Harvard Quantum Initiative Special Seminar

Friday, March 8

11:00 AM

Jefferson 256

Leigh Martin (Berkeley)

Quantum feedback for measurement and control

Many fundamental quantum limits arise from the inevitable disturbance caused by measurement. This disturbance imposes a barrier to precision measurement with no classical analog, but also provides a uniquely quantum mechanism for control. This talk explores both of these aspects in the context of quantum feedback. First, we discuss experimental results showing how feedback can take a measurement of phase to its fundamental limit. By continuously and adaptively changing measurement basis during readout of a single-photon signal, we enhance sensitivity over existing techniques and implement a canonical phase measurement. Second, we present theoretical methods for state control based on measurement back-action. We apply these methods to the task of entanglement generation and propose potential future experiments, including some that should be extremely robust to loss.