IBM unveils 433 qubit quantum computer(newscientist.com)
newscientist.com
IBM unveils 433 qubit quantum computer
https://www.newscientist.com/article/2346074-ibm-unveils-worlds-largest-quantum-computer-at-433-qubits/
19 comments
Sabine Hossenfelder has a good summary of the state of Quantum Computing so far:
https://youtu.be/CBLVtCYHVO8
https://youtu.be/CBLVtCYHVO8
How do we reconcile between these kinds of news and that Quantum Physicist who says that Quantum computers never will amount to anything? I'm confused ...
The claim that quantum computers will never amount to anything is more nuanced than that. There is multiple parts to that claim:
- Shor's algorithm is about the only productive thing we've figured out where a quantum computer has an advantage
- IBM unveils 433 qbit computer, to factor 4096 RSA we're gonna need 8192 logical qbits
- Those 433 qbits are physical qbits, and there's (to the best of my knowledge) no literature on their measurement fidelity, coherence timelines, etc. These are purely experimental machines, it's not like you can plug your laptop into their giant cryogenic machines and run quantum algorithms without a giant team of literal quantum physicists standing by the thing and monitoring it
- How those 433 qbits actually translate into any amount of meaningful computation is up in the air
- The best we figured out was 5 logical qbits running a specialised Shor's algorithm on the 127qbit computer they unveiled a few years back to factor 21=3*7
- Nobody has, to the best of my knowledge, actually run the full Shor's algorithm on anything of note, even on these systems
Not a quantum physicist; I only have vague memories from a quantum computing seminar I took long ago. Feel free to correct if any of the above is incorrect.
- Shor's algorithm is about the only productive thing we've figured out where a quantum computer has an advantage
- IBM unveils 433 qbit computer, to factor 4096 RSA we're gonna need 8192 logical qbits
- Those 433 qbits are physical qbits, and there's (to the best of my knowledge) no literature on their measurement fidelity, coherence timelines, etc. These are purely experimental machines, it's not like you can plug your laptop into their giant cryogenic machines and run quantum algorithms without a giant team of literal quantum physicists standing by the thing and monitoring it
- How those 433 qbits actually translate into any amount of meaningful computation is up in the air
- The best we figured out was 5 logical qbits running a specialised Shor's algorithm on the 127qbit computer they unveiled a few years back to factor 21=3*7
- Nobody has, to the best of my knowledge, actually run the full Shor's algorithm on anything of note, even on these systems
Not a quantum physicist; I only have vague memories from a quantum computing seminar I took long ago. Feel free to correct if any of the above is incorrect.
There's something unsettling about them calling these "quantum computers." There's too much noise for them to be actually usable. It's as if someone constructed one half of an abacus and started calling it "abacus." It just doesn't feel right.
And when we actually build a quantum computer (which, I hope, happens by the end of this century), everybody will be too bored about it.
And when we actually build a quantum computer (which, I hope, happens by the end of this century), everybody will be too bored about it.
Can it do anything faster than a traditional supercomputer yet?
Does it calculate generic Shore?
Do you mean Shor's algorithm [1]? Most likely no, or IBM would have made sure you'll hear about that.
But let's say it can, and somehow IBM forgot to mention.
Shor's algorithm reduces to a quantum Fourier circuit, with 2N qubit inputs and 2N qubit outputs, where N is the number of digits of the number to be factored. That's 4N qubits only for inputs and outputs.
So, in the best case scenario, this computer would be able to factor a 108-binary digit number.
My computer (2020 Intel-based iMac) can do that in one minute.
Here's the code if you want to try it on your computer:
[1] https://en.wikipedia.org/wiki/Shor%27s_algorithm
But let's say it can, and somehow IBM forgot to mention.
Shor's algorithm reduces to a quantum Fourier circuit, with 2N qubit inputs and 2N qubit outputs, where N is the number of digits of the number to be factored. That's 4N qubits only for inputs and outputs.
So, in the best case scenario, this computer would be able to factor a 108-binary digit number.
My computer (2020 Intel-based iMac) can do that in one minute.
Here's the code if you want to try it on your computer:
import sympy
n_digits = 54
p = sympy.randprime(2**(n_digits-1), 2**n_digits)
q = sympy.randprime(2**(n_digits-1), 2**n_digits)
sympy.factorint(N)
[1] https://en.wikipedia.org/wiki/Shor%27s_algorithm
Before the last line you need
N = p * qi've lost interest in the qubit race.
what can this machine do productively?
what can this machine do productively?
Find the prime factorization of some two digit numbers.
There was a time when people used to say these things about conventional computers, remember the 50s?
It can drive IBM brand awareness. Pretty sure some people are amazed by what ibm just “achieved”.
I'm still pretty curious. Can this thing do traveling salesman yet?
There is no known polynomial time algorithm for TSP. AFAIK there are quantum algorithms for TSP with quadratic speedup in comparison to the brute force method (still exponential though).
The one thing quantum computers are (currently and theoretically) able to solve efficiently is the factorization problem, but are very much limited by low qubit number, i.e. engineering problems.
The one thing quantum computers are (currently and theoretically) able to solve efficiently is the factorization problem, but are very much limited by low qubit number, i.e. engineering problems.
Thank you for your informative response!
It can sit there without using any power.
I'm cheering them on!