⁷ quantum parallel universes for (failed) quantum advantage ?

They baselessly claimed IBM 127-qubit quantum computer could utilize (unseen fantasy) quantum superposition or 2¹²⁷ = 10³⁸ different parallel-universe states (= one qubit can allegedly take 2 states of 0 and 1 × 127 qubits ) during qubit operation ( this 7th-paragraph,  this 12th-paragraph ).

This or this 15th-paragraph says
"In fact, exactly simulating all 127 entangled qubits on a classical computer would require an astronomical amount of memory. The quantum state would need to be represented by 2 to the power of 127 (= 2¹²⁷ ) separate numbers. That's 1 followed by 38 zeros (= 10³⁸ superposition or parallel world states )"

↑ This quantum superposition or parallel universes on which the quantum advantage relied are baseless, lacking evidence, because they can observe only one single value or a single universe (= multiple superposition states or parallel universes are unobservable ), when measuring the qubits' results, which is called "superposition collapse".

IBM used a (classical) superconducting circuit called transmon qubit whose amount of electric charge current represented each qubit 0 or 1 (= or the middle of 0 or 1 is called superposition irrelevant to quantum mechanics ) manipulated by (classical) microwave light ( this p.2 ), which has nothing to do with (fantasy) quantum parallel worlds.

The unseen quantum superposition or a (unrealistic) dead-and-alive cat state just means probabilities which which qubits take different states when measured ( this middle,  this p.3~7 ).

Quantum computers are unable to give rights answers, so No evidence of quantum advantage or superposition.

Proving the real quantum advantage or supremacy based on the (unseen) quantum superposition-based simultaneous calculations requires the quantum computers to get right answers far faster than classical computers.

But today's quantum computers cannot get right answers due to too many errors and impossibility of quantum error correction.  ← so No evidence of quantum advantage nor supremacy.

↑ Even when a classical computer was unfairly forced to imitate these unfounded quantum superposition or 2¹²⁷ unrealistic parallel worlds, the classical computer could outperform the quantum computer, as this site's 7~8th-paragraphs say

"To fully represent the wave function of these qubits would require 2^127 = 10^38 numbers,.."

"his colleagues solved the problem on a classical computer with greater accuracy than achieved using the quantum one."  ← Quantum advantage was officially disproved.

IBM had to rely on classical computer for illegitimate error-mitigation guessing right answers, so No quantum advantage.

(Fig.4)  IBM quantum computer always gave wrong values, while classical computer always gave right answers.  ← No quantum advantage

In this IBM illegitimate error-mitigation, physicists paradoxically increased errors and obtained more wrong answers in 127-qubit quantum computers, and tried to guess right answers by using classical computers and ad-hoc error-mitigation model through extrapolation.

This or this 10th-paragraph says
"Paradoxically, IBM researchers controllably increased the noise in their quantum circuit to get even noisier, less accurate answers and then extrapolated backward to estimate the answer"

This IBM research paper p.3-Fig.2 shows IBM 127-error-prone qubits just gave the unmitigated wrong values (= green, red circles ), which were completely different from the ideal classical computer's right answers or values whose errors were mitigated by classical computers (= blue circle or gray dotted line )

IBM's alleged largest 1121-qubit (or Chinese 504-qubit ) quantum computer lacking detailed information is useless, still far from millions of qubits required for a practical quantum computer, and even worse than the far-less qubits ( this 3rd-paragraph ).

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