IQIM Postdoctoral and Graduate Student Seminar

Note the location for this week: 105 Annenberg

Abstract: While the detection in most quantum experimental platforms is noisy and imperfect , the general tools and bounds in quantum metrology assume perfect measurements. In this talk I will present our attempts to derive a theory for quantum metrology with general measurements. We generalize the notion of the quantum Fisher information (QFI) to account for arbitrary detection channels. We find the general form of this imperfect QFI for pure states, we prove that for pure states the optimal control is unitary and derive its general form. We then consider quantum states in a multi-partite system with local detection channels and study the asymptotic behavior of the sensitivity. Interestingly, the achievable sensitivity depends crucially on the allowed control operations. Given local optimal control, the QFI is not attainable and any quantum enhancement is limited to a constant factor. On the other hand, with optimal global control the QFI is always attainable for a generic class of quantum states (including all pure states and symmetric states). Based on https://arxiv.org/abs/2109.01160, https://arxiv.org/abs/2210.11393.

Lunch will be provided, following the talk, on the lawn on the East side of the Annenberg Building

Attendees joining in person must demonstrate that they comply with Caltech's vaccination requirements (present Caltech ID or AWS ID or vaccination and booster confirmation).