Star Trek: 10 Things You Need To Know About Transporters
3. Does The Transporter Send The Atoms And The Bits, Or Just The Bits?
The canon definition of the Transporter states that it sends both the atoms of the person or item, along with the information around said atoms. To put it another way, the Transporter is said to send the original file, in whole, instead of a copy. With that being the case, there are a number of issues in how this is depicted in the franchise.
In the episode The Enemy Within, Captain Kirk is split into two halves. There is the passive good Kirk and the highly aggressive evil Kirk. Though a fun story, written by Richard Matheson no less, if one is to follow the canon explanation of the Transporter, it would be impossible.
Theoretical physicist Lawrence Krauss wrote in his book The Physics of Star Trek that if the atoms and the information are being sent in a transporter beam, then splitting into two distinct people would be impossible, as the beam could only rematerialize the exact same number of atoms. To split Kirk in this fashion, the poor man would have to be biforcated.
However, if the Transporter only sends the information each time, then transporter clones are entirely possible. This would account for evil Kirk, Thomas Riker, and William Boimler - all of whom were created as transporter copies along the way.