PhD and Post Doc Quantum Seminar Series: Spenser Talkington

This Spring semester the QUIEST Center is continuing to expand its new seminar series geared towards PhD and Post Doc students across SEAS and SAS to present on quantum-related topics of their choosing. Read on for more information on this week’s seminar presentation:

Presentation by:

Spenser Talkington, PhD student in Physics

Talk Title:

Tensor Network Approaches to Nuclear Noise in Semiconducting Qubits

Description:

Quantum devices are emerging as controllable platforms for the simulation of quantum many-body dynamics. These devices are parameterized by width (number of qubits) and depth (number of two-qubit gates executable above a specified fidelity). At present circuit depths of at most 10-100 are achievable which prevents the simulation of the long-time dynamics of highly entangled systems. As this is one of the most compelling use cases for these devices it is crucial for their utility that circuit depth increase. In semiconducting qubits the key source of error preventing reaching deeper circuits is not errors introduced during two-qubit gates but rather errors accumulated during idling in between gates. These idling errors are captured by “T2” which includes contributions from electric and magnetic fields, phonons, and spinful nuclei. Here we focus on decoherence due to nuclear spins which can dominate T2 in some devices. First we introduce the process tensor method for central spin models and then we show that magnetic noise varies strongly with nuclear polarization, suggesting that “warm up” procedures on the nuclei may reduce magnetic noise and increase T2.