random_pauli had a method that disregards error probability and had w…

…rong defaults (#257)
QuantumSavory · Apr 10, 2024 · 64f695c · 64f695c · Krastanov · Apr 10, 2024
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,7 +5,11 @@
 
 # News
 
-## v0.9.3 - 2024-04-08
+## v0.9.3 - 2024-04-10
+
+- **(fix)** One of `random_pauli`'s methods was disregarding the error probability and had incorrect kwarg defaults.
+
+## v0.9.2 - 2024-04-08
 
 - The ECC module now has access to an iterative bitflip decoder thanks to `LDPCDecoders.jl`.
 - Provide more configuration options in the `PyBeliefProp` decoders.

diff --git a/Project.toml b/Project.toml
@@ -1,7 +1,7 @@
 name = "QuantumClifford"
 uuid = "0525e862-1e90-11e9-3e4d-1b39d7109de1"
 authors = ["Stefan Krastanov <stefan@krastanov.org> and QuantumSavory community members"]
-version = "0.9.2"
+version = "0.9.3"
 
 [deps]
 Combinatorics = "861a8166-3701-5b0c-9a16-15d98fcdc6aa"

diff --git a/src/randoms.jl b/src/randoms.jl
@@ -30,7 +30,7 @@ function random_pauli!(rng::AbstractRNG, P::PauliOperator; nophase=true, realpha
  P
 end
 random_pauli!(P::PauliOperator; kwargs...) = random_pauli!(GLOBAL_RNG,P; kwargs...)
-function random_pauli!(rng::AbstractRNG,P::PauliOperator,p; nophase=false, realphase=false)
+function random_pauli!(rng::AbstractRNG,P::PauliOperator,p; nophase=true, realphase=true)
  n = nqubits(P)
  p = p/3
  for i in 1:n
@@ -44,7 +44,7 @@ random_pauli!(P::PauliOperator, p; kwargs...) = random_pauli!(GLOBAL_RNG,P,p; kw
 
 random_pauli(rng::AbstractRNG,n::Int; kwargs...) = random_pauli!(rng, zero(PauliOperator, n); kwargs...)
 random_pauli(n::Int; kwargs...) = random_pauli(GLOBAL_RNG, n; kwargs...)
-random_pauli(rng::AbstractRNG,n::Int,p; kwargs...) = random_pauli!(rng, zero(PauliOperator, n); kwargs...)
+random_pauli(rng::AbstractRNG,n::Int,p; kwargs...) = random_pauli!(rng, zero(PauliOperator, n),p; kwargs...)
 random_pauli(n::Int, p; kwargs...) = random_pauli(GLOBAL_RNG,n,p; kwargs...)
 
 ##############################

diff --git a/test/test_random.jl b/test/test_random.jl
@@ -1,4 +1,5 @@
 using QuantumClifford
+using Test
 
 using QuantumClifford: stab_looks_good, destab_looks_good, mixed_stab_looks_good, mixed_destab_looks_good
 
@@ -31,3 +32,27 @@ test_sizes = [1,2,10,63,64,65,127,128,129] # Including sizes that would test off
  @test mixed_destab_looks_good(apply!(ms,sq,phases=false))
  end
 end
+
+@testset "Random Paulis" begin
+ for n in [1, test_sizes..., 200,500]
+ @test all((random_pauli(n).phase[] == 0 for _ in 1:100))
+ @test all((random_pauli(n, 0.1).phase[] == 0 for _ in 1:100))
+ @test any((random_pauli(n; nophase=false, realphase=false).phase[] == 1 for _ in 1:100))
+ @test any((random_pauli(n, 0.1; nophase=false, realphase=false).phase[] == 1 for _ in 1:100))
+ @test any((random_pauli(n; nophase=false).phase[] ∈ [0,2] for _ in 1:100))
+ @test any((random_pauli(n, 0.1; nophase=false).phase[] ∈ [0,2] for _ in 1:100))
+ end
+ for i in 1:10
+ e = 0.2
+ n = 10000
+ expected = 2/3*e * 2 * n
+ bound = 1/sqrt(n)
+ @test expected * (1-10bound) <= sum(count_ones.(random_pauli(10000,0.2).xz)) <= expected * (1+10bound)
+ e = 0.75
+ n = 10000
+ expected = 2/3*e * 2 * n
+ bound = 1/sqrt(n)
+ @test expected * (1-10bound) <= sum(count_ones.(random_pauli(10000).xz)) <= expected * (1+10bound)
+
+ end
+end