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Jayaprasanna Roddam
Jayaprasanna Roddam

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Quantum Computing

1. Mathematical Foundations (Non-negotiable)

Linear Algebra

  • Vector spaces (real vs complex)
  • Basis, dimension
  • Inner product
  • Norms
  • Orthogonality
  • Eigenvalues & eigenvectors
  • Spectral decomposition
  • Unitary matrices
  • Hermitian operators
  • Tensor products (VERY IMPORTANT)

Probability Theory

  • Random variables
  • Conditional probability
  • Bayes theorem
  • Expectation & variance

Complex Numbers

  • Euler’s formula
  • Polar form
  • Complex conjugates

2. Quantum Mechanics Foundations

Postulates of Quantum Mechanics

  • State representation (wavefunction/state vector)
  • Measurement postulate
  • Evolution (Schrödinger equation intuition)
  • Observables as operators

Dirac Notation

  • Bra ⟨ψ| and Ket |ψ⟩
  • Inner product ⟨ψ|φ⟩
  • Outer product |ψ⟩⟨φ|

Quantum States

  • Pure states
  • Mixed states
  • Density matrices

3. Qubits and Multi-Qubit Systems

Single Qubit

  • Representation: α|0⟩ + β|1⟩
  • Normalisation condition
  • Measurement probabilities

Bloch Sphere

  • State as a point on a sphere
  • Rotations = quantum gates

Multi-Qubit Systems

  • Tensor product states
  • Basis states (|00⟩, |01⟩, etc.)
  • State explosion (2ⁿ-dimensional space)

Entanglement

  • Bell states
  • Non-separability
  • Difference from classical correlation

4. Quantum Gates

Single-Qubit Gates

  • Pauli Gates (X, Y, Z)
  • Hadamard (H)
  • Phase gate (S, T)

Multi-Qubit Gates

  • CNOT (controlled NOT)
  • Toffoli gate
  • Controlled-U gates

Properties

  • Unitary transformations
  • Reversibility

5. Quantum Circuits

Circuit Model

  • Wires = qubits
  • Gates = operations

Concepts

  • Circuit depth
  • Parallelism
  • Measurement at end

Universal Gate Sets

  • Gate completeness

6. Quantum Algorithms

Deutsch-Jozsa Algorithm

  • First demonstration of quantum advantage

Grover’s Algorithm

  • Unstructured search
  • Quadratic speedup

Shor’s Algorithm

  • Integer factorization
  • Cryptography implications

Quantum Fourier Transform (QFT)

  • Core subroutine for many algorithms

Variational Quantum Algorithms

  • VQE (Variational Quantum Eigensolver)
  • QAOA (Quantum Approximate Optimisation Algorithm)

7. Quantum Machine Learning (QML)

Data Encoding

  • Basis encoding
  • Amplitude encoding
  • Angle encoding

Quantum Models

  • Quantum Neural Networks (QNN)
  • Variational circuits
  • Quantum kernels

Hybrid Models

  • Classical + Quantum pipelines

Open Problems

  • Data loading bottleneck
  • Noise sensitivity
  • Lack of clear advantage

8. Quantum Hardware

Physical Implementations

  • Superconducting qubits
  • Trapped ions
  • Photonic systems

Challenges

  • Decoherence
  • Noise
  • Error rates

9. Quantum Error Correction

  • Bit flip error
  • Phase flip error
  • Shor code
  • Surface codes

10. Industry Landscape

  • IBM (Qiskit)
  • Google (Quantum AI, Sycamore)
  • Microsoft (Azure Quantum)
  • Rigetti Computing
  • IonQ

11. Limitations & Misconceptions

  • Not all problems get speedup
  • Quantum ≠ universally faster
  • Hardware still immature

12. Future Directions

  • Fault-tolerant quantum computing
  • Quantum internet
  • Quantum advantage in ML

13. Tools & Frameworks

  • Qiskit
  • Cirq
  • PennyLane

14. Research-Level Topics

  • Quantum complexity classes (BQP, NP)
  • Quantum supremacy vs advantage
  • Hamiltonian simulation
  • Adiabatic quantum computing

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