If we encrypt a plain text using Double DES but with **same key** K1,  

Can we get the same result as if we would encrypt the plain text using single DES but with different key, say K2.

What I'm asking is can we achieve this for same size of K1 and K2 :

```
DES(K1,DES(K1,m)) = DES(K2,m)

```

What would be effective key bits for the first ?

I know this is the case for Mono-Alphabetic shift cipher but I'm confused for DES.  

By Key Size I mean like 64 Bit key for which their are 2^55 computations.