Fix some corner cases in state parsing

Author: mtfishman

src/sitetypes/qubit.jl

@@ -6,16 +6,11 @@ alias(::SiteType"SpinHalf=1/2") = SiteType"Qubit"()
 
 Base.length(::SiteType"Qubit") = 2
 
-# `eigvecs(Z)`
-# (::StateName"0", ::Tuple{SiteType"Qubit"}) = [1, 0]
-
 @state_alias "Up" "0"
 @state_alias "↑" "0"
 @state_alias "Z+" "0"
 @state_alias "Zp" "0"
 
-# (::StateName"1", ::Tuple{SiteType"Qubit"}) = [0, 1]
-
 @state_alias "↓" "1"
 @state_alias "Dn" "1"
 @state_alias "Z-" "1"

src/state.jl

@@ -53,12 +53,15 @@ end
 # one-based indexing, as opposed to `state("0") == [1, 0]`.
 stateexpr(n::Integer; kwargs...) = StateName(n; kwargs...)
 
-const DAGGER_STRING = randstring()
-const UPARROW_STRING = randstring()
-const DOWNARROW_STRING = randstring()
-const PLUS_STRING = randstring()
-const MINUS_STRING = randstring()
-const EXPR_REPLACEMENTS = (
+randcharstring() = randstring(['A':'Z'; 'a':'z'], 12)
+const DAGGER_STRING = randcharstring()
+const UPARROW_STRING = randcharstring()
+const DOWNARROW_STRING = randcharstring()
+const PLUS_STRING = randcharstring()
+const MINUS_STRING = randcharstring()
+const VERTICALBAR_STRING = randcharstring()
+const RANGLE_STRING = randcharstring()
+const EXPR_REPLACEMENTS_1 = (
   "†" => DAGGER_STRING,
   "↑" => UPARROW_STRING,
   "↓" => DOWNARROW_STRING,
@@ -67,16 +70,27 @@ const EXPR_REPLACEMENTS = (
   r"(\S)\+" => SubstitutionString("\\1$(PLUS_STRING)"),
   r"(\S)\-" => SubstitutionString("\\1$(MINUS_STRING)"),
 )
+const EXPR_REPLACEMENTS_2 = (
+  r"\|(\S*)⟩" => SubstitutionString("$(VERTICALBAR_STRING)\\1$(RANGLE_STRING)"),
+)
 const INVERSE_EXPR_REPLACEMENTS = (
   DAGGER_STRING => "†",
   UPARROW_STRING => "↑",
   DOWNARROW_STRING => "↓",
   PLUS_STRING => "+",
   MINUS_STRING => "-",
+  # We remove the bra-ket notation and search for states
+  # with names stored inside.
+  VERTICALBAR_STRING => "",
+  RANGLE_STRING => "",
 )
 
 function state_or_op_expr(ntype::Type, n::String; kwargs...)
-  n = replace(n, EXPR_REPLACEMENTS...)
+  # Do this in two rounds since for some reason
+  # one round doesn't work for expressions
+  # like `"|+⟩"`.
+  n = replace(n, EXPR_REPLACEMENTS_1...)
+  n = replace(n, EXPR_REPLACEMENTS_2...)
   depth = 1
   return state_or_op_expr(ntype, Meta.parse(n), depth; kwargs...)
 end

test/test_basics.jl

@@ -142,12 +142,6 @@ const elts = (real_elts..., complex_elts...)
       end
     end
   end
-  @testset "state" begin
-    @test state(1) == [1, 0]
-    @test state(2) == [0, 1]
-    @test state(1, 3) == [1, 0, 0]
-    @test state(2, 3) == [0, 1, 0]
-  end
   @testset "op parsing" begin
     @test Matrix(opexpr("X * Y")) == op("X") * op("Y")
     @test op("X * Y") == op("X") * op("Y")
@@ -167,4 +161,19 @@ const elts = (real_elts..., complex_elts...)
       @test op(name, SiteType("Electron")) == Matrix(OpName(name), SiteType("Electron"))
     end
   end
+  @testset "state" begin
+    @test state(1) == [1, 0]
+    @test state("0") == [1, 0]
+    @test state(2) == [0, 1]
+    @test state("1") == [0, 1]
+    @test state(1, 3) == [1, 0, 0]
+    @test state("0", 3) == [1, 0, 0]
+    @test state(2, 3) == [0, 1, 0]
+    @test state("1", 3) == [0, 1, 0]
+    @test state(3, 3) == [0, 0, 1]
+    @test state("2", 3) == [0, 0, 1]
+
+    @test state("|0⟩ + 2|+⟩") == state("0") + 2 * state("+")
+    @test state("|0⟩ ⊗ |+⟩") == kron(state("0"), state("+"))
+  end
 end