Semiconductor for Quantum Computing is semiconductor technologies implementing quantum bits (qubits) through electron spins, superconducting circuits, or photons, advancing quantum information processing — quantum computing paradigm shift. Semiconductors key to quantum scaling. Superconducting Qubits artificial atoms: Josephson junction-based. Two low-energy states form qubit. Superconductivity enables quantum coherence. Scalable: many qubits on chip. IBM, Google use. Josephson Junction two superconductors separated by thin insulator. Josephson energy = tunneling of Cooper pairs. Transmon qubit most common. Transmon Qubit modified Josephson junction: large shunt capacitance reduces charge noise. Charge-insensitive. Quantum Dots and Spin Qubits electron confined in potential well (quantum dot). Spin up/down = qubit. Silicon quantum dots mature approach. Silicon-Based Qubits silicon MOSFETs adapted for qubits. Natural isotope Si-28 (spin-zero) avoids hyperfine noise. Long coherence times (~1 ms). Hole Spins in Semiconductors holes (absent electrons in valence band) have longer coherence than electrons (smaller hyperfine). Ge/Si heterostructure hole spins. Quantum Well Confinement 2D electron gas in heterostructure confines electrons. Lithography patterns dots. Decoherence and T1/T2 T1 (energy relaxation): qubit loses excitation. T2 (dephasing): loses quantum coherence. Longer T2 allows more gates. Readout Methods single-shot readout of qubit state. Charge detection: Coulomb blockade electrometer. Spin detection: single-spin readout via electron spin resonance. Control and Gating RF pulses drive qubit rotations (π-pulses, π/2-pulses). Microwave frequency ~GHz for superconducting. Two-Qubit Gates entangle qubits: controlled-NOT (CNOT), iSWAP, XX/ZZ gates. Coupling mechanisms: Coulomb interaction, Heisenberg exchange, capacitive. Quantum Error Correction multiple physical qubits encode logical qubit. Errors detected, corrected. Surface codes promising for scaling. Scalability qubits must scale to millions for useful quantum computing. Current: 100-1000s qubits. Scaling challenges: crosstalk, control complexity. Crosstalk and Isolation qubits interact unintentionally. Engineering reduces. Spacing, shielding. Fabrication Precision qubits sensitive to fabrication variations. Yields low. Improving through control techniques (tuning, calibration). Cryogenic Requirements superconducting qubits require T < 100 mK. Dilution refrigerators. Expensive, requires infrastructure. Photonic Quantum Computing encode qubits in photons (polarization, path). Deterministic gates difficult (photons don't interact easily). Probabilistic gates via post-selection. Trapped Ion Qubits ions in RF trap, laser cooled. Ion qubits have exceptional coherence (>1000 s). Individual addressing via laser. Ionq, others developing. Neutral Atom Qubits neutral atoms in optical tweezers/MOT. Tunable interactions via Rydberg states. Atom computing developing. NV Centers in Diamond nitrogen-vacancy center defect in diamond. Spin qubit, optical addressable. Limited coherence (~1 ms), but room temperature. Semiconductor/Superconductor Hybrid hybrid systems combine advantages: semiconductor control ease, superconducting coherence. Quantum Algorithms and Advantage quantum advantage (speedup vs. classical) demonstrated on small instances. Scaling to practically useful algorithms. Quantum Simulation use quantum computer to simulate quantum systems (molecules, materials). Quantum Annealing adiabatic quantum computing: D-Wave systems. Different paradigm than gate-based. Benchmarking and Metrics quantum volume: multi-qubit gate fidelity vs. circuit depth. CLOPS (circuit layer operations per second). Error Rates two-qubit gate fidelity ~99% for best systems. Need >99.9% for error correction. Quantum Networking entanglement distribution between quantum computers. Quantum repeaters, quantum key distribution. Semiconductor quantum computing technologies advance toward practical utility with rapid progress in coherence times and gate fidelities.