Thursday, September 10, 2026

Scratches in the Hardwood: Traces of Seventy-Five Years

342 Holyoke Road by Marion Killacky
My parents built the house in the early 1950s. It was small, single story, about 50 feet by 25 feet with an attached one car garage, one bathroom, three bedroom shared by six of us until the attic was renovated into a bedroom for my two brothers and me. I grew up in it. My Dad passed away on December 26. My Mom couldn't live there alone after that. She's in a long-term care facility now, a beautiful one, with her own little apartment. Last month, we sold the house privately. 

Movers carried the dresser out in February, in about three feet of snow, then the bed frame. The dresser has a large mirror mounted on top, the kind that catches the whole room behind whoever's standing in front of it. The wood is solid all the way through, no veneer over particleboard—the kind of furniture nobody makes anymore because nobody expects to keep anything that long. My parents bought that combo when they built the house. It sat in that bedroom, against that wall, under that light, for roughly 75 years, and it left through a couple feet of snow on a truck ramp. 

Seventy-five years without direct sun—I keep doing that math in my head, more than I do the math on anything else from that week. As a kid, I assumed it was going to stay that way forever. The changes came gradually, and some things didn't change for so long that it was easy to mistake slowness for permanence. I noticed the small changes and chose not to look too closely. I knew what was coming; I spent years managing not to think about it, right up until it was unavoidable. 

Once the furniture was gone, I saw small scratches in the hardwood, faint ones. I have no idea if they happened decades ago or that week, while the movers were maneuvering the dresser out the door. Seventy-five years compressed into a set of marks I can't date, no different from the years themselves, most of which I can't place exactly either. The wall behind the headboard was a shade lighter than the rest of the room, a pale pattern where the sun had never reached. My Dad slept in that bed until December. My Mom slept in that bed for over 70 years. Six of us in a house that size, sharing one bathroom, and somehow the walls felt like they held more privacy than that math suggests they could. That mirror held every version of my parents getting ready for work, for church, for whatever came next, for over 70 years, and it held me too, some mornings, standing in their room asking for something. 

That mirror caught the rhythm of a house that ran hot in summer and cold in winter no matter what anyone did about it. For most of those 70 years, there was no air conditioning. In summer, the windows stayed open and the whole house fan ran all night, pulling the cool night air in from outside and pushing it through every room. Upstairs in the attic, the small window unit for my brothers and me barely made a dent—the heat just sat up there while the unit hummed away doing next to nothing. Winters ran on a wood stove, which meant somebody was always splitting wood, always feeding it, always checking it before bed, and the rooms farthest from it never got quite warm enough. The whole house smelled like woodsmoke all winter long, that dry, faintly sweet smell that got into the curtains and the couch cushions and never fully left, even in July. A couple of mini-splits went in about six years ago, no ductwork, just those two units doing what they could for a house that had gone 70 years without any of it. My parents got a handful of summers with them before the house sold. 

In the kitchen, there was a silverware drawer. Every morning I reached in without looking and pulled out a spoon for cereal. I never thought about that drawer once in 40 years except to reach for it. Now I think about it more than almost anything else in that kitchen. 

The cellar door had a specific squeak, the exact same pitch on the way down as on the way back up. Between that hinge and the distinct rhythm of footsteps on the cellar stairs, I could tell from any room in the house not just whether someone was going down for something or coming back up with it, but exactly who it was. Nobody ever oiled that hinge or tried to quiet those steps. At some point, it stopped being a maintenance problem and became a way of knowing where everyone was.

The last time I went to the house, the bedroom was empty. No dresser, no mirror, no bed, nothing left but those small scratches in the floor, the pale pattern on the wall, and breeze coming through a window that used to be someone's whole summer. 

