QM Talks@CBPF: Slides online!


the last two talks at our QM Talks@CBPF were just great!

Process of parameter estimation

Bruno showed us how to obtain the minimum error in the estimation of a parameter when the dynamical process that the probe undergoes, which depends on the parameter we want to estimate, is a noisy quantum one. This was an open question for almost 30 years! Congratulations to Bruno, Ruynet, and Luiz for a great series of works in quantum metrology!
Here are the slides for Bruno’s talk: Bruno’s slides

Pablo’s talk concerned the theoretical description of the beautiful cQED experiments carried out in the group of Luis Orozco (Maryland).

Experimental setup - cQED group@Maryland

In his very didactic talk, Pablo showed us how to theoretically describe the quantum beats that were measured by Orozco’s team via the two-point correlation function. More than that, he also showed us that by post-selecting some states that leak out the cavity they can suppress the decoherence in the quantum beats. And this is not only a proposal, they measured it!
The slides for Pablo’s talk are here: Pablo’s slides

Thanks again for Bruno and Pablo for the great talks!

…And stay tuned for the next QM Talks@CBPF!


QM Talks@CBPF: Pablo B. Blostein (UNAM) — 24.07, 16h

Continuing with our series of seminars, we have Pablo B. Blostein from Universidad Nacional Autónoma de México (UNAM). He’ll show us how to control decoherence by postselection. Be sure to be there! Details below.

Notice the time change! Our QM Talks@CBPF are now 16h!!

Speaker: Pablo B. Blostein (IIMAS-UNAM)
Title: Using postselection to control ground state quantum beats in Cavity QED
Coordinates: 24.07, 16h @ CBPF Seminar room 601C
Abstract: Ground state quantum beats observed in the second order intensity correlation from a continuously driven atomic ensemble inside a two mode optical cavity are subject to a frequency shift and decoherence. While driving the cavity with light of linear polarization (π transitions) the second order autocorrelation function is measured in the undriven mode (orthogonal polarization): a first photon detection prepares a superposition of atomic ground state Zeeman sublevels and the second measures the ground state beats. Between these two detections, the atoms can become excited and return to the ground state, emitting most of the photons into modes other than the cavity modes. Depending on the drive strength this process can happen several times. Each time there is a relative phase advance between the Zeeman sublevels. The information of this phase advance and its associated decoherence is then leaked into the modes that are not the cavity modes, which form the environment. It is possible to get information about the number of photons leaked into the environment by monitoring the driven mode. Here we propose a scheme to manipulate the loss of amplitude of the beats (decoherence) and the beat frequency shift, by postselecting on the basis of information gathered through measurement of the driven cavity mode. This proposal is a new strategy compared with controlling the decoherence and light shift through turning off the driven field.