[HN Gopher] Worlds first petahertz transistor at ambient conditions
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Worlds first petahertz transistor at ambient conditions
Author : ChuckMcM
Score : 92 points
Date : 2025-05-24 20:06 UTC (3 days ago)
(HTM) web link (news.arizona.edu)
(TXT) w3m dump (news.arizona.edu)
| ChuckMcM wrote:
| This is some great research, the paper is here:
| https://www.nature.com/articles/s41467-025-59675-5.pdf and there
| are two things that stand out in it, the first is that they used
| a "commercial graphene transistor" and the second is that their
| apparatus didn't need to be super-cooled or under tens of
| atmospheres of pressure or in vacuum etc. For me, that means that
| the risks of bringing this into an actual thing are much less
| than they have been for other technologies (like Josephson-
| Junctions).
|
| It's also kind of funny that you could mine the shit out of
| Bitcoin with something like this, which would either pay for
| itself or crash Bitcoin, hard to predict.
| Someone wrote:
| > It's also kind of funny that you could mine the shit out of
| Bitcoin with something like this, which would either pay for
| itself or crash Bitcoin, hard to predict.
|
| Bitcoin has a built-in mechanism to counteract improvements in
| hashing speed (either because of hardware getting faster,
| algorithmic improvements, or more hardware getting devoted to
| hashing).
|
| See https://en.wikipedia.org/wiki/Bitcoin#Mining: _"The
| difficulty of generating a block is deterministically adjusted
| based on the mining power on the network by changing the
| difficulty target, which is recalibrated every 2,016 blocks
| (approximately two weeks) to maintain an average time of ten
| minutes between new blocks"_
|
| I think there's more than enough range available here to handle
| a million-fold increase in hashing power.
| inhumantsar wrote:
| 2016 blocks is a lot though. that's nearly $700 million in
| mining fees.
|
| if someone had a monopoly on chips like these, they could
| dominate the network and freeze out other miners. which would
| likely tank the network and make those BTC worthless
| Someone wrote:
| That is a risk but not a new risk. It existed with the
| transition to ASIC miners, too, and didn't happen.
|
| I guess that didn't happen because making ASICs is
| relatively easy, but even if it isn't, what would be in it
| for a potential monopolist to tank the value of bitcoin in
| that way? They better take a large but not overly large
| part of the market and keep mining money for a long time,
| only speeding up when a competitor steps in.
| jorvi wrote:
| > what would be in it for a potential monopolist to tank
| the value of bitcoin in that way?
|
| Shorting BTC. But you'd have to gather a humongous mining
| farm / pool in secret, wait until right after the
| recalibration and then turn on everything at once, mining
| those 2016 faster. People would panic, enabling you to
| close your short positions.
|
| After those 2016 blocks you can just keep mining for a
| regular return, although I'd just sell the farm to an
| organisation interested in doing so.
|
| It's a fun theoretical attack, if capital intensive. And
| aside from the short positions (which you can cover
| instead of going naked), your capital isn't at risk
| because the worst result is that you'll own a crypto
| mining farm.
| sigwinch wrote:
| Presenting a quantum breakthrough could be cheaper than
| cornering noticeable capacity.
| Someone wrote:
| > because the worst result is that you'll own a crypto
| mining farm.
|
| Bitcoin is fairly popular among criminals, so you might
| also get some people visit you to argue that is best for
| both of you to give them back the money they lost, using
| strong arguments such as threats of bodily harm.
| TheOtherHobbes wrote:
| With enough money you can buy security to keep yourself
| safe from low/mid criminals. Angry rogue nation states
| might be harder to deal with.
| iwontberude wrote:
| They've had more time to prepare than you which is their
| edge in the game.
| Devasta wrote:
| So if you had a machine that could solve blocks at a
| tremendous pace, could you rapidly go through 2016 blocks
| with minimal transactions processed, then just switch your
| machine off?
|
| The difficulty will have gone through the roof and
| transaction processing time by the rest of the network will
| then slow to a crawl.
