22 votes

Harvard physicists working to develop game-changing tech demonstrate 3,000 quantum-bit system capable of continuous operation

Posted by skybrian
Tags: physics, usa, technology, computing.quantum, research, author.kermit pattison, source.harvard
https://news.harvard.edu/gazette/story/2025/09/clearing-significant-hurdle-to-quantum-computing/

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Title
Clearing significant hurdle to quantum computing - Harvard Gazette
Authors
Kermit Pattison
Published
Sep 25 2025
Word count
927 words

10 comments

  1. [6]
    skybrian
    Link
    What could you do with a quantum computer? The Gaslit Asset Class Big if true. However, I think they might have trouble cashing out. Who would buy $460 billion worth of Bitcoin? Wouldn’t this...

    What could you do with a quantum computer?

    The Gaslit Asset Class

    Bitcoin's transition to post-quantum cryptography faces a major problem because, to transfer coins from an ECDSA wallet to a post-quantum wallet, you need the key for the ECDSA wallet. Chainalysis estimates that:

    about 20% of all Bitcoins have been "lost", or in other words are sitting in wallets whose keys are inaccessible

    An example is the notorious hard disk in the garbage dump. A sufficiently powerful quantum computer could recover the lost keys.

    The incentive for it to happen suddenly is that, even if Nakamoto's fix were in place, someone with access to the first sufficiently powerful quantum computer could transfer 20% of all Bitcoin, currently worth $460B, to post-quantum wallets they controlled. This would be a 230x return on the investment in PsiQuantum.

    Big if true. However, I think they might have trouble cashing out. Who would buy $460 billion worth of Bitcoin? Wouldn’t this cause a crash?

    9 votes
    1. [5]
      l_one
      Link Parent
      That's only if you view it through the lens of wanting to convert all of it to any of the standard Fiat currencies. If they were savvy, they would only do that on an as-needed basis and primarily...

      Who would buy $460 billion worth of Bitcoin? Wouldn’t this cause a crash?

      That's only if you view it through the lens of wanting to convert all of it to any of the standard Fiat currencies.

      If they were savvy, they would only do that on an as-needed basis and primarily exploit all of the power that comes from having a gravity-well scale of reserve funds. That behavior pattern has been well observed from the likes of the ultra-wealthy and investment firms. Basically use the power that having tons of money offers without actually needing to spend much of it in order to concentrate more wealth and power.

      Be evil, in other words.

      9 votes
      1. [4]
        skybrian
        Link Parent
        Bitcoin seems pretty inert if it's just sitting there? I suppose it could be used as collateral if they can prove the have the private key. But I still think it would start a panic if word gets...

        Bitcoin seems pretty inert if it's just sitting there? I suppose it could be used as collateral if they can prove the have the private key.

        But I still think it would start a panic if word gets out that nobody's Bitcoin is safe.

        5 votes
        1. [2]
          okiyama
          Link Parent
          Exactly that. What they don't tell you about being a billionaire is that it's literally" free. You get basically free loans against your very profitable collateral

          Exactly that. What they don't tell you about being a billionaire is that it's literally" free. You get basically free loans against your very profitable collateral

          3 votes
          1. skybrian
            Link Parent
            I think the lender would want to make sure that their collateral is very secure, though, and bitcoin is volatile. Compare with loans using stock as collateral. If the stock goes down, they need to...

            I think the lender would want to make sure that their collateral is very secure, though, and bitcoin is volatile. Compare with loans using stock as collateral. If the stock goes down, they need to be able to make a margin call.

            1 vote
        2. l_one
          Link Parent
          It would almost certainly crash the accepted value of Bitcoin if the underlying cryptography was proven compromised. There would be a lesser devaluation if that happened after the underlying...

          But I still think it would start a panic if word gets out that nobody's Bitcoin is safe.

          It would almost certainly crash the accepted value of Bitcoin if the underlying cryptography was proven compromised.

          There would be a lesser devaluation if that happened after the underlying cryptography was transitioned to 'quantum-proof / quantum-resistant' cryptography and only affected forgotten / lost / cold-storage ignored bitcoins.

          2 votes
  2. skybrian
    (edited )
    Link
    From the article: … … … I’ve been assuming quantum computing won’t be practical for many years, but maybe it’s closer than I thought.

