Quantum computing bombshells that are not April Fools • Hacker News Board

Re: Quantum computing bombshells that are not April Fools

#91

Post by Strilanc » Thu, Apr 02, 2026, 4:40 PM UTC

lkm0 wrote: post #38

To put this in context, we've had a streak of improvements to Shor's algorithm that have put the horizon much closer. In 2022, people from Microsoft estimated that it would take more than 10M (physical) qubits to implement factoring. We're now standing at a 1000x improvement. It's still years away for sure, but who can be unhappy with all that progress? ms paper: https://arxiv.org/abs/2211.07629

Caution: that 10M estimate assumes gate error rates 10x lower than the ones assumed in the papers from TFA.

Re: Quantum computing bombshells that are not April Fools

#92

Post by dumbfoundded » Thu, Apr 02, 2026, 4:50 PM UTC

amluto wrote: post #72

Strilanc wrote: post #12

Earlier quoted context omitted.

The best proposal I have heard for rescuing P2SH wallets after cryptographically relevant quantum computers exist is to require vulnerable wallets to precommit to transactions a day ahead of time. The precommitment doesn't reveal the public key. When the public key must be exposed as part of the actual transaction, an attacker cannot redirect the transaction for at least one day because they don't have a valid precom…

That’s kind of adorable. Would you need to pay to record a commitment? If so, how? If not, what stops someone from DoSing the whole scheme?

I don't think you're understanding how cryptography works. A commitment is basically a hash that is both binding and hiding. In this example it's probably easiest to think of it as a hash. So you hash your post-quantum public key (something like falcon-512) and then sign that hash with your actual bitcoin private key (ecdsa, discrete-log, not quantum safe) and then publish that message to the bitcoin network. Then quantum happens at some point and bitcoin needs to migrate but where do funds go? Well you reveal the post-quantum public key and then you can prove that funds from the ecdsa key should go there. From a technical perspective, this is a complete and fool proof system. DoSing isn't really a concern if you publish to the actual bitcoin network and it's impossible for someone to use up the key space (2^108 combinations at least).

The reason this is a dumb idea is because coordination and timing. When does the cutover happen? Who decides which transactions no longer count as they were "broken" b/c of quantum computing? The idea is broken but not from technical fundamentals.

Re: Quantum computing bombshells that are not April Fools

#93

Post by Foobar8568 » Thu, Apr 02, 2026, 5:19 PM UTC

nlarew wrote: post #75

Foobar8568 wrote: post #50

Earlier quoted context omitted.

Replication of quantum factorisation records with a 8bits home computer, Abacus and a dog

What are you trying to say here? This makes no sense.

That's a famous paper that debunk a lot of things related to marketing announcements. Basically nothing has truly factorized 15, let alone 21.

Re: Quantum computing bombshells that are not April Fools

#94

Post by freetonik » Thu, Apr 02, 2026, 5:22 PM UTC

ProllyInfamous wrote: post #83

freetonik wrote: post #25

I worked at a quantum computing company that builds superconducting QC chips (so, not really applicable to one of the “bombshells” from the article). My team was designing the software stack which allows to control the QC, run quantum jobs/algorithms, and calibrate the parameters. I’ve made two attempts to explain the work we’ve been doing and to explain the current realistic state of the industry: 1. A talk at PyCon…

Thank you for posting/sharing. My mid-sized US city (Chattanooga) has recently announced a partnership with Vanderbilt and EPB (local govt-owned fiber ISP) which creates a Quantum Computing Research Facility [$,$$$,$$$,$$$] [1]. As locals are covering this news, I keep having this thought that nobody (perhaps less than a few ?) even knows what those words mean (certainly not me) . You speak confidently and clearly en…

The meme refers to the notion where an observation (i.e. interaction) collapses the wave function to a single value. As in, prior to observation, a system in a quantum superposition is said to be "in multiple states at the same time", and after the obsevation only one state exists, while all other possibilities are gone (or exist in other worlds, according to one of the interpretations of quantum mechanics [0]).

So, in that meme, the guy looks at one girl (the observed state) and "ignores" all other girls (all other possible states).

[0] https://en.wikipedia.org/wiki/Many-worlds_interpretation

Re: Quantum computing bombshells that are not April Fools

#95

Post by freetonik » Thu, Apr 02, 2026, 5:29 PM UTC

regularfry wrote: post #87

sigmoid10 wrote: post #42

Earlier quoted context omitted.

If they're going public I imagine they already sell some kind of QC chips. But, like, who buys them? Yesterday there was a new paper [1] that shows how Shor's algorithm could break realistic encryptions with as little as 10,000 qubits (instead of millions), but as far as I know quantum hardware is still orders of magnitude below even that target. So how big can the market actually be? Shipping to universities or othe…

At this point my bet is that the breakthrough isn't going to be qbits per chip, it's going to be entanglements-per-second in quantum networking. If you could string together simpler processors in a cluster at anything approaching interesting scales then all of a sudden the orders of magnitude become a lot less constrained and it's just a money problem.