| TZubiri wrote:
| Even with difficulty adjustments you could mine a shit ton,
| you would basically be mining all of the blocks every 10
| minutes for yourself. And if the advantage is significant you
| could do a 51% attack.
| HPsquared wrote:
| ~95% of bitcoins have already been mined, market cap is $2T, so
| you'd expect another $100B to go (assuming no price change).
| wslh wrote:
| Mined bitcoins are distinct from the mining process itself:
| even after all bitcoins have been mined, miners will continue
| to operate and earn transaction fees for validating and
| securing the network.
| bee_rider wrote:
| I guess we'll see... I mean, bitcoin transactions will have
| to be valuable enough that we're willing to pay extra (vs
| credit or debit card transactions) to maintain that
| network, right?
| phkahler wrote:
| >> bitcoin transactions will have to be valuable enough
| that we're willing to pay extra (vs credit or debit card
| transactions) to maintain that network, right?
|
| Does handing transactions require similar amounts of
| power to mining?
|
| Edit: also, if transactions are ultimately handled by
| just one or two entities, there will be no point to
| bitcoin any more.
| kragen wrote:
| Mining is the way transactions are handled.
| ted_dunning wrote:
| You didn't answer the question.
|
| The real answer hinges on the leverage of mining one hash
| to certify multiple transactions.
| bee_rider wrote:
| I'm not sure what the real question is or what the real
| answer is.
|
| I'm under the impression that "handling transactions" in
| bitcoin and mining are the same thing. (Although I don't
| work in cryptocurrency so maybe the misunderstanding is
| on my part...)
| Sohcahtoa82 wrote:
| Handling a Bitcoin transaction is two things:
|
| - Broadcasting the transaction throughout the network so
| that all nodes (including miners) are aware of it
|
| - Miners confirming transactions by solving a block
|
| When a miner solves a block, they earn both the block
| reward (Which will eventually become zero) and the fees
| paid by the sender.
|
| Theoretically, as time goes on an the value of Bitcoin
| goes up, the value of the fees will be high enough that
| it will make up for the lack of the block reward.
|
| So the original question of "Does handing transactions
| require similar amounts of power to mining?"
|
| The answer is basically yes. Mining is what confirms
| transactions. A new block is added to the chain, with
| each block containing several transactions.
| Sohcahtoa82 wrote:
| > You didn't answer the question.
|
| It DID answer the question.
|
| > The real answer hinges on the leverage of mining one
| hash to certify multiple transactions.
|
| That's exactly how mining works.
|
| A block is mined when all the data for a block (which
| includes all the transactions of the current block) plus
| a nonce gets hashed and the resulting hash has a value
| that satisfies the current mining difficulty level. If
| hash doesn't satisfy it, you try a new nonce. Mining
| hardware just tries millions/billions of nonces per
| second.
|
| It's possible (though extremely unlikely) that you could
| solve a block in only a single hash.
|
| I think what a lot of people don't understand is that the
| difficulty scales with the amount of hashing power on the
| network. If blocks are being solved too quickly, the
| difficulty rises. If they're too slow, it goes down.
| Difficulty really just changes the odds that your hash
| meets the requirement. It doesn't change the actual
| difficulty of computation, just the odds of success.
| slashdev wrote:
| Currently true. You wouldn't buy a pizza with bitcoin.
| But send several thousand dollars internationally - sure.
| temp0826 wrote:
| As someone who witnessed bitcoin usage in 2012, I assure
| you mistakes were made, and pizzas were in fact involved.
| indoordin0saur wrote:
| If there are fewer miners those that are there get a
| bigger share of the fees. So this self-balances. As long
| as there is _some_ value in BTC and _some_ transactions
| occurring there will be a reward for validating
| transactions.
| jazzyjackson wrote:
| Still whatever volume * fee the market bears becomes the
| cost to attack the network.
| gosub100 wrote:
| Isn't that assuming you could pack enough of these PHz
| transistors to make an asic capable of calculating SHA-256?
