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CATEGORIES:Semiconductor Physics
SUMMARY:Towards a mid-infrared single photon source - Dr. 
 G.R. Nash\, Qinetiq\, Malvern\, UK
DTSTART;TZID=Europe/London:20051121T141500
DTEND;TZID=Europe/London:20051121T151500
UID:TALK4582AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/4582
DESCRIPTION:The development of true single photon sources is o
 f fundamental scientific and technological importa
 nce\, and such sources are particularly important 
 for secure communication via quantum key distribut
 ion\, or quantum cryptography.  Although modulated
  lasers have been used to successfully transmit qu
 antum keys over relatively short distances in free
  space\, it has been shown that this method of tra
 nsmission is insecure from certain types of eavesd
 ropping attack\, due to the inevitable emission of
  pulses containing more than one photon.  It is al
 so standard to modulate the source until\, on aver
 age\, each pulse contains 0.1 photons (to limit th
 e chances of two photon emission)\, which therefor
 e reduces the effective bit rate by a factor of te
 n.  The electrically driven\, surface acoustic wav
 e (SAW) single photon source\, as proposed by Fode
 n et al [Phys. Rev. A. 62\, 1803 (2000)]\, offers 
 the prospect of relatively high GHz frequency oper
 ation\, and therefore high bit-rate.  If the SAW s
 ource could be made to operate in the mid-IR\, it 
 would also offer the prospect for secure\, long di
 stance\, free space communication at wavelengths t
 hat exhibit favourable characteristics.  The funda
 mental building block of the SAW single photon sou
 rce is a lateral\, quantum well n-i-p junction\, a
 nd in this talk I will describe a novel technique 
 for the fabrication of such junctions.  Using this
  technique we have fabricated lateral n-i-p juncti
 ons in InSb/InAlSb quantum wells\, and I will desc
 ribe the progress this represents towards the chal
 lenging goal of fabricating a mid-IR single photon
  source.
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Departm
 ent of Physics
CONTACT:K DAS GUPTA
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