diff --git a/litebird_sim/crosstalk.py b/litebird_sim/crosstalk.py
new file mode 100644
index 00000000..0d81b055
--- /dev/null
+++ b/litebird_sim/crosstalk.py
@@ -0,0 +1,83 @@
+import numpy as np
+from astropy.io import ascii
+from .detectors import DetectorInfo
+
+
+"""
+    Generate a random crosstalk matrix
+    Input:
+
+    dim := number of detectors
+
+"""
+
+
+def GenerateXtalk(dim: int):
+    M = np.zeros((dim, dim))
+    M = M + np.eye(dim)
+    for i in range(dim):
+        for j in range(dim):
+            if j != i:
+                rng = np.random.default_rng()
+                a = rng.uniform(-10, 0)
+                M[i, j] = 1.0e-5 * a
+    return M
+
+
+"""Implement the crosstalk over the TOD
+    Input: 
+    tods:= List of time ordered data
+    X   :=  Crosstalk  matrix
+
+"""
+
+
+def Compute_Xtalk_TOD(tods: np.ndarray, X: np.ndarray):
+    tods_x = X.dot(tods)
+    return tods_x
+
+
+"""
+    Function that reads the full crosstalk matrix 
+    written on an external file. 
+    It returns the crosstalk matrix Xtalk
+    and the dictionary d such that
+      d[detector_name]=i
+    where detector_name is a string specifying the name of the
+    detetcor and i is the index of that detetctor in the 
+    crosstalk matrix.
+"""
+
+
+def Get_Xtalk_from_file(path_matrix: str, path_dictionary: str):
+    Xtalk = np.loadtxt(path_matrix, delimiter=",", unpack=True)
+    d = ascii.read(path_dictionary)
+    return (Xtalk, d)
+
+
+"""
+    This function takes as input a crosstalk matrix for a given squid,
+    its related dictionary d[det.name]=idx, with idx the corresponding index 
+    in the matrix file, and a list of detectors wichi can be a subset
+    of the set of detectors related by the full crosstalk matrix.
+    It returns a smaller matrix with the crosstalk of this subset of detectors.
+    Input: 
+        matrix       := the full crosstalk matrix
+        d            := the associated dictionary
+        detector_list:= list of detectors we want to consider
+"""
+
+
+def create_submatrix(
+    matrix: np.ndarray, det_dict: dict[str, int], detector_list: list[DetectorInfo]
+):
+    N2 = np.size(detector_list)
+    array = np.zeros(N2)
+    dnames = [detector_list[i].name for i in range(N2)]
+    for i, key in enumerate(dnames):
+        array[i] = int(det_dict[key])
+    newmatrix = np.zeros((N2, N2))
+    for i in range(N2):
+        for j in range(N2):
+            newmatrix[i, j] = matrix[int(array[i]), int(array[j])]
+    return newmatrix
diff --git a/litebird_sim/detectors.py b/litebird_sim/detectors.py
index a489c13b..f2d0d981 100644
--- a/litebird_sim/detectors.py
+++ b/litebird_sim/detectors.py
@@ -75,6 +75,9 @@ class DetectorInfo:
 
         - channel (Union[str, None]): The channel. The default is None
 
+        - squid (Union[int, None]): The squid number of the detector.
+             The default value is None.
+
         - sampling_rate_hz (float): The sampling rate of the ADC
              associated with this detector. The default is 0.0
 
@@ -136,6 +139,7 @@ class DetectorInfo:
     pixel: Union[int, None] = None
     pixtype: Union[str, None] = None
     channel: Union[str, None] = None
+    squid: Union[int, None] = None
     sampling_rate_hz: float = 0.0
     fwhm_arcmin: float = 0.0
     ellipticity: float = 0.0
@@ -148,8 +152,6 @@ class DetectorInfo:
     fknee_mhz: float = 0.0
     fmin_hz: float = 0.0
     alpha: float = 0.0
-    bandcenter_ghz: float = 0.0
-    bandwidth_ghz: float = 0.0
     pol: Union[str, None] = None
     orient: Union[str, None] = None
     quat: Any = None
@@ -175,6 +177,7 @@ def from_dict(dictionary: Dict[str, Any]):
         - ``pixel``
         - ``pixtype``
         - ``channel``
+        - ``squid``
         - ``bandcenter_ghz``
         - ``bandwidth_ghz``
         - ``band_freqs_ghz``