in nineteen fifty six hand bring brands standard the scientific community when he reported the
photons emitted by serious the brightest or in the night sky had a tendency to
write together in client on these detectors
that is to say unlike cars on the highway or people passing by or any
other randomly distributed classical objects whose time of arrival would be recorded like this
and bring brian and is mathematician calling twist find out the photons from a thermal
source are detected like this actually more like london buses
there is a way to have photons arrive like cars or people one can use
a laser instead of a chaotic source
the first type information comes from single photon images like a quantum dot the produce
false ones which avoid each other
the lower proposed a consequence g two defined as shown here to describe these situations
g two is equal to one for uncorrelated events
it is greater than one for circle bunching events where photons are clustered it is
more than one ideally zero for so called anti bunching events when photons avoid each
other
for instance one can compute g two from the lighting dated by a quantum dots
in the micro cavity just the following spectral lines right one would find a value
close to zero as the emission is anti bunch this is when detecting we'll phones
on from the system
but what if we select only those in this frequency window is that each to
the same as when detecting at all frequencies one can also correlate photons from two
frequency windows experimentally this is an easy thing to accomplish one million supposes the filter
before catching forms ones
theoretically however such questions are extremely difficult to resolve despite the best efforts of yours
since the links nineteen seventies only the force of heavy algebra and various approximations will
be you results and then only for particular cases of simple systems
in physical review letters we have recently presented a way around this obstacle and show
how to readily computed g n of frequency filtered photons with no restriction whatsoever on
the number of phones or on the type of system
in the new journal of physics we apply this formalism to a wide class of
fundamental quantum images for the case of two phones what coincidences
in this short movie we will show some of the results for the case already
discussed of a two level image or in the cavity
this is the spectral shape again and we're going to present correlations of photons at
all frequencies
this is the results we call this a two photons spectrum
in blue of the anti bunching correlations in white photons are uncorrelated in read their
batch
that is nigh bring our system into strong coupling by making the cavity of better
quality this results in a so-called robbie tablet we see that in the two photons
spectrum new patterns of here when the photon lifetime is very long an incredibly rich
landscape of correlations emerges
to give a qualitative idea of the most important features that just bring in the
level structure of the system the so-called jane's cummings latter horizontal and vertical patterns are
accounted for by successive emissions between this study
this cascade is bunched this sequence on the other hand or this one or anti
but as the system has to change its internal state to shift levels in this
way
more perplexing are these features and also these
let us consider the anti diagonals that correspond to direct two photon emission this relaxes
energy conservation since only the sum of the energies is fixed as the intermediate level
is skipped over we call this type of two photon emission a leap from prior
to photon emission is difficult to observe in general
we shall have to reveal it and make it obvious
there are countless configurations to revisit with this novel technique for instance this shows how
the correlations remap when the quantum dot is teaching from the cavity
and this shows what happens when increasing the pumping right
we illustrate our last example with an important remark while a perfect detector resolution can
be assumed for single photon spectra the filters line width is an integral part of
frequency result photon counting to narrow filters give true results
well blue ones are the features as shown here
and of course in the limit a very broad filters the conventional results of hand
brown and twist is recovered the study of we'll the other frequency ranges is josh
at its beginning