原文
Most quantum speedup claims depend on an oracle that exists only on paper. This course teaches the craft of building practical quantum circuits from scratch.
Choose the problem, build the oracle
1. A different computer
- most AI problems don’t qualify
- CPU, GPU, QPU: different jobs
- for AI search, test one lever: coherent precision
- three questions to ask first
- famous overpromises, dissected
- knowing when to walk away
2. The Monte Carlo speedup
- the folklore, with fine print
- the trick: precision on averages
- how the square root actually happens
- a query-counting proof: classical can’t keep up
- Go flunks, a sampled bandit flunks
- so we invented a game of close calls
3. Ship it
- “assume the oracle exists,” says every paper
- we stop assuming and build it, gate by gate
- a game board made of qubits
- all the randomness, loaded up front
- picking moves without skewing the odds
- the scratch work starts piling up
4. Reversible by design
- the finished circuit must run backward
- every cell updates at once, or bugs
- the self-flip trap
- snapshot the board, then swap
- one qubit holds the score
- the full bill, in qubits
Make it correct
5. Garbage collection
- there is no delete
- leftover junk stays tied to your answer
- and quietly poisons it
- forgetting means undoing history
- compute, use, uncompute
- clean scratch still doesn’t mean right answer
6. Measure to erase
- the rule every course teaches: never peek
- production circuits peek anyway
- measure the garbage on purpose
- patch the damage with phase fixes
- cheapest eraser there is
- machine-checked rules for when it’s safe
7. Calling conventions
- scratch you can use but never inspect
- clean, borrowed, conditionally clean
- returning it as you found it isn’t enough
- promises checked where blocks meet
- Rust’s borrow checker, but for qubits
- mismatched promises, no deal
8. Proof-carrying circuits
- circuits that ace every test, wrongly
- hidden phases, invisible to truth tables
- checking everything costs 2^n
- escape hatch: one proof per circuit family
- every block ships with a seal, checked in milliseconds
- strangers’ code, safely composed
Price it, test it, judge it
9. Where the quantum lives
- every page is a classical drawing
- the animation is impossible
- each step has a classical model; they refuse to glue
- one story per step, no story overall
- where the quantum actually lives
- and the gap has a price, in coherent memory
10. All or nothing
- buying in bulk should get cheaper
- it doesn’t: qubits of memory, zero or linear, nothing between
- no amortizing, no compressing, no caching
- copy 1,000,000 costs what copy 1 cost
- a theorem, not a hunch
- why the flipbook can’t be fixed
11. Test, don’t trust
- a tabletop test for quantum claims
- no lab, no tomography
- fakers pay the qubit memory bill or fold
- any implementation, no peeking inside
- benchmarks that can’t be gamed
- pretenders fail exponentially fast
12. Audit the next claim
- the reigning faith of the AI era
- what the evidence says
- where quantum could fit in AI
- lesson 1’s questions, aimed at the headlines
- wall-clock math, not gut feel
- how to judge the next miracle
Live Tutorial Agenda
Session 1 (90 minutes): Lessons 1 and 2, identifying a problem worth accelerating.
Session 2 (90 minutes): Lessons 3 and 4, building the rollout oracle.
For practitioners and researchers comfortable with qubits, controlled gates, and circuit diagrams.