https://www.quantuminvestornotebook.com/ A physicist-investor's notebook on quantum computing that translates technical progress into investor-relevant judgment. en-us Fri, 30 Oct 2026 12:00:00 GMT Fri, 30 Oct 2026 12:00:00 GMT https://www.rssboard.org/rss-specification https://www.quantuminvestornotebook.com/Images/apple-touch-icon.png https://www.quantuminvestornotebook.com/ https://www.quantuminvestornotebook.com/Notes/what-is-share-dilution https://www.quantuminvestornotebook.com/Notes/what-is-share-dilution Share dilution is what happens to existing owners when a company issues new shares. Why a smaller slice is not automatically a loss, shown with numbers. Fri, 30 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/neural-decoder-real-time-edge-is-simulated https://www.quantuminvestornotebook.com/Notes/neural-decoder-real-time-edge-is-simulated Three Yonsei researchers swapped AlphaQubit's attention for a lighter Mamba design and kept its accuracy. The speed edge at today's code sizes is simulated. Thu, 29 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/data-loading-compiler-cuts-cost-on-paper https://www.quantuminvestornotebook.com/Notes/data-loading-compiler-cuts-cost-on-paper Xanadu and Rolls-Royce cut the estimated T gates for a 20 qubit fluid workflow from 2 × 10²⁰ to 9 × 10¹⁵ with cheaper data loading. Nothing ran on hardware. Thu, 29 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-the-error-correction-threshold https://www.quantuminvestornotebook.com/Notes/what-is-the-error-correction-threshold The error-correction threshold is the error rate below which bigger codes help instead of hurt. What below threshold means, and why it is not a finish line. Wed, 28 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/minecraft-grover https://www.quantuminvestornotebook.com/Notes/minecraft-grover A UIC team designed a quantum search for a Minecraft seed and tested a tiny version on IBM and Quantinuum. The full run needs 1.65 billion two qubit gates. Wed, 28 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-an-rsa-2048-resource-estimate https://www.quantuminvestornotebook.com/Notes/what-is-an-rsa-2048-resource-estimate An RSA-2048 resource estimate says how big a quantum computer must be to break RSA-2048 and how long it runs. How to read its assumptions, and why they move it. Mon, 26 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/News/2026-10-17-to-2026-10-23 https://www.quantuminvestornotebook.com/News/2026-10-17-to-2026-10-23 Quantum computing, October 17 to 23, 2026: Quantinuum's Helios color-code record and its offline decoding, the classical stack that has to keep pace, Florida's quantum-safe link on IonQ technology, and the Treasury's proposed COINS Act rule keeping quantum investment in China banned; plus Sundar Pichai's five-year horizon and IBM's $1 billion Anderon award. Sat, 24 Oct 2026 12:00:00 GMT Weekly News https://www.quantuminvestornotebook.com/Publications/2026-10-17-to-2026-10-23 https://www.quantuminvestornotebook.com/Publications/2026-10-17-to-2026-10-23 Weekly quantum research for October 17 to 23, 2026: below-threshold error correction on a rented IBM chip by outside researchers, with Quantinuum's color code for scale; reality checks on quantum advantage, from BosonSampling under photon loss to classical post-processing of QuEra's Aquila; and links between machines from 80 centimeters to 17 kilometers. Sat, 24 Oct 2026 12:00:00 GMT Weekly Publications https://www.quantuminvestornotebook.com/Notes/what-is-a-cat-qubit https://www.quantuminvestornotebook.com/Notes/what-is-a-cat-qubit A cat qubit stores information in a microwave resonator so that bit flips almost never happen. How biased noise lets a line of checks replace a full grid. Sat, 24 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-q-day https://www.quantuminvestornotebook.com/Notes/what-is-q-day Q-Day is when a quantum computer could break the public-key encryption the internet relies on. What it would take, harvest now, decrypt later, and the defense. Thu, 22 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/News/2026-10-10-to-2026-10-16 https://www.quantuminvestornotebook.com/News/2026-10-10-to-2026-10-16 Quantum computing, October 10 to 16, 2026: IonQ's Elisity deal and $2 billion financing, ORCA's PT-3 beside GPUs, D-Wave's Como inauguration, DOCOMO's