Immortality and identity. 
https://philpapers.org/rec/TURIAI-3
Abstract:
We need understanding of personal identity to develop radical life extension technologies: mind uploading, cryonics, digital immortality, and quantum (big world) immortality. A tentative solution is needed now, due to the opportunity cost of delaying indirect digital immortality and cryonics.

The main dichotomy in views on personal identity and copies can be presented as: either my copy = original or a soul exists. In other words, some non-informational identity carrier (NIIC) may exist that distinguishes the original from its exact copy. Typically, it is often claimed that NIIC is either continuity of consciousness, soul, perspective, sameness of atoms, or position in space. We create an exhaustive map of identity theories.

To resolve the main dichotomy, we must recognize that personal identity requires an overarching validating system: God, qualia world, social agreement, blockchain or evolutionary fitness. This means that we cannot solve identity without solving metaphysics (and the nature of time). It is unlikely we'll solve this before creating superintelligent AI.

Therefore, a conservative approach to personal identity is preferable: as we don't know the nature of identity, we should preserve as much as possible and avoid situations similar to Mars Teleporting unless necessary for survival.

There are several tricks which can help us answer identity-related problems without solving all needed metaphysics; these tricks are variants of the conservative approach:

1. Mind merging: we can escape the Mars Transporter problem (even the broken one) by incorporating mind merging later.
2. Indexical uncertainty: I should care about my copy because I don't know if I am the original or my copy.
3. Dividing the notion of "copy" into "mirror copy," "personality-copy," and "future copy." Many paradoxes can be solved if the correct type of copy is defined.
4. Accepting two types of identity. Human personal identity consists of two intertwined types of identity: informational identity, which predicts sameness, and identity of consciousness, which predicts what I will experience in the next moment of time.
5. Continuity passing eventually through all possible minds. If both cyclic universe and continuity as identity are true, I will eventually become any of my copies. MWI is functionally equivalent to cyclic universe, so I will become any copy in different timesteps. Therefore, we should care about parallel copies only if future copies don't exist (though in MWI future copies always exist, plus the chance to become someone else).
6. Self-defining and evolving identity. Another important feature of human personal identity is that it is observed and measured internally, by the identity subject himself: by redefing my identity I get the power to solve the problem. Human personal identity evolves in time, so it is not sameness. Creation of copy is a step of evolution of my identity.
7. Preserving continuity without mind. We demonstrate that the idea of continuity of consciousness is very similar to the idea of soul, but also has several problems: Continuity also can be paradoxically preserved without preserving body and mind as a separate process like flame. We explore the connection of continuity and the nature of qualia which are always continuous between two points in time.
8. Rainbow of qualia: a specific set of personal qualia becomes the personality carrier.

There are other possible tricks: branching identity, bundle and self-repairing identity, gradual identity, and identity in MWI. All of them do not solve the hard problem of identity.

We suggest a hypothetical test for identity theories: quantum Mars Transporter: if copy ≠ original, I will always experience broken Mars transporter.