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Quantum Technology

Planck through Shor to Willow — physics, qubits, error correction, sensing, and the modality wars

A mind map of quantum technology: the foundational physics; the birth of quantum information theory; the first physical qubits; the modality wars across superconducting, ion-trap, neutral-atom, photonic, spin, and topological platforms; quantum error correction and the path to fault tolerance; and the quantum sensing, communication, and commercial era. Named physicists, algorithms, devices, and benchmarks with dates across six branches.

Quantum Mechanics Foundations, 1900–1982Quantum Information Theory, 1982–1996First Physical Qubits, 1995–2015Modalities — The Modality WarsError Correction & Fault ToleranceSensing, Comms & CommercialThe old quantum theoryWave mechanics and matrix mechanicsFoundations debatesBell test experimentsQuantum optics and squeezingThe 1982 inflectionQuantum computation formalizedThe killer algorithmsFoundational theoremsThe Nielsen-Chuang eraNMR and early demosTrapped ionsSuperconducting qubitsPhotonic qubitsOther modalitiesSuperconducting / transmonTrapped ionsNeutral atomsPhotonicSpin and topologicalNV centers and diamondTheoretical foundationsSurface codeBeyond surface codeMagic states and universal gatesRecent milestonesQuantum sensingQuantum communicationCloud and ecosystemPublic companies and unicornsNational programs and policyNISQ era and the path forwardMax Planck — quantum hypothesis, blackbody, 1900Albert Einstein — photoelectric effect, 1905 (Nobel 1921)Niels Bohr — quantized atomic model, 1913de Broglie — matter waves, 1924Compton effect — 1923 (photon momentum)Werner Heisenberg — matrix mechanics, 1925Erwin Schrödinger — wave equation, 1926Born — probability interpretation of |ψ|², 1926Heisenberg uncertainty principle, 1927Dirac equation — relativistic, 1928Copenhagen interpretation — Bohr-Heisenberg, 1927Einstein-Podolsky-Rosen paradox, Phys Rev 1935Schrödinger's cat thought experiment, 1935 (coins "entanglement")David Bohm — pilot-wave theory, 1952John Bell — Bell inequalities, 1964Hugh Everett — many-worlds interpretation, 1957Stuart Freedman & John Clauser — first Bell test, Berkeley 1972Alain Aspect — definitive Bell tests, Orsay 1982Loophole-free Bell tests — Hensen et al. (Delft), Giustina et al., Shalm et al., 2015Aspect, Clauser, Zeilinger — Nobel Prize 2022Roy Glauber — quantum theory of optical coherence, 1963 (Nobel 2005)Photon antibunching — Kimble, Dagenais, Mandel, 1977Squeezed light — Slusher et al., 1985Two-photon absorption and parametric down-conversionRichard Feynman — Simulating Physics with Computers, IJTP 1982No-cloning theorem — Wootters & Zurek; Dieks, 1982Charles Bennett & Gilles Brassard — BB84 QKD protocol, 1984David Deutsch — quantum Turing machine, Proc. Roy. Soc. 1985Deutsch-Jozsa algorithm, 1992Bernstein & Vazirani — quantum complexity classes, 1993Simon's problem — Daniel Simon, 1994Peter Shor — factoring + discrete log algorithm, FOCS 1994Polynomial-time quantum factoring vs. classical sub-exponentialLov Grover — quantum search, STOC 1996 (quadratic speedup)Quantum simulation of fermionic systems — Lloyd, 1996Quantum teleportation protocol — Bennett et al., 1993Superdense coding — Bennett & Wiesner, 1992Schumacher — quantum source coding, 1995 (qubit term coined)Holevo bound — classical information from quantum statesThreshold theorem — Aharonov-Ben-Or; Knill-Laflamme-Zurek, 1996–1997Nielsen & Chuang — Quantum Computation and Quantum Information, 2000Kitaev — fault-tolerant computation by anyons, 1997Preskill — Caltech quantum computation lectures, 1998Stabilizer formalism — Daniel Gottesman PhD, 1997Liquid-state NMR demonstrations — Chuang, Vandersypen, 1998IBM Almaden NMR factoring of 15 = 3 × 5, 2001 (Shor demo)NMR shown not scalable — limited information per moleculeCirac & Zoller — trapped-ion gate proposal, 1995David Wineland — first single-ion logic gate, NIST Boulder 1995Wineland & Haroche — Nobel Prize 2012Mølmer-Sørensen gate — 1999, the dominant ion two-qubit operationInnsbruck (Blatt) and IonQ Maryland (Monroe) lineagesYasunobu Nakamura — first solid-state qubit (charge), NEC 1999Quantronium qubit — Vion et al., Saclay 2002Transmon qubit — Koch, Schoelkopf, Devoret et al., Yale 2007Circuit QED — Wallraff et al., Yale 2004Josephson junction — Brian Josephson, 1962 (Nobel 1973)D-Wave Systems — first commercial annealer, 2011KLM scheme — Knill, Laflamme, Milburn, 2001 (linear optics computing)Boson sampling — Aaronson & Arkhipov, 2011Cluster-state quantum computing — Raussendorf & Briegel, 2001Pan Jianwei group — USTC photonic milestonesNV centers in diamond — quantum sensing, Wrachtrup, ~2000Silicon spin qubits — Kane proposal 1998; Loss-DiVincenzo 1998Neutral atoms in optical lattices — Bloch group, MPITopological qubits (Majorana) — Kitaev 1997 proposal; Microsoft pursuitIBM Quantum — open-access cloud since 2016IBM Eagle 127 qubits, 2021; Condor 1,121 qubits, 2023IBM Heron 