nationwide rollout, manufacturing renewals and post-quantum migration dates. Sat, 17 Oct 2026 12:00:00 GMT Weekly News https://www.quantuminvestornotebook.com/Publications/2026-10-10-to-2026-10-16 https://www.quantuminvestornotebook.com/Publications/2026-10-10-to-2026-10-16 A 1,265-ion crystal under coherent control, encoded addition that beats its physical circuit but discards attempts, second-long defect lifetimes, deterministic photon fusion and AI-designed quantum arithmetic. Sat, 17 Oct 2026 12:00:00 GMT Weekly Publications https://www.quantuminvestornotebook.com/Notes/what-is-a-decoder https://www.quantuminvestornotebook.com/Notes/what-is-a-decoder A decoder is the classical algorithm that reads error-correction alarms and bets on which errors caused them. Majority vote, matching, and why speed matters. Thu, 15 Oct 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/News/2026-10-03-to-2026-10-09 https://www.quantuminvestornotebook.com/News/2026-10-03-to-2026-10-09 Quantum computing, October 3 to 9, 2026: DARPA's Stage C and DOE's priority applications, four financing figures that mean different things, foundries and packaging, tools for cloud access, and KQC's proposed listing. Sat, 10 Oct 2026 12:00:00 GMT Weekly News https://www.quantuminvestornotebook.com/Publications/2026-10-03-to-2026-10-09 https://www.quantuminvestornotebook.com/Publications/2026-10-03-to-2026-10-09 A tenfold leaner memory from wired-together modules, error correction around a chip’s weak spots, a kilohertz link between two qubit technologies, and the real price of a usable magic state. With selected research from Google, IBM and IonQ. Sat, 10 Oct 2026 12:00:00 GMT Weekly Publications https://www.quantuminvestornotebook.com/Articles/IONQ_Company_Analysis_2026-10-10 https://www.quantuminvestornotebook.com/Articles/IONQ_Company_Analysis_2026-10-10 IonQ company analysis: acquired growth, the latest trailing-twelve-month financials, technical milestones and customer evidence. Sat, 10 Oct 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/News/2026-09-26-to-2026-10-02 https://www.quantuminvestornotebook.com/News/2026-09-26-to-2026-10-02 Five takeaways from quantum computing, September 26 to October 2, 2026: radar studies and a gate-model beta on simulators, tools ahead of deployment, error-correction plans, Pasqal's first public month and a new Albuquerque lab. Sat, 03 Oct 2026 12:00:00 GMT Weekly News https://www.quantuminvestornotebook.com/Publications/2026-09-26-to-2026-10-02 https://www.quantuminvestornotebook.com/Publications/2026-09-26-to-2026-10-02 A claimed chemistry break-even on 120 qubits, a new classical-sampling limit for noisy unital circuits, and spin-qubit initialization without local reservoirs. With selected research from IBM, QuEra and RIKEN. Sat, 03 Oct 2026 12:00:00 GMT Weekly Publications https://www.quantuminvestornotebook.com/News/2026-09-19-to-2026-09-25 https://www.quantuminvestornotebook.com/News/2026-09-19-to-2026-09-25 Five takeaways from quantum computing, September 19–25, 2026: three IonQ Superion deals, two with 2027 installation dates, 30 logical qubits on Infleqtion's Sqale, workload-specific results, public programs and half-year numbers. Sat, 26 Sep 2026 12:00:00 GMT Weekly News https://www.quantuminvestornotebook.com/Publications/2026-09-19-to-2026-09-25 https://www.quantuminvestornotebook.com/Publications/2026-09-19-to-2026-09-25 A quantum advantage claim run through a standard cloud queue, a fast-moving front in new error-correcting codes, and error correction moving into the hardware stack. With selected research from BlueQubit on IBM hardware, MIT and a photonic processor in orbit. Sat, 26 Sep 2026 12:00:00 GMT Weekly Publications https://www.quantuminvestornotebook.com/News/2026-09-12-to-2026-09-18 https://www.quantuminvestornotebook.com/News/2026-09-12-to-2026-09-18 Five takeaways from quantum computing’s push toward shared infrastructure, September 12–18, 2026: CUDA-Q, 300 mm quantum manufacturing, a hybrid engineering workflow and new deployments. Sat, 19 Sep 2026 12:00:00 GMT Weekly News https://www.quantuminvestornotebook.com/Publications/2026-09-12-to-2026-09-18 https://www.quantuminvestornotebook.com/Publications/2026-09-12-to-2026-09-18 Wafer-scale statistics, a 90% optical memory and quantum signals sharing fiber with 10 Gbps traffic: this