rename & add doc

README.md

@@ -12,7 +12,7 @@ Extensions for Yao.
 * variational_circuit(n): construct a random parametrized circuit.
 * heisenberg(n): construct a heisenberg hamiltonian.
 * rand_supremacy2d(nx, ny, depth): construct a quantum supremacy circuit.
-* QFTCircuit(n): construct a quantum fourier transformation circuit.
+* `QFT`(n): construct a quantum fourier transformation circuit.
 
 #### Block extensions
 * Diff: differentiable node. See [example/port_zygote](example/port_zygote.jl) as a using example.

src/block_extension/QFTBlock.jl

@@ -1,20 +1,50 @@
-export QFTBlock
+export QFT
+using YaoBlocks
+using YaoBase
+using BitBasis
+using YaoArrayRegister
+using LinearAlgebra
+using FFTW
 
-struct QFTBlock{N} <: PrimitiveBlock{N} end
-mat(::Type{T}, q::QFTBlock{N}) where {T, N} = T.(applymatrix(q))
+"""
+    QFT{N} <: PrimitiveBlock{N}
 
-apply!(reg::ArrayReg{B}, ::QFTBlock) where B = (reg.state = ifft!(invorder_firstdim(reg |> state), 1)*sqrt(1<<nactive(reg)); reg)
-apply!(reg::ArrayReg{B}, ::Daggered{N, <:QFTBlock}) where {B,N} = (reg.state = invorder_firstdim(fft!(reg|>state, 1)/sqrt(1<<nactive(reg))); reg)
+Quantum Fourier Transform node. See also [`qft_circuit`](@ref).
+"""
+struct QFT{N} <: PrimitiveBlock{N} end
+
+"""
+    qft(n)
+
+Create a Quantum Fourier Transform block. See also [`qft_circuit`](@ref).
+"""
+qft(n) = QFT{n}()
+
+mat(::Type{T}, q::QFT{N}) where {T, N} = T.(applymatrix(q))
+
+function apply!(r::ArrayReg{B}, ::QFT) where B
+    α = sqrt(1 << nactive(r))
+    invorder!(r)
+    lmul!(α, ifft!(statevec(r)))
+    return r
+end
+
+function apply!(r::ArrayReg{B}, ::Daggered{N, <:QFT}) where {B,N}
+    α = sqrt(1 << nactive(r))
+    invorder!(r)
+    lmul!(α, fft!(statevec(r)))
+    return r
+end
 
 # traits
-ishermitian(q::QFTBlock{N}) where N = N==1
-isreflexive(q::QFTBlock{N}) where N = N==1
-isunitary(q::QFTBlock{N}) where N = true
+ishermitian(q::QFT{N}) where N = N==1
+isreflexive(q::QFT{N}) where N = N==1
+isunitary(q::QFT{N}) where N = true
 
-function print_block(io::IO, pb::QFTBlock{N}) where N
-    printstyled(io, "QFT(1-$N)"; bold=true, color=:blue)
+function print_block(io::IO, pb::QFT{N}) where N
+    printstyled(io, "qft(1-$N)"; bold=true, color=:blue)
 end
 
-function print_block(io::IO, pb::Daggered{N,<:QFTBlock}) where {N, T}
-    printstyled(io, "IQFT(1-$N)"; bold=true, color=:blue)
+function print_block(io::IO, pb::Daggered{N,<:QFT}) where {N, T}
+    printstyled(io, "iqft(1-$N)"; bold=true, color=:blue)
 end

