Quantum computers not being a big revolution?

[excreationist]

4:26 Sabine Hossenfelder says:
I'm not saying that quantum computers will never have a commercial use. I just think it'll take a long time to get there. Certainly not in this decade. And the uses will be extremely niche and limited. Not a billion-dollar market. I've noticed that people call me pessimistic when it comes to quantum computers. I think I'm not. It's just that even my most optimistic self thinks it's idiotic that quantum computers will bring a new industrial revolution as some headlines put it.

From Copilot:

Quantum computers do have potential advantages, but recent research shows the bar for proving that advantage is much higher than early hype suggested. The short answer: quantum advantage is not impossible — it’s just far harder, narrower, and more conditional than people assumed.

Why it it looks like quantum computers are unable to have an advantage over traditional computers​

Several major studies in 2026 sharpened the boundary between what quantum computers can do and what classical computers can simulate:

• Many “magic states” — the fuel of quantum computation — turn out to be useless. Researchers at Cambridge showed that a large class of quantum states previously believed to enable quantum speedups can actually be simulated classically. This means many proposed quantum algorithms don’t provide real advantage.
• The set of problems solvable classically is expanding. A new mathematical test (Kirkwood–Dirac nonpositivity) revealed that many quantum states once thought powerful offer no computational edge. This raises the bar for demonstrating true quantum advantage.
• Most claimed “quantum advantage” experiments have been challenged or refuted. A comprehensive review of all quantum advantage claims shows repeated loopholes, classical simulation breakthroughs, and refutations. The status of quantum advantage experiments is extremely fluid.

These findings make it appear that quantum computers can’t outperform classical ones — because many early claims didn’t hold up under scrutiny.

But quantum advantage is still possible — just narrower​

Despite the setbacks, quantum advantage is not dead:

• Quantum hyperdimensional computing has shown speedups for certain high‑dimensional biomedical tasks. Cleveland Clinic researchers demonstrated faster performance than classical methods for specific complex data operations.
• Quantum simulation remains a promising path, especially for chemistry and materials science. A major review argues that more realistic open‑system quantum algorithms could unlock advantages not captured by older, overly idealized models.
• Theoretical work suggests some quantum advantages are inherently unpredictable using classical resources. A 2026 Physical Review X perspective argues that the landscape of quantum advantage is richer than we can currently foresee.

So the picture is nuanced: quantum advantage is not broadly demonstrated, but it is not ruled out.

I think this has interesting implications for simulations. I had previously thought that it might take something like a quantum computer to simulate a quantum computer. But if quantum computers don't have an advantage then maybe quantum computers can be simulated on non-quantum computers (maybe related to generative AI). Maybe the creators of the simulation deliberately made it so that quantum computers would be very limited. But anyway back to the topic...

 

[Tigers!]

We could put quantum computers inside the data centres. Make them useful at least.

 

[excreationist]

We could put quantum computers inside the data centres. Make them useful at least.

Maybe this is relevant:

ibm_kingston is a 133‑qubit superconducting quantum processor that IBM made publicly accessible through its free Open Plan in 2026. Anyone with an IBM Quantum account can submit circuits to it.

I thought I'd find out what quantum circuits are...

Here are the core building blocks of a quantum circuit, explained briefly but clearly so you can see how each piece fits into the computation.

1. Qubits
The wires (horizontal lines) in the circuit.
They hold quantum states that can be 0, 1, or a superposition of both.

2. Single‑qubit gates
Operations applied to one qubit at a time.

Hadamard (H): Creates superposition.

Pauli gates (X, Y, Z): Basic flips and phase changes.

Rotation gates (Rx, Ry, Rz): Rotate the qubit’s state by a chosen angle.

These gates shape the quantum state.

3. Multi‑qubit gates
Operations involving two or more qubits.

CNOT: Entangles qubits by flipping the target when the control is 1.

CZ / Controlled‑U: Apply a gate only if another qubit is in a certain state.

These gates create entanglement, which is essential for quantum advantage.

4. Circuit structure / sequencing
The order of gates matters.
Quantum circuits are read left to right, and the timeline determines how states evolve.

5. Measurement
The final step.
Measurements collapse qubits into classical bits (0 or 1) and produce the output of the computation.