Coupling Between Quantum Dot Qubits And A Superconducting Microwave Resonator PDF Download

Quantum computing has the potential to achieve better scaling for factoring large numbers, simulating quantum behavior of molecules, and sampling random number distributions. Quantum dot qubits in silicon show strong promise as a qubit platform due to the long decoherence times measured as well as the possibility of leveraging techniques from classical processor fabrication towards scaling to large qubit systems. We examine coupling quantum dot qubits to a superconducting coplanar waveguide, which functions as a single-photon resonator, and this system enables coherent communications between qubit systems. We are concerned with both the hardware and low-level software of quantum computation. We examine geometric modifications to the heterostructure and the electrode geometry to boost the capacitive coupling between a triple dot system and a resonator. We find decreasing the vertical separation between the electrode connected to the resonator and the dots has a positive impact on the coupling strength. Continuing hardware simulations, we consider the issue of low device yield in Si-MOS devices, where despite large singlet-triplet splittings, there was no evidence of Pauli spin blockade. We attributed this to impurities within the oxide and performed a series of simulations that allowed us to determine the required impurity density to lift spin blockade, and found this density consistent with the device yield. Switching to considering different qubit encodings, we compared and contrasted the behavior of three qubits that are resonantly coupled to a superconducting resonator. The three encodings were the charge dipole (CD) qubit, the charge quadrupole (CQ) qubit, and the quantum dot hybrid qubit (QDHQ). In terms of entangling a one photon state with a qubit state, the CD qubit and the CQ qubit behaved similarly, however the CQ qubit does allow arbitrary single qubit gates while being protected from quasistatic charge noise. The QDHQ exhibited better performance (measured by infidelity) when operated at a second-order-sweet spot than both other encodings in the typical charge noise regime. Furthermore, the quantum dot hybrid qubit enables multiple operating points, offering greater tuning flexibility when considering implementation in actual devices.