week’s research made deployment constraints measurable. With selected research from the University of Illinois, LuxQuanta and IBM. Sat, 19 Sep 2026 12:00:00 GMT Weekly Publications https://www.quantuminvestornotebook.com/Notes/what-is-qaoa https://www.quantuminvestornotebook.com/Notes/what-is-qaoa QAOA, the Quantum Approximate Optimization Algorithm, writes each answer's score into phase, then uses interference to favor better ones. MaxCut as the example. Sat, 19 Sep 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-grovers-algorithm https://www.quantuminvestornotebook.com/Notes/what-is-grovers-algorithm Grover's algorithm finds a marked item among N candidates in about √N queries instead of N. The oracle's phase flip, the diffusion step, and its limits. Fri, 18 Sep 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-the-quantum-fourier-transform https://www.quantuminvestornotebook.com/Notes/what-is-the-quantum-fourier-transform The quantum Fourier transform turns patterns hidden in a state's phases into measurable outcomes, as in phase estimation and Shor's. Not simply a faster FFT. Thu, 17 Sep 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-the-ghz-state https://www.quantuminvestornotebook.com/Notes/what-is-the-ghz-state A GHZ (Greenberger-Horne-Zeilinger) state puts three or more qubits in one all-or-nothing state. How it is built and how a parity test checks its coherence. Wed, 16 Sep 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-a-bell-state https://www.quantuminvestornotebook.com/Notes/what-is-a-bell-state A Bell state is two qubits sharing one joint state. Why 00/11 correlation alone proves nothing, how a Hadamard and a CNOT build one, and the four Bell states. Tue, 15 Sep 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/News/2026-09-05-to-2026-09-12 https://www.quantuminvestornotebook.com/News/2026-09-05-to-2026-09-12 Six takeaways from quantum computing’s industrial buildout, September 5–12, 2026: CHIPS funding, foundries, software, control loops and the milestones still ahead. Mon, 14 Sep 2026 12:00:00 GMT Weekly News https://www.quantuminvestornotebook.com/Publications/2026-09-05-to-2026-09-11 https://www.quantuminvestornotebook.com/Publications/2026-09-05-to-2026-09-11 The systems around the qubit come into focus: control, the cost of quantum algorithms, and the connections needed to scale. With selected research from IBM, NTT, and JPMorgan Chase. Mon, 14 Sep 2026 12:00:00 GMT Weekly Publications https://www.quantuminvestornotebook.com/Articles/Week_8_Part_2_A_Model_Cannot_Know_What_You_Missed_2026-09-12 https://www.quantuminvestornotebook.com/Articles/Week_8_Part_2_A_Model_Cannot_Know_What_You_Missed_2026-09-12 A weekly-paper notebook entry on where noise models run out: Quantinuum's thermal-state experiment missing its own consistency check by six standard deviations, and Pasqal's cross-device model meeting a systematic offset it did not contain. Sat, 12 Sep 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/Week_8_Breakeven_Is_Where_the_Race_Starts_2026-09-12 https://www.quantuminvestornotebook.com/Articles/Week_8_Breakeven_Is_Where_the_Race_Starts_2026-09-12 A weekly-paper notebook entry on IonQ's breakeven demonstration of high-rate qLDPC codes: nine codes on forty barium ions, measurement without moving ions, what a correction cycle costs, and why the larger codes did not do better. Sat, 12 Sep 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/Week_8_Part_1_Not_How_Much_Noise_but_Which_Kind_2026-09-12 https://www.quantuminvestornotebook.com/Articles/Week_8_Part_1_Not_How_Much_Noise_but_Which_Kind_2026-09-12 Two papers from Quantinuum and Pasqal show why noise amount sets reach, error type shapes the answer, and the dominant limitation changes with workload. Sat, 12 Sep 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/Week_7_Part_3_Cheap_to_Believe_Expensive_to_Run_2026-08-22 https://www.quantuminvestornotebook.com/Articles/Week_7_Part_3_Cheap_to_Believe_Expensive_to_Run_2026-08-22 A weekly-paper notebook entry on IBM Research and the University of Chicago's doped Clifford sampling experiment: a fidelity certificate built into the circuit rather than inferred from a noise model, what it proves, what it costs, and what all three of IBM's advantage claims add up to. Sat, 22 Aug 