Matthew J. Farinelli

Enhanced thermoelectric cooling at cold junction interfaces

We describe a thermoelectric device structure that confines the thermal gradients and electric fields at the boundaries of the cold end, and exploits the reduction of thermal conductivity at the interfaces and the poor electron-phonon coupling at the junctions. The measured temperature–current and voltage–current characteristics of a prototype cold point-contact thermoelectric cooler based on a p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.9Se0.1 material system indicate an enhanced thermoelectric figure-of-merit ZT in the range of 1.4–1.7 at room temperature.

Quantum information storage using tunable flux qubits

We present details and results for a superconducting quantum bit (qubit) design in which a tunable flux qubit is coupled strongly to a transmission line. Quantum information storage in the transmission line is demonstrated with a dephasing time of T(2)∼ 2.5 µs. However, energy lifetimes of the qubit are found to be short (∼ 10 ns) and not consistent with predictions. Several design and material changes do not affect qubit coherence times. In order to determine the cause of these short coherence times, we fabricated standard flux qubits based on a design which was previously successfully used by others. Initial results show significantly improved coherence times, possibly implicating losses associated with the large size of our qubit.