Quantum networking is a lesser problem than changing the state and keeping intact long enough. You can already move quantum state over fiber optics pretty reliably, so transport exists, but what then? You need to put the qubits of the connected chip into the corresponding state (which takes time), and do it many times, and all that time is an overhead.

Superconducting QCs are fast, but the state degrades incredibly quickly, so you only have a fraction of a second (maybe a millisecond at best, currently) until the entire state is garbage. Some other modalities like trapped ion are the opposite: state can live long, but each operation is orders of magnitude slower.

Re: Quantum computing bombshells that are not April Fools

#96

Post by Strilanc » Thu, Apr 02, 2026, 5:38 PM UTC

amluto wrote: post #72

Strilanc wrote: post #12

Earlier quoted context omitted.

The best proposal I have heard for rescuing P2SH wallets after cryptographically relevant quantum computers exist is to require vulnerable wallets to precommit to transactions a day ahead of time. The precommitment doesn't reveal the public key. When the public key must be exposed as part of the actual transaction, an attacker cannot redirect the transaction for at least one day because they don't have a valid precom…

That’s kind of adorable. Would you need to pay to record a commitment? If so, how? If not, what stops someone from DoSing the whole scheme?

Yes, that would be a concern. You could require a proof of work to submit a precommitment, so that DoSing was at least expensive to do. You could have some sort of deposit mechanism, where a precommitment would lock down 0.1 bitcoins (from a quantum-secure wallet) until the precommitment was used. I admit I'm glad I don't have to figure out those details.

Re: Quantum computing bombshells that are not April Fools

#97

Post by jb1991 » Thu, Apr 02, 2026, 5:39 PM UTC

Jbird2k wrote: post #85

jb1991 wrote: post #40

This site is almost impossible to read on mobile unless you have good vision. Normally I can just hit the button in my phone browser to read it in reader mode, but this site doesn’t support that either. It’s a shame. I am surprised that in 2026 more websites don’t seem so concerned about responsive design, especially when the goal is to read the content.

iPhone user here I have a button that I can adjust the text size on this site.

which browser on iphone?

Re: Quantum computing bombshells that are not April Fools

#98

Post by Strilanc » Thu, Apr 02, 2026, 5:45 PM UTC

dumbfoundded wrote: post #92

amluto wrote: post #72

Earlier quoted context omitted.

That’s kind of adorable. Would you need to pay to record a commitment? If so, how? If not, what stops someone from DoSing the whole scheme?

I don't think you're understanding how cryptography works. A commitment is basically a hash that is both binding and hiding. In this example it's probably easiest to think of it as a hash. So you hash your post-quantum public key (something like falcon-512) and then sign that hash with your actual bitcoin private key (ecdsa, discrete-log, not quantum safe) and then publish that message to the bitcoin network. Then qu…

The DoS attack in this scenario is someone just submitting reasonable-looking but ultimately bad precommitments as fast as possible. The intuition is that precommitments must be hard to validate because, if there was an easy validation mechanism, you would have just used that mechanism as the transaction mechanism. And so all these junk random precommitments look potentially legitimate and end up being stored for later verification. So all you have to do to take down the system is fill up the available storage with junk, which (given the size of bot networks and the cost of storing something for a day) seems very doable.

Re: Quantum computing bombshells that are not April Fools

#99

Post by sMarsIntruder » Thu, Apr 02, 2026, 5:45 PM UTC

tsimionescu wrote: post #64

sMarsIntruder wrote: post #34

Earlier quoted context omitted.

I’m impressed by the BTC obsession: this will definitely impact the banking sector as a whole even before. Quantum FUD, here we come.

The banking sector can relatively trivially move to a new encryption scheme - this is one of the huge advantages of centralized systems. Also, the banking sector, rather than trying to provide anonymity/pseudonimity, has KYC - they can relatively simply disable remote access if they think a current system is no longer secure, and get everyone to come in to a physical office and get a secure version, after manually ve…

Upgrading decades old legacy systems? Good luck with that.

Re: Quantum computing bombshells that are not April Fools

#100

Post by lifty » Thu, Apr 02, 2026, 5:52 PM UTC

timbowhite wrote: post #86

ozim wrote: post #58

Earlier quoted context omitted.

Your bank doesn’t depend only on cryptography. It would be still a lot of effort to simply make transfer from a bank account. Quantum computer will not magically give an answer for a password of a hash you don’t have. TLS is moving to post quantum as we speak. For crypto currency you have all the data you need to break whole system ready in your hands as you will be able to produce private key from public keys of wal…

In Bitcoin's case, public keys are only revealed during a transaction. And every transaction completely spends the source keypairs' funds. So the only attack vector a quantum computer could use is: 1. Observing newly broadcast/unconfirmed transactions 2. Deriving the private key(s) from the public key(s) 3. Creating and broadcasting its own transaction using the stolen keypairs before the original transaction confirm…

So everything basically.