new pswap instruct (#22)

src/instruct.jl

@@ -398,3 +398,29 @@ function YaoBase.instruct!(
     end
     return state
 end
+
+function YaoBase.instruct!(
+        state::AbstractVecOrMat{T},
+        ::Val{:PSWAP},
+        locs::Tuple{Int, Int},
+        theta::Real) where T
+    mask1 = bmask(locs[1])
+    mask2 = bmask(locs[2])
+    mask12 = mask1|mask2
+    a = T(cos(theta/2))
+    c = T(-im * sin(theta/2))
+    e = T(exp(-im/2*theta))
+    for b in basis(state)
+        if b&mask1==0
+            i = b+1
+            i_ = b ⊻ mask12 + 1
+            if b&mask2==mask2
+                u1rows!(state, i, i_, a, c, c, a)
+            else
+                mulrow!(state, i, e)
+                mulrow!(state, i_, e)
+            end
+        end
+    end
+    return state
+end

test/instruct.jl

@@ -91,6 +91,12 @@ end
     @test instruct!(copy(ST), Val(:SWAP), (1, 2)) ≈ SWAP * ST
 end
 
+@testset "pswap instruction" begin
+    ST = randn(ComplexF64, 1 << 2)
+    θ = π/3
+    @test instruct!(copy(ST), Val(:PSWAP), (1, 2), θ) ≈ (cos(θ/2)*IMatrix{4}() - im*sin(θ/2)* SWAP) * ST
+end
+
 @testset "Yao.jl/#189" begin
     st = rand(1<<4)
     @test instruct!(st, IMatrix{2, Float64}(), 1) == st