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Comment by RivieraKid | Hacker News Reader

What's the most significant useful application of quantum computing, in other words, why should we be excited about QC, how will it improve people's lives?

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Chemistry applications, which may be possible using the current or near-future era of quantum computers. It helps to have actual quantum effects to compute with. For example (I am not affiliated with this company and don't know if it works) https://www.quantinuum.com/products-solutions/inquanto

Next step room temperature super conductor yeah!

If we extend the definition of "computing" slightly to include "coding and cryptography", then I find superdense coding quite exciting [0]. In a hypothetical quantum internet we could encode and transmit two classical bits in every qubit, which effectively doubles your bandwidth. There's also quantum key distribution [1]. In principle, quantum theory allows Alice and Bob to establish a shared private key which cannot be broken without breaking the laws of physics. You can chat privately with people secure in the knowledge that not even the NSA can possibly be listening.

[0] https://en.wikipedia.org/wiki/Superdense_coding

[1] https://en.wikipedia.org/wiki/Quantum_key_distribution

> You can chat privately with people secure in the knowledge that not even the NSA can possibly be listening.

Well, from one possible attack vector, anyway. They can still point lasers at your windows.

>In a hypothetical quantum internet we could encode and transmit two classical bits in every qubit, which effectively doubles your bandwidth.

Hmm... What exactly are you transmitting in such a scenario? What's the physical layer protocol? I.e. what are the wires made of and what flows through them?

Photons, most of the current efforts for quantum entanglement pairs transmission is using good old lasers over optical fiber

Well, fair enough I suppose. Although a superficial reading would suggest this sort of technology is at least fifty years away from being deployable at opposite ends of a submarine cable to double the capacity without doubling the cable-laying. It reads like it's in the very early experimental stage, where they're barely demonstrating the plausibility, let alone the viability.

The question was why is quantum computing exciting, not when can we get it.

The "although" wasn't meant to invalidate it as an example, it was a link between two separate ideas.

Only 2x bandwidth improvement?

that one dude that has tried since forever to convince that one city to allow him to dig up that garbage dump for his lost bitcoin wallet password should be able to get the coins without digging then.

oh and all other passwords/pass phrases/secrets might get broken too, if they're not yet based on quantum save algos.

Optimization problems like placing trains on a network become computationally viable. We're currently using unoptimal solutions because calculating an optional solution would require way too much time.

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