diff --git a/CHANGELOG.md b/CHANGELOG.md
index d48259f..89fe257 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # News
 
+## Unreleased
+
+- Align `GaussianState`, `GaussianUnitary`, and `GaussianChannel` parameterization with QuantumInterface basis API.
+  - `GaussianState` now subtyped as `StateVector{B,V}` instead of `StateVector{M,V}`.
+  - `GaussianUnitary` and `GaussianChannel` now subtyped as `AbstractOperator{B,B}` instead of `AbstractOperator{D,T}` and `AbstractOperator{D,T}`.
+  - Added `basis_l` and `basis_r` fields to `GaussianUnitary` and `GaussianChannel` for QuantumInterface compatibility; these fields mirror the `basis` field.
+
 ## v1.3.4 - 2026-01-05
 
 - Add optional rng arguments to random methods.
diff --git a/src/types.jl b/src/types.jl
index a619071..23bbafa 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -22,7 +22,7 @@ covariance: 2×2 Matrix{Float64}:
  0.0  1.0
 ```
 """
-@kwdef struct GaussianState{B<:SymplecticBasis,M,V} <: StateVector{M,V}
+@kwdef struct GaussianState{B<:SymplecticBasis,M,V} <: StateVector{B,V}
     basis::B
     mean::M
     covar::V
@@ -53,6 +53,7 @@ Defines a Gaussian unitary for an N-mode bosonic system over a 2N-dimensional ph
 ## Fields
 
 - `basis`: Symplectic basis for Gaussian unitary.
+- `basis_l`, `basis_r`: For QuantumInterface compatibility; always equal to `basis`.
 - `disp`: The displacement vector of length 2N.
 - `symplectic`: The symplectic matrix of size 2N x 2N.
 - `ħ = 2`: Reduced Planck's constant.
@@ -80,14 +81,16 @@ symplectic: 2×2 Matrix{Float64}:
  0.0  1.0
 ```
 """
-@kwdef struct GaussianUnitary{B<:SymplecticBasis,D,S} <: AbstractOperator{D,S}
+@kwdef struct GaussianUnitary{B<:SymplecticBasis,D,S} <: AbstractOperator{B,B}
     basis::B
+    basis_l::B = basis
+    basis_r::B = basis
     disp::D
     symplectic::S
     ħ::Number = 2
     function GaussianUnitary(b::B, d::D, s::S; ħ::Number = 2) where {B,D,S}
         all(size(s) .== length(d) .== 2*(b.nmodes)) || throw(DimensionMismatch(UNITARY_ERROR))
-        return new{B,D,S}(b, d, s, ħ)
+        return new{B,D,S}(b, b, b, d, s, ħ)
     end
 end
 
@@ -133,6 +136,7 @@ Defines a Gaussian channel for an N-mode bosonic system over a 2N-dimensional ph
 ## Fields
 
 - `basis`: Symplectic representation for Gaussian channel.
+- `basis_l`, `basis_r`: For QuantumInterface compatibility; always equal to `basis`.
 - `disp`: The displacement vector of length 2N.
 - `transform`: The transformation matrix of size 2N x 2N.
 - `noise`: The noise matrix of size 2N x 2N.
@@ -166,15 +170,17 @@ noise: 2×2 Matrix{Float64}:
  4.0   2.0
 ```
 """
-@kwdef struct GaussianChannel{B<:SymplecticBasis,D,T} <: AbstractOperator{D,T}
+@kwdef struct GaussianChannel{B<:SymplecticBasis,D,T} <: AbstractOperator{B,B}
     basis::B
+    basis_l::B = basis
+    basis_r::B = basis
     disp::D
     transform::T
     noise::T
     ħ::Number = 2
     function GaussianChannel(b::B, d::D, t::T, n::T; ħ::Number = 2) where {B,D,T}
         all(length(d) .== size(t) .== size(n) .== 2*(b.nmodes)) || throw(DimensionMismatch(CHANNEL_ERROR))
-        return new{B,D,T}(b, d, t, n, ħ)
+        return new{B,D,T}(b, b, b, d, t, n, ħ)
     end
 end