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Willow, Our Quantum Chip

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Re: Willow, Our Quantum Chip

#411

Post by tsimionescu »

webXL wrote: post #349
bangaladore wrote: post #326

Earlier quoted context omitted.

So the first company that can break bitcoin addresses using quantum computers gets a prize of how many billion(?) dollars by stealing all the non-migrated addresses. Is that a crime? Lots of forgotten keys in there.

A very interesting philosophical and moral can of worms you just opened there. Bitcoin is governed by the protocol, so if the protocol permits anyone who can sign a valid transaction involving a given UTXO to another address, then it technically isn't a "crime". Morally I'm not sure I'd be able to sleep well at night if I unilaterally took what I didn't exchange value for. As for the forgotten key case, I think the o…

Morally, there is no quandary: it's obviously morally wrong to take someone else's things, and knowing their private key changes nothing.

Legally, the situation is the same: legal ownership is not in any way tied to the mechanism of how some system or another keeps track of ownership. Your BTC is yours via a contract, not because the BTC network says so. Of course, proving to a judge that someone else stole your BTC may be extremely hard, if not impossible.

Saying "if the protocol permits anyone who can sign a valid transaction involving a given UTXO to another address, then it technically isn't a "crime"" is like saying "traditional banking is governed by a banker checking your identity, so if someone can convince the banker they are you, then it technically isn't a "crime"".

The only thing that wouldn't be considered a crime, in both cases, is the system allowing the transaction to happen. That is, it's not a crime for the bank teller to give your money to someone else if they were legitimately fooled; and it's not a crime for the Bitcoin miners to give your money to someone else if that someone else impersonated your private key. But the person who fooled the bank teller /the miners is definitely committing a crime.

Re: Willow, Our Quantum Chip

#412

Post by JanisErdmanis »

AlexCoventry wrote: post #393
thrance wrote: post #71

Earlier quoted context omitted.

The error rates given are still horrendous and nowhere near low enough for the Quantum Fourier Transform used by Shor's algorithm. Taking qubit connectivity into account, a single CX between 2 qubits that are 10 edges aways gives an error rate of 1.5%. Also, the more qubits you have/the more instructions are in your program, the faster the quantum state collapses. Exponentially so. Qubit connectivity is still ridicul…

In addition to that, the absolutely enormous domains that the Fourier Transform sums over (essentially, one term in the sum for each possible answer), and the cancellations which would have to occur for that sum to be informative, means that a theoretically-capable Quantum Computer will be testing the predictions of Quantum Mechanics to a degree of precision hundreds of orders of magnitude greater than any physics ex…

Beautiful analogy.

Re: Willow, Our Quantum Chip

#413

Post by tsimionescu »

movpasd wrote: post #305
wasabi991011 wrote: post #35

Earlier quoted context omitted.

I was also really taken aback by this quote. I have no idea who put it there, but I can assure you the actual paper contains no such nonsense. I would have thought whoever writes the google tech blogs is more competent than bottom tier science journalists. But in this case I think it is more reasonable to assume malice, as the post is authored by the Google Quantum AI Lead, and makes more sense as hype-boosting buzzw…

There are compelling arguments to believe in the many-worlds interpretation. No sign of a Heisenberg cut has been observed so far, even as experiments involving entanglement of larger and larger molecules are performed, which makes objective-collapse theories hard to consider seriously. Bohmian theories are nice, but require awkward adjustments to reconcile them with relativity. But more importantly, they are philoso…

I think the key point that makes the quoted statement sciencey gibberish is that the Many Worlds Interpretation is just that - an interpretation. There is no way to prove or disprove it (except if you proved that the world is not actually quantum mechanical, in which case MWI might not be a valid interpretation of the new theory). Saying "this is more evidence for MWI" is thus true of any quantum mechanical experiment, but anything that is evidence for MWI is also exactly as much evidence for Pilot Waves (well, assuming it is possible to reconcile with quantum field theory), the Copenhagen Interpretation, QBism, and so on.

As a side note, there is still a huge gap between the largest system we've ever observed in a superposition and the smallest system we've ever observed to behave only classically. So there is still a lot of room for objective collapse theories, even though that space has shrunk by some orders of magnitude since it was first proposed. Of course, objective collapse has other, much bigger, problems, such as being incompatible with Bell's inequalities.

