Replacing Quantum Feedback with Open-Loop Control and Quantum Filtering

TL;DR

This paper presents a novel quantum control method combining open-loop control with quantum filtering, effectively overcoming feedback delay issues and achieving performance comparable to traditional feedback protocols.

Contribution

It introduces a new control approach that replaces feedback with open-loop control and filtering, expanding quantum control capabilities without delay constraints.

Findings

Achieves rapid quantum purification and measurement without feedback delays

Derives lower bounds on control performance matching feedback protocols

Demonstrates effectiveness through analytical results

Abstract

Feedback control protocols can stabilize and enhance the operation of quantum devices, however, unavoidable delays in the feedback loop adversely affect their performance. We introduce a quantum control methodology, combining open-loop control with quantum filtering, which is not constrained by feedback delays. For the problems studied (rapid purification and rapid measurement) we analytically derive lower bounds on the control performance that are comparable with the best corresponding bounds for feedback protocols.