It’s blocked by design choices.”

That was one of thestrongest realizations from Part 2 of my deepdive with Ish Dhand, co-founder of QCDesign, on Beyond the Qubit.

Most people talkabout fault-tolerant quantum computing as if it’s a single problem.

In reality, it’s a design-space explosion.

That reframed how Ithink about progress in quantum.

What stood out to mein this part of the conversation:

• Hardware teamsdon’t struggle with one error, they struggle with many interacting imperfections at the same time

• Open-sourcesimulators can scale to thousands of qubits, but usually only by assuming very simplified error models

• Real hardware hasto deal with leakage, coherent errors, pulse timing, idling, cross-talk,  all at once

• Many of theseeffects only become visible at the scale of thousandsof physical qubits per logical qubit

This is where QCDesign plays a unique role.

Rather than bettingon a single error-correction code or architecture, they help hardware teams simulate realistic fault-tolerant systems beforebuilding them,  across platforms,codes, decoders, and noise models.

What really changedmy perspective:

Error correctionisn’t just about finding a better code.

It’s aboutunderstanding where engineering effort actuallypays off.

If leakage hurtsyour logical qubits more than erasures,

why spend yearsoptimizing the wrong thing?

If longer pulsesimprove gate fidelity but quietly destroy system performance through idlingerrors,

where’s the realoptimum?

These aren’tacademic questions.

They determine cost, timelines, and whether scaling is even feasible.

One line from Ishreally stuck with me:

Today, the cost of a truly useful fault-tolerantquantum computer is effectively infinite.

The real progress is making that number finite, andthen bringing it down.

That single sentencereframes the entire industry.

In this episode, wego deep into:

• why decoding speedmatters as much as code efficiency

• why “software willfix it later” is usually the wrong mindset

• why logicalfidelity matters more than raw qubit counts

• and why faulttolerance is becoming a full-stack engineeringproblem

If you care about how quantum computers will actually be built,  not just announced,  this conversation is worth your time.

🎙️Beyond the Qubit — Part 2 with Ish Dhand

🔗https://youtu.be/ugo3g1Mws2M

#FaultTolerantQuantum#QuantumArchitecture

#ErrorCorrection#QuantumSoftware #BeyondTheQubit

⁨@IshDhand⁩ ⁨@QC_Design⁩

📌 Disclaimer: This post is shared on a personal basis and I do notrepresent any company