Coherence and entanglement of spin qubits in semiconductor nanostructures

The aim of this project is an improved theoretical understanding of the fundamentals of quantum phase coherence of single spins in quantum dots and quantum wires. To this end, the relevant physical processes leading to decoherence (loss of coherence) will be investigated. For electron spins, one of the dominant decoherence mechanisms is the hyperfine coupling to the surrounding nuclear spins. For both electron and hole spins, the spin-orbit coupling to the lattice vibrations (phonons) also needs to be taken into consideration. A better theoretical understanding of spin decoherence in semiconductor structures is urgently needed, as electron spins in semiconductor structures have been identified as promising candidates for carriers of quantum information (qubits). Also, new structures are currently being fabricated in the laboratory for which spin decoherence has not (or not sufficiently) been studied. To model decoherence of single spins, analytical methods such as the superoperator formalism are suitable. However, as a single electron spin is coupled to an ensemble of typically 10e5 to 10e6 nuclear spins in a quantum dot, we also plan to apply numerical methods such as the time-dependent density matrix renormalization group.