, , , ,

Difference between revisions of "Activities"

From Camilo's web
Jump to: navigation, search
Mountain View
m
 
(4 intermediate revisions by the same user not shown)
Line 7: Line 7:
More specifically, my interest is in the development and application of strongly correlated light, which are the building blocks of technological applications such as quantum spectroscopy, novel sources of quantum light (lying beyond the classical description).  
More specifically, my interest is in the development and application of strongly correlated light, which are the building blocks of technological applications such as quantum spectroscopy, novel sources of quantum light (lying beyond the classical description).  


== Emitter of quantum light ==
== Emitters of quantum light ==


The concept of ''quantum light'' rises from the counterposition to the ''classical light''. While the latter is well described by the classical theory of electromagnetism, i.e.,  the theory formalized by Maxwell, the former is not. In fact, quantum light has properties that are not predicted and cannot be described with the classical theory. Perhaps the most important of them is the capability of quantum light to display the so-called ''antibunching'', which is related to the way in which photons in a beam are separated in time. A laser (which is a classical source of light) emits its photons in a random way, which means that once a photon is emitted, we have no idea when the next one might come: it could follow immediately, or it can be emitted a very long time afterward. Such a random behaviour is well described through a Poisson distribution of the emission times. On the other hand, sources of quantum light are able to emit their photons in a more organized way, namely, the emission of a photon gives us some information about the time at which the next photon will be emitted. Thus, when the photons emitted by a quantum source are more separated from each other than they would if they had been emitted by a laser, we say that these photons are antibunched.


Using quantum emitters to excite optical targets opens an infinitude of possibilities and new behaviors, as the excitation itself brings to the target a quantumness, which otherwise had to rise from the internal dynamics of the driven object. Furthermore, the correlations between the photons (the way in which the photons are organized in time) can be exploited to unveil the internal structure of the driven system, thus allowing the development of quantum spectroscopic techniques.


== Polaritons ==
== Polaritons ==


Exciton-polaritons (or simply polaritons) are pseudo-particles arising from the strong coupling between a photon and an exciton (an electron-hole pair), which live confined in two dimensions inside a semiconductor microcavity. Polaritons inherit properties from their constituent particles, such as the lightweight from its photonic component and the interacting character from the excitonic counterpart. As such, polaritons can be thought of as interacting photons on which quantum information can be encoded, and which can be transported along great distances. Besides, their high-efficiency operation takes place in the micrometer scale, which place them as an interesting platform to develop quantum technologies.


== Coronavirus ==
<!--
==Outreach==


 
* Quanta Magazine: You can pitch ideas by filling this [https://www.quantamagazine.org/contact-us/ form].
Using the data that the UK goverment is making [https://www.arcgis.com/apps/opsdashboard/index.html#/f94c3c90da5b4e9f9a0b19484dd4bb14 available], updating it on a daily basis, one can fit the number of cases (of both infected people in different regions and of deaths across the island) $n(t)$ as a simple equation
* Scientific American: The submission guidelines are [https://www.scientificamerican.com/page/submission-instructions/ here].
\begin{equation*}
* Wired: You can pitch ideas by sending an email to submit@wired.com.
n(t) = n_0 \,\chi^t\,,
-->
\end{equation*}
where $t$ is the time in units of days and&nbsp;$n_0$ is the number of cases at ''day 1'', which is defined as the day where the first deaths were reported (we started with six deaths on March 10$^\mathrm{th}$), and&nbsp;$\chi$ is the rate at which the cases increase from day to day, namely&nbsp;$n(t+1) = \chi n(t)$.
 
====Early stage====
 
At the early stage of the outbreak, while the government was still trying to tackle the pandemia with the so-called [https://en.wikipedia.org/wiki/Herd_immunity ''herd immunity''], which in practical terms it means that no action was taken, and the contagions was left free to propagate. This measure was in the opposite direction that Europe was taking, where the mobility restrictions were starting to appear. At this early stage, the evolution of the cases was as shown in the figure below, which is shown in logarithmic scale:
<wz tip="Early stage of the pandemia in the UK">[[File:Covid-UK-early.png|600px|center|Early stage of the pandemia in the UK.|link=]]</wz>
The open circles represent the data and the dashed lines correspond to the Eq.&nbsp;(1) with the following parameters:
 
{| class="wikitable" style="margin: auto; text-align: center;"
|
|$n_0$
|$\chi$
|-
|'''Wolverhampton'''
|2.55
|1.31
|-
|'''Birmingham'''
|1.36
|1.44
|-
|'''London'''
|86.96
|1.34
|-
|'''England'''
|315.25
|1.27
|-
|'''Deaths in the UK'''
|7.14
|1.39
|}
 
which means that at this stage the rate of contagion in the three cities above was larger than the average of the entire county. The case of London can be understood in terms of a multicultural city that serves as the connection from and to Europe, seeing thousands of passengers per day; and also to the high density of population. Birmingham is the second largest urban center of England, and Wolverhampton is very close to it, also with a high-density of population.
 
