Non-Hermitian quantum information

Motivated by fundamental aspects of decoherence and the need for information retrieval in lossy quantum channels, we investigate how distinct quantum measurement bases evolve through interaction with the environment. It is shown that a pair of mutually unbiased bases, which are generalized polarization bases of high-dimensional photonic qubits, can be non-unitarily connected through an exceptional point degeneracy. This non-Hermitian connection leads to a gate operation that does not require rotation and offers a new approach for constructing other key measurement bases. In addition to revealing the non-unitary structure among mutually unbiased bases, our work bridges two separate fields of quantum information theory and non-Hermitian photonics.