Quantum metrology based on symmetry-protected adiabatic transformation: imperfection, finite time duration, and dephasing

Abstract

The aim of quantum metrology is to estimate target parameters as precisely as possible. In this paper, we consider quantum metrology based on symmetry-protected adiabatic transformation. We introduce a ferromagnetic Ising model with a transverse field as a probe and consider the estimation of a longitudinal field. Without the transverse field, the ground state of the probe is given by the Greenberger-Horne-Zeilinger state, and thus the Heisenberg limit estimation of the longitudinal field can be achieved through parity measurement. In our scheme, full information of the longitudinal field encoded on parity is exactly mapped to global magnetization by symmetry-protected adiabatic transformation, and thus the parity measurement can be replaced with global magnetization measurement. Moreover, this scheme requires neither accurate control of individual qubits nor that of interaction strength. We discuss the effects of the finite transverse field and nonadiabatic transitions as imperfection of adiabatic transformation. By taking into account finite time duration for state preparation, sensing, and readout, we also compare performance of the present scheme with a classical scheme in the absence and presence of dephasing.

Spin‐Chain‐Star Systems: Entangling Multiple Chains of Spin Qubits

“…Indeed, the disclosure of symmetry-protected (sub-)dynamics in different physical systems [54,55] can lead to discover physical effects which turn out to be useful and applicable to different fields such as quantum metrology. [56][57][58][59]…”

Quantum annealing with twisted fields

“…Actually, the system during the QA is in the first excited state for a time around t/T = 0.3. This suggests that there is a symmetry [78,79] in the Hamiltonian to induce the level-crossing [66,80,81]. Thus, to check whether the adiabatic condition is satisfied, we need to investigate the energy gap and the transition matrices between the first excited state and the jth excited states (j 2) when we consider a time around t/T = 0.3 in the conventional scheme.…”

Spin-chain-star systems: entangling multiple chains of spin qubits

“…More in general, the symmetries, besides allowing to analytically treat some models, have profound physical implications. Indeed, the disclosure of symmetry-protected (sub-)dynamics in different physical systems [54,55] can lead to discover physical effects which turn out to be useful and applicable in different fields such as quantum metrology [56,57].…”