*
Knowledge of the laser physics covered in paper
B2.III will be assumed.*

**Lasers:**
Line broadening mechanisms, linewidths and gain saturation. Q-switched
operation. Modelocking. Frequency control and frequency locking. Solid state
lasers. Semiconductor lasers. Fibre lasers. Ultrafast lasers: chirped pulse
amplification, terawatt and petawatt laser systems.
Examples of laser systems: Nd:Glass, Nd:YAG. Ti:sapphire; Er:Glass fibre lasers
and the Er-doped fibre amplifier (EDFA); AlGaAs and GaN semiconductor lasers.

**Optics:**
Diffraction. Ray matrices and Gaussian beams. Cavity eigenfunctions: the concept
of cavity mode, the stability criterion, cavity design. Beamsplitters.
Transverse coherence and Michelson stellar interferometer. Longitudinal
coherence: optical coherence tomography and Fourier transform spectroscopy. (Not
correlation functions, Wiener-Khintchine theorem). Optics in Structured
Materials: optical fields in planar waveguides and fibres.

**Non-linear Optics:** Crystal symmetries and the linear electrooptic tensor. Amplitude and
phase modulation of light using the linear electro-optic effect. Second harmonic
generation. Critical,non-critical and quasi-phase matching. Sum and difference
frequency generation and optical parametric down conversion.

**Quantum optics:**
Elementary introduction to quantum fields and
photons. Light-matter interactions and the Jaynes-Cummings model. Generation and
detection of nonclassical states of light: parametric down conversion and photon
entanglement, photon action at a beam splitter, bosonic statistics. Berry and
Pancharatnam phases.

**Quantum mechanics and Quantum Bits:**
Two level systems as quantum bits. Superposition states, the Bloch sphere, mixed
states, density matrices, Pauli matrices. Single qubit dynamics (gates): NOT,
square root of NOT-gate, Hadamard, phase shift, networks of gates, the
measurement gate. Implementations: atom/ion in a laser field, photon polarisation, spin in a
magnetic field. Mechanisms: Raman transitions, Rabi flopping, Ramsey fringes,
spin echoes. Decoherence (simple treatment). Separable and inseparable (entangled) states of
two spin systems. Two qubit gates: controlled-NOT, controlled-phase.
Universality of gates (result only). Characterising an unknown state, state and
gate fidelity (very basic), the no-cloning theorem. EPR, the four Bell states,
the Bell inequalities.

**Quantum Computation:**
Reversible computation with unitary
gates. Quantum parallelism and readout. The Deutsch and Grover algorithms. Other
quantum algorithms: Shor (result only), quantum simulation. Error correction (3
qubit code for phase or flip only) and decoherence free subspaces. DiVincenzo
criteria. Experimental methods with trapped atoms and ions. The controlled phase
gate by "collisions". Optical lattices and massive entanglement. Experimental
methods with NMR. Qualitative treatment of other quantum computing technologies.

**Quantum Communication:**
Elementary
ideas about information content. Quantum dense coding. Testing Bell
inequalities. Quantum key distribution, the BB84 protocol and detecting
eavesdropping (only intercept/resend strategy). EPR based cryptography.
Fibre and free space cryptography, polarisation and phase encoding. Phase
encoding methods. Quantum teleportation and entanglement swapping