Edit: I'd also note some things about MWI. First, there are many versions of it, some historical, some current. Some versions, at least older ones, absolutely did involve explicit branching. And the ones that don't have a big problem still with explaining why, out of the many ways to choose the basis vectors for a measurement, we always end up with the same classical measurables in every experiment we perform on the world at large. Especially given that we know we can measure quantum systems in another other basis if we want to. It also ultimately doesn't answer the question of why we need the Born rule at all, it still postulates that an observer only has access to one possible value of the wave function and not to all at once. And of course, the problem of defining probabilities in a world where everything happens with probability 1 is another philosophically thorny issue, especially when you need the probabilities to match the amplitude of the wave function.

So the MWI is nice, and it did spawn a very useful and measurable observation, decoherence. But it's far from a single, satisfying, complete, self-consistent account of the world.

Re: Willow, Our Quantum Chip

#414

Post by bgnn »

fidotron wrote: post #28

The slightly mind blowing bit is detailed here: > https://research.google/blog/making-quantum-error-correction... “the first quantum processor where error-corrected qubits get exponentially better as they get bigger” Achieving this turns the normal problem of scaling quantum computation upside down.

Hmm why? I thought the whole idea was this would work eventually. Physical qubit vs logical qubit distinction is there already for a long time.

The scaling problem is multifaceted. IMHO the physical qubits are the biggest barrier to scaling.

Re: Willow, Our Quantum Chip

#415

Post by a2128 »

codeyperson wrote: post #345

If we are in a simulation. This seems like a good path to getting our process terminated for consuming too much compute.

I doubt we would even register as a blip. The universe is absolutely massive and there's celestial events that are unthinkably massive and complex. Black hole mergers, supernovae, galaxies merging. Hell, think of what chaos happens in the inside of our own sun, and multiply that by 100 billion stars in a galaxy, and multiply that by 100 billion galaxies. Humanity is ultimately inconsequential.

Re: Willow, Our Quantum Chip

#416

Post by orliesaurus »

rhubarbtree wrote: post #259
qnleigh wrote: post #249

Earlier quoted context omitted.

You need to distinguish between "physical qubits" and "logical qubits." This paper creates a single "first-of-a-kind" logical qubit with about 100 physical qubits (using Surface Code quantum error correction). A paper from Google in 2019 estimates needing ~20 million physical qubits ("How to factor 2048 bit RSA integers in 8 hours using 20 million noisy qubits" - https://arxiv.org/abs/1905.09749 ), though recent adva…

This is correct. I worked in quantum research a little.

any books for beginners that you recommend?

Re: Willow, Our Quantum Chip

#418

Post by kortilla »

HeatrayEnjoyer wrote: post #334
kortilla wrote: post #332

Earlier quoted context omitted.

> quantum computers would be able to retroactively break any public keys that were stored Use a key exchange that offers perfect forward secrecy (e.g. diffie Hellman) and you don’t need to worry about your RSA private key eventually being discovered.

Not exactly, they can just reverse the entire chain.

What chain are you talking about?

Re: Willow, Our Quantum Chip

#419

Post by kortilla »

ramchip wrote: post #392
kortilla wrote: post #332

Earlier quoted context omitted.

> quantum computers would be able to retroactively break any public keys that were stored Use a key exchange that offers perfect forward secrecy (e.g. diffie Hellman) and you don’t need to worry about your RSA private key eventually being discovered.

> Forward secrecy is designed to prevent the compromise of a long-term secret key from affecting the confidentiality of past conversations. However, forward secrecy cannot defend against a successful cryptanalysis of the underlying ciphers being used, since a cryptanalysis consists of finding a way to decrypt an encrypted message without the key, and forward secrecy only protects keys, not the ciphers themselves.[8]…

I’m talking specifically about RSA being eventually broken. If just RSA is broken and you were using ECDHE for symmetric keying, then you’re fine.

The point is that you can build stuff on top of RSA today even if you expect it to be broken eventually if RSA is only for identity verification.

Re: Willow, Our Quantum Chip

#420

Post by kortilla »

ReptileMan wrote: post #335
kortilla wrote: post #332

Earlier quoted context omitted.

> quantum computers would be able to retroactively break any public keys that were stored Use a key exchange that offers perfect forward secrecy (e.g. diffie Hellman) and you don’t need to worry about your RSA private key eventually being discovered.

Perfect forward secrecy doesn't work that well when NSA motto is - store everything now decrypt later. If they intercept the ephemeral key exchange now they can decrypt the message 10 or 50 years later.

Diffie Hellman doesn’t ever send the key over the wire, that’s the point. There is nothing to decrypt in the packets that tells you the key both sides derived.

Unless they break ECDHE, it doesn’t matter if RSA gets popped.

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