# Quantum Computing — Map of Content A first-principles map of the key concepts behind error-corrected, atom-based quantum computing. Each idea is explained generically and links to the concepts it depends on. Start anywhere and follow the wikilinks. > [!abstract] How to read this map > The field stacks into three layers: you need **good qubits** (a platform), built into **error-corrected logical qubits** (codes), wired by a **control architecture** that decides which codes are practical — and the whole thing runs as an **accelerator inside classical computing**. ## 1 · Foundations The bedrock concepts every other note rests on. - [[Qubit]] — the unit of quantum information; superposition and measurement - [[Quantum Entanglement|Entanglement]] — the non-classical correlation that powers quantum computing - [[Coherence Time]] — how long a qubit's state survives before noise erases it - [[Gate Fidelity]] — how accurately an operation is performed; why errors compound ## 2 · The Neutral-Atom Platform How identical atoms, held and steered by light, become qubits. - [[Neutral Atom Qubits]] — atoms as identical, movable qubits - [[Laser Cooling]] — slowing atoms with light so they can be trapped - [[Optical Tweezers]] — holding single atoms in focused-laser traps - [[Rydberg Interactions]] — switchable strong forces that make two-qubit gates - [[Nuclear-Spin Qubits]] — encoding in the nucleus for very long coherence ## 3 · Quantum Error Correction Turning many noisy physical qubits into a few reliable logical ones. - [[Quantum Error Correction]] — the central idea: protect without looking - [[Physical vs Logical Qubits]] — encoding, overhead, and why counts soar - [[Stabilizer Codes]] — the dominant framework of parity checks - [[Syndrome Extraction]] — the repeating cycle that locates errors safely - [[Code Distance and Threshold Theorem]] — when adding qubits actually helps - [[Mid-Circuit Measurement]] — reading some qubits without disturbing the rest ### Specific codes - [[Toric Code]] — the original topological code (information in global shape) - [[Surface Code]] — the practical 2D-local workhorse - [[qLDPC Codes]] — sparse checks with long-range links → low overhead - [[Permutation-Invariant Codes]] — a non-stabilizer code built on symmetry ## 4 · Control & Architecture How qubits are connected and commanded — which decides which codes are cheap. - [[Qubit Connectivity and Reconfigurability]] — fixed vs all-to-all vs movable - [[Global Control Fields]] — one signal addressing every qubit at once - [[Bosonic Bus]] — a single shared channel all qubits talk through - [[Hybrid Quantum-Classical Computing]] — the QPU as an accelerator, not a rival ## Concept map ```mermaid graph TD Q[Qubit] --> ENT[Entanglement] Q --> COH[Coherence Time] Q --> FID[Gate Fidelity] NA[Neutral Atom Qubits] --> Q LC[Laser Cooling] --> NA OT[Optical Tweezers] --> NA RYD[Rydberg Interactions] --> NA NS[Nuclear-Spin Qubits] --> COH QEC[Quantum Error Correction] --> PL[Physical vs Logical Qubits] QEC --> STAB[Stabilizer Codes] QEC --> SYN[Syndrome Extraction] QEC --> THR[Code Distance and Threshold Theorem] SYN --> MCM[Mid-Circuit Measurement] FID --> THR ENT --> QEC STAB --> TOR[Toric Code] TOR --> SUR[Surface Code] STAB --> QLDPC[qLDPC Codes] STAB --> PIC[Permutation-Invariant Codes] CON[Qubit Connectivity and Reconfigurability] --> SUR CON --> QLDPC GCF[Global Control Fields] --> PIC BUS[Bosonic Bus] --> PIC NA --> CON QEC --> HYB[Hybrid Quantum-Classical Computing] class Q,ENT,COH,FID,NA,LC,OT,RYD,NS,QEC,PL,STAB,SYN,THR,MCM,TOR,SUR,QLDPC,PIC,CON,GCF,BUS,HYB internal-link; ``` ## The through-line > [!tip] One sentence that connects everything > Identical, movable atoms ([[Neutral Atom Qubits]]) give long [[Coherence Time|coherence]] and flexible [[Qubit Connectivity and Reconfigurability|connectivity]]; that flexibility lets a machine run whichever [[Quantum Error Correction|error-correcting code]] is cheapest — from the local [[Surface Code]] to low-overhead [[qLDPC Codes]] to symmetric [[Permutation-Invariant Codes]] — and the resulting reliable logical qubits act as an [[Hybrid Quantum-Classical Computing|accelerator inside classical computing]].