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Events on Monday, August 23rd, 2021

Coherent and cavity-based measurement of two-particle states
Time: 4:00 pm
Place: Zoom link below
Speaker: Joelle Corrigan, Physics PhD Graduate Student
Abstract: With their small footprint and compatibility with industry fabrication techniques, semiconducting quantum dots have shown great potential as a platform for quantum computing.Though one of the most basic qubit implementations requires only a single electron within one quantum dot, many other platforms or readout schemes involve coupling between multiple quantum dots and differentiating between two-particle, singlet-triplet states. In silicon or Si/SiGe systems, the most basic singlet-triplet splitting depends on the valley state, which is much lower than the quantum dot’s potential-defined orbital state and can vary widely based on dot confinement and position (typically 5-40GHz). In this talk I first introduce a tunable latched readout scheme and demonstrate its use in charge-mapped readout of the quantum dot hybrid qubit. This scheme is then used to characterize a series of two-particle states using both Rabi and Ramsey pulsing, revealing 8 different transitions below 10GHz. The presence of these low energy levels is explained by considering electron-electron interactions within the system, and the data are fit using a six-level Hamiltonian. The last part of the talk will focus on a 3D integrated resonator-dot system. Driving the double-quantum-dot detuning at the cavity frequency reveals an enhanced coupling response of the cavity to the double-quantum-dot tunneling transition. This response is fit to using theory for a modulated longitudinal coupling between the dots and the cavity to good agreement. Finally, fast dc pulses are used to probe the singlet-triplet splitting in the system by populating excited states in the quantum dot. Join Zoom Meeting https://uwmadison.zoom.us/j/4083305280?pwd=LzIrOXluaEFTMVRPYWJFakVDLzNkdz09 Meeting ID: 408 330 5280 Passcode: qubit
Host: Mark Eriksson, Faculty Advisor
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