From 3cdf46b5359ded01406fc1cca2e99b24a740c765 Mon Sep 17 00:00:00 2001
From: ismoldayev <76691869+ismoldayev@users.noreply.github.com>
Date: Thu, 18 Apr 2024 13:12:16 -0400
Subject: [PATCH] configure two gate noise in various code evaluation setups
 (#253)

---------

Co-authored-by: Stefan Krastanov <stefan@krastanov.org>
---
 CHANGELOG.md                                  |  1 +
 .../QuantumCliffordQuantikzExt.jl             |  2 +-
 src/ecc/decoder_pipeline.jl                   | 38 ++++++++++++++++---
 src/noise.jl                                  |  8 ++--
 4 files changed, 40 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 666b0afec..75c4fd6a8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 
 ## v0.9.4 - dev
 
+- Gate errors are now conveniently supported by the various ECC benchmark setups in the `ECC` module.
 - Remove printing of spurious debug info from the PyBP decoder. 
 
 ## v0.9.3 - 2024-04-10
diff --git a/ext/QuantumCliffordQuantikzExt/QuantumCliffordQuantikzExt.jl b/ext/QuantumCliffordQuantikzExt/QuantumCliffordQuantikzExt.jl
index 8f78f858b..f5d9ca858 100644
--- a/ext/QuantumCliffordQuantikzExt/QuantumCliffordQuantikzExt.jl
+++ b/ext/QuantumCliffordQuantikzExt/QuantumCliffordQuantikzExt.jl
@@ -71,7 +71,7 @@ function Quantikz.QuantikzOp(op::Reset) # TODO This is complicated because quant
         Quantikz.Initialize("$str",affectedqubits(op)) # TODO make Quantikz work with tuples and remove the collect
     end
 end
-Quantikz.QuantikzOp(op::NoiseOp) = Quantikz.Noise(op.indices)
+Quantikz.QuantikzOp(op::NoiseOp) = Quantikz.Noise(collect(op.indices))
 Quantikz.QuantikzOp(op::NoiseOpAll) = Quantikz.NoiseAll()
 Quantikz.QuantikzOp(op::ClassicalXORConcreteWorkaround) = Quantikz.ClassicalDecision(sort([op.store, op.bits...]))
 
diff --git a/src/ecc/decoder_pipeline.jl b/src/ecc/decoder_pipeline.jl
index 1c9828b67..d1fbe897f 100644
--- a/src/ecc/decoder_pipeline.jl
+++ b/src/ecc/decoder_pipeline.jl
@@ -79,18 +79,46 @@ struct ShorSyndromeECCSetup <: AbstractECCSetup
     end
 end
 
+function add_two_qubit_gate_noise(g, gate_error)
+    return ()
+end
+
+"""Applies gate_error to a given two-qubit gate g."""
+function add_two_qubit_gate_noise(g::AbstractTwoQubitOperator, gate_error)
+    qubits = affectedqubits(g)
+    return (PauliError(qubits, gate_error), )
+end
+
 function physical_ECC_circuit(H, setup::NaiveSyndromeECCSetup)
     syndrome_circ, n_anc, syndrome_bits = naive_syndrome_circuit(H)
-    noisy_syndrome_circ = syndrome_circ # add_two_qubit_gate_noise(syndrome_circ, gate_error)
-    mem_error_circ = [PauliError(i, setup.mem_noise) for i in 1:nqubits(H)];
+    noisy_syndrome_circ = []
+
+    for op in syndrome_circ
+        push!(noisy_syndrome_circ, op)
+        for noise_op in add_two_qubit_gate_noise(op, setup.two_qubit_gate_noise)
+            push!(noisy_syndrome_circ, noise_op)
+        end
+    end
+
+    mem_error_circ = [PauliError(i, setup.mem_noise) for i in 1:nqubits(H)]
     circ = [mem_error_circ..., noisy_syndrome_circ...]
-    circ, syndrome_bits, n_anc
+    return circ, syndrome_bits, n_anc
 end
 
+
 function physical_ECC_circuit(H, setup::ShorSyndromeECCSetup)
     prep_anc, syndrome_circ, n_anc, syndrome_bits = shor_syndrome_circuit(H)
-    noisy_syndrome_circ = syndrome_circ # add_two_qubit_gate_noise(syndrome_circ, gate_error)
-    mem_error_circ = [PauliError(i, setup.mem_noise) for i in 1:nqubits(H)];
+
+    noisy_syndrome_circ = []
+    for op in syndrome_circ
+        push!(noisy_syndrome_circ, op)
+        for noise_op in add_two_qubit_gate_noise(op, setup.two_qubit_gate_noise)
+            push!(noisy_syndrome_circ, noise_op)
+        end
+    end
+
+    mem_error_circ = [PauliError(i, setup.mem_noise) for i in 1:nqubits(H)]
+
     circ = [prep_anc..., mem_error_circ..., noisy_syndrome_circ...]
     circ, syndrome_bits, n_anc
 end
diff --git a/src/noise.jl b/src/noise.jl
index fabc748c9..c4e7b095a 100644
--- a/src/noise.jl
+++ b/src/noise.jl
@@ -52,11 +52,13 @@ function applynoise!(s::AbstractStabilizer,noise::UnbiasedUncorrelatedNoise,i::I
 end
 
 """An operator that applies the given `noise` model to the qubits at the selected `indices`."""
-struct NoiseOp <: AbstractNoiseOp
-    noise::AbstractNoise
-    indices::AbstractVector{Int}
+struct NoiseOp{N, Q} <: AbstractNoiseOp where {N, Q}
+    noise::N #<:AbstractNoise
+    indices::NTuple{Q, Int}
 end
 
+NoiseOp(noise, indices::AbstractVector{Int}) = NoiseOp(noise, tuple(indices...))
+
 """A convenient constructor for various types of Pauli errors,
 that can be used as circuit gates in simulations.
 Returns more specific types when necessary."""