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Quantum computers move closer to the assembly line

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Re: Quantum computers move closer to the assembly line

#31

Post by n4r9 »

bowsamic wrote: post #26
n4r9 wrote: post #22

Earlier quoted context omitted.

> this assumes that we have some way to evolve a quantum system precisely according to input data, a much harder problem than the linear algebra itself That's a fair point. I guess I was interpreting OP's question as "what can we do once we have engineered quantum computers", and would categorise this "harder problem" as an engineering problem.

> would categorise this "harder problem" as an engineering problem. I'm not sure what your relation to the field is, but I have found that a lot of things that look like engineering problems from the outside, end up being theoretical and fundamental problems from within. This is often the case when I discuss quantum noise of gravitational wave detectors. I often see people say things like "I wouldn't want to be the g…

Again, a totally fair point. I just mean that when you posed the question "what exactly are quantum computers useful for?", I kind of assumed you meant an ideal quantum computer that had this kind of control over its state.

For reference I am out of my depth! My doctorate was in quantum information theory but I've been out of academia for many years now.

Re: Quantum computers move closer to the assembly line

#32

Post by rbanffy »

tambourine_man wrote: post #30
rbanffy wrote: post #29

Earlier quoted context omitted.

PQC is useful because you can capture and hoard data now and decrypt it later when the hardware becomes available.

I know, but I'm thinking about the timing. Just speculating.

The sooner you get it, the less vulnerable data will be captured.

Re: Quantum computers move closer to the assembly line

#33

Post by bowsamic »

n4r9 wrote: post #31
bowsamic wrote: post #26

Earlier quoted context omitted.

> would categorise this "harder problem" as an engineering problem. I'm not sure what your relation to the field is, but I have found that a lot of things that look like engineering problems from the outside, end up being theoretical and fundamental problems from within. This is often the case when I discuss quantum noise of gravitational wave detectors. I often see people say things like "I wouldn't want to be the g…

Again, a totally fair point. I just mean that when you posed the question "what exactly are quantum computers useful for?", I kind of assumed you meant an ideal quantum computer that had this kind of control over its state. For reference I am out of my depth! My doctorate was in quantum information theory but I've been out of academia for many years now.

Yeah, I did mean that, and I stand by my opinion that even the ideal cases are not particularly compelling. I'm just also pointing out that the ideal case is not actually possible, even theoretically. There will also be decoherence, for example, and even the tomography of the state (i.e. actually measuring the state) is limited by fundamental quantum noise (e.g. ultimately the Heisenberg limit).

Re: Quantum computers move closer to the assembly line

#34

Post by singularity2001 »

smurda wrote: post #3

5 years ago I was at MIT’s QC lab and 4 qubits was the max number of entangled qubits their machine could reach, sustainably. All the marketing fluff from IBM and Google about hundreds, or thousands, of entangled qubits is misleading - they don’t maintain those entangled states for long durations. Only when we can get hundreds of qubits to maintain entangled states for sustainable periods of time can we then attempt…

I still need to be convinced that the exponential power of n qubits grows faster than the exponential complexity of aligning, programming and reading n qubits.

Re: Quantum computers move closer to the assembly line

#35

Post by n4r9 »

bowsamic wrote: post #33
n4r9 wrote: post #31

Earlier quoted context omitted.

Again, a totally fair point. I just mean that when you posed the question "what exactly are quantum computers useful for?", I kind of assumed you meant an ideal quantum computer that had this kind of control over its state. For reference I am out of my depth! My doctorate was in quantum information theory but I've been out of academia for many years now.

Yeah, I did mean that, and I stand by my opinion that even the ideal cases are not particularly compelling. I'm just also pointing out that the ideal case is not actually possible, even theoretically. There will also be decoherence, for example, and even the tomography of the state (i.e. actually measuring the state) is limited by fundamental quantum noise (e.g. ultimately the Heisenberg limit).

I guess it depends on what you find compelling. I'm not interested in finance. A lot of it just seems like moving money around to make wealthy people wealthier. But it does make sense that a lot of heads will perk up if there's a potential for speeding up market simulation models.

Re: Quantum computers move closer to the assembly line

#36

Post by mst_moonshine »

bjoli wrote: post #18
tambourine_man wrote: post #8

The recent changes in iMessages and Signal for PQC made me think there may be something imminent going on in this realm

Related: i was under the impression that AES was safe (even aes-128). If it is so, why did Apple go for full pqc and not just the key exchange? Would it be a good idea for signal to double the key size?

That's a good question. I thought they are only using PQC for key exchange (which is referred to as Level 2) but they are not.

In the article, Apple explains why they choose to use Level 3:

> At Level 2, the application of post-quantum cryptography is limited to the initial key establishment, providing quantum security only if the conversation key material is never compromised. But today’s sophisticated adversaries already have incentives to compromise encryption keys, because doing so gives them the ability to decrypt messages protected by those keys for as long as the keys don’t change. To best protect end-to-end encrypted messaging, the post-quantum keys need to change on an ongoing basis to place an upper bound on how much of a conversation can be exposed by any single, point-in-time key compromise — both now and with future quantum computers. Therefore, we believe messaging protocols should go even further and attain Level 3 security, where post-quantum cryptography is used to secure both the initial key establishment and the ongoing message exchange, with the ability to rapidly and automatically restore the cryptographic security of a conversation even if a given key becomes compromised.

Article link: https://security.apple.com/blog/imessage-pq3/

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