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Dave Bacon

@dabacon.tachyon.institute

780 followers 140 following 240 posts

Theoretical ski bum. Former pseudo professor. Quantum bridge builder. Will math for food. mastodon: @[email protected] https://dabacon.org

dabacon.org

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Dave Bacon @dabacon.tachyon.institute · Apr 25

Much Madness is divinest Sense -
To a discerning Eye -
Much Sense - the starkest Madness -
’Tis the Majority
In this, as all, prevail -
Assent - and you are sane -
Demur - you’re straightway dangerous -
And handled with a Chain -

—Emily Dickinson

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Dave Bacon @dabacon.tachyon.institute · 20h

PRL made us remove the word supercoherent from the title (no new words in title is policy) but we still used it in the paper.

Dave Bacon @dabacon.tachyon.institute · 20h

Or at least that is what I sort of remember when I looked at this many careers ago. It was partly what inspired arxiv.org/abs/quant-ph... which we originally called “supercoherent” for this reason.

Coherence-Preserving Quantum Bits

Real quantum systems couple to their environment and lose their intrinsic quantum nature through the process known as decoherence. Here we present a method for minimizing decoherence by making it ener...

arxiv.org

Dave Bacon @dabacon.tachyon.institute · 20h

So for entanglement the state is mostly like a product of a lot of two electron entangled states, with the crazy thing that the phase in the entangled states is the same (that is the macroscopic phase, conjugate to the number operator)

Dave Bacon @dabacon.tachyon.institute · 20h

*Cooper fun fact: Cooper pairs are error detecting codes, a singlet and a space part that is a symmetric |k,-k>+|-k,k>

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Dave Bacon @dabacon.tachyon.institute · 20h

The relevant state is probably the BCS ground state? Though it is an ansatz arxiv.org/abs/quant-ph... so it’s macroscopic in that it’s a large number of things that are like copper pairs.

Quantifying ground state entanglement of the BCS model

The concept of local concurrence is used to quantify the entanglement between a single qubit and the remainder of a multi-qubit system. For the ground state of the BCS model in the thermodynamic limit...

arxiv.org

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Reposted by Dave Bacon

Bob Kopp @bobkopp.net · 1d

for the EPA legally to use the report under Information Quality Act guidelines) and (2) hey, there’s an 85+ author, 450-page review of the cherry-picking, misrepresenting, selectively citing DOE report there to discuss (and which Koonin conveniently ignores, talk about pot calling the kettle black)

Climate Experts’ Review of the DOE Climate Working Group Report

In response to the Department of Energy's recent climate report, more than 85 scientists came together to submit a detailed rebuttal. Our motivation was simple: the DOE report misrepresents the state ...

essopenarchive.org

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Reposted by Dave Bacon

Douglas Natelson @nanoscaleviews.bsky.social · 1d

🧪⚛️ The 2025 Nobel Prize in Physics - a brief writeup about what is meant here by macroscopic quantum tunneling. nanoscale.blogspot.com/2025/10/2025...

2025 Physics Nobel: Macroscopic quantum tunneling

As announced this morning, the 2025 Nobel Prize in Physics has been awarded to John Clarke , Michel Devoret , and John Martinis , for a ser...

nanoscale.blogspot.com

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Dave Bacon @dabacon.tachyon.institute · 1d

Jinx

Dave Bacon @dabacon.tachyon.institute · 1d

All sound awesome, but am a bit intrigued by the connection between quantum logic and projective geometry

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Dave Bacon @dabacon.tachyon.institute · 2d

Macroscopic quantum coherence still blows my mind.

Dave Bacon @dabacon.tachyon.institute · 2d

Nice result on inherent size of fault-tolerance scirate.com/arxiv/2510.0...

"Our work contributes to this broader effort by providing evidence of inherent limits: Even when codes
have good rate, there may be fundamental constraints on how much they can reduce the volume of
fault-tolerant circuits."

Tradeoffs on the volume of fault-tolerant circuits

Dating back to the seminal work of von Neumann [von Neumann, Automata Studies, 1956], it is known that error correcting codes can overcome faulty circuit components to enable robust computation. Choos...

scirate.com

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Dave Bacon @dabacon.tachyon.institute · 3d

Portland is, I can attest from many personal visits, not a disaster or whatever hate that is tossed at it by people who don’t know how to love. We’re with you southern neighbor.

Dave Bacon @dabacon.tachyon.institute · 3d

Why hasn’t Shor won the Turing award? Inquiring minds want to know. (And Alan Turing would love it, he actually wrote some stuff on the foundations of quantum theory…a sort of argument that the Zeno effect was deadly for measurement problem iirc)

Reposted by Dave Bacon

Steve Flammia @sflammia.bsky.social · 3d

Charlie Bennett should win the Nobel prize in Physics this year.

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Reposted by Dave Bacon

🪾santiago, phd 🐈‍⬛ @santiagokique.bsky.social · 4d

Like...this is the biggest corruption scandal the NIH has experienced in its entire history and its not even close. Half of a BILLION dollars to a single project as a result of political spoils. That's the equivalent of several hundred R01s.

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Dave Bacon @dabacon.tachyon.institute · 5d

I see Oedipa Maas crying

Reposted by Dave Bacon

Huck Bennett @huckbennett.bsky.social · 6d

CU computer science is doing a search for a tenure-track position in quantum computing this year: jobs.colorado.edu/jobs/JobDeta.... The scope of the search in particular includes quantum CS theory!

AMA about how awesome Boulder and Colorado are!

Tenure-Track Faculty in Quantum Computing

jobs.colorado.edu

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Dave Bacon @dabacon.tachyon.institute · 6d

Not sure why the extra E appeared here lol.

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Dave Bacon @dabacon.tachyon.institute · 6d

blog.google/technology/r...

E

We’re scaling quantum computing even faster with Atlantic Quantum.

Google Quantum AI was founded in 2012 and our mission today remains the same — build quantum computers that can solve otherwise unsolvable problems. We’re making steady …

blog.google

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Dave Bacon @dabacon.tachyon.institute · 6d

Oh man I don’t think I’m up to that this is complex stuff that I barely grok. Maybe I’ll try to blog about it using the simplest example of how all this works. Dear universe please give me extra time to do fun stuff.

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Dave Bacon @dabacon.tachyon.institute · 6d

Nice result! Link is broken scirate.com/arxiv/2510.0...

Advantage for Discrete Variational Quantum Algorithms in Circuit Recompilation

The relative power of quantum algorithms, using an adaptive access to quantum devices, versus classical post-processing methods that rely only on an initial quantum data set, remains the subject of ac...

scirate.com

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Dave Bacon @dabacon.tachyon.institute · 7d

Wat?

Sort of answers what was original motivation for iswap, at least for me, is iswap better for some code? Did not expect the color code to be the answer!

Craig Gidney @craiggidney.bsky.social · 7d

For their student researcher-ship, Satoshi Yoshida extended our work on dynamic surface code circuits to color codes. They built and simulated iswap color code circuits and wiggling color code circuits. The iswap circuits use fewer entangling layers than CX circuits!

arxiv.org/abs/2510.00370