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code. This means that the [[7 , 1 , 5; 2]] and [[7 , 1 , 5; 3]] EAQEC codes cannot be obtained by the construction of [10]. Therefore, the [[7 , 1 , 5; 2]] and [[7 , 1 , 5; 3]] EAQEC codes are new. 

In addition, all the [[7 , 1 , 5; 2]] EAQEC codes we found are degenerate codes, for some simplified stabilizer generators are of weight 4 from the check matrix. For example, a sim- plified check matrix and its simplified logical matrix of a [[7 , 1 , 5; 2]] EAQEC code are 

<img src='content_image/307802.jpg'>

with T = { 1 , 4 } . On the other hand, all the [[7 , 1 , 7; 6]] EAQEC codes are nondegener- ate codes, while the [[7 , 1 , 5; 3]], [[7 , 1 , 5; 4]],[[7 , 1 , 5; 5]] EAQEC codes can be degenerate or nondegenerate. 

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