String order melting of spin-1 particle chains in superconducting transmons using optimal control

Abstract

Utilizing optimal control to simulate a model Hamiltonian is an emerging strategy that leverages the intrinsic physics of a device with digital quantum simulation methods. Here we evaluate optimal control for probing the non-equilibrium properties of symmetry-protected topological (SPT) states simulated with superconducting hardware. Assuming a tunable transmon architecture, we cast evolution of these SPT states as a series of one-and two-site pulse optimization problems that are solved in the presence of leakage constraints. From the generated pulses, we numerical simulate time-dependent melting of the perturbed SPT string order across a six-site model with an average state infidelity of 10 −3 . The feasibility of these pulses as well as their efficient application indicate that high-fidelity simulations of string-order melting are within reach of current quantum computing systems.

Tunable photon-mediated interactions between spin-1 systems

“…Since quantum emitters, like atomic systems, can have a much richer level structure, there is an increasing interest in the last few years [48][49][50][51] on harnessing them to find exotic phenomena, such as multicritical behavior in Dicke phase transitions [48] or emergent dark entangled states [51], as well as to develop * a.gonzalez.tudela@csic.es new applications, such as new multiphoton sources [51]. One very attractive reason for considering multilevel emitters is the possibility to engineer photon-mediated interactions between higher-dimensional spins, which can find applications in the quantum simulation of nontrivial high-energy physics problems [52][53][54][55][56][57], to prepare symmetry-protected topological states in spin-1 chains [58,59], to solve complex optimization problems [60], and, more generally, to engineer universal quantum gates between spin-1 systems [61,62].…”