Hi everyone,
How many physicists does it take to get a superconducting qubit chip up and running?
The answer is often just one.
But here is the catch: that single person has to fulfill many different roles to get there. In the industry, we usually specialize these roles into entire departments to help us scale. Yet, if you walk into a university lab today, you will still find many young scientists doing it all.
So today, I want to look at exactly what it takes to get a chip up and running, and the specific "personas" you have to adopt to make it happen.
Where do you even start?
First, you become The Quantum Device Designer. You live in tools like Quantum Metal (formerly Qiskit Metal), KLayout, AutoCAD and Ansys HFSS. You aren't just drawing circuits; you are engineering Hamiltonians and simulating electromagnetic environments to ensure your qubit parameters will land exactly where you want them.
Next, you put on the cleanroom suit to become The Nanofabrication Engineer. You need to understand semiconductor fabrication techniques intimately. You are the one turning that design into an actual on-chip device, cycling through electron-beam lithography, metal deposition, dry/wet etching, and SEM imaging. It is a rigorous process, all in the hope that when you finally look under the microscope, your 'hero device' is actually there.
Stop. Breathe. Test.
Before you even think about the dilution refrigerator, you need to save yourself some pain. You don't bond a blind chip. You perform Room Temperature probing on the test structures first (which you hopefully did not forget in your design!). You check the resistance of the Josephson Junctions on a probe station at 300 K. If the resistance isn't within the target range, the frequency will be wrong at 10 mK. You catch it now, while the chip is still warm, rather than wasting a week cooling down a dead device.
Next in your journey: you become The Packaging Expert. You take the fabricated chip, bond it to a PCB, and mount it into a package. Crucially, this isn't just a box. It is a light-tight, magnetically shielded environment. Without it, the qubit will see the world's noise and die.
At this point, you get excited. Very excited. You have a fridge secured, and you are finally ready to load the device.
But wait. The fridge isn't ready.
While you might have a team of engineers to install the beast initially, the day-to-day maintenance falls on you. You become The Integration Specialist. You have the massive task of getting the fridge experiment-ready. This means installing additional lines, filters, attenuators, and amplifiers, and torquing many SMA connectors.
And then: leakage testing. Because the fridge exterior gets assembled and disassembled in this process, and nothing ruins a week like a bad seal.
After a lot of hard work and sweat, you finally press "full cool down." You go to bed, praying to the gods that the fridge actually reaches base temperature (~10 mK) by the next morning.
Once cold, it’s time for The Measurement Engineer to ramp up. You are someone who understands quantum control, has wired up the electronics, and set up the software stack. You are all too familiar with debugging the setup—likely having already measured a test chip in a previous cooldown to verify the environment and calibrate components like parametric amplifiers.
Finally, the fun begins on the actual quantum device. You start the characterization and qubit calibration routines, moving steadily from simple spectroscopy to the calibration of single and two-qubit gates.
The Reality Check
This snapshot sounds organized, but here is the reality: At any moment, something can go wrong.
A specific tool in the cleanroom is out of order? You wait.
Accidentally left the chip too long in the etchant? Start over.
You press cool down, but the fridge doesn't hit base temperature? Warm up. Try again. Debug, disassemble,... whoosh, there go a few more days.
And even when it gets cold, you face the yield problem. You might measure 20 qubits, but find only 15 are alive. And of those 15, 10 might have very low coherence, making calibration a nightmare.
You end up giving feedback to the quantum device designer and the nanofabrication engineer (who are also you)—and the cycle starts all over again. 🙂
Until next time,
