Single Photon Transistor

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Introduction to Single Photon Transistor

Surface plasmons

Nanowires

The concept of emitter atom SPT as a switch

Nanotip for storing photon

Limitations of nanowires

Advantages

Applications

Conclusion


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Single Photon transistor is an optical transistor .

Propagation of the signal is controlled by the presence or

absence of a Single Photon.

The propagating signal is another Photon or a flow of

Photons itself.

Photons rarely interact with each other. Any possibleinteraction will be very weak at a single Photon level.

Converting photons to charges in the form of surface

plasmons will strengthen the interactions between Photons.


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The word plasmon means charges.

Surface plasmons form at a metal-dielectric interface.

When stream of photons are applied to the interface , field

associated with Photons polarizes the interface by inducing

charges.

The opposite charges align at the interface to form a waveof density that propagate along the metal-dielectric interface.


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WHY NANOWIRES ??? Surface plasmons do not interact well with optical fibers.

A possible solution is using conducting metal nanowires.


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Typical nanowires has diameters less

than 100nm.

Metallic nanowires with diameters of

40 - 60nms can be used for guidingsurface plasmons.

Nanowire acts as the metal and the

air surrounding the nanowire acts asdielectric.


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EMITTER ATOM for inducing INTERACTION

Surface plasmons cannot be made to hit each other.

Use an emitter atom as anintermediary.

Photons are shot at the atomusing nanowires.

When they hit the atom an interaction occurs between thephotons.

One Photon imparts information to the other Photon.


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Emitter atom can achieve two

energy levels;

ground(|g>) and excited(|e>).

State g

The reflection coefficient isapproximately,

r=-1(1-1/p)

P= Purcell factor

state eemitter will act like an open gate.

TWO LEVEL EMITTER


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The system is initialized in state g.Then a control pulse is sent(may or may not have a photon)

If there was a photon present, the emitter will undergo a spin slip

from g to s, and remain unchanged otherwise..

Transistor is OFF when there is no external photon,and it is ON when single photon is present in theincoming field.

continued


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Nanotip is a nanowire tapered at the end.

Single photon travels from one end of nanotip toemitter atom at the tapered end.

Emitter is located along the z-axis of the nanotip.

NANOTIP FOR STORING SINGLE PHOTON

SPTNanotip


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Long way efficient transportation is not possible

Amplitude reduction

Reduced clarity of surface plasmons

Photons can effectively propagate through waveguides.

Wave guide transfers photons to nanowires only atthe emitter .


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DielectricNanowire Interfacing:


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Work on broad range of frequencies of light

Easy to fabricate

Reduced size

Very efficient


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Optical computers

Optical communications

Photon detectors


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The operation of the SPT is controlled by a single

external photon stored in a nanotip.

The flow of signal Photons through a nanowire can be

controlled by changing the internal state of emitter atom

assisted by a control field.

A new world of optical circuits can be produced using SPT.


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http://www.spectrum.ieee.org/aug07/5497Scheme for a Single-Photon Transistorbysaswato das // august 2007

www.nature.com/naturephysics

Nature Physics Vol 3 November 2007

A single-photon transistor using nanoscale

surface plasmons

Darrick E. Chang, Anders S. Srensen, Eugene A.Demler and Mikhail D. Lukin

www.springerlink.com/index/U5L25Q114741QP2V.pdf


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Single Photon Transistor

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