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Optical transistors can be directly linked to [[Optical fiber cable|fiber-optic cables]] whereas electronics requires coupling via [[photodetectors]] and [[LEDs]] or [[lasers]]. The more natural integration of all-optical signal processors with fiber-optics would reduce the complexity and delay in the routing and other processing of signals in optical communication networks.
It remains questionable whether optical processing can reduce the energy required to switch a single transistor to be less than that for electronic transistors. To realistically compete, transistors requiring a few tens of photons per operation are required. It is clear, however, that this is achievable in proposed single-photon transistors<ref>{{
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Perhaps the most significant advantage of optical over electronic logic is reduced power consumption. This comes from the absence of [[capacitance]] in the connections between individual [[logic gate]]s. In electronics, the transmission line needs to be charged to the [[signal voltage]]. The capacitance of a transmission line is proportional to its length and it exceeds the capacitance of the transistors in a logic gate when its length is equal to that of a single gate. The charging of transmission lines is one of the main energy losses in electronic logic. This loss is avoided in optical communication where only enough energy to switch an optical transistor at the receiving end must be transmitted down a line. This fact has played a major role in the uptake of fiber optics for long distance communication but is yet to be exploited at the microprocessor level.
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* [[electromagnetically induced transparency]]
** in an [[optical cavity]] or microresonator, where the transmission is controlled by a weaker flux of gate photons<ref>{{
** in free space, i.e., without a resonator, by addressing strongly interacting [[Rydberg state|Rydberg states]]<ref>{{
* a system of indirect [[exciton]]s (composed of bound pairs of [[electrons]] and [[electron hole|holes]] in double [[quantum well]]s with a static [[dipole moment]]). Indirect excitons, which are created by light and decay to emit light, strongly interact due to their dipole alignment.<ref>{{
* a system of microcavity polaritons ([[exciton-polaritons]] inside an [[optical microcavity]]) where, similar to exciton-based optical transistors, [[polariton]]s facilitate effective interactions between photons<ref>{{
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* [[photonic crystal]] cavities with an active Raman gain medium<ref>{{
* [[nanowire]]-based cavities employing polaritonic interactions for optical switching<ref>{{cite doi|10.1038/nnano.2012.144}}</ref>
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* silicon microrings placed in the path of an optical signal. Gate photons heat the silicon microring causing a shift in the optical resonant frequency, leading to a change in transparency at a given frequency of the optical supply.<ref>{{cite doi|10.1364/FIO.2012.FW6C.6}}</ref>
* a dual-mirror optical cavity that holds around 20,000 [[cesium]] atoms trapped by means of optical tweezers and laser-cooled to a few microkelvin. The cesium ensemble did not interact with light and was thus transparent. The length of a round trip between the cavity mirrors equaled an integer multiple of the wavelength of the incident light source, allowing the cavity to transmit the source light. Photons from the gate light field entered the cavity from the side, where each photon interacted with an additional "control" light field, changing a single atom's state to be resonant with the cavity optical field, which changing the field's resonance wavelength and blocking transmission of the source field, thereby "switching" the "device". While the changed atom remains unidentified, [[quantum interference]] allows the gate photon to be retrieved from the cesium. A single gate photon could redirect a source field containing up to two photons before the retrieval of the gate photon was impeded, above the critical threshold for a positive gain.<ref>{{
== See also ==
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