    From the article:

    In the new study, the team devised a system to continually and rapidly resupply qubits using “optical lattice conveyor belts” (laser waves that transport atoms) and “optical tweezers” (laser beams that grab individual atoms and arrange them into grid-like arrays). The system can reload up to 300,000 atoms per second.

    “We’re showing a way where you can insert new atoms as you naturally lose them without destroying the information that’s already in the system,” said Elias Trapp, the paper co-author and a Ph.D. student in the Kenneth C. Griffin School of Arts and Sciences studying physics. “That really is solving this fundamental bottleneck of atom loss.”

    The new system operated an array of more than 3,000 qubits for more than two hours — and in theory, the researchers said, could continue indefinitely. Over two hours, more than 50 million atoms had cycled through the system.

    …

    In follow-up experiments, the team plans to apply this approach to perform computations.

    …

    The new study advances a fast-developing frontier of research. In fact, this week a team from Caltech published a 6,100-qubit system, but it could only run for less than 13 seconds.

    …

    In a third paper published in Nature this week, the team demonstrates a quantum architecture with new methods for error correction. With this new body of research, Lukin believes that it is now possible to envision quantum computers that can execute billions of operations and continue running for days.

    I’ve been assuming quantum computing won’t be practical for many years, but maybe it’s closer than I thought.

    8 votes
  3. [2]
    talklittle
    Link
    I'm having trouble finding it but there was an interesting graphic, maybe on Mastodon or Bluesky, illustrating how adding one logic gate to a quantum circuit could increase the required components...

    I'm having trouble finding it but there was an interesting graphic, maybe on Mastodon or Bluesky, illustrating how adding one logic gate to a quantum circuit could increase the required components by an order of magnitude? Very fuzzy but it was something like: 5 logic gates requires around 20 fundamental gates, and 6 logic gates requires hundreds of fundamental gates. Does anyone know the graphic I'm talking about?

    Is that quantity at all related to the 3000 qubits talked about here? Implying that going from 300 qubits to 3000 qubits allows one additional logic calculation added to a circuit?

    Ah, I see this article that explains it better: https://interestingengineering.com/innovation/microsoft-new-quantum-chip-explained

    One inherent issue is that qubits are notoriously error-prone; building error-corrected systems typically requires a massive overhead of additional qubits to stabilize just a few “logical qubits” that do the calculations.

    (Referring to Microsoft's "Majorana 1" quantum chip that they announced earlier this year, claiming it will lead to a million qubits on a single chip.)

    The major problem with the terminology is that "qubit" is so overloaded. Can't tell at a glance if the qubits are doing actual logical work, or if they are helpers there to stabilize the logic qubits. Even with these systems that introduce stability like in the posted article, it's unclear to me if that means fewer qubits are needed on a circuit to do the same amount of work.

    6 votes
    1. talklittle
      Link Parent
      Answering myself: After thinking and rereading, I realized this stability presented in this article is separate from the circuit design. There's not any claimed breakthrough in number of qubits or...

      Answering myself: After thinking and rereading, I realized this stability presented in this article is separate from the circuit design. There's not any claimed breakthrough in number of qubits or the circuit size. The decay is happening in the circuit itself due to the materials and tiny nanoscale environment it's dealing with. So temporally a quantum circuit will naturally decay, and these researchers found a way to stabilize that temporal decay by replacing the atoms leaving the system.

      2 votes
  4. skybrian
    Link
    Meanwhile: PsiQuantum Raises $1 Billion, Says Its Computer Will Be Ready in Two Years https://archive.is/AEuan

    Meanwhile:

    PsiQuantum Raises $1 Billion, Says Its Computer Will Be Ready in Two Years

    https://archive.is/AEuan

    While many competitors are starting small and gradually building larger and larger systems, PsiQuantum differentiates itself with a bold approach. It plans to build a 1-million-qubit fault-tolerant machine right off the bat. A fault tolerant quantum computer is one that can correct the small, unavoidable errors that arise in computation and consistently deliver reliable results.

    A quantum computer in Brisbane, Australia, is expected to be online by the end of 2027 and one in Chicago in 2028, the company said. Some of the newly raised money will also go toward building large-scale test systems and ramping up production of materials.

    1 vote