The combo is in her bedroom at the facility now, mirror and all. Same dresser, same bed, and they still don't look right in there. The proportions are off somehow, or the light is different, or it's just me looking for reasons this doesn't fit anymore. She falls asleep looking at the same wood grain she's looked at for most of her life, in the same bed, in an apartment that is by every account nicer than the room she left, kept at a temperature the old house never quite managed. None of that seems to matter to the two pieces of furniture sitting in it. 

We sold the house quietly. A handshake, a closing date, no listing, no strangers walking through. Nobody outside the family will ever know which floorboard creaked, or why, or the pitch of the cellar door hinge, or how six people made one bathroom work for as long as we did. The new owners will refinish the floor and sand out scratches they'll never know the story behind. In a year, there will be no evidence we were ever there. 

I'll still be thinking about that dresser and bed sitting in an apartment that doesn't suit them, and standing in an empty room in last month looking at a wall the sun never touched—in a house that held six of us, that I grew up in and thought would always be there, and won't walk into again.

Tuesday, September 8, 2026

Quantum from the Ground Up: Second Edition, September 2026

A free PDF pulling together posts from this blog into a single volume. Written for someone entering the quantum workforce, or seriously considering it, who has a technical background but has not taken a graduate course in quantum mechanics.

This edition folds in 22 posts published between June 3 and August 26 into the same 19 chapters as the first edition: quantum networking over existing fiber, the physics-versus-engineering distinction, six qubit fabrication platforms, protein simulation and AI-assisted hardware calibration, post-quantum cryptography, the hardware landscape as it stands in late summer 2026, and the quantum workforce.

Download PDF: Second Edition, September 2026

Edition

Second edition, September 2026

Pages

73

Chapters

19

Source posts

39 posts, October 2025 to August 2026

Updates

Quarterly

License

CC BY-NC-ND 4.0: free to share with attribution, no commercial use, no modifications

 

What's new in this edition

      Quantum memory repeaters tested on a live network by IonQ and EPB in Chattanooga

      A free-space quantum network link built by Brookhaven and Stony Brook

      Two linked quantum cryostats from IBM, a step toward fault-tolerant systems

      A sputtering-gas fix for a superconducting qubit manufacturing defect, from Cornell

      A universal gate set on 28 qubits using code-switching magic states, from Quantinuum

      Two June 22 executive orders: new post-quantum cryptography migration deadlines and the QC-ADDS program

      IonQ's acquisition of its own chip foundry

      Quantum key distribution deployed on production Cisco routers

      IBM's free Quantum Learning certification path

Updates

This page will always link to the current edition. Updates are planned quarterly as new posts on quantum hardware, security, and workforce development are published on this blog. The next edition covers Q3 2026, due around December 1.

Support this work

The book is free and will stay free. If you find it useful and want to support future editions, contributions are welcome at ko-fi.com/gordostuff.

Tuesday, September 1, 2026

A Plain-Language Edition of Quantum from the Ground Up


Einstein called it spooky action at a distance. He meant quantum entanglement, and
he thought it couldn't be real. He was wrong!

I published a plain-language edition of Quantum from the Ground Up today, built for that reader.

The original book is written for people with a technical background who haven't taken a graduate course in quantum mechanics. It works well for that reader. It does not work for someone who has never had a reason to think about qubits, cryogenics, or post-quantum cryptography and just wants to know what the technology actually does.

The two audiences want different things. Someone building a career in the field wants precision: exact fidelity numbers, fabrication steps, the difference between a physical qubit and a logical one. Someone reading a headline about a new quantum computing milestone wants to know what it means and whether it matters to them. The plain-language edition is built for the second person.

It covers the same 19 chapters as the technical edition, at a fifth of the length: 13 pages instead of 73. It leaves out the math, the fabrication chemistry, and the dense statistics tables. It keeps the facts that matter: what quantum computers actually do right now, why companies are spending billions of dollars building them, why your bank account and your medical records are already part of this story, and where the actual jobs are for people without a physics degree.

Both editions are free. Both get updated quarterly as new research and hardware announcements come out. The next technical edition publishes tomorrow.