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/Week_7_Part_1_Nothing_Left_to_Check_Against_2026-08-22 https://www.quantuminvestornotebook.com/Articles/Week_7_Part_1_Nothing_Left_to_Check_Against_2026-08-22 A weekly-paper notebook entry on IBM Research and Algorithmiq's operator Loschmidt echo experiment: why benchmarking a quantum result against a classical simulation is circular, how an unverifiable estimate is made defensible, and why the method carrying real error bars runs only where a classical reference still exists. Sat, 22 Aug 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/Week_7_Part_2_The_Classical_Methods_Could_Not_Settle_2026-08-22 https://www.quantuminvestornotebook.com/Articles/Week_7_Part_2_The_Classical_Methods_Could_Not_Settle_2026-08-22 A weekly-paper notebook entry on the Qedma, IBM, RIKEN and BlueQubit driven-magnet experiment: a subharmonic rhythm that survives as the system grows, an inference the classically simulable sizes could not settle, and what the error mitigation carrying it actually costs. Sat, 22 Aug 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/Week_6_Still_the_Referee_2026-08-01 https://www.quantuminvestornotebook.com/Articles/Week_6_Still_the_Referee_2026-08-01 A weekly-paper notebook entry on IBM Research and the University of Chicago's LASSQD, a hybrid quantum-classical workflow for strongly correlated chemistry: what the quantum processor actually contributes, why connectivity matters more than qubit count, what the four validation layers show, and why the one calculation beyond exact classical fragment diagonalization cannot name a ground state. Sat, 01 Aug 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Notes/what-is-an-observable https://www.quantuminvestornotebook.com/Notes/what-is-an-observable An observable is the property a quantum measurement asks about. How it differs from an outcome and an expectation value, and why estimates take many runs. Tue, 28 Jul 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Articles/Week_5_Frontier_Moves_Both_Ways_2026-07-25 https://www.quantuminvestornotebook.com/Articles/Week_5_Frontier_Moves_Both_Ways_2026-07-25 A weekly-paper notebook entry on the Science paper by Tindall and colleagues that reproduced an important part of D-Wave's quantum spin-glass benchmark classically using lattice-matched tensor networks and belief propagation: what it reproduced, what it left open, how D-Wave answered, and why quantum computing may not be a winner-takes-most market. Sat, 25 Jul 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/Week_4_Errors_as_Telemetry_2026-07-18 https://www.quantuminvestornotebook.com/Articles/Week_4_Errors_as_Telemetry_2026-07-18 A weekly-paper notebook entry on Google Quantum AI's reinforcement-learning control of quantum error correction on Willow: error-detection events repurposed as a training signal that re-tunes the machine as it drifts, what it delivered, what it costs, and the investor's read on Alphabet's full-stack position. Sat, 18 Jul 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/Week_3_Memory_Survives_Protection_2026-07-11 https://www.quantuminvestornotebook.com/Articles/Week_3_Memory_Survives_Protection_2026-07-11 A weekly-paper notebook entry on Quantinuum's first end-to-end error-corrected computation of a molecule's energy: quantum phase estimation on a color code, partial fault tolerance, and why memory noise, not the gates, was the limiting error in this circuit. Sat, 11 Jul 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Notes/what-is-quantum-phase-estimation https://www.quantuminvestornotebook.com/Notes/what-is-quantum-phase-estimation Quantum phase estimation reads a quantity like a molecule's energy off a quantum computer by hiding it in a phase. The textbook and single-ancilla versions. Mon, 06 Jul 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Articles/Week_2_A_Gap_or_a_Crowded_Room_2026-07-04 https://www.quantuminvestornotebook.com/Articles/Week_2_A_Gap_or_a_Crowded_Room_2026-07-04 A weekly-paper notebook entry on the published Nature dispute over Microsoft's topological-qubit evidence: Henry Legg's critique, Microsoft's reply, and what a crowded gap means for the Majorana bet. Sat, 04 Jul 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Notes/what-is-a-majorana-qubit https://www.quantuminvestornotebook.com/Notes/what-is-a-majorana-qubit A