Protocol for the transfer of a quantum state from a photonic qubit to a gate-defi ned quantum dot

Mr Benjamin Joecker
4pm Thursday 16 February 2017
CQC2T Conference Room Level 2, Newton Building, UNSW

An interface between a well-functioning, scalable stationary and a photonic qubit could substantially advance quantum communication applications and serve as an interconnect between future quantum processors. Qubits consisting of gate-defi ned quantum dots in GaAs are electrically controllable with high delity, whereas qubits that can realize bound exciton states are established as an optical interface. Here, I present a protocol to transfer the state of a photonic qubit to a gate-defined quantum dot single-spin qubit as well as to a two-spin qubit. We use eff ective Hamiltonians to model the gate-de fined quantum dots tunnel-coupled to the optically addressable exciton state. The two general steps of the transfer protocol are creation of a bound exciton state followed by adiabatic tunneling to gate-de fined quantum dot. In the case of the singlet-triplet qubit the protocol furthermore involves resonantly driven transitions. I apply simple but realistic noise models to analyze the viability of the derived protocols taking into account optical coupling, the adiabatic transfer condition, the influence of recombination, the decoherence due to charge and nuclear spin noise as well as the resonant driving. As an example I discuss the performance of a self-assembled quantum dot as the optical interface. Using experimental parameters, the protocols can generally be completed within the coherence time with a fi delity above 95% in the case of the two-spin qubit.