If a couple purchases an estate and the deed is filed jointly, if one spouse dies would it be opened in probate?

Probate has a few purposes, but one of the main purposes is to transfer property when the owner is no longer alive to sign the deed.  If the property is held jointly the language on the deed should be similar to the following:"held as joint tenants with right of survivorship." 

Just because both spouses signed the deed does not mean that they are both owners.  Nebraska, along with most other states, require both spouses to sign deeds as evidence that the non-owner spouse was aware of the transfer.

If the property is held as joint tenants, the property would pass to the living owner at the death of one of the owners.  It may not require a probate case to accomplish the change in title but you probably have to file the death certificate with the register of deeds as proof.

The safest route to a clean title is to file a probate case, clear the deceased estate of all debts and file a new deed.