| That's quite an endeavor if they have just created one.
|
| Has anyone even made a flip-flop or latch with any optical
| transistor yet?
| jlokier wrote:
| Since you asked, yes, optical flip-flops have been around for
| decades.
|
| That said, you don't need flip-flops or latches to calculate
| SHA-256 for mining Bitcoins. You only need them at the edges
| of the circuit, to use the results. But you can do that with
| electronics at the edge, if you want to avoid stateful logic
| in the all-optical part.
| dgfl wrote:
| This is an optical transistor, meaning that a current is
| controlled with an optical pulse. That means that you can't
| pipe these things into each other, unless you can build an
| equivalently fast and efficient light->charge transducer (i.e.
| a photodetector). Moreover, this physically can't be scaled
| below approximately the wavelength of the laser (meaning at
| least 10x larger than CMOS transistors).
|
| It might turn out to be great for the applications that they
| point out in the paper itself, not so much for logic. I would
| say bitcoin mining discussions are a bit premature, and
| potentially not relevant.
| programjames wrote:
| > That means that you can't pipe these things into each
| other, unless you can build an equivalently fast and
| efficient light->charge transducer (i.e. a photodetector).
|
| These exist:
|
| https://ultrafast.mit.edu/
| knome wrote:
| >(meaning at least 10x larger than CMOS transistors)
|
| at petahertz (10^15) speeds, you could sacrifice a lot of
| space for larger components, and still come out on top vs
| gigahertz speeds (10^9) by doing more work but a hell of a
| lot faster, no?
|
| if you can build a chip that's a million times faster, you
| can sacrifice 3/4 of that speed to doing more work with fewer
| components and still be 250,000x faster.
| formerly_proven wrote:
| No, because propagation delay is the same.
| Jabrov wrote:
| Yep! That's a key thing to keep in mind here. As chips
| get bigger (especially at higher frequencies),
| propagation delay becomes an important blocker
| adgjlsfhk1 wrote:
| it would be really interesting to see how this played
| out. the entire way you build circuits changes. e.g.
| current adder designs use extra transistors to save carry
| propagation latency, but for optical, that might make the
| latency worse...
| colechristensen wrote:
| Propagation delay is _not_ the same, electrical signals
| travel much slower in semiconductors than light in a
| vacuum. If you could make an entirely optical chip, size
| would matter a whole lot less because light will travel
| much faster through whatever that material will be.
| tbrownaw wrote:
| Make wave pipelining cool again?
| hulitu wrote:
| > This is an optical transistor, meaning that a current is
| controlled with an optical pulse.
|
| So more like an optical triode (the transistor apnplifies).
| stretchwithme wrote:
| Or maybe just take ownership of Bitcoin nobody can access,
| potentially much more profitable.
|
| Just don't sell it all at once.
| bjourne wrote:
| So rather than electrons flowing through regular transistors you
| would have photons flowing through phototransistors? Wouldn't one
| problem be casting light rays that with widths in the nano or
| picometer range?
| IAmBroom wrote:
| It's not clear at all what path the photons are taking. I read
| it at first as them travelling as a standing wave, blocking the
| electrons until the transistor "flips".
|
| If the path of the photons is indeed transverse to the flow of
| charge, millions of transistors could share a single wavefront.
| booli wrote:
| This seems very huge, or am I missing something fundamental
| that's not included in the paper?
| misja111 wrote:
| Yes, the fact that contrary to what the title claims, at this
| point there is no transistor working at petaherz frequency at
| all. All there is, is a promising new technology.
| amelius wrote:
| Maybe they should have mentioned that interconnect on a chip
| cannot handle these speeds.
| dgfl wrote:
| This is a laser controlled device. Even the terminology of
| "interconnect" is not really applicable. Your best hope is an
| optical waveguide coupled to the device, definitely not a
| metal line. It's not even a transistor in the traditional
| sense really.
