Kavli Affiliate: Birgitta Whaley
| First 5 Authors: Ievgen I. Arkhipov, Philippe Lewalle, Franco Nori, Şahin K. Özdemir, K. Birgitta Whaley
| Summary:
Non-Hermitian systems have been at the focus of intense research for over a
decade, partly due to their nontrivial energy topology formed by intersecting
Riemann manifolds with branch points known as exceptional points (EPs). This
spectral property can be exploited, e.g., to achieve controlled state
permutations that are necessary for implementing a wide class of classical and
quantum information protocols. However, the imaginary spectra of typical
non-Hermitian systems lead to instabilities and breakdown of adiabaticity,
which impedes the practical use of EP-induced energy topologies in quantum
information protocols that explicitly rely on symmetric state flips. On the
other hand, techniques that help to suppress non-adiabatic transitions in
non-Hermitian systems have also been developed, but these advances have so far
been limited to single qubits. In this work, we address this long-standing
problem by introducing a model of interacting qubits governed by an effective
non-Hermitian Hamiltonian that hosts EPs and possesses a completely real energy
spectrum. We demonstrate that such non-Hermitian Hamiltonians enable
realization of permutation groups in the multi-qubit eigenspace. Our findings
indicate that, contrary to previous beliefs, non-Hermiticity can be utilized to
achieve controlled state permutations in time-modulated multiqubit systems,
thus paving the way for the advancement and development of novel quantum
information protocols.
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