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SUMMARY:Measurement and control of electron wavepackets from a single-elec
 tron source (SP Workshop) - Miss Joanna Waldie\, University of Cambridge\,
  Semiconductor Physics Group
DTSTART:20150729T131500Z
DTEND:20150729T141500Z
UID:TALK59559@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:Circuits that can perform triggered emission\, coherent contro
 l and sensitive detection of single electrons are highly desirable for qua
 ntum information processing [1] and studies of the fermionic quantum prope
 rties of electrons\, such as single-electron analogs of quantum optics [2]
 . Semiconductor single-electron pumps [3] are a promising source of single
  electrons ``on demand'' for use in these single-electron circuits. For th
 ese applications it is important to understand and control the properties 
 of the emitted electrons. Here we study the time and energy distributions 
 of single-electrons and pairs of electrons emitted by a semiconductor tuna
 ble-barrier quantum-dot electron pump. Single electrons emitted by the pum
 p are guided by edge states to an energy-selective detector barrier [4]. B
 y controlling the barrier transparency on picosecond timescales\, we image
  the electron wavepackets in the time and energy domain\, with a temporal 
 resolution of 30 ps. Using an arbitrary waveform generator (AWG)\, we stud
 y the link between the electron time and energy distributions and the shap
 e of the rf waveform driving the pump. We find that the digital nature of 
 the AWG waveform gives rise to distinct features in the electron energy di
 stribution\, which we use to develop a tunnelling model of the electron em
 ission process [5] and to pin-point the electron emission time within the 
 pumping cycle. Using these insights\, we show that by engineering the pump
  drive waveform we can manipulate the electron wavepackets\, using the exa
 mple of controlling the time and energy difference between a pair of elect
 rons. This technique could be particularly useful when combined with studi
 es of the electron partitioning noise [6]\, to determine the origins of co
 rrelations between the pumped electrons.\n\n[1] D. Loss and D.P. DiVincenz
 o\, Phys. Rev. A 57\, 120 (1998).\n\n[2] E. Boquillon et al\, Phys. Rev. L
 ett. 108\, 196803 (2012).\n\n[3] M.D. Blumenthal et al\, Nature Physics 3\
 , 343 (2007).\n\n[4] J.D. Fletcher et al\, Phys. Rev. B 111\, 216807 (2013
 ).\n\n[5] V. Kashcheyevs and B. Kaestner\, Phys. Rev. Lett. 104\, 186805 (
 2010).\n\n[6] N. Ubbelohde et al\, Nat. Nano. 10\, 46 (2015).\n
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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