You can find current and older versions of each in this folder.

If you have been putting off understanding quantum computing because every explanation you found assumed a physics background you don't have, this edition removes that excuse.

Wednesday, August 26, 2026

Brookhaven and Stony Brook Just Linked a Quantum Network Through Open Air

In my last post, I laid out the fiber problem: quantum networks can't use classical repeaters because the no-cloning theorem forbids copying an unknown quantum state, so every photon has to survive, unassisted, from source to destination. Fiber compounds that: it loses about 0.2 dB/km, and its only efficient band (1550 nm) doesn't match the wavelengths most atomic memories emit, forcing lossy conversion steps at each end.

Commercial telecom has been married to one wavelength band for as long as I've been in the field, going back to writing the telecommunications curriculum for Verizon's NextStep program in 1995 and later directing NSF-funded Centers of Excellence in telecommunications and optics and photonics. My dad worked the generation before that, retiring in 1984 back when the network still ran on copper and fiber hadn't arrived yet. Brookhaven National Laboratory and Stony Brook University just did something a little different. 

Photons travel 13 miles through open air from Stony Brook's Quantum Watchtower to Brookhaven's Quantum Lighthouse, using adaptive optics instead of fiber. Link connects to existing 161 mile fiber network, with a 30 mile extension to Yale planned next.


On August 21, researchers sent single photons and entangled photon pairs 13 miles through open air, from Stony Brook's Quantum Watchtower to Brookhaven's Quantum Lighthouse in Upton, New York, no fiber involved for that leg of the trip. The daytime event was a formal demonstration for DOE and state officials. The actual first detection happened two days earlier, in the dark: at 12:26 a.m. on August 19, the Lighthouse recorded entangled photon pairs arriving from the Watchtower, confirmed through phase folded photon analysis comparing on-phase detection counts against background noise rates.

Both facilities exist to solve one problem: Brookhaven and Stony Brook need an unbroken line of sight to each other, which is why the Lighthouse sits on the only Brookhaven building with that sightline, a seven story rooftop installation, while the Watchtower sits atop Stony Brook's Health Sciences Center. Fog blocks the link outright. Bright daylight is a subtler problem. It raises atmospheric turbulence and buries the faint photon signal in background light, a limitation the Brookhaven team has compared to trying to spot a flashlight beam from a rooftop in broad daylight.

The optics came out of Brookhaven's Instrumentation Department, built on adaptive optics designs borrowed from the Vera C. Rubin Observatory. Photons leave the Watchtower through a fiber core five microns wide, about a tenth the width of a human hair. A telescope expands that pinprick of light into a 25 inch, 0.6 meter beam to match the primary mirror, while deformable mirrors correct for atmospheric turbulence in real time at kilohertz frequencies. At the Lighthouse, the process runs in reverse: the beam narrows back down and threads into a matching five micron fiber core for detection.

Commercial fiber networks are locked into wavelengths near 1550 nanometers because that band travels through glass with the least loss over distance. A free-space link carries no such requirement. Researchers can transmit infrared wavelengths native to the atomic systems and quantum processors themselves, opening a direct channel to entangle remote atomic memories without a wavelength conversion step.

The new link folds into an existing fiber network spanning 161 miles and eight nodes across Long Island and the New York City area, the longest metropolitan quantum network in the country. DOE Under Secretary for Science Dario Gil cut the ribbon on the receiving aperture at the August 21 event, framing the connection as a step toward linking individual quantum computers into something larger.

A third facility, functionally identical to the Lighthouse and Watchtower, is already built at Yale University in New Haven, Connecticut, with a 30 mile free-space link across Long Island Sound planned to connect Stony Brook and Yale directly. Past that, the team plans to repurpose the same rooftop telescope infrastructure to track low-earth-orbit satellites, laying groundwork for satellite-based quantum key distribution and a longer-term global quantum network. Funding comes from DOE's Office of Science, the National Science Foundation, and $300 million in New York Empire State Development money tied to Stony Brook's Quantum Innovation initiative.

