Two-photon spectra of quantum emitters
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| Number of Parts | 63 | |
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| License | CC Attribution 3.0 Unported: You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
| Identifiers | 10.5446/39052 (DOI) | |
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00:00
QuantumParticle physicsPlain bearingVideoElectric power distributionPhotonCartridge (firearms)Beam emittanceOptical cavityEmissionsvermögenPhotonicsAudio frequencyAstronomisches FensterTypesettingShip classSpectral lineLaserQuantumSource (album)Hose couplingSingle (music)Railroad carPhotonBusFundamental frequencySensorVisible spectrumForceStarNightSkyAntiparticleWhiteEnergy levelSpeckle imagingComputer animationDiagram
03:01
Hose couplingDumpy levelEnergy levelVisible spectrumPhotonDirect currentQuality (business)AntiparticleAngeregter ZustandEnergiesparmodusOptical cavityTypesettingHose couplingEmissionsvermögenElektronenkonfigurationCrystal structureVertical integrationPattern (sewing)Social network analysisPotenzialströmungDiagram
04:16
QuantumOptical cavityDiagram
04:26
SensorDiagram
04:33
SensorFilter (optics)Audio frequencyFilter (optics)Single (music)LimiterPhotonVideoSpare partSpectral linewidthBroadbandDiagram
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Filter (optics)Diagram
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DiagramProgram flowchart
Transcript: English(auto-generated)
00:06
In 1956, Hanbury-Brown stunned the scientific community when he reported that photons emitted by Sirius, the brightest star in the night sky, had a tendency to arrive together in clumps on his detectors. That is to say, unlike cars on the highway or people
00:24
passing by or any other randomly distributed classical objects whose time of arrival would be recorded like this, Hanbury-Brown and his mathematician colleague Twiss found out that photons from a thermal source are detected like this. Actually more like London buses.
00:43
There is a way to have photons arrive like cars or people. One can use a laser instead of a chaotic source. A third type of emission comes from single photon emitters like a quantum dot that produce photons which avoid each other. Glauber proposed
01:00
a quantity called G2 defined as shown here to describe these situations. G2 is equal to 1 for uncorrelated events. It is greater than 1 for so-called bunching events where photons are cluttered. It is smaller than 1, ideally 0, for so-called anti-bunching events when photons avoid each other.
01:22
For instance, one can compute G2 from the light emitted by a quantum dot in a micro cavity which has the following spectral line shape. One would find a value close to 0 as the emission is anti-bunched. This is when detecting all photons from the system. But what if we select only those in this frequency window? Is the G2 the same as when detecting
01:42
at all frequencies? One can also correlate photons from two frequency windows. Experimentally this is an easy thing to accomplish. One merely interposes a filter before counting photons. Theoretically however, such questions are extremely difficult to resolve despite the best efforts of theorists since the late 1970s
02:03
only the force of heavy algebra and various approximations would yield 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 compute GN of frequency filtered photons with no
02:21
restriction whatsoever on the number of photons or on the type of system. In the New Journal of Physics we apply this formalism to a wide class of fundamental quantum emitters for the case of two photon coincidences. In this short movie we will show some of the results for the case already discussed of a two-level emitter in a cavity.
02:42
This is the spectral shape again and we're going to present correlations of photons at all frequencies. This is the result. We call this a two-photon spectrum. In blue are the anti-bunching correlations. In white photons are uncorrelated. In red they're bunched. Let us now bring our system into strong coupling by making
03:03
the cavity of better quality. This results in a so-called Rabi doublet. We see that in the two-photon spectrum new patterns appear. When the photon lifetime is very long an incredibly rich landscape of correlations emerges. To give a qualitative idea of the most important features
03:22
let us bring in the level structure of the system, the so-called Jaynes-Cummings ladder. Horizontal and vertical patterns are accounted for by successive emissions between the states. This cascade is bunched. This sequence on the other hand or this one are anti-bunched as the system has to change its internal state
03:42
to shift levels in this way. More perplexing are these features and also these. Let us consider the anti-diagonals. They 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
04:01
two-photon emission a leapfrog process. Two-photon emission is difficult to observe in general. We show how 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 detuned from the cavity and this shows what happens
04:24
when increasing the pumping rate. We illustrate our last example with an important remark. While a perfect detector resolution can be assumed for single-photon spectra the filter's line width is an integral part of frequency resolved photon counting. Two narrow filters give trivial results
04:44
while broad ones blur the features as shown here and of course in the limit of very broad filters the conventional result of Hanbury-Brown and twist is recovered. The study of all the other frequency ranges is just at its beginning.