| parsimo2010 wrote:
| This has limited applications. It doesn't have a viable path to
| being used in a CPU or GPU. So we're not going to see a
| zillion-fold increase in compute speeds from this. Maybe some
| physicists find it useful for an experiment, but the average
| joe won't notice anything different about the world.
| manmal wrote:
| I thought that the speed of light limits the max possible
| frequency to the sub THz range, at current chip sizes.
| GuB-42 wrote:
| Petahertz?
|
| It makes me raise so many questions. 1 PHz corresponds to a
| wavelength of 300nm, UV light. How does it make sense? It can't
| be the transistors we are used to, that's all quantum weirdness
| at this point. How do you even use them? Things like copper wires
| feel meaningless at these scales.
| AnimalMuppet wrote:
| At that clock rate, propagation delays are going to be a severe
| issue.
| manmal wrote:
| The speed of light is a hard limit, the only way to make use of
| this switching speed is to make the chip infinitesimally small.
| mjrpes wrote:
| > A study published in Nature Communications highlights how the
| technique could lead to processing speeds in the petahertz range
| - over 1,000 times faster than modern computer chips.
|
| A 1 petahertz chip would be 200,000 faster than a 5 gigahertz
| chip. You've skipped past the terahertz range.
| kragen wrote:
| https://www.nature.com/articles/s41467-025-59675-5 is the paper,
| claiming "~1.6 petahertz speed." That would be 190-nanometer
| wavelength, which is into the so-called "far ultraviolet" band of
| germicidal UVC, 6.6eV photon energy, on the edge of vacuum
| ultraviolet. And they're switching it with light. So, I wonder
| how long these devices will last if you keep using them?
|
| They say the light pulse is 6.5fs FWHM, so they weren't able to
| switch it on and off 1.6 quadrillion times per second; it's just
| that the transition from on (29nA) to off (<1nA) was only 630
| attoseconds long, which is what they're describing as
| "petahertz". But "petahertz" implies a whole cycle time under a
| femtosecond, a cycle which would involve _two_ transitions, which
| would presumably be 1.26 femtoseconds at this speed. (If they
| measured the speed of the off-to-on transition, I missed it
| skimming the paper.) And the actual light they 're making the
| 6.5fs pulse out of is a "supercontinuum laser beam that spans
| over 400-1000 nm". That's still blue enough to raise some
| concerns about device longevity (though maybe graphene will prove
| tougher than certain other semiconductors which shall not be
| named here), but not to the same degree as if they were using
| actual petahertz light.
|
| I think the 2x exaggeration is sort of forgivable, and nothing
| else seems to be intentionally misleading, but it would still be
| easy to draw incorrect conclusions from the headline.
| Aurornis wrote:
| I'm also confused about this. In EE it's normal to use rise
| times to calculate bandwidth, but unless I'm missing something
| they didn't do that correctly either.
|
| It would be such a strange mistake to occur on a paper about a
| topic of this caliber that I feel like I must be missing
| something.
| kragen wrote:
| I suspect that maybe the rise time was much slower than the
| fall time, so it was the fall time they were excited about.
| But yeah, I'd think a 630-attosecond fall time represents
| 500-800 terahertz of bandwidth, not a petahertz or more.
| kerblang wrote:
| For those playing subsecond bingo at home, wikipedia reference
| table
|
| https://en.wikipedia.org/wiki/Orders_of_magnitude_(time)#Les...
| stretchwithme wrote:
| Moore's Law ain't over til it's over.
| actinium226 wrote:
| I can't wait to watch cat videos at petahertz speed.
| mkoryak wrote:
| Just don't watch too many or you will experience the catahurtz
| speed.
| amelius wrote:
| They're aiming a bit high. I'm ok with a terahertz CPU for the
| coming years.
| ziofill wrote:
| In 630as light travels half a micron. If that's the clock cycle,
| a chip would need to do some amazing coordination for bits to
| reach gates at the same time, and there would be many many cycles
| before a signal reaches the other side of the chip. Bonkers.
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