====Social distancing====
 
On March 24$^\mathrm{th}$ (which is Day 15 since the start of the data) the Prime Minister Boris Johnson announced that people should remain in their houses, and only get out in four exceptional cases: i) buying essential groceries, ii) getting medical attention, iii) going to work (provided that you are an essential worker) and iv) to do one form of exercise. However, due to the incubation period of the virus, which is though to be around 10 to 15 days, the social distancing measures had to be implemented for an extended period of time.  
 
'''3$^\mathrm{rd}$ of April''': As of today the updated figure for the cases is the following:
<wz tip="Two weeks of social distancing.">[[File:Covid-UK-social-distancing.png|600px|center|Two weeks of social distancing.|link=]]</wz>
where we see that the slope of all the curves are reduce more or less on day 11 (20$^\mathrm{th}$ of March). It is suspicious that the change happens all across the cities at the same time: maybe different ways to measure the confirmed cases (and also the causes of the deaths) were introduce, or maybe people started self-isolating (even before it was imposed by the government). Regardless of the motive for the change, the curves are following these parameters:
 
{| class="wikitable" style="margin: auto; text-align: center;"
|
|$n_0$
|$\chi$
|-
|'''Wolverhampton'''
|14.73
|1.12
|-
|'''Birmingham'''
|18.64
|1.17
|-
|'''London'''
|463.51
|1.13
|-
|'''England'''
|515.21
|1.19
|-
|'''Deaths in the UK'''
|13.25
|1.25
|}
 
for which now the really relevant parameters is&nbsp;$\chi$. It seems alarming that the rate of contagion in Birmingham is larger than in London. Wolverhampton, on the other hand, remains growing at a rate a 6.25% lower than the national average. Note that the number of confirmed cases at day 24 (April 2), which is clearly above the fitting line, corresponds to 12 days after Mother's Day in the UK. At this point the number of deaths double every 3 days and triples every 5: unless we see something changing drastically during the weekend, UK will reach 10000 deaths on Wednesday next week.
 
It is also interesting to see the ratio between the number of deaths to the total number of confirmed cases. The figure is shown below
<wz tip="Ratio of deaths to confirmed cases.">[[File:Covid-UK-deaths.png|480px|center|Ratio of deaths to confirmed cases.|link=]]</wz>
which indicates that the rate of death after 25 days is of 10%. Such a high rate might be inflated by the fact that UK is only testing patients at hospital when the test is ''the difference between a diagnosis that can save them'', which means that the confirmed cases are only those that got sick enough to require medical attention (which supposedly only a fraction of all the people).

Latest revision as of 12:11, 11 July 2020


Research Fields

I study the interaction of light with matter.

More specifically, my interest is in the development and application of strongly correlated light, which are the building blocks of technological applications such as quantum spectroscopy, novel sources of quantum light (lying beyond the classical description).

Emitters of quantum light

The concept of quantum light rises from the counterposition to the classical light. While the latter is well described by the classical theory of electromagnetism, i.e.,  the theory formalized by Maxwell, the former is not. In fact, quantum light has properties that are not predicted and cannot be described with the classical theory. Perhaps the most important of them is the capability of quantum light to display the so-called antibunching, which is related to the way in which photons in a beam are separated in time. A laser (which is a classical source of light) emits its photons in a random way, which means that once a photon is emitted, we have no idea when the next one might come: it could follow immediately, or it can be emitted a very long time afterward. Such a random behaviour is well described through a Poisson distribution of the emission times. On the other hand, sources of quantum light are able to emit their photons in a more organized way, namely, the emission of a photon gives us some information about the time at which the next photon will be emitted. Thus, when the photons emitted by a quantum source are more separated from each other than they would if they had been emitted by a laser, we say that these photons are antibunched.

Using quantum emitters to excite optical targets opens an infinitude of possibilities and new behaviors, as the excitation itself brings to the target a quantumness, which otherwise had to rise from the internal dynamics of the driven object. Furthermore, the correlations between the photons (the way in which the photons are organized in time) can be exploited to unveil the internal structure of the driven system, thus allowing the development of quantum spectroscopic techniques.

Polaritons

Exciton-polaritons (or simply polaritons) are pseudo-particles arising from the strong coupling between a photon and an exciton (an electron-hole pair), which live confined in two dimensions inside a semiconductor microcavity. Polaritons inherit properties from their constituent particles, such as the lightweight from its photonic component and the interacting character from the excitonic counterpart. As such, polaritons can be thought of as interacting photons on which quantum information can be encoded, and which can be transported along great distances. Besides, their high-efficiency operation takes place in the micrometer scale, which place them as an interesting platform to develop quantum technologies.


Retrieved from "http://camilopez.org/mediawiki-1.37.2/index.php?title=Activities&oldid=2029"