Definition of a new bosonic state

ITensor Julia Questions
4

Hi Yotam,

I don’t think you need to pass alpha explicitly because its a variable in the function D. I ran a quick test

using ITensors

let
  N = 2 # number of bosons
  d = 5 # local oscillator cutoff dimension
  sites = siteinds("Boson", N; dim=d); # create the site indices for MPS representation
  α = 0.01 # the coherent state's parameter
  a_op(d) = diagm(1 => [sqrt(i) for i in 1:(d-1)]) # annihilation operator
  D(α, d) = exp(α*a_op(d)'-α'*a_op(d)) # matrix elements of the displacement operator
  function ITensors.state(::StateName"coherent", ::SiteType"Boson", s::Index) 
    @show α
    D(α, dim(s))*[if n==1 1 else 0 end for n=1:dim(s)]
  end
  ψ₀ = MPS(sites, "coherent")
  println("Finished with ψ₀")
  α = 0.2
  ϕ = MPS(sites, "coherent")
  println("Finished with ϕ")
  return
end

and see this as the output

α = 0.01
α = 0.01
Finished with ψ₀
α = 0.2
α = 0.2
Finished with ϕ
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