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SUMMARY:Towards a mid-infrared single photon source - Dr. G.R. Nash\, Qine
 tiq\, Malvern\, UK
DTSTART:20051121T141500Z
DTEND:20051121T151500Z
UID:TALK4582@talks.cam.ac.uk
CONTACT:K DAS GUPTA
DESCRIPTION:The development of true single photon sources is of fundamenta
 l scientific and technological importance\, and such sources are particula
 rly important for secure communication via quantum key distribution\, or q
 uantum cryptography.  Although modulated lasers have been used to successf
 ully transmit quantum keys over relatively short distances in free space\,
  it has been shown that this method of transmission is insecure from certa
 in types of eavesdropping attack\, due to the inevitable emission of pulse
 s containing more than one photon.  It is also standard to modulate the so
 urce until\, on average\, each pulse contains 0.1 photons (to limit the ch
 ances of two photon emission)\, which therefore reduces the effective bit 
 rate by a factor of ten.  The electrically driven\, surface acoustic wave 
 (SAW) single photon source\, as proposed by Foden 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 source could be made to o
 perate in the mid-IR\, it would also offer the prospect for secure\, long 
 distance\, free space communication at wavelengths that exhibit favourable
  characteristics.  The fundamental building block of the SAW single photon
  source is a lateral\, quantum well n-i-p junction\, and in this talk I wi
 ll describe a novel technique for the fabrication of such junctions.  Usin
 g this technique we have fabricated lateral n-i-p junctions in InSb/InAlSb
  quantum wells\, and I will describe the progress this represents towards 
 the challenging goal of fabricating a mid-IR single photon source.
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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