This ties directly to Chapter 1 of Quantum from the Ground Up, which opens on the fiber problem: how to move quantum information over distance without destroying the fragile state that makes it quantum in the first place. Fiber solved part of that by forcing everything into a wavelength band it can carry efficiently. This link solves a different part by removing the requirement to force anything at all. This post will roll into the next quarterly edition of the book, out September 1. You can read the current edition here.

Tuesday, August 25, 2026

The Fiber Problem: Why Distance Breaks Quantum Networks

Every quantum network built so far runs into the same wall: how do you move a quantum state across distance without destroying the property that makes it quantum in the first place. That's the fiber problem. 

Diagram shows the photon's path: native wavelength out, up-converted into the fiber band, lossy fiber crossing, down-converted back, with the no-cloning constraint called out separately underneath since it's the reason none of that loss can be patched mid-flight.

Classical data degrades over distance too, but repeaters fix it. A signal gets weak, a repeater reads it, copies it, and sends a fresh copy further down the line. Quantum states can't do that. The no-cloning theorem, a hard result in quantum mechanics, says you cannot create an identical copy of an unknown quantum state. There's no way to read a photon's quantum state, copy it, and pass along a clean version. Doing so destroys the very state you were trying to preserve. Whatever leaves the source has to survive, unassisted, all the way to the destination.

Fiber makes survival harder the farther a photon travels. Standard telecom fiber loses roughly 0.2 decibels of signal per kilometer at the wavelength commercial networks use, a small number that compounds fast over distance. A classical signal can be boosted past that loss. A single photon carrying a quantum state can't be boosted, only lost. Every kilometer of fiber is another chance for that photon to get absorbed or scattered before it arrives.

There's a second problem. Commercial fiber carries light efficiently only in narrow bands, mainly around 1550 nanometers, because that's where glass loses the least light over distance. The atomic systems used to store and process quantum information, trapped ions, neutral atoms, certain solid-state qubits, usually don't emit or absorb light at 1550 nanometers. A photon leaving an atomic memory typically needs a wavelength conversion step just to enter the fiber network, and another one on the far end to be absorbed by the receiving memory. Each conversion is one more place to lose or degrade the state.

You can't clone a quantum state to fix loss along the way, and fiber adds distance-dependent loss plus a wavelength mismatch on top of photons that are already fragile.

In my next post I'll describe how Brookhaven National Labs and Stony Brook University have worked around the fiber "problem."

This is the problem Chapter 1 of Quantum from the Ground Up opens on. You can read the current edition of the book here.

Saturday, August 22, 2026

IBM Links Two Quantum Cryostats Toward Fault Tolerance

Chapter 3 of Quantum from the Ground Up makes one argument: the physics works, and the engineering catches up slowly, one specialized system at a time. The chapter leans on the dilution refrigerator as its example, a device that cools a quantum chip down to a few thousandths of a degree above absolute zero. A separate post here, The Chandelier, walked through why that cooling matters. Below a certain temperature, the metal on a quantum chip becomes a superconductor, meaning electricity flows through it with no resistance. That property is what lets a qubit hold information as a quantum state instead of losing it to heat and vibration almost instantly. IBM's announcement on August 19 is the next chapter in that same argument. Instead of one isolated refrigerator, two of them, joined.

What IBM Actually Did

On August 19, IBM announced it had physically connected two cryogenic modules—each its own standalone refrigerator—into a single integrated cold environment. Crucially, this initial milestone served as a structural, thermal, vacuum, and EMI-shielding validation of the empty joined cells, rather than a live multi-QPU execution. IBM plans to install its next-generation Nighthawk quantum processors into these coupled modules later in 2026 to execute live inter-module quantum gate operations.