Majorana qubit splits its information across two Majorana zero modes, out of easy reach of local noise. How it is run by measurement, and why it is contested. Sun, 28 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-a-random-telegraph-signal https://www.quantuminvestornotebook.com/Notes/what-is-a-random-telegraph-signal A random telegraph signal is noise that jumps between two fixed levels as one flaw switches. How it builds 1/f noise and makes a qubit's quality drift. Sun, 28 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-the-topological-gap-protocol https://www.quantuminvestornotebook.com/Notes/what-is-the-topological-gap-protocol The topological gap protocol is Microsoft's pre-registered pass/fail test of whether a device is topological and hosts Majorana zero modes. How the test works. Sun, 28 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Articles/Week_1_Networked_Qubits_2026-06-27 https://www.quantuminvestornotebook.com/Articles/Week_1_Networked_Qubits_2026-06-27 A weekly-paper notebook entry on the first fully distributed three-node GHZ state shared across remote atomic qubits (Goetting et al., 2026), what it cost in fidelity and rate, and what it means for IonQ's networking story. Sat, 27 Jun 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Notes/what-is-the-mermin-inequality https://www.quantuminvestornotebook.com/Notes/what-is-the-mermin-inequality The Mermin inequality is a many-qubit test that proves a system is genuinely quantum when its score beats the classical limit. Why the gap grows with qubits. Tue, 23 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-a-quantum-circuit https://www.quantuminvestornotebook.com/Notes/what-is-a-quantum-circuit A quantum circuit is a recipe of gates: wires are qubits, read left to right in time, ending in measurement. Universal gate sets, width, depth and noise. Sat, 20 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-measurement https://www.quantuminvestornotebook.com/Notes/what-is-measurement Measurement turns a qubit's blend of possibilities into one definite 0 or 1. The Born rule, collapse and back-action, how readout works, and why it matters. Fri, 19 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-a-physical-qubit https://www.quantuminvestornotebook.com/Notes/what-is-a-physical-qubit A physical qubit is a real two-level quantum system built in hardware. The DiVincenzo criteria, how platforms compare, and why one is never enough on its own. Thu, 18 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-a-quantum-gate https://www.quantuminvestornotebook.com/Notes/what-is-a-quantum-gate A quantum gate is a reversible operation that changes the state of one or more qubits. Why a few gates can build any computation, and why fidelity is the wall. Wed, 17 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/the-billion-qubit-paradox https://www.quantuminvestornotebook.com/Notes/the-billion-qubit-paradox Why factoring a 2,000-bit number would take about 4,000 logical qubits and roughly a billion physical ones, and how the surface code computes with holes. Tue, 16 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-a-logical-qubit https://www.quantuminvestornotebook.com/Notes/what-is-a-logical-qubit A logical qubit is one reliable unit of quantum information spread across many fragile physical qubits. How the surface code builds it and what it costs. Mon, 15 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-entanglement https://www.quantuminvestornotebook.com/Notes/what-is-entanglement Entanglement is particles sharing one joint state with correlations stronger than anything classical. Einstein's objection, Bell's test, and why it is fragile. Sun, 14 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-superposition https://www.quantuminvestornotebook.com/Notes/what-is-superposition Superposition is a quantum system holding several possible states at once until measured. The double-slit evidence, why decoherence ends it, and why it matters. Sat, 13 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-does-fault-tolerant-mean https://www.quantuminvestornotebook.com/Notes/what-does-fault-tolerant-mean Fault tolerance: running a long quantum computation correctly even though every part is noisy. Why it goes beyond error correction, and the threshold theorem. Fri, 12 