Quantum information dynamics in a high-dimensional parity-time-symmetric system

Abstract

Non-Hermitian systems with parity-time (PT) symmetry give rise to exceptional points (EPs) with exceptional properties that arise due to the coalescence of eigenvectors. Such systems have been extensively explored in the classical domain, where second or higher order EPs have been proposed or realized. In contrast, quantum information studies of PT-symmetric systems have been confined to systems with a two-dimensional Hilbert space. Here by using a single-photon interferometry setup, we simulate quantum dynamics of a four-dimensional PT-symmetric system across a fourth-order exceptional point. By tracking the coherent, non-unitary evolution of the density matrix of the system in PT-symmetry unbroken and broken regions, we observe the entropy dynamics for both the entire system, and the gain and loss subsystems. Our setup is scalable to the higher-dimensional PT-symmetric systems, and our results point towards the rich dynamics and critical properties.

Maximal quantum entanglement at exceptional points via unitary and thermal dynamics

“…When higher-dimensional representations of SU(2)-qutrits, qudits-are considered, results in Sec. II remain valid with higher-order EP contours [33,34]. They also remain qualitatively same for other Hermitian couplings K µν σ µ ⊗ σ ν between the unitary and thermal qubits.…”

“…Since EPs are branch points of Riemann manifolds that represent complex energies, they are responsible for the enhanced sensing and adiabatic mode-switch phenomena [25,26]. Their novel properties have intensified the efforts to engineer EP landscapes [27][28][29] and higher-order EPs in the classical and quantum domains [30][31][32][33][34] .…”

Experimental Demonstration of Fine-Grained Steering Inequality of Two-Qubit Mixed States

“…In order to achieve the maximal violation of CFFW inequality, we scan the whole permitted measurement strategies of Alice and Bob since the observables are unknown but keeping B 1 and B 2 mutually unbiased. In the experiment, we only need to add certain QWPs in the original measurement setup, namely, a combination of sandwich type QWP-HWP-QWP sequence [36][37][38], and a following PBS to realize the measurement operators. The coincidence counting of the APDs {D1, D3} represent the result a = b = 0, simultaneously.…”

Probing phase transitions in non-Hermitian systems with Multiple Quantum Coherences

“…In Figs. 8(b) and 8(c) we set the system sizes N = 50 and N = 100, respectively, and plot the quantity F (ρ, H 2 ) averaged over 3000 realizations, for W ∈ [4,6]. Overall, the larger the system, the higher the fluctuations on F (ρ, H 2 ), which in turn also exhibits higher amplitudes.…”

“…Dissipative quantum systems have been widely studied in different contexts [1][2][3][4][5][6]. Among them, physical systems which can be described by non-hermitian Hamiltonians are particularly important.…”