156 qubits with improved fidelity, 2024Google Sycamore — 53 qubits, quantum supremacy 2019Google Willow — 105 qubits, error-correction crossover Dec 2024Rigetti Computing — Aspen series; founded 2013Two-qubit fidelity ~99.5–99.7% state of art 2025T1 ~100 μs, T2 ~50 μs typical for transmonsIonQ — Monroe + Kim, founded 2015; NASDAQ 2021Quantinuum — Honeywell + Cambridge Quantum merger, 2021Quantinuum H2-1 — 56 qubits, all-to-all, 2024Two-qubit fidelity >99.9% state of artT1, T2 in seconds (vs. μs for superconducting)Slower gates (μs–ms vs. ns for superconducting)171Yb+, 137Ba+, 9Be+ as common qubit ionsQuEra — Mikhail Lukin, Markus Greiner, founded 2018QuEra Aquila — 256 atoms, 2022; Gemini 256-256 logical, 2024Atom Computing — 1,180 atoms, 2023Pasqal — Antoine Browaeys, FranceRydberg-atom interactions for two-qubit gatesOptical tweezer arrays for arbitrary lattice geometryPsiQuantum — Jeremy O'Brien, founded 2016PsiQuantum aims for 1M qubit fault-tolerant via fusion-based QCXanadu — Toronto, photonic continuous-variable; Borealis 2022Quandela — France, single-photon sourcesUSTC Jiuzhang 2.0 — photonic quantum advantage, 2021Intel Tunnel Falls 12-qubit silicon spin chip, 2023Quantum Motion, Diraq — silicon-spin startupsMicrosoft Majorana 1 — topological qubit announcement, Feb 2025Topological qubits would have intrinsic error protection (if realized)Kitaev chain — theoretical Majorana zero-mode foundationNitrogen-vacancy centers in diamond — ms coherence at room tempWrachtrup, Jelezko (Stuttgart) — pioneering NV labsNV-based magnetometry, biosensing, quantum networkingQuantum Diamond Technologies, Element SixPeter Shor — first quantum error-correcting code, 1995 (9-qubit)Steane code — 7-qubit CSS code, 1996CSS codes — Calderbank-Shor-Steane constructionThreshold theorem — fault-tolerant computation possible if error < ~1%Stabilizer formalism — efficient simulation of Clifford groupKitaev toric code, 1997Surface code — Bravyi & Kitaev, 1998; Fowler et al., 2012Threshold ~1% — practically achievable with current hardwareLogical qubit overhead: ~1,000–10,000 physical per logicalLattice surgery for logical operations — Horsman et al., 2012Color codes — Bombin & Martin-Delgado, 2006Cat codes — bosonic encoding, AT&T → Yale lineageGKP codes — Gottesman-Kitaev-Preskill, 2001QLDPC codes — quantum low-density parity-checkIBM bivariate bicycle codes, 2024 — order-of-magnitude overhead reductionClifford gates are easy; T-gate is hard (non-Clifford)Magic state distillation — Bravyi & Kitaev, 2005T-gate distillation dominates fault-tolerant resource costCode switching as alternative to magic statesGoogle Sycamore — quantum supremacy claim, Oct 2019USTC Jiuzhang — photonic quantum advantage, 2020Quantinuum logical qubit — error rate below physical, 2024Google Willow — surface-code error suppression below threshold, Dec 2024Distance 3, 5, 7 codes show exponential error suppression Λ ≈ 2.1Microsoft + Quantinuum — 12 logical qubits demonstrated, 2024Gidney-Ekerå — 20M physical qubits to break 2048-bit RSA, 2019 estimateAtom interferometry — Kasevich & Chu, Stanford 1991Optical lattice clocks — strontium, ytterbium; 10⁻¹⁹ fractional uncertaintySqueezed-light injection at LIGO — improved gravitational-wave sensitivity, 2019NV magnetometry — sub-cellular field imagingQuantum-enhanced radar and LIDAR — proof-of-conceptQuantum gravimeters — gravity-aided inertial navigationBB84 protocol — Bennett & Brassard, 1984 (most-deployed QKD)Ekert protocol (E91) — entanglement-based QKD, 1991MDI-QKD — measurement-device-independent, Lo et al. 2012DI-QKD — device-independent QKD, 2022 first experimental demonstrationsTwin-field QKD — secure key over 800+ km, 2024Micius satellite — China-Austria QKD, 2017Jinan-1 satellite — Chinese QKD constellation node, 2022Quantum repeater theory — DLCZ protocol; not yet experimentally matureIBM Quantum Experience launched, May 2016Amazon Braket, 2020Microsoft Azure Quantum, 2019Qiskit (IBM), Cirq (Google), PennyLane (Xanadu), pyQuil (Rigetti)Quantinuum InQuanto, IBM Qiskit RuntimeIonQ NYSE listing, Oct 2021Rigetti SPAC merger, Mar 2022D-Wave SPAC, Aug 2022Quantinuum private, $5B valuation 2024PsiQuantum private, $3B+ raised by 2024Xanadu, Pasqal, QuEra, Atom Computing — well-capitalized privateUS National Quantum Initiative Act, 2018 ($1.2B)EU Quantum Flagship — €1B over 10 years, 2018UK National Quantum Strategy, 2023 (£2.5B)China Hefei National Lab — Pan Jianwei, $10B+Japan Q-LEAP, Korea Quantum InitiativeNIST PQC standardization driven by quantum threat horizonJohn Preskill — NISQ term, "Quantum Computing in the NISQ era," 2018Variational quantum eigensolver (VQE) — Peruzzo et al., 2014QAOA — quantum approximate optimization, Farhi et al., 2014Quantum advantage vs. supremacy — terminology evolvingAaronson on quantum supremacy claims and verification"Quantum useful" still requires fault-tolerance for industrially relevant problemsQuantum TechnologyBrian Tighe · Mind Maps
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