Notes
The notes are the building blocks of this notebook: each one takes a single concept, claim, or investor question and works through it from the science up. They are organized below by topic, the same four clusters as the research map, with the newest notes pinned on top. If you are new, begin with a “start here” note and follow its links.
Reading a molecule's energy off a quantum computer by hiding it in a phase and reading it back out. The textbook inverse-QFT method and why it is too deep for today's hardware, the leaner single-qubit version that trades qubits for thousands of measurements, and the first error-corrected demonstration: molecular hydrogen's ground-state energy on a Quantinuum trapped-ion machine.
Read the note →Microsoft's bet: a qubit that stores one bit of information across two Majorana zero modes at opposite ends of a wire, so no local noise can read the whole of it. How topological protection works, why quasiparticle poisoning is the enemy, why the modes' very existence is still contested, and why it is the qubit hardest to build but, in theory, easiest to scale.
Read the note →The simplest noise there is: a quantity that jumps at random between two levels, the fingerprint of one microscopic flaw flipping back and forth. How a crowd of these fluctuators blurs into the 1/f noise that limits coherence, how a single defect made a Google qubit's lifetime drift, and why it keeps a benchmark from ever sitting still.
Read the note →Both answers at once, and hard to hold: the basic unit of quantum information.
The particle that interferes with itself, and why that is a resource.
The price of looking: reading a qubit ends its quantum behavior.
The bond Einstein bet against, with correlations nothing classical can match.
A solved idea, an unsolved machine: how qubits are steered.
A recipe written in gates, from input to answer.
Hiding a molecule’s energy in a phase, then reading it back as bits.
All together, or not at all: entanglement’s gold standard.
How to catch a computer being quantum, with a score no classical trick can beat.
The qubit families compared, and why this is a winner-takes-most bet on physics.
The fragile raw material every quantum machine is built from.
The clock every qubit races before its information fades.
The cost of distance: which qubits can talk to which.
Why a good qubit will not stay good: noise that jumps between two levels.
A bit hidden where noise cannot reach, and still contested.
A test built to not fool itself, gatekeeping Microsoft’s qubit claim.
Fixing what you cannot look at.
Safety in numbers: many fragile qubits acting as one dependable one.
Computing right through the noise.
Why a useful machine needs thousands of physical qubits per logical one.
The probability an operation did what it claimed.
How an investor should read a headline full of nines.
The scoreboard that isn’t.
