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Superconducting qubits from scratch

A free course I’m writing on the hardware I work with: twelve chapters from “what is a qubit?” to a first look at error correction, and twelve labs you can run on a laptop.

Read it on GitHub ↗ Start with chapter 01 ↗ Learning path and exercises ↗

I started compiling it in June 2026, after being a teaching assistant for PH3410 Quantum Hardware at NTU, and writing it doubles as preparation for my qualifying exam. It is the introduction I wish I’d had when I started: one that explains why the hardware looks the way it does, not just what it is. It builds a transmon up one circuit element at a time (the LC oscillator, the Josephson junction, the qubit, the resonator beside it), then follows it through control, readout, the cryogenic chain, benchmarking and a first look at error correction.

Every explanation is in my own words and teaches standard, published physics. The chapters are meant to make the standard reviews easier to read, not to replace them. Each one ends with a checkpoint and pointers to the literature.

Reading is good; doing sticks. Each lab simulates the physics of a chapter with NumPy, SciPy and QuTiP, and all twelve run with numerical checks. The review notes record every correction so far.

Chapters

  1. 01 Why superconducting qubits
  2. 02 The quantum LC oscillator
  3. 03 The Josephson junction and anharmonicity
  4. 04 The transmon qubit
  5. 05 Circuit QED: qubits and resonators
  6. 06 Dispersive readout
  7. 07 Single-qubit gates and control
  8. 08 Two-qubit gates
  9. 09 Coherence, noise and decoherence
  10. 10 The cryogenic and microwave chain
  11. 11 Calibration and benchmarking
  12. 12 A first look at quantum error correction

Labs

Each paired with the chapter it brings to life.

  • Lab 02: Rabi oscillations at three drive strengths.

  • Lab 04: the cavity field separating by qubit state.

  • Lab 07: a randomized-benchmarking decay and its fit.

  • Lab 08: the repetition code below and above break-even.

  1. 01

    Bloch sphere Qubit states and a driven trajectory.

    Ch. 07
  2. 02

    Rabi oscillations A qubit flipping under a drive.

    Ch. 07
  3. 03

    T1 and T2 Relaxation and Ramsey dephasing.

    Ch. 09
  4. 04

    Dispersive readout The qubit states separating in IQ.

    Ch. 06
  5. 05

    Leakage and DRAG A three-level transmon under fast pulses.

    Ch. 07
  6. 06

    CZ gate The |11⟩–|20⟩ avoided crossing and the conditional phase.

    Ch. 08
  7. 07

    Randomized benchmarking Error per Clifford from an RB decay.

    Ch. 11
  8. 08

    Repetition code Majority-vote error correction and break-even.

    Ch. 12
  9. 09

    Transmon spectrum The exact spectrum, charge dispersion and cutoff convergence.

    Ch. 03–04
  10. 10

    Jaynes–Cummings Avoided crossing, vacuum-Rabi exchange and perturbative limits.

    Ch. 05
  11. 11

    Noise and echo Ramsey and echo filters against a noise spectrum.

    Ch. 09
  12. 12

    Microwave chain Thermal attenuators and the amplifier noise budget.

    Ch. 10

Read alongside

The full annotated reading list ↗