Quantum computer completes verified task beyond practical reach of classical simulations

Phys.org ^ | 08/01/2026 | University of Chicago

[BenLurkin]

IBM and researchers from the University of Chicago announced a demonstration in quantum computing that meets the fundamental criteria for "quantum advantage"—the point where quantum computers can be confirmed to have outperformed classical computers on trusted computations.

The collaboration said its system had performed computations beyond the reach of leading classical simulation methods while providing confidence that the computation returned accurate results.

In their new paper, the researchers showed that these two goals could be achieved through a novel construction of encoded quantum circuits—one of the largest demonstrations of logical quantum computing to date. The paper is published on the arXiv preprint server.

Building trust into quantum results For years, researchers have used a benchmark known as random circuit sampling, or RCS, to test whether quantum computers could outperform classical systems.

In simple terms, RCS asks a quantum computer to generate patterns so complex that a classical computer cannot efficiently reproduce them.

The challenge has been verification: As the problem becomes harder, it becomes increasingly difficult, then infeasible, to prove the quantum computer's answer is correct without making strong assumptions about the inner workings of the quantum computer.

In their experiment, researchers addressed this obstacle with a structured alternative to RCS. The team was able to prove that this alternative retains the same hardness criteria as RCS, but crucially, the new structure can be used to detect errors during the computation

[Libloather]

Worked it all out back in the 70s.

[BenLurkin]

"The team successfully executed 70 logical qubits while shielding them from errors. They ran 2,415 logical two-qubit operations and 468 logical "T gates," both metrics that quantify the complexity of a quantum circuit."

[Red Badger]

Just build a hundred more data centers to check their work...............

[cb]

if you can’t tell the difference, what is the difference?

[sauropod]

.

[17th Miss Regt]

The quantum computer showed that the last digit of the decimal expansion of pi is 3. That is quite something! (/sarc)

[srmanuel]

I don’t pretend to understand the intricacies of Quantum Computing, some of the advocates for it have said that a fully functioning Quantum computer could be up to 1 millions times more powerful than modern computers of today.

Think of all current encryption methods being hacked in a few minutes.

Think of the complexity of the human body and all the different kinds of proteins, now think of modeling new drugs and other aspects of the human anatomy.

IMO, it’s pure science fiction at this point, just imagine in 20 years or more with fully operating Quantum Computers combined with the advances in AI in 20 years and it’s pretty scary what could be done.

[Red Badger]

Back in the early 90’s Intel had a problem with the then new Pentium microprocessors that had a built-in math co-processor that would give inaccurate answers in certain circumstances.

Ever since then manufacturers and high end customers have been extra diligent in confirming any new systems and their math capabilities.

BRAVE AI:

This refers to the Pentium FDIV bug, a hardware flaw in the floating-point unit (FPU) of early Intel Pentium processors released in 1993 that caused incorrect results during specific floating-point division operations. Discovered in 1994 by mathematics professor Thomas Nicely, the error stemmed from five missing entries in the chip’s radix-4 SRT division lookup table. Although the flaw was statistically rare for average users, Intel’s initial refusal to replace affected chips sparked massive public outcry, leading the company to issue a full recall in December 1994 that cost Intel approximately $475 million.

More info:

https://people.willamette.edu/~mjaneba/pentprob.html

[Blueflag]

Absent the error checking, quantum computing is just an IT parlor trick.

With the error checking ... we have a legit ‘big deal.’

Thanks for posting this.

[Theophilus]

What good is information if you can’t quant on it?

[GOPJ]

Maybe showing a little respect for our AI machine friends might be a good start.

[captmar-vell]

The biggest problem is decoherence where even a stray molecule or photon will drop the superpositioning and entanglement. There are competing technologies on how to best accomplish this.

Encryption analysts know that every locked door will soon be opened.

[Zathras]

I know a great deal about the floating point flaw as I was in Intel Validation at the time.
The big problem is when it made an error, the exception flag never got set.
The coverup was done by Vinod Dahm, head of the marketing team as his stock options were linked to the number of Pentium sold.

Vinod was quietly fired and he moved to an x86 clone company, then to AMD.
Last time I heard he was hiding out in FL running a H1b scam company.

It was discovered by the design team working on Pentium II and the simulations were getting different results.

[Zathras]

I can’t comment too much about Quantium other than IBM is investing in the design.
It would be interesting to see how it compares with their Power11 design.

[Red Badger]

Thanks for that bit of historical trivia!.............

[Sirius Lee]

Let's see a quantum calculator do this!

[Opinionated Blowhard]

it becomes increasingly difficult, then infeasible, to prove the quantum computer's answer is correct without making strong assumptions about the inner workings of the quantum computer.

[Disambiguator]

That was Intel’s “Ford Pinto” moment.

[fuzzylogic]

It’s all amazing and everything...but let me know when it no longer requires near-absolute zero to function!

:)