From ed9979ad7cce686086bc91db7c6de537909dd540 Mon Sep 17 00:00:00 2001
From: Feroz Ahmad <93876775+Fe-r-oz@users.noreply.github.com>
Date: Thu, 18 Jul 2024 01:00:39 +0500
Subject: [PATCH] `inv` implementation for `SingleQubitOperator` (#314)

---------

Co-authored-by: Stefan Krastanov <github.acc@krastanov.org>
---
 CHANGELOG.md              |  4 ++++
 Project.toml              |  2 +-
 src/symbolic_cliffords.jl | 13 +++++++++++++
 test/test_symcliff.jl     | 14 +++++++++++++-
 4 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 18c7f5a8b..ec4e15c24 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@
 
 # News
 
+## v0.9.6 - 2024-07-12
+
+- `inv` implementation for single-qubit "symbolic" Clifford operators (subtypes of `AbstractSingleQubitOperator`).
+
 ## v0.9.5 - 2024-07-04
 
 - Implementation of random all-to-all and brickwork Clifford circuits and corresponding ECC codes.
diff --git a/Project.toml b/Project.toml
index 92a6bbb5d..2f3303f4b 100644
--- 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 = "0.9.5"
+version = "0.9.6"
 
 [deps]
 Combinatorics = "861a8166-3701-5b0c-9a16-15d98fcdc6aa"
diff --git a/src/symbolic_cliffords.jl b/src/symbolic_cliffords.jl
index b143589b3..0d2c26c40 100644
--- a/src/symbolic_cliffords.jl
+++ b/src/symbolic_cliffords.jl
@@ -227,6 +227,19 @@ function random_clifford1(rng::AbstractRNG, qubit)
 end
 random_clifford1(qubit) = random_clifford1(GLOBAL_RNG, qubit)
 
+function LinearAlgebra.inv(op::SingleQubitOperator)
+    c = LinearAlgebra.inv(CliffordOperator(SingleQubitOperator(op), 1, compact=true))
+    return SingleQubitOperator(c, op.q)
+end
+
+LinearAlgebra.inv(h::sHadamard) = sHadamard(h.q)
+LinearAlgebra.inv(p::sPhase) = sInvPhase(p.q)
+LinearAlgebra.inv(p::sInvPhase) = sPhase(p.q)
+LinearAlgebra.inv(p::sId1) = sId1(p.q)
+LinearAlgebra.inv(p::sX) = sX(p.q)
+LinearAlgebra.inv(p::sY) = sY(p.q)
+LinearAlgebra.inv(p::sZ) = sZ(p.q)
+
 ##############################
 # Two-qubit gates
 ##############################
diff --git a/test/test_symcliff.jl b/test/test_symcliff.jl
index 9cfddb976..2af1fd538 100644
--- a/test/test_symcliff.jl
+++ b/test/test_symcliff.jl
@@ -1,6 +1,5 @@
 using Random
 using QuantumClifford
-
 using QuantumClifford: stab_looks_good, destab_looks_good, mixed_stab_looks_good, mixed_destab_looks_good
 using QuantumClifford: apply_single_x!, apply_single_y!, apply_single_z!
 using InteractiveUtils
@@ -66,3 +65,16 @@ end
         @test op1 == op2
     end
 end
+
+@testset "SingleQubitOperator inv methods" begin
+    for gate_type in [sHadamard, sX, sY, sZ, sId1 , sPhase, sInvPhase]
+        n = rand(1:10)
+        @test CliffordOperator(inv(SingleQubitOperator(gate_type(n))), n) == inv(CliffordOperator(gate_type(n), n))
+        @test CliffordOperator(inv(gate_type(n)), n) == inv(CliffordOperator(gate_type(n), n))
+    end
+    for i in 1:10
+        random_op = random_clifford1(i)
+        @test CliffordOperator(inv(random_op), i) == inv(CliffordOperator(random_op, i))
+        @test CliffordOperator(inv(SingleQubitOperator(random_op)), i) == inv(CliffordOperator(random_op, i))
+    end
+end