A cryogenic module in this context is a sealed, vacuum-insulated box that removes heat in stages as you go deeper inside it, ending at a chamber cold enough to keep a chip in its quantum state. IBM reached a base temperature more than 180 times colder than deep space, which works out to below 15 millikelvin, or 15 thousandths of a degree above absolute zero. Getting there took five days at 4 Kelvin, the temperature of liquid helium, before a final drop to that base temperature shortly after. Standalone, each module stands about 8 feet tall and 8 feet wide, closer in size to an industrial appliance or plant assembly than a benchtop instrument.

The two modules IBM cooled down were empty, no chips installed. IBM plans to install Nighthawk quantum processors into the modules later this year, then test whether chips connected across the module boundary can run operations reliably enough to be useful. IBM itself has said that reliability across the L-coupler connection is still active engineering work, not a finished result. This week's announcement is the refrigerator working, not chips talking to each other across it.

Each module is a self contained casing that steps a chip down through three stages: room temperature electronics at the top, a 4 kelvin stage in the middle, then the chip itself below 15 millikelvin at the bottom. The line between the two chip stages is the L-coupler, the connection that lets Module A and Module B behave as one cooled environment instead of two separate refrigerators.

Why Wiring Is the Bottleneck

A quantum chip does not run itself. Every qubit on it needs a wire carrying a control signal in and a readout signal out, and those wires have to pass through every cooling stage without carrying stray heat down with them. That is the actual scaling problem, not the chip. IBM's new module design gives each vacuum enclosure up to 12 times more wiring space than today's most common IBM systems. More wiring space is what will let more chips be wired up and connected, both inside one module and across two joined modules, once IBM installs chips and runs them through the connector it calls the L-coupler. IBM describes the goal as processors reliably working on the same problem together, not just sitting side by side, which is a different requirement than just packing more qubits onto one chip.

Physical Qubits Versus Logical Qubits

This is also a good place to separate two terms I’ve used a little loosely. A physical qubit is one actual quantum circuit on a chip. A logical qubit is a group of many physical qubits, wired together and error corrected as a unit, that behaves like one reliable qubit for the purpose of running a calculation. Fault tolerant means a system can keep correcting its own errors fast enough to finish a long calculation before the errors pile up and ruin the answer.

IBM's roadmap calls for at least 1,000 programmable qubits by 2027 using L-couplers, feeding into IBM Quantum Starling, the system the company expects to deliver in 2029 as the first fault-tolerant quantum computer, running 100 million quantum gates across 200 logical qubits. Two hundred logical qubits sounds small next to 1,000 physical qubits, and that gap is the whole point. Error correction is expensive. However, while standard 2D surface codes typically require an overhead of 1,000+ physical qubits per logical qubit, IBM relies on quantum Low-Density Parity Check (qLDPC) codes. This reduces the overhead to roughly 50 physical qubits per logical qubit (~10,000 physical qubits for 200 logical qubits), making fault tolerance achievable on a substantially smaller hardware scale.

None of that works if the chips cannot be wired together and kept at the same ultra low temperature at the same time. The cryogenic housing announced this week is the part of the plan nobody puts on the cover of a press release, even though Live Science frames it as one of the field's biggest infrastructure bottlenecks. Without a way to link cryostats, a 200 logical qubit machine stays a slide in a roadmap deck.

What This Changes in the Book

Chapter 5 covers IBM's Condor chip: 1,121 physical qubits inside one standard cylindrical cryostat. That chapter treats the cryostat as fixed, one chip, one refrigerator. This announcement breaks that assumption. The box shaped modular design, not the cylinder, is now IBM's stated path past a single chip's qubit ceiling. Chapter 3's engineering argument gets a dated, measured example: five days to 4 Kelvin, then to base temperature, in a system built to add modules rather than grow one tank.

