page_title: Quantum point contact
hierarchical_section_title: Quantum point contact
caption_attribution_description: English: Point-contact conductance as a function of gate voltage. The conductance shows plateaus.
context_page_description: A quantum point contact is a narrow constriction between two wide electrically conducting regions, of a width comparable to the electronic wavelength.
  The importance of QPC lies in the fact that they prove quantisation of ballistic conductance in mesoscopic systems. The conductance of QPC is quantized in units of, the so called conductance quantum.
  Quantum point contacts were first reported in 1988 by a Dutch team from Delft University of Technology and Philips Research and, independently, by a British team from the Cavendish Laboratory. They are based on earlier work by the British group which showed how split gates could be used to convert a two-dimensional electron gas into one-dimension, first in silicon and then in gallium arsenide
  This quantisation is reminiscent of the quantisation of the Hall conductance, but is measured in the absence of a magnetic field. The zero-field conductance quantisation and the smooth transition to the quantum Hall effect on applying a magnetic field are essentially consequences of the equipartition of current among an integer number of propagating modes in the constriction.
context_section_description: A quantum point contact (QPC) is a narrow constriction between two wide electrically conducting regions, of a width comparable to the electronic wavelength (nano- to micrometer).
  The importance of QPC lies in the fact that they prove quantisation of ballistic conductance in mesoscopic systems. The conductance of QPC is quantized in units of , the so called conductance quantum. 
  Quantum point contacts were first reported in 1988 by a Dutch team from Delft University of Technology and Philips Research (Van Wees et al. ) and, independently, by a British team from the Cavendish Laboratory (Wharam et al. ). They are based on earlier work by the British group which showed how split gates could be used to convert a two-dimensional electron gas into one-dimension, first in silicon (Dean and Pepper ) and then in gallium arsenide (Thornton et al., Berggren et al. )
  This quantisation is reminiscent of the quantisation of the Hall conductance, but is measured in the absence of a magnetic field. The zero-field conductance quantisation and the smooth transition to the quantum Hall effect on applying a magnetic field are essentially consequences of the equipartition of current among an integer number of propagating modes in the constriction.
caption: Point-contact conductance as a function of gate voltage. The conductance  shows plateaus at multiples of 
    
      
        
          
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