A single quantum cannot be teleported

TL;DR

This paper demonstrates that quantum teleportation cannot perfectly clone a single qubit due to fundamental quantum uncertainties, challenging the belief that teleportation can serve as an infallible copying method.

Contribution

It shows that quantum field theory imposes fundamental limits on teleportation, invalidating the assumption of perfect copying even with destroyed original qubits.

Findings

Teleportation cannot achieve perfect cloning of single qubits.

Fundamental quantum uncertainties introduce unavoidable errors.

Teleportation's error level is small but non-zero, affecting experimental accuracy.

Abstract

Due to the Heisemberg uncertainty principle, it is impossible to design a procedure which permits perfect cloning of an arbitrary, unknown "qubit" (the spin or polarization state of a single quantum system)1,2. However, it is believed that a perfect copying protocol can be achieved, at least in principle, if the qubit to be copied is destroyed in the original system. Quantum teleportation3,4 is supposed to allow for such a result. Here, this belief is shown to be invalidated by a fundamental uncertainty about the number of particles involved in any process, as predicted by Quantum Field Theory. As a result, teleportation cannot provide an infallible copying procedure for the single qubits, not even in the limit of perfect experimental sensitivities. The no-cloning theorem1,2 can then be generalized to the case of destroying the original. Teleportation remains an interesting statistical procedure, having an unavoidable theoretical error at the percent level or few orders of magnitude smaller, depending on the physical process that is used. Although it cannot be made arbitrarily small, such an error is small enough to remain hidden in present experiments.