This post rolls into the next edition of the book, due September 1. The current edition is available at gordostuff.com/p/quantum-from-ground-up-hardware.html

Friday, August 21, 2026

A Gas Swap Fixes a Manufacturing Problem in Superconducting Qubits

Chapter 5 of Quantum From The Ground Up covers superconducting qubits: Josephson junctions, the Dolan bridge fabrication technique, and IBM's 1,121-qubit Condor chip running at 99.0 to 99.5 percent two-qubit fidelity. That chapter never asks how the metal underneath those junctions gets onto the chip in the first place. A new paper out of Cornell fixes a problem in that step, and it matters more than another fidelity number would.

A superconducting qubit is a tiny circuit built from metal that, once cooled near absolute zero, behaves like a single quantum object instead of an ordinary wire. The part that makes it a qubit rather than just a very cold wire is the Josephson junction: two superconducting metal layers separated by an insulating gap so thin that electrons tunnel straight through it. Tantalum has become a favorite metal for those layers because tantalum-based qubits hold their quantum state longer than most alternatives. But tantalum only works if its atoms land on the chip in one specific crystal arrangement, called the alpha phase. Getting that arrangement has required heating the substrate past 400°C during deposition. Most semiconductor factories run their fabrication lines with a hard ceiling near that same 400°C, so there was almost no margin between what tantalum needed and what a foundry could tolerate, as Cornell's team describes the manufacturing squeeze.

Cornell's group, led by Assistant Professor Valla Fatemi, builds these tantalum layers by sputtering: a process gas is ionized and fired at a block of tantalum, knocking atoms loose so they land on a silicon wafer and build up a thin film. The standard process gas is argon. Fatemi's team swapped in krypton, a heavier noble gas, and found that the heavier atoms push the tantalum into the alpha phase at temperatures as low as 200°C, half of what argon requires, according to the published results in Nature Materials on August 18, 2026. The resulting films also carried noticeably higher electronic conductivity than tantalum deposited the old way.

Krypton ions hit the tantalum target at the top, knock atoms loose, and those atoms travel down to build the alpha-tantalum film on the heated silicon substrate. Note 200°C, half the temperature argon sputtering needs.

The work builds on an earlier study from Fatemi's lab that sputtered niobium films with argon and mapped out how surface chemistry during deposition shapes final qubit performance. Swapping the metal to tantalum and the gas to krypton let the team apply what that niobium work taught them about controlling film quality. Qubits built from the new tantalum films performed, in Fatemi's own assessment, at the leading edge for the field.

None of this sets a new fidelity record. It removes a bottleneck that sits underneath every fidelity number in the chapter: a qubit design cannot scale to production if the fabrication step it needs falls outside what an ordinary chip factory can actually run.

This result covers one sample film deposited at one lab. Scaling it to production is a separate engineering problem, not a physics problem, and it is the harder one. A foundry running krypton sputtering needs the crystal phase, conductivity, and thickness to stay uniform across every chip on a wafer and across every wafer in a batch, not just in the sample that made it into the paper. It needs the process to hold up next to every other step already running on that line, since real chips stack tantalum with silicon oxide, aluminum wiring, and the Josephson junction itself, each with its own temperature limits and contamination risks. And it needs the equipment: krypton sputtering targets, gas handling, and chamber tuning are not yet standard equipment at most semiconductor fabs the way argon sputtering is. Lowering the temperature ceiling was the physics half of the problem. Building a repeatable, monitored, high-yield process around that lower ceiling, at the volume a real qubit chip production line runs, is the engineering half, yet to be figured out.

What This Changes in the Book

Chapter 5 lists IBM's Condor at 1,121 qubits and 99.0 to 99.5 percent two-qubit fidelity, built with Dolan-bridge Josephson junctions. This post adds a manufacturing footnote to the process. A lower-temperature tantalum deposition route now exists that fits inside standard semiconductor foundry limits. The path to building chips at that quality, at scale, gets wider.

This post will fold into the next edition of Quantum from the Ground Up, due September 1. The current edition is available on the book page.