Gupta/Bleuler Quantization Method

• Four modes of transmission:
  1. Two transverse waves.
  2. One longitudinal wave.
  3. One scalar wave.
  
  
• Transverse waves are photons for EM.
  
  
• The supplementary condition is imposed to eliminate scalar and longitudinal modes for photons as real particles. There can be no scalar or longitudinal modes for a spin 1 4D wave field.