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-a-qubit https://www.quantuminvestornotebook.com/Notes/what-is-a-qubit A qubit is the basic unit of quantum information: it can be both 0 and 1 at once. How entanglement adds power, and why decoherence makes qubits hard to keep. Thu, 11 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-quantum-error-correction https://www.quantuminvestornotebook.com/Notes/what-is-quantum-error-correction Quantum error correction fixes errors in data that cannot be copied or looked at: one logical qubit across many physical ones, syndrome checks, the threshold. Wed, 10 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-qubit-connectivity https://www.quantuminvestornotebook.com/Notes/what-is-qubit-connectivity Qubit connectivity is which qubits can run a two-qubit gate directly. Why limited connectivity forces SWAP gates that add depth and noise to a circuit. Tue, 09 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-coherence-time https://www.quantuminvestornotebook.com/Notes/what-is-coherence-time Coherence time is how long a qubit holds its quantum state before noise scrambles it. T1 and T2, why decoherence causes it, and why gate speed matters too. Mon, 08 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Articles/QNT_Company_Story_2026-06-06 https://www.quantuminvestornotebook.com/Articles/QNT_Company_Story_2026-06-06 A narrative-and-numbers company analysis of Quantinuum, told as a notebook. Sat, 06 Jun 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/MSFT_Company_Story_2026-06-05 https://www.quantuminvestornotebook.com/Articles/MSFT_Company_Story_2026-06-05 A narrative-and-numbers company analysis of Microsoft's quantum bet, told as a notebook. Fri, 05 Jun 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Notes/why-qubit-count-is-not-a-score https://www.quantuminvestornotebook.com/Notes/why-qubit-count-is-not-a-score Qubit count measures only width. Why it ignores gate fidelity, connectivity and circuit depth, and how quantum volume and volumetric benchmarks do better. Fri, 05 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/reading-a-gate-fidelity-claim https://www.quantuminvestornotebook.com/Notes/reading-a-gate-fidelity-claim A gate-fidelity number is not a full score for a quantum computer. What to ask before trusting one: which gate, measured how, on what system, at what scale. Wed, 03 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Notes/what-is-gate-fidelity https://www.quantuminvestornotebook.com/Notes/what-is-gate-fidelity Gate fidelity measures how closely a physical quantum gate reproduces the ideal operation, and why going from 99.9% to 99.99% is a tenfold cut in error. Mon, 01 Jun 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Articles/XNDU_Company_Story_2026-05-26 https://www.quantuminvestornotebook.com/Articles/XNDU_Company_Story_2026-05-26 A narrative-and-numbers company analysis of Xanadu (XNDU), told as a notebook. Tue, 26 May 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/RGTI_Company_Story_2026-05-23 https://www.quantuminvestornotebook.com/Articles/RGTI_Company_Story_2026-05-23 A narrative-and-numbers company analysis of Rigetti Computing (RGTI), told as a notebook. Sat, 23 May 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/QBTS_Company_Story_2026-05-23 https://www.quantuminvestornotebook.com/Articles/QBTS_Company_Story_2026-05-23 A narrative-and-numbers company analysis of D-Wave, told as a notebook. Sat, 23 May 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Articles/QUBT_Company_Story_2026-05-23 https://www.quantuminvestornotebook.com/Articles/QUBT_Company_Story_2026-05-23 A narrative-and-numbers company analysis of Quantum Computing Inc (QUBT), told as a notebook. Sat, 23 May 2026 12:00:00 GMT Articles https://www.quantuminvestornotebook.com/Notes/qubits-overview https://www.quantuminvestornotebook.com/Notes/qubits-overview Today's qubits come from four physics fields: atomic, solid-state, photonics and topological matter. Why the choice of physics is itself the bet being made. Thu, 21 May 2026 12:00:00 GMT Notes https://www.quantuminvestornotebook.com/Articles/IONQ_Company_Story_2026-05-12 https://www.quantuminvestornotebook.com/Articles/IONQ_Company_Story_2026-05-12 A narrative-and-numbers company analysis of IonQ, told as a notebook. Tue, 12 May 2026 12:00:00 GMT Articles