Kevin Smith, Leveraging measurements and symmetry to speed-up the preparation of a matrix product state

Monday 9 Jan 2023, 14:00 → 16:00 US/Eastern

The ground state of the spin-1 Affleck, Kennedy, Lieb and Tasaki (AKLT) model is a paradigmatic example of both a matrix product state and a symmetry-protected topological phase, and additionally holds promise as a resource state for measurement-based quantum computation. Having a nonzero correlation length, the AKLT state cannot be exactly prepared by a constant-depth unitary circuit composed of local gates. In this talk, I will demonstrates that this no-go limit can be evaded by augmenting a constant-depth circuit with fusion measurements, such that the total preparation time is independent of system size. I will present experimental results collected on an IBM Quantum processor that indicate our measurement-assisted scheme outperforms purely unitary protocol. I will also demonstrate the utility of prepared AKLT states as "quantum wires" for teleportation. This work serves to provide an efficient strategy to prepare a specific resource in the form of the AKLT state and, more broadly, experimentally demonstrates the possibility for realizable improvement in state preparation afforded by measurement-based circuit depth reduction strategies on NISQ-era devices.