The Quantum Investor's Notebook: Articles https://www.quantuminvestornotebook.com/ A physicist-investor's notebook on quantum computing that translates technical progress into investor-relevant judgment. en-us Sat, 10 Oct 2026 12:00:00 GMT Sat, 10 Oct 2026 12:00:00 GMT https://www.rssboard.org/rss-specification https://www.quantuminvestornotebook.com/Images/apple-touch-icon.png The Quantum Investor's Notebook: Articles https://www.quantuminvestornotebook.com/ IonQ Has Built a Bigger Company 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 A Model Cannot Know What You Missed 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 Breakeven Is Where the Race Starts 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 Not How Much Noise, but Which Kind 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 Cheap to Believe, Expensive to Run: What It All Adds Up To 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 Nothing Left to Check Against: When Classical Verification Runs Out 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 The Answer the Classical Methods Could Not Settle 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 Still the Referee: A Number Nobody Can Use 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 D-Wave and the Classical Counterattack 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 Errors as Telemetry: How Google Taught Willow to Tune Itself 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 The Memory Has to Survive the Protection 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 A Gap, or a Crowded Room? Microsoft's Majorana Dispute 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 Three Atoms, One State: The Promise and the Price of Networked Qubits 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 Quantinuum: A Decade in the Lab, a Day on the Tape 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 Majorana 2: The Quantum Bet Microsoft Can Afford to Lose 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 Xanadu: Building a Quantum Computer Out of Light, and Against the Clock 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 Rigetti: The $7 Million Company With an $8 Billion Story 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 Show Me the Code: The Long Vindication of D-Wave 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 The Stock That Went Shopping: The Quantum Computing Inc Story 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 IonQ: The Quantum Company That Decided to Become an Industry 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