src/easybuild/QFTCircuit.jl

@@ -1,6 +1,32 @@
-using FFTW
-export QFTCircuit
+export qft_circuit
 
-CRk(i::Int, j::Int, k::Int) = control([i, ], j=>shift(2π/(1<<k)))
-CRot(n::Int, i::Int) = chain(n, i==j ? put(i=>H) : CRk(j, i, j-i+1) for j = i:n)
-QFTCircuit(n::Int) = chain(n, CRot(n, i) for i = 1:n)
+"""
+    cphase(i, j, k)
+
+Control phase gate.
+"""
+cphase(i::Int, j::Int, k::Int) = control(i, j=>shift(2π/(1<<k)))
+hcphases(n::Int, i::Int) = chain(n, i==j ? put(i=>H) : cphase(j, i, j-i+1) for j = i:n)
+
+"""
+    qft_circuit(n)
+
+Create a Quantum Fourer Transform circuit. See also [`QFT`](@ref).
+"""
+qft_circuit(n::Int) = chain(n, hcphases(n, i) for i = 1:n)
+
+qft(l, n) = l == n ? H : chain(
+    chain(n, l==j ? put(l=>H) : cphase(j, l, j-l+1) for j = l:n),
+    qft(l-1, n)
+)
+
+function qft(l, n)
+    if l == n
+        return put(n, l=>H)
+    else
+        return chain(
+            chain(n, l==j ? put(l=>H) : cphase(j, l, j-l+1) for j = l:n),
+            qft(l+1, n)
+        )
+    end
+end

src/easybuild/openbox.jl

@@ -5,8 +5,8 @@ export openbox
 
 For a black box, like QFTBlock, you can get its white box (faithful simulation) using this function.
 """
-openbox(q::QFTBlock{N}) where N = QFTCircuit(N)
-openbox(q::Daggered{<:QFTBlock, N}) where {N} = QFTCircuit(N)'
+openbox(q::QFT{N}) where N = qft_circuit(N)
+openbox(q::Daggered{<:QFT, N}) where {N} = qft_circuit(N)'
 
 function openbox(fs::FSimGate)
     if fs.theta ≈ π/2

test/block_extension/QFTBlock.jl

@@ -7,12 +7,12 @@ using FFTW
 
 @testset "QFT" begin
     num_bit = 5
-    fftblock = QFTCircuit(num_bit)
+    fftblock = qft_circuit(num_bit)
     ifftblock = fftblock'
     reg = rand_state(num_bit)
     rv = copy(statevec(reg))
 
-    @test Matrix(mat(chain(3, QFTCircuit(3) |> adjoint, QFTCircuit(3)))) ≈ IMatrix(1<<3)
+    @test Matrix(mat(chain(3, qft_circuit(3) |> adjoint, qft_circuit(3)))) ≈ IMatrix(1<<3)
 
     # test ifft
     reg1 = apply!(copy(reg), ifftblock)
@@ -28,24 +28,24 @@ using FFTW
 end
 
 
-@testset "QFTBlock" begin
+@testset "QFT" begin
     num_bit = 5
-    qft = QFTCircuit(num_bit)
+    qft = qft_circuit(num_bit)
     iqft = adjoint(qft)
-    qftblock = QFTBlock{num_bit}()
-    iqftblock = QFTBlock{num_bit}() |> adjoint
+    qftblock = QFT{num_bit}()
+    iqftblock = QFT{num_bit}() |> adjoint
     @test openbox(qftblock) == qft
     @test openbox(iqftblock) == iqft
     reg = rand_state(num_bit)
 
-    @test Matrix(mat(chain(3, QFTBlock{3}() |> adjoint, QFTBlock{3}()))) ≈ IMatrix(1<<3)
+    @test Matrix(mat(chain(3, QFT{3}() |> adjoint, QFT{3}()))) ≈ IMatrix(1<<3)
 
     # permute lines (Manually)
-    @test apply!(copy(reg), iqft) ≈ apply!(copy(reg), QFTBlock{num_bit}() |> adjoint)
+    @test apply!(copy(reg), iqft) ≈ apply!(copy(reg), QFT{num_bit}() |> adjoint)
 
     # test fft
     @test apply!(copy(reg), qft) ≈ apply!(copy(reg), qftblock)
 
     # regression test for nactive
-    @test apply!(focus!(copy(reg), 1:3), QFTBlock{3}()) |> isnormalized
+    @test apply!(focus!(copy(reg), 1:3), QFT{3}()) |> isnormalized
 end