Exercises: Chapter 31 — The Quantum Computing Industry

Exercise 31.1: Comparative Qubit Analysis

Create a table comparing superconducting, trapped ion, neutral atom, and photonic qubits across the following dimensions: coherence time, gate fidelity, gate speed, connectivity, operating temperature, and scalability. For each dimension, identify which modality is currently leading and explain the physical reason for its advantage.

Exercise 31.2: IBM Quantum Cloud

Sign up for an IBM Quantum account (free tier). Run a Bell state preparation circuit on a real IBM quantum processor. Report: (a) the backend name and number of qubits, (b) the measured counts, (c) the fidelity compared to the ideal distribution, and (d) the primary sources of error you observe.

Exercise 31.3: Resource Estimation

Using the Azure Quantum Resource Estimator (or a manual calculation based on literature values), estimate the number of physical qubits and runtime required to factor RSA-2048 using Shor's algorithm with surface code error correction. Assume physical gate error rate $p = 10^{-3}$ and surface code distance $d = 27$. Compare your estimate with published results (Gidney & Ekerå, 2021).

Exercise 31.4: Startup Deep Dive

Choose one quantum startup (IonQ, Rigetti, Quantinuum, PsiQuantum, QuEra, Xanadu, or D-Wave). Research their most recent technical milestone, funding status, and roadmap. Write a 500-word analysis addressing: (a) their technical approach and its advantages/disadvantages, (b) their business model and path to revenue, (c) the biggest risks they face, and (d) your assessment of their likelihood of long-term success.

Exercise 31.5: Career Path Planning

Based on your current skills and interests, map out a 3-year plan to enter the quantum computing industry. Identify: (a) specific skills you need to develop, (b) courses or programs you would pursue, (c) open-source projects you would contribute to, (d) conferences or communities you would join, and (e) target companies or roles. Be specific — name actual programs, projects, and organizations.

Exercise 31.6: Gate Fidelity Impact Calculation

For a superconducting quantum processor with two-qubit gate fidelity 99.7% and single-qubit gate fidelity 99.98%, calculate the expected circuit fidelity for: (a) a Bell state circuit (1 H + 1 CNOT), (b) a 10-qubit GHZ state circuit (1 H + 9 CNOT), (c) a QAOA circuit with $p=3$ on a 5-qubit graph (3 layers × ~10 CNOTs per layer). At what depth does the circuit fidelity drop below 50%?

Exercise 31.7: Cross-Platform Comparison

Write a Qiskit program that implements a 4-qubit random circuit benchmark and run it (or simulate it with noise models) for each major qubit modality. Use realistic noise models for: (a) superconducting qubits (T1=100μs, T2=80μs, CX error=0.3%), (b) trapped ions (T1=10s, T2=5s, CX error=0.01%, gate time=10μs), (c) neutral atoms (T1=5s, T2=3s, CZ error=0.5%, gate time=1μs). Compare the results and explain which modality performs best for this circuit and why.

Exercise 31.8: Startup Valuation Analysis

IonQ went public via SPAC in 2021 at a valuation of ~$2 billion. At the time, they had 32 algorithmic qubits and ~$2M in annual revenue. Compare this to: (a) a classical computing company with similar revenue (e.g., an early-stage semiconductor startup), (b) the total addressable market for quantum computing, and (c) the expected time to profitability. Is the valuation justified? What assumptions does it make?

Exercise 31.9: Quantum Software Comparison

Implement the same quantum circuit (e.g., a 3-qubit QFT) in Qiskit, Cirq, and PennyLane. Compare: (a) the number of lines of code, (b) the transpilation/compilation capabilities, (c) the available backends, (d) the documentation quality, and (e) the community support. Which framework would you recommend for: (i) a beginner learning quantum computing, (ii) a researcher developing new algorithms, (iii) an engineer deploying quantum circuits on hardware?

Exercise 31.10: Supply Chain Analysis

Research the quantum computing supply chain. For each of the following components, identify the top 3 suppliers, estimate the annual production capacity, and assess whether supply could meet demand if quantum computing scales to 1 million qubits by 2035: (a) dilution refrigerators, (b) microwave control electronics, (c) cryogenic wiring, (d) laser systems for trapped ions, (e) custom photonic chips. What are the key bottlenecks?