Comment by Udik | Hacker News Reader

Comment by Udik | Hacker News Reader

Parent Full thread

Here's the relevant part of the twitter rant- seems interesting but I can't tell myself whether it makes sense or not :)

"they repeatedly asked the quantum processor for outputs to a random circuit, and the “quantum supreme computation” was that the outputs were not actually random, but subject to bias due to quantum interference, which they check by solving the path integral in classical simulation

which, to me, is an infuriating thing to label “quantum supremacy” because quantum interference is EXACTLY WHY WE CAN’T USE CURRENT QUANTUM PROCESSORS TO “BREAK ALL CRYPTO” IN THE FIRST PLACE BECAUSE WE CANNOT DO EFFICIENT QUANTUM ERROR CORRECTING CODES

it’s like pointing at a fucking Zener diode and saying, “quantum supremacy” simply because quantum electromagnetic domain wall tunnelling happens at random, followed by a non-justification of “well your iphone can’t do that”"

Sorry but no. The poster is taking a simplistic view of things. Random circuit sampling is a generally accepted method of establishing quantum supremacy.

See this paper from Dr. Vazirani (Berkeley) saying as much https://arxiv.org/pdf/1803.04402.pdf

This is just nonsense. It equivocates between two separate things by calling both of them "quantum interference":

1) A quantum computer uses computational gates to very deliberately orchestrate interference patterns. This is the reason quantum computers are faster than classical ones at certain problems.

2) On top of (1), there's a ton of undesired interference because of dirty real-world constraints. Quantum computers are not fully isolated from their environment, and executing a gate cannot be done without also affecting qubits that are not supposed to be part of the gate.

> subject to bias due to quantum interference, which they check by solving the path integral in classical simulation

This is an instance of (1)

> because quantum interference is EXACTLY WHY WE CAN’T USE CURRENT QUANTUM PROCESSORS TO “BREAK ALL CRYPTO” IN THE FIRST PLACE BECAUSE WE CANNOT DO EFFICIENT QUANTUM ERROR CORRECTING CODES

This is an instance of (2).

Quantum supremacy is all about showing that you can implement (1) with enough fidelity even in the presence of (2). Now keep this in mind while reading the rant again, and you'll quickly realize it's absolute nonsense.

Reply on news.ycombinator.com