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Zero X One

01 · Quantum computing

A qubit is a question, not a bit.

A bit answers. A qubit holds every answer until you ask. We design circuits where superposition, entanglement and interference do the work. Build one here: this simulator runs the real linear algebra in your browser.

Circuit builder3Q · 3 gates
Qubits
Gates

Drag gates onto the wires. Click a gate to select it, Delete removes it. Controlled gates link two wires.

q0q1q2
H
Presets
W-state target (3 qubits)fidelity = 0.0000Match the W state to solve

Copy circuit exports JSON as { "qubits": n, "gates": [ { type, target, control?, theta? } ] } with θ in radians — the exact shape /api/recruit/verify accepts. Load "W state (target)" to see the goal, or build your own and reach fidelity ≥ 0.99.

Amplitudes2^3 = 8
  • |00050.0%
  • |0010.0%
  • |0100.0%
  • |0110.0%
  • |1000.0%
  • |1010.0%
  • |1100.0%
  • |11150.0%

Bar length is the probability of each basis state |b⟩. The dial shows the complex phase φ = atan2(Im, Re).

Bloch spheres3Q
q0|r|=0.00
mixed · entangled
q1|r|=0.00
mixed · entangled
q2|r|=0.00
mixed · entangled

Each sphere is one qubit's reduced state. When |r| < 1 the qubit is entangled with the others — the vector shrinks toward the center.

Measurement probabilities

Sample an outcome from the current distribution.

  • |00050.0%
  • |0010.0%
  • |0100.0%
  • |0110.0%
  • |1000.0%
  • |1010.0%
  • |1100.0%
  • |11150.0%
  • n qubits hold 2ⁿ amplitudes. Three hundred qubits exceed the atoms in the universe.
  • Shor factors in polynomial time. RSA-2048 falls to a few thousand logical qubits.
  • Error correction spends thousands of physical qubits per logical one. That is the real frontier.

02 · Binary & assembly

The abstraction lies. The metal does not.

Every framework ends in instructions. We read binaries the way others read prose, and when the abstraction gets in the way we write the instructions ourselves. This is ZX1, a machine we built for this page: eight registers, 64 KiB, thirty-two opcodes. Step through it.

ProgramsLoad one — real code on the real machine
Source13 ln
Disassembly0 op

Assemble a source to see the disassembly.

Registersready
r0
0x00000000
0
r1
0x00000000
0
r2
0x00000000
0
r3
0x00000000
0
r4
0x00000000
0
r5
0x00000000
0
r6
0x00000000
0
r7
0x00000000
0
PC
0x0000
SP
0x10000
Flags
ZC
Steps
0
Memory
000102030405060708090A0B0C0D0E0FASCII
000000000000000000000000000000000000................
001000000000000000000000000000000000................
002000000000000000000000000000000000................
003000000000000000000000000000000000................
004000000000000000000000000000000000................
005000000000000000000000000000000000................
006000000000000000000000000000000000................
007000000000000000000000000000000000................
008000000000000000000000000000000000................
009000000000000000000000000000000000................
00A000000000000000000000000000000000................
00B000000000000000000000000000000000................
stdin0 b

Applied when you Assemble or Reset.

Output0 b
No output yet — assemble and run.
Instruction set
opmnemonicoperands
0x00nop
0x01hlt
0x10movrd, imm32
0x11movrd, rs
0x12ldbrd, [rs]
0x13stb[rd], rs
0x20addrd, rs
0x21subrd, rs
0x22xorrd, rs
0x23andrd, rs
0x24orrd, rs
0x25shlrd, imm8
0x26shrrd, imm8
0x27rolrd, imm8
0x28rorrd, imm8
0x29mulrd, rs
0x2Aaddrd, imm32
0x2Bxorrd, imm32
0x2Candrd, imm32
0x2Dsubrd, imm32
0x30cmprd, rs
0x31cmprd, imm32
0x40jmpaddr
0x41jzaddr
0x42jnzaddr
0x43jcaddr
0x50outrd
0x51inrd
0x60pushrd
0x61poprd
0x62calladdr
0x63ret
  • A byte is eight decisions. A 32-bit register is four billion states, and one of them is right.
  • Compilers are excellent. They are also predictable. Predictable is what an attacker needs.
  • The ISA above is the same one that runs metal.bin on the recruiting page.

03 · Neural networks & machine learning

Linear algebra that learned to doubt.

A network is weights and a loss. Everything else is the story we tell about it. Draw two classes of points and watch a small network train live, in a worker thread, until its decision boundary blooms around your data.

PlaygroundPaused

Click to add points. Hold Shift for class 1. Drag to paint.

Epoch

0

Accuracy

0%

Loss

0.000

Layers: 2 · 8 · 2

  • Backpropagation is the chain rule, applied with discipline.
  • A model that is 99% accurate can be 100% wrong on the input you craft. That is the adversarial frontier, and it is where we work.
  • The playground above trains in a Web Worker. The page never stutters.

04 · Cryptography

The adversary is part of the specification.

Cryptography is the only engineering that assumes a genius is trying to break the design. Type below. Every keystroke recomputes SHA-256 and about half of its 256 bits flip: the avalanche, live.

SHA-256 · Avalanchelive
256 bits
SHA-256
78cd7eecfa8e560fdae6fd92f45ac1a1d7baa2e9e1238676e394612de4a3eb0b
bits flipped
0/ 256
0expected ≈ 128256
message bytes
10
blocks
1 × 512 bit
64 roundsworking variables a–h after each round of the last block
Post-quantum: latticesML-KEM · CVP

Shor breaks RSA and elliptic curves. Lattice problems, so far, resist quantum computers. ML-KEM hides a secret in noise that only the right basis removes.

|b₁| 1.01 · |b₂| 1.01 · ∠ 90°
b₁b₂

Drag the target, or tap anywhere in the square. Arrow keys move it too.

Babai rounding
q = 1.68·b₁ + 0.70·b₂
⌊q⌉ = (2, 1) →
Decoded: rounding landed on the true closest lattice point.
  1. 01Same points, two descriptions. The good basis is short and nearly orthogonal; the bad one is long and nearly parallel.
  2. 02Decoding means writing the target in your basis and rounding the coordinates. Only the good basis lands on the true closest point.
  3. 03The good basis is the private key. Noise hides the message near a lattice point; without the key, near is not enough.
  • A hash is a one-way street with 2²⁵⁶ lanes.
  • Nonce means number used once. Most real breaks happen when it was used twice.
  • We implement, audit and break protocols. Sometimes in that order.

05 · Cyber security

What remains after every assumption is attacked.

Security is not a product. It is the residue of every attack you already survived. This terminal is real: a shell we wrote, with a file system we chose. Look around. Some of what you find is meant to be found.

zx1 shell

A real shell running in your browser. `submit` and `vault` reach the live backend; everything else stays on this page. Type `help` to begin.

  • The perimeter is gone. Identity is the perimeter.
  • We hire people who read the response headers.
  • Offense informs defense. We do both, on paper first.

Measurement · Work with us

The last gate is a measurement.

Solve a challenge, skip the interview queue.

MOpen the tracks
Zero X One — We flip the state